Assessment of entrance skin dose and effective dose for some

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					                               King Saud University
                                Collage of Science
                        Department of Physics and Astronomy




Assessment of Entrance Skin Dose and Effective
Dose of Some Routine X-ray Examinations Using
            Calculation Technique.

A thesis submitted in partial fulfillment of the requirements for the degree of Master of
   Science in the department of Physics and Astronomy at the Collage of Science at
                                   King Saud University




                                           by

                         Hanan Fawaz Akhdar

                                     Supervised by

                            Dr. Maha Turjman
                           Dr. Ahmed M. Outif
                           Dr. Abdullah Al Jaffali


                                    2006/2007 G
ii
                                                                                             i
                                       Abstract
Introduction
X-rays play an important role in diagnosing and treating many kinds of diseases. This
important medical X-ray role is always associated with biological effects and risks to the
patients and medical staff. The growing concern regarding medical X-ray exposure and
their possible risks, has resulted in the initiation of quality control programs and patients
dose survey and assessment in many countries. Patients dose have been always measured
using thermoluminesence dosimeter (TLD) or transmission ionization chamber (TIC).
These two dosimeters though highly accurate, are expensive time consuming and may
intervene with patient exposure. A much easier and costless method of dose assessment can
be done using calculation methods.
Aims
The aims of the current work were to survey different entrance skin dose (ESD) calculation
methods and then use the most accurate calculation method to assess patients’ entrance
doses for selected X-ray exams at the Security Forces Hospital in Riyadh. Different organs
doses resultant from different X-ray scans will also be assessed.
Methods
The study was conducted at Security Forces Hospital and was divided into three stages:
Stage 1: In this stage survey of all published calculation methods for ESD was conducted.
The accuracy of these published methods in comparison with the method that is based on
direct measurement of machine output (method 2) was then performed. During this stage,
modelings of different parameters necessary for different ESD calculation methods were
also done. Stage 2: In this stage the most accurate method (method 2) was used to survey
patients ESD for selected general X-ray examinations. Stage 3: In this stage calculation of
organs doses that resulted from different X-ray examinations were performed using
XDOSE software.
Results and discussions
The literature review revealed 7 equations for ESD calculation. Five of these equations
were adopted in this work, because they depend on parameters that could be known from
the measured exposure parameters, results of quality control test or from modeling of
published data. The performance of all other methods in comparison with method 2 was
assessed in the studied 2470 patients (views). It was noted that apart from method 1, all
other methods performed are well compared with method 2. It was also noted that among
the other methods (other than method 1), method 3 was superior to methods 4 and 5
(R2=0.9285, P>0.001 for method 3, R2=0.917, P>0.001 for method 4, and R2=0.9266,
P>0.001 for method 5.). A new method was also devised and was found to perform better
compared to all other methods (R2=0.9985 and P=0.00267). It was also noted that (a part
from chest scan) the calculated ESD (using method 2) for most x-ray examinations was less
than that published or recommended in other countries. Although, the ESD found in this
study was less than that found in other countries, it was noted that (for most scans) the
variation in ESD can not be explained by the variation in organ thickness and this may be
attributed to the fact that automatic exposure control is not routinely used by the
technologists. This was also reflected on the statistical distribution of the ESD. The results
of organs doses follow the same patterns as that of ESD. Organs that are within the
scanning field receive the highest dose. The ovaries receive the highest dose from LSS
                                                                                         ii
(0.52 mSv for AP) and pelvic (0.25 mSv for AP) scans. The other scans have no (or
minimum) dose burden on ovaries. The testes on the other hand, receive the highest dose
from pelvic (0.95 mSv) and LSS (0.1 mSv forr AP) scans. Other scans deliver much lower
doses to the testes. The thyroid receive the highest dose from C-spine (0.25 mSv) and chest
(0.04 mSv for AP) scans. Other scans deliver variable range of dose to the thyroid. Bones
receive the highest dose from the LSS (0.12 mSv for AP) scans. All other scans deliver
variable doses to the bones. Uterus receives the highest dose for LSS (0.69 mSv for AP),
pelvic (0.34 mSv) and KUB AP (0.02 mSV). Other scans deliver minimum doses to the
uterus. On the whole body, the maximum radiation burden was from LSS scan (0.19 mSv
for AP).
Conclusion
All the assessed ESD calculation methods were comparable. The newly suggested method
performed is better compared to other methods. The calculated ESD in the current work
was found to be (in general) less than that published in other countries. The high dose
found in chest scan need reduction from radiology technologists. Neglecting the use of
AEC resulted in bad distribution of ESD that can not be explained by variation in organ or
patient thickness in most of the studied scans. A new method for ESD estimation was
developed and found to perform well compared to other calculation method and software
was developed to calculate the ESD (using the new method) and the organ doses using the
Monte Carlo pre calculation data.
                                                                           iii
                        Acknowledgements
As I look back into the past three years, I see precious memories, difficult
moments and unforgettable people. People, who had a big impact on my life,
people who were very supportive, people whom I feel very lucky to have had
around me. People whom I would like to take this opportunity to thank.

I express my sincere gratitude to Dr. Maha Turjman the head of the female
physics department in KSU and my supervisor for her guidance,
encouragement and support.

I am extraordinarily grateful to the person who guided me throughout the long
hard process of the preparation of this thesis; my supervisor Dr. Ahmed
    Outif;
M. Outif Consultant and Head of Medical Physics Department/ King Fahad
Medical City, for his patience, advice, support and thoughtful effort.

I would like to express my gratitude to staff members at the Special Forces
Hospital for their assistance and support.

                                      Al
I thank my co-supervisor Dr. Abdullah Al Jaffali for his understanding and
support.

I extend my appreciation to all members of the physics department at King
Saud University. Specially Dr. Omar Al Dossary the head of the physics and
astronomy department at KSU and Dr. Safar Al Ghamdi the head of the
nuclear physics committee at KSU.

I would like to thank the Thesis committee members; Dr. Nabil Maalej and
Dr. Mohammed Al Garaawi for dedicating their time and effort towards this
project.

I wish to thank my uncle Dr. Fathi Akhdar for his great support and
encouragement.

I owe my dearest thanks to the most precious people in my life, my parents;
                   Nabila
Fawaz Akhdar and Nabila Yaghmour for their support, encouragement and
guidance when I needed them most.

Finally, I would like to thank my husband Awwad Al Ghamdi for his
imperative help, patience, support, care, hard work and for being there for
me.
                                                                  iv
                          Dedication
I would like to dedicate this work to my Parents, my husband, and my
children; Samar, Turkei and Fouz.
                                                                                                                                               v
                                                Table of Contents
Abstract ............................................................................................................................................ i
Acknowledgements ....................................................................................................................... iii
Dedication .....................................................................................................................................iv
Table of Contents............................................................................................................................v
List of Figures ................................................................................................................................vii
List of Tables ..................................................................................................................................ix
List of Abbreviations .......................................................................................................................x
          Introduction
Chapter 1 Introduction .................................................................................................................. 1
   1.1 Discovery of X-rays and its characteristics........................................................................... 1
   1.2 Theory of X-ray production................................................................................................. 5
   1.3 X-ray spectrum and beam characteristics ............................................................................ 8
   1.4 Interaction of X-ray with matter......................................................................................... 14
   1.5 Radiation quantities ............................................................................................................ 17
   1.6 Radiation biological effects................................................................................................. 25
Chapter 2 Literature review ......................................................................................................... 29
   2.1 Calculation methods of entrance dose .............................................................................. 33
   2.2 Calculation methods of organ doses.................................................................................. 37
   2.3 Aims of the project ............................................................................................................. 40
Chapter 3 Equipments ................................................................................................................. 41
   3.1 X-ray machine .................................................................................................................... 41
   3.2 X-ray detectors.................................................................................................................... 45
                                ethods.................................................................................. 52
                               methods
Chapter 4 General experimental methods
   4.1 Calculation of ESD............................................................................................................. 52
   4.2 Calculation of organ doses ................................................................................................. 55
Chapter 5 Results and discussion ................................................................................................ 56
   5.1 Results of literature review ................................................................................................. 56
   5.2 Results of FAE formula...................................................................................................... 57
   5.3 Results of BSF modeling.................................................................................................... 64
   5.4 Results of HVL modeling .................................................................................................. 70
   5.5 Comparison of different ESD calculation methods.......................................................... 73
   5.6 Results of HVL modeling .................................................................................................. 76
                                                                                                                                         vi

   5.7 Results of organ doses servey............................................................................................. 83
   5.8 X-ray dose calculator .......................................................................................................... 92
Chapter 6 Conclusion .................................................................................................................. 93
Refferences ................................................................................................................................... 95
Appendices ................................................................................................................................. 102
                                                                                                                              vii
                                            List of Figures
Figure 1.1: A photograph of William C. Roentgen ........................................................... 1
Figure 1.2: The image of Roentgen's wife hand ................................................................. 2
Figure 1.3: The photon may behave as a wave .................................................................. 3
Figure 1.4: The photon may behave as a particle .............................................................. 3
Figure 1.5: Schematic diagram of the excitation process ................................................... 6
Figure 1.6: Schematic diagram of the ionization process................................................... 7
Figure 1.7: Schematic diagram of the bremstrahlung process ........................................... 7
Figure 1.8: Example of X-ray spectrum.............................................................................. 8
Figure 1.9: Effect of Tube current on X-ray spectrum .................................................... 10
Figure 1.10: Effect of Tube potential on X-ray spectrum................................................ 11
Figure 1.11 Effect of filtration on X-ray spectrum ........................................................... 12
Figure 1.12: Effect of atomic number of target material on X-ray spectrum .................. 13
Figure 1.13: Schematic diagram of classical scattering..................................................... 14
Figure 1.14: Schematic diagram of compton scattering ................................................... 15
Figure 1.15: Schematic diagram of photoelectric effect................................................... 15
Figure 1.16: Schematic diagram of pair production......................................................... 16
Figure 1.17: Schematic diagram of photodisintegration .................................................. 16
Figure 1.18: Kerma and absorbed dose ........................................................................... 21
Figure 1.19: Radiation damage ......................................................................................... 25
Figure 1.20: Skin burn: example of deterministic effect .................................................. 27
Figure 2.1: Monte Carlo photon tracing diagram............................................................. 38
Figure 3.1: X-ray tube main parts ..................................................................................... 41
Figure 3.2: The filtered and non filtered X-ray spectrum................................................ 43
Figure 3.3: Effect of Collimation ...................................................................................... 44
Figure 3.4: Schemed diagram of photomultiplier tube.................................................... 45
Figure 3.5: Schemed diagram of a semiconductor detector ............................................ 46
Figure 3.6: Schemed diagram of a gas filled detector ...................................................... 47
Figure 3.7: Variation of pulse height with voltage ............................................................ 47
Figure 3.8: Schemed diagram of gas multiplication process............................................ 48
Figure 3.9: The definition of optical density, D ............................................................... 50
Figure 3.10: The Characteristic Curve of X-ray film........................................................ 51
Figure 4.1: Sample patients' survey table .......................................................................... 52
Figure 5.1: The relationship between out put and kVp2 of room 1 ................................ 58
Figure 5.2: The relationship between out put and kVp2 of room 2 ................................ 59
Figure 5.3: The relationship between out put and kVp2 of room 3 ................................ 60
Figure 5.4: The relationship between out put and kVp2 of room 4 ................................ 61
Figure 5.5: The relationship between out put and kVp2 at room 5................................. 62
Figure 5.6: The relation between BSF and FS at HVL = 1 ............................................. 66
Figure 5.7: The relation between BSF and FS at HVL = 1.5 .......................................... 66
Figure 5.8: The relation between BSF and FS at HVL = 2 ............................................. 67
Figure 5.9: The relation between BSF and FS at HVL = 2.5 .......................................... 67
Figure 5.10: The relation between BSF and FS at HVL = 3 ........................................... 68
Figure 5.11: The relation between BSF and FS at HVL = 4 ........................................... 68
Figure 5.12: The relation ship between the constant A and HVL .................................. 69
Figure 5.13: The relation ship between the constant B and HVL .................................. 69
Figure 5.14: The linear relation between HVL and kVp for machine 1 ........................ 71
                                                                                                               viii
Figure 5.15: The linear relation between HVL and kVp for machine 2 ........................ 71
Figure 5.16: The linear relation between HVL and kVp for machine 3 ........................ 71
Figure 5.17: The linear relation between HVL and kVp for machine 4 ........................ 71
Figure 5.18: The relation between the constant a and HVL90 ......................................... 72
Figure 5.19: The relation between b and HVL90 .............................................................. 72
Figure 5.20: The relation between method 1 and method2............................................ 74
Figure 5.21: The relation between method 3 and method2............................................ 74
Figure 5.22: The relation between method 4 and method2............................................ 74
Figure 5.23: The relation between corrected method 1 and method2 ........................... 75
Figure 5.24: The relation between method 5 and method2............................................ 75
Figure 5.25: The relation between new method and method2 ....................................... 75
                                                                                                                          ix
                                             List of Tables
Table 1.1: Quality factor of different radiation types....................................................... 23
Table 1.2: Tissue Weighting Factors................................................................................ 24
Table 1.3: Radiation effects classification......................................................................... 28
Table 5.1: Summarized skin dose calculation methods .................................................. 56
Table 5.2: Out put of room 1 versus tube voltage (HVL = 3.33 mm AL at 90 kVp) .... 58
Table 5.3: Out put of room 2 versus tube voltage (HVL = 3.5 mm AL at 90 kVp)....... 59
Table 5.4: Out put of room 3 versus tube voltage (HVL = 4.3 mm AL at 90 kVp)....... 60
Table 5.5: Out put of room 4 versus tube voltage (HVL = 4.69 mm AL at 90 kVp) .... 61
Table 5.6: Out put of room 5 versus tube voltage (HVL = 3.13 mm AL at 90 kVp) .... 62
Table 5.7: Out put of different X-ray machines............................................................... 63
Table 5.8: Measured BSF for different HVLs and field sizes......................................... 64
Table 5.9: Measured HVL for different kVps ................................................................. 70
Table 5.10: The number of patients of the studied scans ............................................... 76
Table 5.11: Comparison between experimental study and the current work................. 77
Table 5.12: Comparison of ESD with other countries .................................................... 78
Table 5.13: Average organ doses of different X-ray examinations.................................. 85
Table 5.14: Comparison of organ doses with different countries ................................... 88
                                                                                                                                          x
                                          List of Abbreviations
AP ............................................................................................................ Anterior Posterior
BSF ........................................................................................................ Back Scatter Factor
ESAK ...................................................................................... Entrance Surface Air Kerma
ESD....................................................................................................... Entrance Skin Dose
FAE......................................................................................................... Free Air Exposure
HVL...........................................................................................................Half Value Layer
IAEA.......................................................................... International Atomic Energy Agency
ICRP .............................................. International Commission on Radiological Protection
Kerma ....................................................................Kinetic Energy Released per Unit Mass
KUB......................................................................................... Kidney, Ureter and Bladder
LAT ............................................................................................................................Lateral
LSS.......................................................................................................Lumbar Sacral Spine
NRPB.........................................................................National Radiation Protection Board
OBL ..........................................................................................................................Oblique
PA ............................................................................................................ Posterior Anterior
PNS........................................................................................... Peripheral Nervous System
QC ............................................................................................................... Quality Control
SCD ........................................................................................Source to Chamber Distance
SSD .................................................................................................Source to Skin Distance
TIC ................................................................................Transmission Ionization Chamber
TLD .................................................................................Thermoluminescence Dosimeter
                                                                              1


                                   Chapter 1
                                 Introduction


                 X-             characteristics:
1.1 Discovery of X-rays and its characteristics:
X-rays were accidentally discovered in 1895, when William C. Roentgen
(figure 1.1) was experimenting with a cathode ray tube [1, 2].




                Figure 1.1: A photograph of William C. Roentgen [1]


Roentgen was working in his laboratory at Würzburg University in Germany.
He had darkened his laboratory and completely enclosed his tube with a
black paper so that he could better visualize the effects of the cathode rays in
the tube [1, 2]. A plate coated with barium platinocyanide (a fluorescent
material) happened to be laying on a bench top several feets from the tube
he was using. No visible light escaped from his tube because of the black
paper enclosing the tube, but Roentgen noted that the barium platinocyanide
fluoresced regardless of its distance from the tube [1, 2]. Because the
cathode rays Roentgen was studying could not travel more than a few
                                                                              2


centimeters in air, he concluded that the source of that glow of the plate he
noted was another kind of unknown rays. He called these unknown rays as
X-rays [1, 2].


Roentgen started placing different objects between the tube and the
fluorescent plate and was able to study several characteristics of X-rays. He
was able to publish and reproduce his work and was awarded in 1901 the
first Nobel Prize in physics [1, 2]. Roentgen recognized the value of his
discovery to medicine and was able to produce and publish the first medical
X-ray image, the image of his wife's hand (figure 1.2) in 1896. This discovery
of X-ray and its application in medicine paved the way for a new field of
medicine called now radiology or diagnostic radiology [1, 2].




                 Figure 1.2: The image of Roentgen's wife hand [1]


X-rays now play an important role in health life of all communities. Its
examinations are now the most common examination in all hospitals [1, 2].
X-rays are very high frequency electromagnetic radiation or photons. They
can be counted individually using Geiger counter which make them seem
like particles, But at the same time they diffract like waves when directed at a
crystal. This means that X-rays can be treated as particles (photons) or as
waves [3].
                                                                                           3


The energy of the wave is dependant on its wavelength λ and the energy of
the particle is dependant on its momentum p [4, 5]. Thus the energy of a
photon (as a wave) (see figure 1.3) may be described either by the equation:
                                          c
                             E = hν = h                       1.1
                                          λ
Where E is the energy, h is plank's constant, ν is the frequency, c is the speed of light and
λ is the wavelength.


Or (as a particle) (see figure 1.4) by the equation:
                             E = pc                           1.2
Where m is the mass of the particle and p is its momentum.


This indicates that the photon momentum can be given by:
                                      h
                                 p=                     1.3
                                      λ
This last equation is called deBroglie's relation.




                     Figure 1.3: The photon may behave as a wave [1]




                   Figure 1.4: The photon may behave as a particle [1]
                                                                         4


X-rays have many properties in common with light. However, the unique
properties of X-rays are what make them invaluable in diagnostic imaging.
Some of these characteristics are:


1- X-rays are able to penetrate material that absorb or reflect light.
2- When X-rays are absorbed by a certain material, they may produce
   light.
3- Like light, X-rays can produce an image on a photosensitive film.
4- X-rays can ionize the atoms they pass through and so they can damage
   cells of the human body when they interact with it [4, 5].
                                                                              5


              X- production:
1.2 Theory of X-ray production:
Any X-ray tube consists of an evacuated glass tube that contains two main
components, the cathode and the anode (target). X-ray photons are
produced when an accelerated electron hits and interacts with an anode or
target material.


In the X-ray tube, the cathode (negative electrode) and the anode (positive
electrode) are held at very high potential difference. The electrons as a result
are accelerated from the cathode to the anode and gain a very high kinetic
energy. The electrons are allowed to hit the anode with a very high energy
and X-ray photons may be produced [5].
The electrons travel with a kinetic energy given by:
                                 1
                            K=     mv 2          1.4
                                 2
Where m is the rest mass of the electron and v is its velocity [5].


When the projectile electrons travel from the cathode and hit the atoms of
the heavy metal anode, they interact with these atoms and transfer their
kinetic energy to the target atoms. The projectile electrons interact with
either the orbital electrons or the electric field of the nuclei of the target
atoms. The interactions result in the conversion of the kinetic energy of the
electron into thermal energy (heat) and electromagnetic energy (X-rays) [5].
The accelerated electron interact with the anode via any of the following
three processes; excitation, ionization or bremsstrahlung. Each of these
processes is discussed separately in the following section.
                                                                                     6


      Excitation:
1.2.1 Excitation:
In this interaction (figure 1.5), the projectile electrons interact with the outer
shell electrons of the target atoms, the outer shell electrons get excited and
raised to higher energy levels. The outer shell electrons then immediately
drop back to the normal energy state with the emission of infrared radiation.
In the X-ray tube this emitted infrared radiation heat the anode of the X-ray
tube [5].
                                      outer shell electrons raise to higher
                                      level then drop back
                 Infrared radiation
                                                                 incoming electron




              Figure 1.5: Schematic diagram of the excitation process [5]


      Ionization:
1.2.2 Ionization:
In this interaction (figure 1.6), the projectile electrons interact with inner
shell electrons where the energy of the incident electrons exceed the binding
energy of the electrons in their shells, these inner shell electrons as a result
gets ejected from their inner orbits of the target atom and the atom gets
ionized and a hole is created in the place of the ejected electron. This hole is
then filled by an electron from a higher energy level and characteristic X-ray
lines are produced. These X-rays are called characteristic because its energy
is specific to the target element [1, 5, 6].
                                                                              7
                                 higher energy electron falls into hole


                 X-ray photon                             incoming electron




              ejected electron


              Figure 1.6: Schematic diagram of the ionization process [5]


      Bremstrahlung:
1.2.3 Bremstrahlung:
In this interaction (figure 1.7), the electrons completely avoid the orbital
electrons and come sufficiently close to the nucleus of the atom. The
electrons are attracted by the strong electric field of the nucleus which causes
a sudden change in the motion of the electrons and constitutes a violent
deceleration that disturbs the electromagnetic field and a photon is emitted.
At each interaction an X-ray is produced, which may have an energy between
zero and a maximum value equal to the initial kinetic energy of the incident
electron [1, 5, 6].




            Figure 1.7: Schematic diagram of the bremstrahlung process [5]
                                                                            8


    X-                          acteristics:
                            characteristics
1.3 X-ray spectrum and beam characteristics:
      X-
1.3.1 X-ray spectrum:
Figure 1.8 shows a typical X-ray spectrum. This spectrum consists of a
continuous spectrum overlapped by number of discrete lines. The
continuous spectrum represents Bremstruhlung X-rays which have energies
ranging from zero to a maximum value corresponding to the applied tube
voltage. The discrete lines represent the characteristic X-rays which have
precise fixed energies and that are produced by target ionization. These
energies are characteristic of the differences between binding energies of the
particular used element [5].




                    Figure 1.8: Example of X-ray spectrum [5]
                                                                                 9


      X-
1.3.2 X-ray beam characteristics:
X-ray beam can be described by its quality and or its quantity. Each of these
characteristics is discussed separately in the following sections.


        X-
1.3.2.1 X-ray beam quantity:
The X-ray beam quantity is the X-ray intensity (number of photons per unit
area per unit time)or the radiation exposure; and is affected by the change in
any of the following factors: Milliampere seconds, kVps and distance and
filtration.


Milliamper seconds: (mAs) is the product of X-ray tube current by the time
of exposure, it controls the number of electrons accelerated towards the
anode [3]. If the current is doubled, twice as many electrons will flow from
the cathode to the target, and hence twice as much X-ray photons will be
produced [5, 7]. Thus, X-ray quantity is directly proportional to the mAs [5],
Thus:
                             I 1 mAs1
                                =                1.5
                             I 2 mAs 2

Where I1 is the X-ray intensity that is produced when a current mAs1, is
applied on the tube, and I2 is the X-ray intensity that is produced when
current mAs2 is applied on the X-ray tube. Thus increasing X-ray tube
current will also increase X-ray quantity with the same ratio (see figure 1.9)
                                                                            10




               Figure 1.9: Effect of Tube current on X-ray spectrum [7]


                (kV
                 kVp):
Applied voltage (kVp): The increase in the applied voltage will increase the
probability of bremstruhlung interaction and hence more X-ray photons will
be produced. It was found that X-ray quantity is approximately proportional
to the square ratio of the applied voltage [5], thus.
                                             2
                              I1  kVp1 
                                 =                1.6
                              I 2  kVp2 
                                        
Where I1 is the intensity of the beam produced when kVp1 voltage is applied
on the tube and I2 is the intensity of the beam when kVp2 voltage is applied
on the tube.


Any change in the potential will affect both the amplitude and the position of
the X-ray spectrum. The area under the curve increases with the square of
the factor by which kVp is increased and the relative distribution of emitted
X-ray photons shifts to the right (higher energies) [5, 7]. Thus for the same
mAs increasing the applied voltage will increase X-ray beam quantity [7].
                                                                              11




              Intensity


                              Low kVp                   High kVp



                                             Energy
             Figure 1.10: Effect of Tube potential on X-ray spectrum [7]




Distance: The intensity of X-rays is inversely proportional to the square
distance from the target [5], thus:
                                             2
                              I1  d 2   
                                 =                  1.7
                              I 2  d1
                                  
                                         
                                         


Where I1 is the intensity of the beam when a distance d1 is used and I2 is the
intensity of the beam when a distance d2 is used.


Filtration: Any material that lies in the path of the X-ray beam is called
Filtration:
filtration. There are two types of filtration; inherent and added filtration. The
X-ray tube housing for example is an inherent filter material. Any added
material to the beam is called added filtration. Filtration reduces the X-ray
quantity by selectively removing low energy X-ray photons that do not add
any information to the diagnosing image and hence improving the X-ray
beam quality (see section 1.3.2.2) [5].
                                                                                 12


Thus the total effect of filtration on the X-ray beam [7]:
   – Change in the X-ray spectrum shape (figure 1.11)
   – The peak of the spectrum shifts towards higher energies
   – The maximum energy remains unchanged
   – The minimum energy shifts towards higher energies




                                                Without Filter
            Intensity




                                      With Filter




                                                 Energy

                        Figure 1.11 Effect of filtration on X-ray spectrum [7]
                                                                                   13


        X-
1.3.2.2 X-ray beam quality:
The X-ray quality is a measure of the penetrating ability of the X-ray beam
and it is measured by the half value layer (HVL) of the beam. HVL is the
thickness of a substance needed to reduce the intensity of the beam into half
of its original value. The larger the HVL, the higher the beam quality. The
following factors affect the X-ray beam quality:


                (kVp):
Applied voltage (kVp): The kVp controls the speed of the accelerated
electrons and therefore controls the energy of the produced X-rays and the
half value layer [5].


Target material: The atomic number of the target material affects both the
number and the effective energy of the X-rays. When the atomic number of
the target is increased, the spectrum is shifted to the right (figure 1.12) [5, 7].




                          Tungsten
             Intensity




                            Molybdenum


                                    Energy


       Figure 1.12: Effect of atomic number of target material on X-ray spectrum
        (Tungsten atomic number = 74, Molybdenum atomic number = 42) [7]


Filtration:
Filtration: As mentioned in section 1.3.2.1, the increase of total filtration will
increase the beam quality by removing low energy photons.
                                                                                 14


                   X-         matter:
1.4 Interaction of X-ray with matter:
X-ray photons may interact with matter via any of the following five
interaction processes:


                scattering:
1.4.1 Classical scattering:
In this interaction (figure 1.13), the incident photon suffers change in its
direction not in wavelength. This kind of interaction is sometimes called
coherent scattering, and there are two types of coherent scattering: Thomson
scattering and Rayleigh scattering. Thomson scattering involve one electron
in the interaction where in Rayleigh scattering the interaction happens with
the whole atom. As this kind of interaction does not involve energy loss and
hence no ionization of the atom and only a very small percentage of the
radiation undergo coherent or classical scattering, this interaction never play
any important role in diagnostic radiology [1].

                                                          λ
                                                              Scattered Photon


                              λ

               Figure 1.13: Schematic diagram of classical scattering [1]


1.4.2 Compton scattering:
In this interaction (figure 1.14) a high energy photon strikes a free electron in
the target and ejects it; the photon changes its direction and looses some of
its energy as a kinetic energy given to the ejected electron. The scattered
photons produce noise to the image, and cannot be completely removed by
the use of grids [1]. The scattered radiation increases the dose to the patient
and staff, and contributes nothing to the diagnostic information.
                                                                            15


The change in the wavelength of the scattered photon is given by:
                               c    c   h
                  λ ′ − λ0 =      −   =     (1 − cos θ )         1.8
                               υ ′ υ 0 m0 c

Where λ 0 is the wavelength of the incident photon, λ` is the wavelength of
the scattered photon and θ is the scattering angle of the photon [6].




                                λ0
                                                            λ`

              Figure 1.14: Schematic diagram of Compton scattering [1]


                    effect:
1.4.3 Photoelectric effect:
In this interaction (figure 1.15) the incident photon ejects an electron from
the atom by giving it energy, which leaves the atom in an ionized state with an
electron vacancy that is filled immediately by an electron from a higher
energy level accompanied by an emission of characteristic radiation. The
kinetic energy of the ejected electron is the difference between the binding
energy and the incident photon energy [8].




              Figure 1.15: Schematic diagram of photoelectric effect [1]
                                                                             16


           production:
1.4.4 Pair production:
In this interaction (figure 1.16) a photon with a high energy interacts with the
nucleus where the photon disappears and in its place an electron positron
pair appears. For this interaction to take place, the energy of the incident
photon must be at least 1.02 MeV. This is because the total rest mass of the
electron positron pair is about 1.02 MeV/c2 [1]. Because its high energy, this
interaction is not important in diagnostic radiology.




                Figure 1.16: Schematic diagram of pair production [1]


      Photodisintegration:
1.4.5 Photodisintegration:
In this interaction (figure 1.17) the incident photon has an energy greater
than 10 MeV and hence it interacts directly with the nucleus and split it in
parts with emission of neutrons. Because of the high photon energy required
for this interaction this interaction does not occur in diagnostic X-ray and as
such plays no role [1].




              Figure 1.17: Schematic diagram of photodisintegration [1]
                                                                               17


                             units:
1.5 Radiation quantities and units:
There are two types of radiation quantities:
1- Quantities that describe radiation beam itself.
2- Quantities that describe the amount of energy deposited in tissue or
matter by a beam of radiation.


      Quantities
1.5.1 Quantities that describe radiation beam:
        Fluence:
1.5.1.1 Fluence:
The fluence ( Φ ) of a beam of radiation that contains photons can be
described by specifying the number of particles (dN) that cross an area (da)
perpendicular to the beam, Thus [9].
                                     dN
                               Φ=                1.9
                                     da
The SI unit of the fluence is m-2[9].


                      Flux):
1.5.1.2 Fluence rate (Flux):
The fluence rate ( φ ) of a beam describes the number of particles (dN) that
cross a unit area (da) perpendicular to the beam per unit time (dt) [9].
                               d 2 N dΦ
                          φ=        =                1.10
                               da dt dt
The SI unit of flux is m-2s-1 [9].


               fluence:
1.5.1.3 Energy fluence:
The energy fluence ( Ψ ) of a beam is the amount of radiation energy (dEbeam)
passing through a unit area (da) [10].
                                     dE beam
                               Ψ=                1.11
                                      da
The SI unit of energy fluence is MeV/m2 [10].
                                                                               18


In the case of monoenergetic photons with energy hυ , where h is the Plank
constant and υ is the radiation frequency, equation 1.11 can be written as:
                                  dN .hυ
                            Ψ=                  1.12
                                   da


                       rate:
1.5.1.4 Energy fluence rate:
The energy fluence rate (ψ ) of a beam is the amount of radiation energy
carried by a beam crossing a unit area (da) perpendicular to the beam per
unit time (dt) [10].
                                  dΨ
                            ψ =                 1.13
                                   dt
The SI unit of energy fluence rate is MeV/(m2.s) [10].


                               deposited
1.5.2 Quantities that describe deposited energy:
The amount of energy a beam deposits in matter such as tissue relates to the
amount of damage caused by the beam. The transfer of energy from a
radiation beam to a medium can occur in a single stage for direct ionizing
radiation or in two stages for indirect ionizing radiation, such as photons.
When a photon interacts with a matter, it gives all or part of its energy to an
electron of the matter. The electron then gives its energy to the medium via
excitation or ionization (see section 1.2)


        Kerma:
1.5.2.1 Kerma:
The kinetic energy released from ionizing radiation per unit mass is called
Kerma and is measured in J/Kg or Gray (Gy) [10].
                                  dEtr
                            K=                  1.14
                                  dm
Where dEtr is the average energy transferred from indirect ionizing
radiation, to the medium.
If the incident beam is a monoenergetic beam, kerma is given by:
                                                                            19


                             µ
                        K = Φ  E tr
                             ρ                  1.15
                              

Where  µ ρ  is the mass attenuation coefficient of the medium for the
           
           
incident beam energy, Φ is the fluence where the kerma occurred and

Φ µ  is the number of interactions per unit mass.
  ρ
    


                 dose:
1.5.2.2 Absorbed dose:
Although the incident photon transfers all or part of its energy to an electron
at a point, not all the transferred energy is given to the medium. As such, the
absorbed dose may be defined as:
                                 dE ab
                           D=                  1.16
                                  dm
Where dE ab is the average energy imparted by charged particles to the
medium. The unit of absorbed dose is the same as that of kerma J/Kg or Gy
[10].


      Exposure:
1.5.3 Exposure:
We cannot sense radiation directly so we have to detect a quantity that it
effect. Radiation ionizes the atoms of the medium that it passes through. The
medium that has been used to quantity radiation is air. The amount of ions
produced by a certain beam of photons in a sample of air is called exposure
[11]. The exposure is defined as the number of electric charges dQ that is
produced per unit mass of air (dm).
                                 dQ
                           X =                 1.17
                                 dm
The unit of exposure is Coulomb per Kilogram (C/Kg).
                                                                                   20


If the average energy required to produce one ion pair in air is Wair and the

charged particle energy released per unit mass of air is Ψ  µ en ρ  where Ψ
                                                                   
                                                                         air

is the energy fluence and  µ en ρ 
                                           is the mass energy absorption coefficient
                                     air

of air, which is defined as:
 µen  =  µ  Eab

    ρ  air  ρ  hν
               

Thus, the total charges produced per unit mass of air (exposure) is given by:
                                µ   e 
                                 ρ  W 
                           X = Ψ en                   1.18
                                    air  air 

Where e is the charge of the electron.


      Absorbed
1.5.4 Absorbed dose and kerma relation:
Part of the incident photon energy is transferred to an electron at a point, but
not all the transferred energy is given to the medium. Part of the electron
energy is irradiated away as bremsstrahlung. The absorbed dose is the
amount of energy actually retained in the medium. Because the length of the
electron tracks may be appreciable, kerma and absorbed dose do not take
place at the same location (figure 1.18).


The absorbed dose (D) is given by:
                             dE       µ
                        D =  ab
                             dm    = Φ  E ab
                                       ρ                  1.19
                                       

Where E ab is the part of the average kinetic energy transferred to electrons
that contributes to ionization excluding the energy loss by bremsstrahlung.
E ab depends on the photon energy and the absorbent medium. Equation

(1.19) can also be written as:
                             µ
                        D = Φ  E ab = K (1 − g )
                             ρ                             1.20
                              
                                                                              21


Where g is the fraction of energy that is lost to bremsstrahlung. For low
energy photons g is very small and hence E ab = Etr and kerma = dose.




                    Figure 1.18: Kerma and absorbed dose [12]




If the dose to air is measured at a certain point, it is very simple to calculate
dose to any other material in the same place and subject to the same energy
fluence. The ratio of the dose to any two different materials subject to the
same energy fluence is given by:
                     D1 ψ (µ ρ )1 (µ ρ )1
                        =         =                    1.21
                     D 2 ψ (µ ρ )2 (µ ρ )2

This means that the ratio of the absorbed doses is equal to the ratio of the
mass attenuation coefficients of the two materials.
                                                                              22


1.5.5 Kerma in air, dose and exposure:
From equation 1.18, energy fluence can be given by:
                                           
                                           
                             Ψ=
                                    X        Wair 
                                                            1.22
                                 µ en     e 
                                       
                                          
                                ρ       

From the definition of kerma:
                                       µ     
                             K air = Ψ  en
                                        ρ    
                                                             1.23
                                              air

If we substitute from equation 1.22 into equation 1.23:
                                    µen  
                                         X Wair 
                                                
                          Wair    ρ              e
              K air   = X                    =                   1.24
                           e    µen        (1 − g )
                                      
                                        
                                    ρ air 
                                            

Where  µen ρ   µen ρ   = 1(1 − g ) and g is the fraction of electron energy
                      
                     air 

lost in bremsstrahlung. As stated before, g is very small for diagnostic
radiography range, and as such K air can be given by:
                                       W 
                             K air = X  air                 1.25
                                        e 
Thus kerma can directly be calculated from exposure, using equation 1.25.
Since the effect of bremsstrahlung is negligible in the diagnostic radiography
range, and using equation 1.20, one can note that absorbed dose is equal to
kerma and hence absorbed dose may be given by:
                                       W 
                             D air = X  air                 1.26
                                        e 


                 dose:
1.5.6 Equivalent dose:
The absorbed dose contains neither information on the type of radiation
nor the degree of damage. The study of radiation dose indicated that
receiving the same dosage from gamma radiation suffered much less harm
                                                                               23


than from alpha particles. Alpha particles cause 3 times more damage than
do gamma rays or beta particles. For this reason a quality factor (Q) or
relative biological effectiveness was introduced to reflect the relative
harmfulness of different types of radiation [13]. Table 1.1 summarizes the Q
factor for different types of radiation.


                                  Radiation Type          Q
                                   β,γ and X-rays         1
                               Thermal neutrons (n)       3
                               Fast n, α, and protons     10
                              Heavy and recoil nuclei 20

                Table 1.1: Quality factor of different radiation types [13]


Dose equivalent (H) is the multiplication of the absorbed dose (D) by the
quality factor (Q) which reflects the ability of a particular type of radiation to
cause damage.
                               H = D×Q                  1.27
The SI unit of the dose equivalent is the sivret (Sv).


                           dose:
1.5.7 Effective equivalent dose:
It has also been noted that different tissues have different susceptibilities to
radiation, so in order to take this into consideration the effective dose was
introduced by adding different weighting factors for different organs. The
multiplication of equivalent dose by the organ weighting factor is called
effective dose and is given by:
                           H E = ∑ WT H T                 1.28
Where WT is a weighting factor represents the relative contribution of that
tissue to the total detriment resulting from uniform irradiation of the whole
                                                                         24


body and HT is the dose equivalent in tissue. Table 1.2 summarizes weighting
factors for different organs.


                   Tissue                   Weighting Factor (wT)
        Bone Surface, Skin, Brain,
                                                      0.01
               Salivary glands
           Thyroid, Esophagus,
                                                      0.04
               Bladder, Liver
                  Gonads                              0.08
          Lung, Stomach, Colon,
           Bone marrow, Breast,                       0.12
                Remainder
                Total Body                             1.0

                      Table 1.2: Tissue Weighting Factors [14]
                                                                            25


                         effects:
1.6 Radiation biological effects:
The human body consists of tissues and organs. These tissues and organs are
composed of cells which consists of molecules and other biological materials.
The molecules are a combination of atoms.


The cell is composed mainly of nucleus, a surrounding liquid known as the
cytoplasm and a membrane which forms the cell wall. The cytoplasm is the
factory of the cell while the nucleus contains all the information which the
cell needs to carry out its function and reproduce itself. The nucleus contains
the chromosomes which are small threadlike structures made of genes. The
genes consist of deoxyribonucleic acide (DNA) and protein molecules and
carry the information, which determines the characteristics of the daughter
cell.


Radiation may cause changes in complex molecular systems, such as living
cells, in two ways (figure 1.19): direct interaction with the DNA in the cells
and indirect interaction where the radiation may interact with other atoms or
molecules in the cell (particularly water) to produce free radicals [11].




                        Figure 1.19: Radiation damage [15]
                                                                                26


In the case of direct interaction, the incident radiation (photons in our case)
ionizes the atoms of the DNA molecules and break different bonds of the
molecules. In the case of indirect interaction and since the most abundant
substance in cells is water, the incident radiation breaks the bonds of the
water molecules, which produce the free radicals H+ and OH-. These radicals
have unpaired electrons and are chemically highly reactive and could cause
damages by chemical interaction with important molecules of the cell [11].


The process of water ionization may be written as:
                      H 2 O radiation → H 2 O + + e −
                                                        1.29
Where H2O+ is the positive ion and e- is the negative ion.
The produced ions interact with other water molecules resulting in new
products such as follows:
                          H 2 O + → H + + OH             1.30
The negative ion e- may also attach to a neutral water molecule and form
H2O- ion which may then dissociate and form H and OH- as follows:
                          H 2O + e − → H 2O −            1.31
                          H 2 O − → H + OH −             1.32
Another reaction product is hydrogen peroxide H2O2, which is strong
oxidizing agent and is formed by the reaction:
                          OH + OH → H 2 O2               1.33


      Classification
1.6.1 Classification of radiation effects:
The biological effects of ionizing radiation can be classified according to the
statistic nature of its effects and its occurring times [16]. Each of these effects
is discussed in the following section.
                                                                             27


        Statistical
1.6.1.1 Statistical nature of the effects:
The effects of radiation on the biological matter may be divided statistically
into deterministic and stochastic effects.


Deterministic effects are those effects that have a certain level (Threshold),
below which the effect will be absent. Examples of these effects are skin
burns (figure 1.20).




              Figure 1.20: Skin burn: example of deterministic effect [16]


Stochastic effects are those effects that do not depend on the absorbed dose.
There is no threshold but the probability of having the effects is proportional
to the dose absorbed [16]. Examples of those effects are cancer and genetic
mutation.


        Tim
1.6.1.2 Time of occurrence of the effects:
Radiation effects may also be categorized according to the time frame of
occurrence into acute and late effects.


Acute effects are caused by relatively high doses of radiation delivered over a
short period of time. These effects depend on how much and what area of
the body is exposed and over what time [17]. Examples of these effects are
skin burns (figure 1.20).
                                                                                28


Delayed (late) radiation effects may result from previous acute high-dose
exposure or from chronic low-level exposures over a period of years [17].
Examples of these effects are Cancer and genetic mutation.


Summarization:
Table 1.3 below summarizes different types of radiation effects:

        Statistical nature of   Occurring
                                                       Effects on organs
              effects              time

                                                          Skin damage
                                                Damage of reproductive system
                                  Acute        Damage of blood forming system
           Deterministic          Effects         Damage of digestive system
              Effects                             Damage of central nervous
                                                             system

                                                            Cataract
                                               Damage of immunization system
                                  Latent
                                  Effects                    Cancer
         Stochastic Effects
                                                        Heredity effects



                     Table 1.3: Radiation effects classification [16]
                                                                               29


                                  Chapter 2
                              Literature Review


Diagnostic X-ray examinations play an important role in the health care of
the population in Saudi Arabia and worldwide. These examinations may
involve significant irradiation of the patient and probably represent the
largest man-made source of radiation exposure for the population. Radiation
has been long known to be harmful to humans. The radiation exposure
received in X-ray examinations is known to increase the risk of malignancy as
well as, above a certain dose, the probability of skin damage and cataract.


The biological effect of radiation depends on the total energy of radiation
absorbed (in joules) per unit mass (in kg) of tissue or organ. This quantity is
called absorbed dose and is expressed in Gray (Gy).


If a patient is exposed to an X-ray beam, some X-ray photons will pass
through the patient without any interaction, and therefore will produce no
biological effect. On the other hand X-ray photons which are absorbed may
produce effects. Absorbed dose of radiation can be measured and/or
calculated and form basic evaluation of the probability of radiation induced
effects. In evaluating biological effects of radiation after a particular exposure
of the body, further factors such as the varying sensitivity of different tissues
and absorbed doses to different organs have to be taken into consideration.
To compare risks of partial and whole body irradiation in diagnostic
radiology effective dose is commonly used, and is expressed in severet (Sv).


In today’s diagnostic radiology, there is a growing concern about radiation
exposure. This can be seen in the recommendations of the International
Commission on Radiation Protection (ICRP) [18, 19, 20] and many other
                                                                              30


national publications. All these recommendations advice that X-ray
examinations should be conducted using techniques that keep patients doses
as low as compatible with the medical purposes of the examinations. In
order to achieve this recommendation, it is necessary to understand the
factors that affect the exposure and to be able to evaluate patients doses.


Intensive studies in the field of patient dose were conducted in the United
Kingdom (UK) [21, 22, 23]. These studies eventually lead to the
introduction of the European Union Council Directive [24] which made it
compulsory that patients dose be measured in every hospital and that doses
should be compared to reference dose levels established by the competent
authorities.


The need for standardization of radiation exposure and guidance levels for
various radiographic examinations has also been proposed by the
International Atomic Energy Agency (IAEA) as a safety standard [25]. The
guidance levels by IAEA are based on UK and European studies. Several
guidelines and dose reference levels were also published by number of
international organizations and was recently summarized by ICRP [26].
These guidelines have stimulated worldwide interest in patients’ doses and
several major dose surveys have been conducted [27, 28, 29].


Patient dose has often been described by the entrance skin dose (ESD) as
measured in the centre of the X-ray beam. Because of the simplicity of its
measurement, ESD is considered widely as the index to be assessed and
monitored. ESD is measured directly using Thermo luminescence
Dosimeter (TLD) placed on the skin of the patient or indirectly from the
measurements of dose-area product using a large area Transmission
Ionization Chamber (TIC) placed between the patient and the X-ray tube.
                                                                          31


The use of TLD method in ESD assessment is a time consuming process.
TLD technique requires prolonged annealing and reading process,
Furthermore, the use of TLD technique requires special equipments and
thorough calibration facilities which may not be available in most X-ray
departments. On the other hand TIC method does not provide direct
measurement of skin dose and mathematical equations are needed to
convert TIC reading into Skin dose.


Because of the limitations associated with both TLD and TIC, several
mathematical equations have been suggested to relate skin dose to the used
exposure factors such as the applied mAs, surface to skin distance (SSD),
filtration, field size, output, and the applied kVp (See section 2.1). These
equations provide an easy and more practical mean of estimating skin dose
even before exposure. They also provide the easiest and cheapest technique
can be employed in any kind of patient dose survey or audit. Despite the
attractive nature of the calculation methods of patient dose, one should make
sure that the used X-ray equipment has an adequate QC protocol that
ensures the accuracy of the measured exposure factors.


For the purpose of dose estimate, charts and monograms have been
published [30, 31, 32]. These monograms and charts allow skin dose to be
determined graphically over the diagnostic range of kVp, source to skin
distance SSD and filtration. The use of those monograms and charts may be
difficult and time consuming. An easier approach is to develop a functional
relation between skin dose and the radiographic parameters such as kVp,
mAs, SSD and filtration. Such an equation would make skin dose estimation
much easier and practical.
                                                                            32


Although ESD may be sufficient for quality control measurements where the
stability of the X-ray equipment is often of concern, the entrance dose is not
sufficient for comparison or evaluation of actual patient dose and associated
risk. If the risk involved in an X-ray examination is to be estimated, ESD is
not sufficient and patient dose needs to be described by other quantity that is
more directly related to radiation effect. At present, it is considered that
radiation-induced effect can be assessed by virtue of the radiation doses in
different organs or tissues in the body [1]. Such data (organ dose) cannot be
measured directly in patients undergoing X-ray examinations, and are
difficult and time consuming to be obtained by experimental measurements
using physical phantoms.


One way of estimating internal dose of a patient is the percentage depth dose
method. Percentage depth dose is defined as the ratio of the absorbed dose
at a certain depth to the dose at a reference depth (usually skin dose).
Percentage depth dose is usually measured using a water phantom and
ionization chamber. The dose is measured at the surface of the phantom and
at various depths within the phantom. The percentage depth doses at various
depths are then calculated. Patients organ dose is then calculated from the
knowledge of the organ depth and the previously calculated percentage
depth [33].


Provided that sufficient information regarding the exposure technique and
patient size are available, organ doses can be calculated to a reasonable
approximation using Monte Carlo simulation [34, 35] or depth-dose [36]
techniques.
                                                                                          33


                                    dose:
2.1 Calculation methods of entrance dose:
The first set of skin dose calculation was published by Birtch et al in 1974
[32] . A more simple equation of skin dose was then published by Edmond
[37] in 1984. Edmonds used the data published by Birtch and proved that
these radiation doses can be reduced to a simple function that depends on
kVp, mAs, filtration and SSD. Edmonds noted that skin dose is proportional
to (kVp)1.74 and as such , skin dose may be given by:
                                  836(kVp)1.74 (mAs ) 1
           skin − dose( µGy ) =                      ( + 0.114)               2.1
                                       ( SSD ) 2      T

Where T is the total filtration in mm Aluminum, SSD is the source to skin
distance in cm, and kVp is the applied kilo voltage.


Unfortunately, Edmonds did not differentiate between skin dose and air
kerma, as his equation may only be accurate for kerma in air and not for
dose. Edmonds formula was then chalenged by Shrimpton [38] who
compared the results obtained using Edmonds formula with that obtained by
direct measurement of skin dose using TLD. Shrimpton noted that
Edmond's formula produce an estimate of air kerma in the absence of
patients, and its use in estimating skin dose may involve significant error.
Edmond's formula over-estimates skin dose. Edmond's formula needs to be
corrected by multiplying it by the backscattering factor and the mean energy
absorption coefficient of tissue to that of air. The corrected form of
Edmonds equation may be as follows:
                                                                     tissue
                         836(kVp) 1.74 (mAs ) 1             µ     
    skin − dose( µGy ) =              2
                                             ( + 0.114) BSF  en
                                                             ρ    
                                                                                   2.2
                              ( SSD )         T                    air



The second trace of skin dose can be found in the literature was the two
formulas published by Tung and Tsai in 1999 [39]. Similar to the approach
used by Edmonds [37], Tung and Tsai studied the relationship between
                                                                                        34


entrance skin dose and X-ray tube potential and between entrance skin dose
and Aluminum filtration. These two relations allowed Tung and Tsai to
propose the following equation for three phase X-ray generators:
                                              2
                               KVp   mAs 
                       ESD = c                                     2.3
                               FSD   mm. Al 
Where ESD is the entrance skin dose, kVp is the applied tube potential,
mAs is the applied mAs (tube current multiplied by exposure time), FSD is
the focus to skin distance, and c is the proportionality constant or machine
dependant constant which depends on the X-ray machine and is about 2.775
for all manufacturers and X-ray machines studied by Tong and Tsai.


Tong and Tsai also suggested the use of free air exposure (as obtained from
National Council on Radiation Protection data [39], and convert it into
entrance skin dose by multiplying it by the ratio of the mean energy
absorption coefficient of tissue to that of air and backscattering factor. This
second formula suggested by Tong and Tsai was:
                                       µ en               
                                           
                                                            
                                       ρ  tissue          
               ESD = FAE × 0.00877 ×                         × BSF         2.4
                                       µ en 
                                                           
                                       ρ                  
                                              air         
Where ESD (mGy) is the entrance skin dose, FAE is the free air exposure in
mR, The 0.00877 (mGy/mR) is the factor used to convert the FAE into free
                      µ en           µ en  
air dose in mGy,          ρ  tissue  ρ  air  is   the ratio of mean energy absorption
                                           


coefficient of tissue to air and is about 1.06 for all diagnostic X-ray energies ,
and BSF is the backscatter factor.


Tong and Tsai compared the performance of equations 2.3 and 2.4 with that
obtained using TLD and found that equation 2.3 is quite accurate and that
Birtch equation performed well compare to TLD measurements.
                                                                                   35


A similar equation to equation 2.4 was used by Mcparland [40] to estimate
entrance skin dose,
                                                          Tissue
                                                  µ     
               ESD = K   0
                         c , air   ( FSD) BSF ( A) en
                                                   ρ    
                                                                            2.5
                                                         Air

Where Koc,air(FSD) is the air kerma at the focus to skin distance (FSD) and
BSF(A) is the backscatter factor at a field area A.


Another two approaches were used by scientists for dose survey. The first
approach [41] was based on the direct measurement of exposure and half
value layer for each exposure setup. The measured exposure was then
converted into skin dose using the following equation:

                  ESD = X air f ( BSF ) SCD  (     SSD
                                                       )   2
                                                                       2.6


Where ESD is the entrance surface dose in Gray, Xair is exposure at SCD of
100 cm in C/kg, f is skin absorbed dose conversion factor, SCD is source to
chamber distance and SSD is source to skin distance.


Once again, it should be noted that this formula used by Japanese scientist
calculates dose to air not dose to skin as it neglects the difference in mean
energy absorption coefficients between air and tissue.


The second Japanese formula for dose survey was introduced by Shiguch et
al [42] and was based on Birtch work [32]. A factor called non dosimeter
dosimetry (NDD) [43] was calculated for different factors and then
multiplied by mAs and scaled for the used FSD. The actually used formula
was:
                                                                   2
                                            1 
               ESD = NDD − M ( f ) × mAs ×                                 2.7
                                            FSD 
                                                                           36


Where NDD-M(f) is the calculated non dosimeter dosimetry modified
factor for each exposure setup (coefficient of kVp and HVL).
Shignch compared equation 2.7 with direct TLD measurements and found
that equation 2.7 performed well in some examination and bad in other
examinations.


In Switzerland, a nationwide survey was conducted in 1998 on 3072
institutions to estimate entrance surface air kerma of chest X-ray
examination. The used formula was [44]:
                                2
                            kVp  3    1
           ESAK (mGy ) = K       F Q FSD 2                   2.8
                            100  A

Where kVp is the tube voltage, Q is the tube charge, FA is the filtration, FSD
is the focus spot distance and K is a constant that was determined empirically
and equals 0.1 mGy(m2)/mAs [44].


In Saudi Arabia no ESD calculation based survey were conducted
previously. The only previous work one can be found is that conducted by
Al Habeeb S [45] using TLD direct measurements technique.
                                                                          37


                                 doses:
2.2 Calculation methods of Organ doses:
Percentage depth dose method has been used by a few authors for organ
dose calculation, Example Juha Lampinen [46] who developed a computer
program called (ODS-60) that uses a size and sex adjustable phantom and
mathematical equations that represent relative depth dose and dose profiles
to calculate absorbed dose at an arbitrary point in a water slab. The program
divides the organs into voxels for which the absorbed doses are calculated.
The organ dose is the average absorbed doses in the voxels of an organ [46].


The advantage of percentage depth dose calculations is that they could be
made from the knowledge of the properties of the X-ray beam without the
need for individual patient measurements. The disadvantage of this method
is that the percentage depth dose of each machine should be constructed
prior to applying this method, furthermore knowledge of organ depth is
required, such depth is not usually known [33].


Another way of estimating organ dose is the Monte Carlo simulation
technique which has been widely used in radiation physics. Monte Carlo
simulation process simulates different interaction processes of the photon
within the media. Each time a photon is generated, its path through the body
is simulated, the dose delivered to different volumes within the medium is
stored in corresponding voxels. Following the path of different photon the
delivered dose to different organ is estimated.


Several Monte Carlo codes have been developed. An example of those
computer codes is the EGS4 which was developed at Stanford University.
The Monte Carlo computer code follows the history of photons and
secondary electrons inside the phantom. A free path of the photon is
selected before the next interaction according to the energy of the photon
                                                                                                   38


and the media involved. The interactions that are usually simulated are
photoelectric absorption and Compton scattering. Each of these two
interactions have a probability depending on the energy of the photon before
the interaction [41]. The history of the photon is terminated when the
photon has been absorbed or if the energy of the photon falls below a user
defined cutoff or when the photon leaves the geometry of interest. Flow
chart 2.1 shows the photon transport process used by EGS4 Monte Carlo
code [47].


Monte Carlo data on organ doses have been reported for general
radiography of adult [35, 48, 49, 50] and children [51, 41, 52, 43] and
mammography [53, 54]. Several Monte Carlo based softwares have also
been produced [55, 56, 57].


 Photon Transport
                        Place initial photon’s parameters on stack


                       pick up energy, position, direction, geometry
                                                                           NO
                                of current particle from top of stack           Is stack empty ?
                                Photon energy < cutoff ?
                                                              YES
                                              NO                                Terminate history
                          Determine distance to next interaction and
                      transport photon taking geometry into account

                           Has photon left volume of interest ?
                                                                     YES
                                              NO

             Determine what occurs (photoelectric, Compton, pair production)


                       Determine energies and directions of resultant
                               particles & store parameters on stack

                   Figure 2.1: Monte Carlo photon tracing diagram [47]
                                                                           39


Monte Carlo simulation method has been verified against direct
measurements and has been found very accurate [58].


The main disadvantage of Monte Carlo simulation is that it is a time
consuming process. It is therefore more practical to use a precalculated
conversion factor that is based on a precalculated (measured) quantities such
as entrance surface dose, ESD [Gy], air kerma [Gy] or dose-area product,
DAP [Gy×cm2].


Many computer programs were developed based on the Monte Carlo
simulation to calculate patients' doses. An example of these programs is
XDOSE which allow calculation of organ doses for many radiographic
projections and examinations and uses two sets of 68 data files containing the
results of Monte Carlo calculations performed at the National Radiation
Protection Board (NRPB). The incident radiation can be specified in terms
of entrance surface dose or dose area product for each projection [56].
Another example of such computer software is PCXMC (PC program for X-
ray Monte Carlo) which allow calculation of both ESD and organ doses [57].
A third example of Monte Carlo based program is MS-DOS [55]. MS-DOS
calculate organ dose for the knowledge of entrance surface dose or the dose
area product for a specific radiographic view [55].


In the current work XDOSE computer program was employed to calculate
organ doses of different patients based on their skin doses that was also
calculated using different mathematic equation methods.
                                                                       40


2.3 Aims of the current work:
The aims of the current work are:
   1. Survey of the published equations for ESD calculations.
   2. Compare these methods and assess the accuracy associated with each
      method.
   3. Survey of the available techniques for organ dose calculation.
   4. If possible, suggest better methods for ESD and/or organ dose
      calculations.
   5. Assessment of both ESD and organ dose for selected routine X-ray
      examination at the Security Forces Hospital.
                                                                          41


                                   Chapter 3
                                  Equipment
    X- machine:
3.1 X-ray machine:
The X-ray machine (figure 3.1) usually consists of X-ray tube, beam
restrictor (collimator), and (in many cases) a grid. Each of these components
of X-ray machine is discussed separately in the following sections:


      X-
3.1.1 X-ray tube:
An X-ray tube (figure 3.1) is an evacuated glass envelope that contains an
anode, and a cathode with voltage applied between them. The X-ray tube is
enclosed in a protective housing which gives mechanical support and
prevents the tube from being damaged and provides protection against
electrical shocks. The housing is supported by a structure usually a ceiling
structure to support its weight [59].


The tube must be evacuated so that the accelerated electrons will not collide
with gas molecules and loose energy and produce secondary electrons. The
shape and size of the X-ray tube is designed to prevent electric discharge
between the electrodes [1].




                        Figure 3.1: X-ray tube main parts [1]
                                                                            42


The negative electrode (called the cathode) is made up of a wire filament
which acts as electrons source, when the filament is connected to a power
supply.


When an electric current is allowed to flow through the filament, electrons
are emitted via thermal emission process. These electrons are focused to the
anode via the negative voltage applied to the focusing cup. These electrons
then accelerate to the anode via the high potential difference applied
between the cathode and the anode. The focusing cup is usually made of
molybdenum and is designed to prevent spreading of the electrons and to
focus the electron stream onto the target in the required size and shape [60].


The positive electrode (anode) consists of a target material, usually tungsten,
placed on copper. The target material should be made up of a high atomic
number and with a high melting point. Some anodes are made rotating to
spread the heat on a large area, this makes it possible for the tube to stand
the heat generated by large exposures [1].


The accelerated electrons gain energy which can be calculated by the
formula:
                                m0 c 2
                          K=                 − m0 c 2    3.1
                                         2
                                   v
                                 1− 2
                                   c

Where K is the kinetic energy in joules, m0 is the rest mass of the electron, v
is the velocity of electrons, c is the speed of light.


The accelerated electrons that hit the anode interact with it via any of the
three electron interaction processes (see section 1.2). Only electrons that
interact with the anode via bremsstruhlung produce X-ray photons. Then
                                                                            43


photons are produced with a wide energy range, from zero to a maximum
energy equal to the maximum kinetic energy of the electrons (equation 3.1).
The low photons energy are of low penetration ability and are of no clinical
value. These low energy photons are absorbed by the envelope of the X-ray
tube (called inherent filtration); and by the added material that are added to
the path of the X-ray beam. These added material are called added filtration.


Figure 3.2 shows the effect of filtration on the X-ray spectrum. The presence
of the filtration material in the X-ray beam reduces X-ray beam quantity (see
section 1.3.2.1 and figure 3.2). X-ray beam quality is usually assessed via the
measurement of half value level (see section 1.3.2.2).




                          Without added filtration

                                              With added filtration




             Figure 3.2: The filtered and non filtered X-ray spectrum [1]


      X-ray
3.1.2 X-ray beam restrictors:
X-ray beam restrictors are attached to the opening of the tube to regulate the
size and shape of the X-ray beam. There are three types of restrictors:
aperture diaphragms, cones, cylinders and collimators [1].


Aperture diaphragms: is a sheet of lead with a hole in the center, the size and
shape of the hole determines the shape and size of the X-ray beam [1].
                                                                             44


Cones and cylinders: are lead shaped as cones and cylinders where the X-ray
beam passes through. The disadvantage of cones and cylinders are that they
limit the available field sizes [1].


Collimators: are the best restrictors, they consist of attenuating shutters that
can be moved inwards and outwards to shape X-ray beam [1]. Figure 3.3
below shows the difference between collimated (A) and non collimated (B)
X-ray beams [60]. With the use of collimation the X-ray beam can be
restricted to the scanning site, and limit radiation dose to other parts of the
body. Without the use of the collimator, the whole body of the patient may
be exposed to X-ray beam.




                            A                  B

                         Figure 3.3: Effect of Collimation [60]


Grids: Scattered radiation causes an unsharp image, the grid is used to
absorb scattered radiation and allow only radiation that are aligned with the
grid to hit the detector and produce an image. The grid consists of a series of
lead strips separated by X-ray transparent spacers. The primary radiation is
oriented in the same axis as the lead strips and passes between them [1].
                                                                           45


              detectors:
3.2 Radiation detectors:
Radiation detectors are based on either scintillation, ionization or chemical
process to detect radiation.


                    detectors:
3.2.1 Scintillation detectors:
Scintillation detectors emit visible light when ionizing radiation passes
through them. The light intensity is proportional to the energy of the
incident radiation. The emitted light is then detected by a light detector
called photomultiplier tube (figure 3.4). The photomultiplier tubes convert
the light output into electric pulses, where the energy of the released photon
is absorbed by an electron in a light sensitive material (photocathode) and
leaves the photocathode and get amplified by a series of dynodes [6]. This
kind of detectors is sometimes used as a detector in automatic exposure
control system to optimize patient dose.




               Figure 3.4: Schemed diagram of photomultiplier tube [6]
                                                                           46


                 detectors:
3.2.2 Ionization detectors:
Detectors based on ionization could be semiconductor detectors or gas filled
detectors. Semiconductor detectors (figure 3.5) have a very strong stopping
power and are very efficient in detecting X-rays and gamma rays [61]. When
an X-ray photon strikes a semiconductor detector it raises some electrons to
the conduction band and leaves an electron hole in the valence band.
Because the presence of an electron hole in the valence band is unstable, it
attracts an electron from the valence band of a neighboring atom, leaving an
electron hole in that atom which is filled from the valence band of its
neighbor and so on [62]. The detector is enclosed in its own vacuum, and
maintained at liquid nitrogen temperature with a cold finger and liquid
nitrogen drawer [62]. This kind of detector was not used in the current work.




             Figure 3.5: Schemed diagram of a semiconductor detector [6]


Gas filled detectors on the other hand consist of a chamber filled with gas
and two voltage plates (electrodes) (figure 3.6) [6].
                                                                              47


Radiation interacts with the gas and produces ion pairs and because of the
applied voltage, the positive ions are attracted towards the cathode and the
negative ions towards the anode causing change in voltage which can be
converted into a pulse [6]. The pulse height varies with the applied voltage
and the variation in the pulse height shows different regions (figure 3.7) [6]:




               Figure 3.6: Schemed diagram of a gas filled detector [6]




                 Figure 3.7: Variation of pulse height with voltage [6]
                                                                             48


The recombination region:
When the applied voltage is low, the force on the ions is also low. This
means that, after an ion has been formed it may recombine before it can be
collected by the electrodes. Gas-filled detectors are not normally operated in
this region [6].


The ion chamber region:
When the voltage is large enough, almost all ions are collected and the
number of ions recombining is negligible and the pulse stops increasing with
the voltage and gives a plateau shape (see figure 3.7) where the current
reaches a maximum value (saturation current) which is proportional to the
amount of incident radiation [6].


The proportional region:
When the voltage increases beyond the ion region the pulse height starts
increasing again. The ions gain enough energy to get accelerated and these
accelerated ions causes more ion pairs to be produced through secondary
ionization (gas multiplication) (figure 3.8) [6].




             Figure 3.8: Schemed diagram of gas multiplication process [6]
                                                                             49


           Mü
The Geiger Müller region:
When the applied voltage is increased, the gas multiplication is so great that
a single ionizing particle produces multiple avalanches resulting in a very
large pulse. The size of the pulse is the same, regardless of the quantity of
incoming energy [6].


The continuous discharge region:
When the voltage is increased beyond the Geiger-Müller region, the voltage
is high enough to ionize the gas molecules directly and a large signal is
generated even when the radiation field is removed. This is called the
continuous discharge region and radiation detectors should not be operated
in this region [6].


In the current work all the X-ray machines were equipped with an AEC
which uses ionization chamber in their operation.


                     detectors:
3.2.3 Chemical based detectors:
An X-ray photographic film is one of the most important chemical X-ray
detectors, it consists of a radiation sensitive emulsion coated on both sides of
a transparent sheet of plastic (base), the film base should provide strong
support for the emulsion and must not absorb too much light when viewed
and must be thick, flexible and strong enough to allow ease developing and
to be conveniently snapped into the view box repeatedly [1].


When X-ray beam passes through the body tissues, variable fractions of the
beam will be absorbed, depending on the composition and thickness of the
tissues and the quality of the beam. The information content of this X-ray
image must be transformed into a visible image. The X-ray image is first
converted into a light image using an intensifying screen which absorbs the
                                                                                50


energy in the X-ray beam that has penetrated the patient and convert this
energy into a light pattern which has as nearly as possible the same
information as the original X-ray beam. The more light a screen produces
for a given input of X-radiation, the less X-ray exposure and thus shorter
exposure time are needed to expose the film [6].


The amount of blackness on the film is called the optical density, D (figure
3.9), which is given by:
       I    
D = log 0
       I    
                                                                         3.2
        1   
Where I0 is the intensity of a light beam before passing through the film and
I1 is the intensity after passing through the film [1] .




                  Figure 3.9: The definition of optical density, D [63]


If the relationship between the logarithm of the radiation exposure and the
optical density is plotted we obtain a curve known as the Characteristic Curve
(figure 3.10). The curve is characterized by a toe or region of low gradient at
low exposures, a region of relatively steep increase in density for minimal
exposure increases, and a third relatively flat region called the shoulder at
high exposures [63].
                                                                                  51




                 Figure 3.10: The Characteristic Curve of X-ray film [63]


The ability of an X-ray film to respond to a minimum quantity of X-ray
exposure is a measure of its sensitivity or its speed. The definition of film
speed is given by [5]:
Speed = 1/(Number of roentgens needed to produce an optical density of 1)   3.3


The films used in the current work are high speed Kodak (MinR-M) films.
                                                                                                                                          52


                                                                Chapter 4
                                       General experimental Methods


                   ESD:
4.1 Calculation of ESD:
The literature review (see section 2.1) revealed seven equations used to
calculate ESD. Five of these equations were adopted in this work, because
they depend on parameters that could be known from the exposure
parameters, the quality control data or from modeling of published data.


A table includes all the necessary exposure parameters (see figure 4.1) was
constructed and distributed to the technologists who were asked to fill in all
the necessary data for each patient they scan. These tables were then
collected from the technologists and were entered in Excel sheets for further
calculation. The quality control data for each X-ray machine was then
reviewed and modeled as shown later.


             Please be kind enough to fill out this form .

             ---------------------------------------------------------------------------------------------


Room           Patient                        Organ              Field size                       Exposure Setup         Type of      Dose
                                    Views
Num.                                          Thick.                                                                      Film Charge Gray
       Age    Weight Height                             Width Length          Area      mAs        kVp       OD    FSD




                                                                                                                                   Thank You !



                                     Figure 4.1: Example of patients' survey table.
                                                                              53


                                         AE)
                                       (FAE
4.1.1 Measurement of Free Air Exposure (FAE):
One of the important routine QC tests that is usually constructed on each X-
ray machine is the output (FAE) accuracy at different kVps. This test must
yield a straight line relationship between kvp2 and output (FAE). The output
vs kVp2 relation was measured for each X-ray machine used in the current
work. This relation was then used to calculate output for each kVp of each
patient and view. The data for this modeling is stated in section 5.2.


                  BSF:
4.1.2 Modeling of BSF:
BSF is almost needed in each formula of ESD (see section 2.1). The BSF
was modeled from the data published by Harrison [64] for different X-ray
machines and field sizes. The BSFs for each HVL was plotted against field
                                                                          b

size (FS) and was then fitted using an equation of the form BSF = a( FS ) .
                                                                         FS



The constants a and b were then derived from the fit of their values at
different HVL against HVL. The result of this modeling is stated in section
5.3.


                  HVL:
4.1.3 Modeling of HVL:
Some of the ESD calculation methods require knowledge of the half value
layer (HVL) of different machines at different kVp settings. Such
measurements of HVL at different kVp settings are not usually performed
during quality control processes and instead the HVL is usually measured at
a constant kVp (90 kVp in the current work).


HVLs for different kinds of X-ray machines at different kVp settings were
published by Harrison [64]. These data were adopted in the current work
and a relationship between HVL, kVp and HVL at 90 kVp was constructed
as follows:
                                                                             54


First: A relationship between HVL and kVp for different machines was
constructed by plotting the HVL at different kVp settings for different kind
of machines. This yielded a straight line equation (see section 5.4), (figures
5.14, 5.15, 5.16, 5.17).


Second: The constants of these straight line equations (a and b) were then
each plotted against HVL at 90 kVp. The resultant equations of the
constants a and b were then substituted in the HVL vs kVp equation, and
this yielded a general equation to calculate HVL at any kVp setting with the
knowledge of the HVL at 90 kVp which was measured during QC tests. The
result of this modeling is stated in section 5.4, (figures 5.18 and 5.19).


                                              methods:
4.1.4 Comparison of different ESD calculation methods:
For this purpose ESD for each patient was calculated using different ESD
calculation methods (see table 5.1). As method 2 was based on direct
measurement of machine output, this method was considered as the most
accurate method. All other methods were compared to method2.
                                                                           55


                         dose:
4.2 Calculation of Organ dose:
XDOSE software [56] was used in the current work to calculate different
organ doses for all patients and different examinations and views. Those
calculated organ dose were then compared with that published in other
countries (sea table 5.13).


In XDOSE the incident radiation upon the patient is specified in terms of
entrance surface dose for each projection that forms part of the examination.
The kVp, filtration (HVL) and projection frequency are also required for
each projection. XDOSE then determines organ doses for each examination
and projection based on the ESD, HVL, kVp and type of examination.
Furthermore, it calculates the ICRP dose indices, effective dose and effective
dose equivalent.
                                                                                                                56


                                                  Chapter 5
                              Results and Discussion


                          review:
5.1 Results of literature review:
Table 5.1 summarizes the different published ESD formulas. It was noted
that method 1 (equation 2.3) has a clear inherent physical error. This
                                                                2
equation was corrected to                   KVp   mAs                          where c is 0.2775 instead of
                                    ESD = c              
                                            FSD   mm. Al 

2.775 that was mentioned by Tung and Tsai [39]. Both the corrected and
uncorrected equations were used in the current patient survey.
                                                                                                 Equation
  Method                                  Equation                                              number in Reference #
                                                                                                  the text
                                              2

 Method 1                        KVp   mAs 
                         ESD = c              
                                                            , c = 2.775                           2.3        [39]
                                 FSD   mm. Al 


                                                  µ          
                                                  
                                                                                               2.4        [39]
                                                   ρ  tissue 
                           ESD = FAE × 0.00877 ×                × BSF
                                                  µ 
                                                     
                                                  ρ 
                                                    air 
 Method 2
                                                   or
                                                                          Tissue
                                                        µ            
                         ESD = K c0,air ( FSD ) BSF ( A) en
                                                         ρ           
                                                                                                 2.5        [40]
                                                                      Air

                                                            2
                                        kVp  3    1
 Method 3               ESAK (mGy) = K          Q                                                2.8        [44]
                                        100  FA FSD 2
                                             
                                         836(kVp)1.74 (mAs) 1
 Method 4      skin − dose( µGy ) =                        ( + 0.114)                             2.1        [22]
                                              ( SSD) 2      T
                                                                                       tissue
                                    836(kVp )1.74 ( mAs) 1             µ
 Method 5     skin − dose( µGy) =                       ( + 0.114) BSF  
                                                                       ρ                        2.2        [38]
                                         ( SSD) 2        T               air
 Method 6                   ESD = X air f ( BSF ) SCD   (           SSD
                                                                          )
                                                                          2
                                                                                                  2.6        [41]
                                                                              2
                                                      1 
 Method 7                ESD = NDD − M ( f ) × mAs ×                                            2.7        [43]
                                                      FSD 
 Corrected                                2
                                KVp   mAs               , c = 0.2775
                        ESD = c              
 Method 1                       FSD   mm. Al 



               Table 5.1: Summarized skin dose calculation methods
                                                                                              57


      New
5.1.1 New ESD calculation method:
A new method was developed empirically from an existing method (method
5), by multiplying it by a correction factor of HVL/HVL90, where we noted
that at 90 kVp when the HVL=HVL90 the ESD calculated by method 5 is
equal to that calculated by method 2 and the further the kVp is from 90; the
further is the ESD calculated by method 5 when compared to that calculated
by method 2, we also needed a factor that corrects the method's results
without interfering with the units of the formula. This correction factor was
found to yield results that are very close to that obtained by using method 2.
Thus this new method yields more accurate ESD results without the need
for output measurement of different X-ray machines. The formula of the
new method is:
                                                  tissue
                 0.836(Kvp )
                           1.74
                                  (mAs ) µ ρ 
                                                         (BSF )              HVL 
                                               air                1
  ESD(mGy ) =                                                         + 0.114 
                                                                                       
                                                                                           5.1
                                  (FSD )    2
                                                                  HVL          HVL90 

Where HVL is modeled from the data published by Harrison [64] (see
section 4.1.3.


                   formula:
5.2 Results of FAE formula:
Five rooms were served in the current work. The FAE of each room at
different kVp was modeled separately as follows:


5.2.1 Modeling of FAE of room 1:
Table 5.2 shows the measured output at different kVp settings. The plot of
the output/mAs vs (kVp)2 was found to be linear (figure 5.2) and was
represented to by the equation:
 FAE
 mAs
        (
     = − 0.10132 + 0.00118(kVp )
                                2
                                        )
Thus the FAE can be given by the equation:
                                                                                                                                                58

                                                                                                             2

                      (                        107 
              FAE = − 0.10132 + 0.00118(kVp )       (mAs )
                                                                                             2
                                                                                                 )                            5.2
                                               FSD 
Where 107 cm is the source to detector distance at the time of QC
experiment.



STD (cm) = 107 , mAs = 10, FIELD.S = 19 X 18 cm                                  2




       kVp                 Output (mR)                                                               kVp 2
                                                                                                                          Output/mAs (mR/mAs)
       40                                             14.88                                          1600                        1.49
       45                                             21.18                                          2025                        2.12
       50                                             28.16                                          2500                        2.82
       75                                             67.69                                          5625                        6.77
       81                                             79.06                                          6561                        7.91
       90                                             97.48                                          8100                        9.75
       99                                             117                                            9801                        11.7
       109                                            138.9                                          11881                       13.89
       121                                            168.5                                          14641                       16.85

   Table 5.2: Out put of room 1 versus tube voltage (HVL = 3.33 mm AL at 90 kVp)

                                                      20       Y =-0.10132+0.00118 X

                                                      18

                                                      16
                             (Room 1) Out Put / mAs




                                                      14

                                                      12

                                                      10

                                                      8

                                                      6

                                                      4

                                                      2                              P= 0.00231

                                                      0

                                                      -2
                                                           0    2000   4000   6000   8000 10000 12000 14000 16000 18000
                                                                                         2
                                                                                      Kvp




             Figure 5.1: The relationship between output and (kVp)2 of room 1


5.2.2 Modeling of FAE of room 2:
Table 5.3 shows the measured output at different kVp settings. The plot of
output vs kVp2 was found to be linear (figure 5.3) and was represented to by
the equation:
FAE
mAs
        (
    = − 0.06986 + 0.00102(kVp )
                                2
                                                                       )
                                                                                                                                                 59


Thus the FAE can be given by the equation:
                                                                                                                2

                     (                       107 
            FAE = − 0.06986 + 0.00102(kVp )       (mAs )
                                                                                                 2
                                                                                                     )                         5.3
                                             FSD 
Where 107 cm is the source to detector distance at the time of QC
experiment.


           STD (cm) = 107,    mAs = 10,                             FIELD.S = 19X 18 cm2



     kVp                     Output (mR)                                                                 kVp2              Output/mAs (mR/mAs)
      40                                  13.09                                                          1600                     1.31
      45                                  18.77                                                          2025                     1.88
      50                                  24.81                                                          2500                     2.48
      75                                  58.66                                                          5625                     5.87
      81                                  68.12                                                          6561                     6.81
      90                                  84.28                                                          8107                     8.43
      99                                  101.8                                                          9801                    10.18
     109                                               121                                               11881                   12.10
     121                                               146                                               14641                   14.60
   Table 5.3: Out put of room 2 versus tube voltage (HVL = 3.5 mm AL at 90 kVp)

                                                       18
                                                                Y =-0.06986+0.00102 X
                                                       16

                                                       14

                                                       12
                              (Room 2) Out Put / mAs




                                                       10

                                                       8

                                                       6

                                                       4

                                                       2                              P = 0.00231

                                                       0

                                                       -2   0    2000   4000   6000   8000 10000 12000 14000 16000 18000
                                                                                             2
                                                                                       Kvp




           Figure 5.2: The relationship between output and (kVp)2 of room 2


5.2.3 Modeling of FAE of room 3:
Table 5.4 shows the measured output at different kVp settings. The plot of
output vs (kVp)2 was found to be linear (figure 5.4) and was represented to
by the equation:
                                                                                                                                               60

FAE
mAs
        (
    = − 0.1946 + 0.000813232(kVp )
                                   2
                                                                             )
Thus the FAE can be given by the equation:
                                                                                                            2

                  (                             110 
            FAE = − 0.1946 + 0.000813232(kVp )       (mAs )
                                                                                            2
                                                                                                )                                5.4
                                                FSD 
Where 110 cm is the source to detector distance at the time of QC
experiment

STD (cm) =110 , mAs =10, FIELD.S= 19 X 18 cm                                 2




      kVp                  Output (mR)                                                              kVp 2
                                                                                                                         Output/mAs (mR/mAs)
       40                                             9.50                                          1600                        0.95
       45                                            13.84                                          2025                        1.38
       50                                            18.61                                          2500                        1.86
       75                                             44.5                                          5625                        4.45
       81                                            52.72                                          6561                        5.27
       90                                             65.3                                          8100                        6.53
      109                                            95.12                                          11881                       9.51
      121                                            115.4                                          14641                       11.54
Table 5.4: Out put of room 3 versus tube voltage (HVL = 4.3 mm AL at 90 kVp)

                                                     14
                                                              Y =-0.1946+8.13232E-4 X

                                                     12


                                                     10
                            (Room 3) Out Put / mAs




                                                      8


                                                      6


                                                      4


                                                      2
                                                                                    P = 0.0016
                                                      0

                                                          0    2000   4000   6000   8000 10000 12000 14000 16000 18000
                                                                                        2
                                                                                     Kvp




              Figure 5.3: The relationship between output and (kVp)2 of room 3
                                                                                                                                                   61


5.2.4 Modeling of FAE of room 4:
Table 5.5 shows the measured output at different kVp settings. The plot of
output vs kVp2 was found to be linear (figure 5.5) and was represented to by
the equation:
FAE
mAs
        (
    = − 0.54111 + 0.00084577(kVp )
                                   2
                                                                                )
Thus the FAE can be given by the equation:
                                                                                                                   2

                  (                             107.5 
            FAE = − 0.54111 + 0.00084577(kVp )         (mAs )
                                                                                                   2
                                                                                                       )                             5.5
                                                FSD 
Where 107.5 cm is the source to detector distance at the time of QC
experiment

STD (cm) =107.5 , mAs =10, FIELD.S= 19 X 18 cm                                      2




       kVp                 Output (mR)                                                                     kVp 2
                                                                                                                             Output/mAs (mR/mAs)
       40                                             4.185                                                1600                    0.4185
       45                                             12.32                                                2025                     1.23
       50                                             16.69                                                2500                     1.67
       75                                             42.97                                                5625                     4.30
       81                                             51.19                                                6561                     5.12
       90                                                 64.5                                             8100                     6.45
       99                                             78.78                                                9801                     7.88
       109                                            95.09                                                11881                    9.51
       121                                            116.1                                                14641                    11.61

   Table 5.5: Out put of room 4 versus tube voltage (HVL = 4.69 mm AL at 90 kVp)

                                                                 Y =-0.54111+8.4577E-4 X
                                                     14


                                                     12


                                                     10
                            (Room 4) Out Put / mAs




                                                      8


                                                      6


                                                      4


                                                      2


                                                      0
                                                                                        P = 0.0193


                                                     -2    0      2000   4000   6000    8000 10000 12000 14000 16000 18000
                                                                                               2
                                                                                         Kvp




              Figure 5.4: The relationship between output and (kVp)2 of room 4
                                                                                                                                               62


5.2.5 Modeling of FAE of room 5:
Table 5.6 shows the measured output at different kVp settings. The plot of
output vs kVp2 was found to be linear (figure 5.1) and was represented to by
the equation:
FAE
mAs
        (
    = − 0.10666 + 0.00129(kVp )
                                2
                                                                      )
Thus the FAE can be given by the equation:
                                                                                                              2

                      (                        100 
              FAE = − 0.10666 + 0.00129(kVp )       (mAs )
                                                                                              2
                                                                                                  )                          5.6
                                               FSD 
Where 100 cm is the source to detector distance at the time of QC
experiment


STD (cm) =100 cm , mAs =10 , FIELD.S = 19 X 18 cm                                   2




      KVp                   Output (mR)                                                               KVp 2
                                                                                                                         Output/mAs (mR/mAs)
       40                                             16.73                                           1600                      1.67
       45                                             22.74                                           2025                      2.27
       50                                             31.3                                            2500                      3.13
       75                                             73.75                                           5625                      7.38
       81                                             86.29                                           6561                      8.68
       90                                             106.5                                           8100                      10.65
       99                                             127.8                                           9801                      12.78
       109                                            152.8                                           11881                     15.28
       121                                            184.2                                           14641                     18.42

   Table 5.6: Out put of room 5 versus tube voltage (HVL = 3.13 mm AL at 90 kVp)

                                                     22       Y =-0.10666+0.00129 X

                                                     20

                                                     18

                                                     16
                            (Room 5) Out Put / mAs




                                                     14

                                                     12

                                                     10

                                                      8

                                                      6

                                                      4
                                                                               P = 0.00287
                                                      2

                                                      0

                                                     -2   0    2000   4000   6000   8000 10000 12000 14000 16000 18000
                                                                                          2
                                                                                        Kvp




             Figure 5.5: The relationship between output and (kVp)2 at room 5
                                                                                 63


5.2.6 Summary of FAE formulas:
The following table summarizes the output formulas for different machines
used in the current work.




 Machine                               Output formula
                                                                         2

 Room 1                          (                           )
                                                        107 
                       FAE = − 0.10132 + 0.00118(kVp ) 
                                                         2
                                                              (mAs )
                                                        FSD 
                                                                         2

 Room 2                          (                           )
                                                      2  107 
                       FAE = − 0.06986 + 0.00102(kVp )        (mAs )
                                                         FSD 
                                                                             2

 Room 3                      (                            110 
                      FAE = − 0.1946 + 0.000813232(kVp )            )
                                                                (mAs )
                                                                 2

                                                          FSD 
                                                                             2

 Room 4                      (                           107.5 
                     FAE = − 0.54111 + 0.00084577(kVp ) 
                                                             2
                                                                 )
                                                                 (mAs )
                                                         FSD 
                                                                         2

 Room 5                          (                           )
                                                        100 
                       FAE = − 0.10666 + 0.00129(kVp ) 
                                                         2
                                                              (mAs )
                                                        FSD 
                  Table 5.7: Output of different X-ray machines



These equations were then used in equation 2.3 to calculate ESD at different
applied kVp.
                                                                                      64


                    modeling:
 5.3 Results of BSF modeling:
 Table 5.8 summarizes the data published by Harrison [64] for BSF at
 different field sizes (FS). The fit of BSF at different field sizes (see figures
 5.6, 5.7, 5.8, 5.9, 5.10 and 5.11) yielded an equation of the form
                                               B

                            BSF = A( FS ) FS             5.7

               2
 Field size (cm )                    (mm-
                                 HVL (mm-Al)               BSF
2x2                          1                            1.05
                             1.5                          1.07
                             2                            1.09
                             2.5                          1.11
                             3                            1.11
                             4                            1.12
4x4                          1                            1.11
                             1.5                          1.14
                             2                            1.17
                             2.5                          1.19
                             3                            1.21
                             4                            1.21
7x7                          1                            1.16
                             1.5                          1.2
                             2                            1.23
                             2.5                          1.25
                             3                            1.27
                             4                            1.27
10 x 10                      1                            1.18
                             1.5                          1.22
                             2                            1.26
                             2.5                          1.28
                             3                            1.3
                             4                            1.32
 Table 5.8: Measured BSF for different HVLs and field sizes (data adopted from ref[64])
                                                          65

               2
 Field size (cm )           (mm-
                        HVL (mm-Al)                 BSF
15 x 15             1                              1.19
                    1.5                            1.24
                    2                              1.28
                    2.5                            1.31
                    3                              1.33
                    4                              1.37
20 x 20             1                              1.2
                    1.5                            1.25
                    2                              1.29
                    2.5                            1.32
                    3                              1.35
                    4                              1.39
25 x 25             1                              1.2
                    1.5                            1.25
                    2                              1.3
                    2.5                            1.33
                    3                              1.36
                    4                              1.4
30 x 30             1                              1.2
                    1.5                            1.26
                    2                              1.3
                    2.5                            1.34
                    3                              1.37
                    4                              1.41
                            Table 5.8: continued
                                                               66




  BSF
                                                 −0.4083
                         BSF = 1.202( FS )         FS




                             Reduced Chi-Square = 1




                              Field size (cm2)




Figure 5.6: The relation between BSF and FS at HVL = 1
  BSF




                                                      −0.484
                            BSF = 1.254( FS )           FS




                              Reduced Chi-Square = 1




                              Field size (cm2)




Figure 5.7: The relation between BSF and FS at HVL = 1.5
                                                           67




      BSF
                                              −0.5304
                        BSF = 1.297( FS )       FS




                          Reduced Chi-Square = 1




                          Field size (cm2)




 Figure 5.8: The relation between BSF and FS at HVL = 2
BSF




                                              −0.5535
                        BSF = 1.327( FS )       FS




                             Reduced Chi-Square = 1



                                 Field size (cm2)




Figure 5.9: The relation between BSF and FS at HVL = 2.5
                                                          68




BSF
                                             −0.6096
                        BSF = 1.355( FS )      FS




                            Reduced Chi-Square = 1




                          Field size (cm2)




Figure 5.10: The relation between BSF and FS at HVL = 3
      BSF




                                             −0.6912
                        BSF = 1.389( FS )      FS




                            Reduced Chi-Square = 1



                          Field size (cm2)




Figure 5.11: The relation between BSF and FS at HVL = 4
                                                                          69


The constants A were then plotted against HVL (see figure 5.12) and the
resultant graph was then fitted using an equation of the form
                  A = 1.201 + (0.1371) ln( HVL)                   5.8


              A




                                             HVL

           Figure 5.12: The relationship between the constant A and HVL


Similarly the constant B for different field sizes were also plotted against
HVL (see figure 5.13), and the resultant graph was also fitted by an equation
of the form
                                      1
                    B=                                      5.9
                         − 2.39 + (0.6796 ) ln( HVL)
              B




                                               HVL

           Figure 5.13: The relationship between the constant B and HVL
                                                                                            70


A and B were then substituted in the general BSF equation (equation 5.7) to
arrive to a general equation to calculate BSF at any field size FS and any half
value layer HVL. This general equation was of the form:
                                                                1

       BSF = [1.201 + 0.1371{ln( HVL)}]( FS )   FS ( −2.39 +{0.6796 [ln( HVL ) ]})
                                                                                     5.10


5.4 Results of HVL modeling
Table 5.9 summarizes the published data by Harrison [64] for HVL at
different kVp and for different kinds of x-ray machines. Figures 5.14, 5.15,
5.16 and 5.17 show the relationship between HVL and kVp for different X-
ray machines. It was noted that HVL was directly proportional to kVp for all
kinds of machines and that the relationship between HVL and kVp can be
represented to by a general equation of the form:
                          HVL = a + bKVP                           5.11


       Machine                       kVp
                                     kVp                     HVL (mm Al)
       Machine 1                      60                         1.14
                                      75                         1.39
                                      90                         1.67
                                     100                         1.96
       Machine 2                      60                         1.54
                                      75                         1.82
                                      90                         2.17
                                     100                         2.55
       Machine 3                      60                         1.89
                                      75                         2.22
                                      90                         2.63
                                     100                         3.10
       Machine 4                      60                         2.29
                                      75                         2.72
                                      90                         3.25
                                     100                         3.79
                 Table 5.9: Measured HVL for different kVps [64]
                                                                             71


                          2.0
                                 Y =-0.09163+0.02008 X

                          1.8



                          1.6




                    HVL
                          1.4



                          1.2
                                        HVL = −0.09163 + 0.02008KVP

                                                 P = 0.00724
                          1.0
                                                Kvp
                           50     60   70        80         90   100   110




Figure 5.14: The relationship between HVL and kVp for X-ray machine 1


                          2.6    Y =0.01252+0.02471 X
                          2.4


                          2.2


                          2.0
                    HVL




                          1.8
                                            HVL = 0.01252 + 0.02471KVP
                          1.6
                                                  P = 0.01652

                          1.4

                           50     60   70        80         90   100   110
                                                Kvp



Figure 5.15: The relationship between HVL and kVp for X-ray machine 2


                          3.2    Y =0.0634+0.0295 X
                          3.0


                          2.8


                          2.6
                    HVL




                          2.4


                          2.2
                                              HVL = 0.0634 + 0.0295 KVP
                          2.0
                                              P = 0.02697
                          1.8


                          1.6
                            50    60   70        80         90   100   110
                                                Kvp



Figure 5.16: The relationship between HVL and kVp for X-ray machine 3


                          4.0

                          3.8
                                 Y =0.02007+0.03683 X
                          3.6

                          3.4

                          3.2

                          3.0
                    HVL




                          2.8

                          2.6
                                            HVL = 0.02007 + 0.03683 KVP
                          2.4

                          2.2                    P = 0.04191

                          2.0
                           50     60   70        80         90   100   110
                                                Kvp



Figure 5.17: The relationship between HVL and kVp for X-ray machine 4
                                                                                                                                                                       72


The constant a for different machines were then plotted against HVL at 90
kVp (HVL90) (see figure 5.18) and this yielded an equation of the following
form:
            a = −0.96579 + 0.75361( HVL90 ) − 0.13843( HVL2 90 )                                                                                              5.12


                                                                                                                                                   2
                                   0.08
                                                  Y =-0.96579+0.75361 X-0.13843 X
                                   0.06

                                   0.04

                                   0.02

                                   0.00

                                   -0.02

                                   -0.04
                               a




                                   -0.06

                                   -0.08

                                   -0.10

                                   -0.12

                                   -0.14

                                   -0.16
                                           1.4     1.6     1.8     2.0     2.2     2.4     2.6         2.8     3.0     3.2     3.4     3.6
                                                                                  HVL90



                  Figure 5.18: The relation between the constant a and HVL90


The constant b was also plotted against HVL at 90 kVp (figure 5.19) and this
yielded a straight line equation of the form:
                       b = 0.00198 + 0.01062( HVL) 90                                                                                                  5.13

                                       0.040

                                       0.038
                                                         Y =0.00198+0.01062 X
                                       0.036

                                       0.034

                                       0.032

                                       0.030

                                       0.028
                                   b




                                       0.026

                                       0.024

                                       0.022

                                       0.020

                                       0.018

                                       0.016
                                                 1.4     1.6     1.8     2.0     2.2     2.4       2.6       2.8     3.0     3.2     3.4     3.6
                                                                                         HVL90



                        Figure 5.19: The relation between b and HVL90


The constants a and b were substituted in the HVL equation (equation 5.14)
and this yielded the following general equation to calculate HVL at any kVp
setting with the knowledge of the HVL at 90 kVp which was measured
during QC tests.


        (
HVL = − 0.96579 + 0.75361[HVL90 ] − 0.13843[HVL90 ] + (0.00198 + 0.01062[HVL90 ])kVp
                                                                                               2
                                                                                                   )                                                                 5.14
                                                                            73


                                            methods:
5.5 Comparison of different ESD calculation methods:
In this part of the study, the ESD for each of the studied patients (a total of
2470 patients) was calculated using different ESD calculation method
including the newly suggested method.


As method 2 is based on direct measurements of the machine output, it was
regarded as the most accurate method; furthermore method 2 has been
proved experimentally to be the most accurate method among different ESD
calculation methods in a previous study done by Al Shehri S [65], and as
such the performance of other methods in comparison with method 2 was
performed. All ESD calculation methods including the new method (see
section 5.1.1) were compared with method 2. The results are summarized in
figures 5.20, 5.21, 5.22, 5.23, 5.24, 5.25.


It was noted that apart from method 1, all methods of ESD performed well
compared with method 2. It was also noted that among the other methods
(other than method 1), method 3 was superior to methods 4 and 5
(R2=0.9285, P>0.001 for method 3, R2=0.917, P>0.001 for method 4,
R2=0.9266, P>0.001 for method 5, and R2=0.9203, P>0.001 for the corrected
method 1). On the other hand, the new method was found to perform better
than all other methods with R2=0.9985 and P=0.00267 in comparison with
method 2.


As this work was based on modeling data from previously published data, it
may be wise to assess the performance of this new method practically by
direct measurement of HVL at different kVps.


It is true that the X-ray output (and hence ESD) is proportional to kVpx,
where x ranges from 1.4 to 2.4 and to mAs, however this dependence on
                                                                                                           74


kVp vary from machine to another. Furthermore, the actual output/mAs
vary between X-ray machines. These two important points explain the week
correlation found between method 2 and method 1.

                                                     Method 1 vs Method 2
                                                                                   y = -0.0006x + 1.9233
                                                                                   R2 = 0.0495, P<0.001
                                       25.00
                  ESD (method 1) mGy

                                       20.00
                        Method 1




                                       15.00

                                       10.00

                                        5.00

                                        0.00
                                           0.00   500.00    1000.00 1500.00 2000.00 2500.00 3000.00
                                                                 Method 2
                                                            ESD (method 2) mGy

                 Figure 5.20: The relation between method 1 and method2 *

                                                     Method 3 vs Method 2
                                                                                   y = 0.9144x + 0.0512
                                                                                   R2 = 0.9285, P<0.001
                                       25.00

                                       20.00
                  ESD (method 3) mGy
                          Method 3




                                       15.00

                                       10.00

                                        5.00

                                        0.00
                                           0.00     5.00        10.00     15.00     20.00        25.00
                                                                   Method 2
                                                            ESD (method 2) mGy

                 Figure 5.21: The relation between method 3 and method2 *

                                                     Method 4 vs Method 2          y = 0.8317x + 0.0503
                                                                                   R 2 = 0.9179, P<0.001
                                       20.00
                  ESD (method 4) mGy




                                       15.00
                          Method 4




                                       10.00

                                        5.00


                                        0.00
                                           0.00     5.00        10.00     15.00     20.00       25.00
                                                                   Method 2
                                                           ESD (method 2) mGy

                 Figure 5.22: The relation between method 4 and method2 *

* Data for these graphs are found in appendix A
                                                                                                                         75


                                                             corection Method 1 vs Method 2
                                                                                                  y = 0.625x + 0.0387




                  ESD (correction method 1)1mGy
                                                                                                 R2 = 0.9203, P<0.001
                                                  14.00
                                                  12.00




                        Correction Method
                                                  10.00
                                                   8.00
                                                   6.00
                                                   4.00
                                                   2.00
                                                   0.00
                                                      0.00       5.00        10.00    15.00        20.00       25.00
                                                                    ESD (method 2) mGy
                                                                            Method 2


           Figure 5.23: The relation between corrected method 1 and method2 *

                                                                 Method 5 vs Method 2
                                                                                                  y = 1.1931x + 0.0635
                                                                                                 R2 = 0.9266, P<0.001
                                                  30.00
                           Method mGy




                                                  25.00
                                                  20.00
                     ESD (method 5)5




                                                  15.00

                                                  10.00
                                                   5.00

                                                   0.00
                                                      0.00       5.00        10.00    15.00        20.00       25.00
                                                                                Method 2
                                                                        ESD (method 2) mGy

                 Figure 5.24: The relation between method 5 and method2 *

                                                                New Method vs Method 2
                                                                                                y = 1.0308x + 0.0056
                                                                                              R2 = 0.9985, P=0.002671
                                                  25.00
                  ESD (new method) mGy




                                                  20.00
                         New Method




                                                  15.00

                                                  10.00

                                                   5.00

                                                   0.00
                                                      0.00       5.00        10.00    15.00        20.00       25.00
                                                                                Method 2
                                                                         ESD (method 2) mGy

               Figure 5.25: The relation between new method and method2 *




* Data for these graphs are found in appendix A
                                                                                               76


5.6 Patient survey
For this part of the study, method 2 was adopted. The data for all surveyed
patients (a total of 2470 patients) are tabulated in appendix B together with
statistical graphs representing the statistical distribution of data. The
following table contains the number of patients of all the scans that were
studied. All patients were adults (above 15 years old). Both males and
females patients were surveyed.


      View
                                                                     Towne     Ball
                     AP      PA     LAT     OBL      Spot   Waters                      Caldwell
                                                                       s      catcher
 Part of the body
      Chest          13      309     145     --      --      --       --        --        --
      Pelvis         53       --     16      --      --      --       --        --        --
      KUB            185      --      --     --      --      --       --        --        --
       LSS           82       --     83       6      58      --       --        --        --
    Humerus          21       --     18      --      --      --       --        --        --
   Abdomen           123      --      --     --      --      --       --        --        --
     C-spine         66       --     65      --      --      --       --        --        --
      Knee           61       --     52      --      --      --       --        --        --
  Parsal sinuses      --     14      21      --      --      20       --        --         3
      Foot           47       6      33      46      --      --       --        --        --
     Femur           24       --     24      --      --      --       --        --        --
  Dorsal spine       27       --     27      --      11      --       --        --        --
     Finger          26       --     28      20      --      --       --        --        --
 Shoulder            87       --      --     --      --      --       --        --        --
      Wrist          27       9      33      25      --      --       --        --        --
   Tibia fibula      14       --     14      --      --      --       --        --        --
      Skull          22      10      32      --      --      --       16        --        --
      Hand           41      10      25      27      --      --       --        10        --
      Ankle          50       --     36      31      --      --       --        --        --
    Forearm          25       --     24      --      --      --       --        --        --
     Elbow           19       --     19      --      --      --       --        --        --
     Sinuses          --      --     10      --      --      10       --        --         7
      PNS             --      --     14      --      --      16       --        --        16
    Clavicle          7       --      --     --      --      --       --        --        --
       Leg            7       --      7      --      --      --       --        --        --
                    Table 5.10: The number of patients of the studied scans
                                                                                                             77


5.6.1 Comparison with a previous TLD work
The results of the current work were compared with a previous TLD work
conducted in the same hospital but different X-ray machines. Table 5.10
summarizes the results of this comparison.
 Examination                      Current work                             Previous TLD work [45]
               Mean    Number         Organ                      Mean     Number       Organ
                ESD       of        thickness    kVp     mAs      ESD        of      thickness   kVp   mAs
               (mGy)   patients        (cm)                      (mGy)    patients      (cm)
  Chest PA      0.35    309          22.76      116.96   4.24     0.22      20         22        114    4
Abdomen AP      2.89     23          25.59       73.09   53.25    4.57      20         26        73     36
   Skull PA     0.68     10          28.3        66.8     16      1.32      20         21        71     23
 Skull LAT      0.58     32          14.7        64.94   14.39    0.91      20         17        66     15
  Knee AP       0.19     61          14.32       62.02   4.91     0.26      20         15        64     8
 Knee LAT       0.13     52          11.88       62.09   3.35     0.24      23         14        64     7
  Pelvis AP     1.28     53          20.98       70.82   24.6     2.77      20         22        72     34
  Elbow AP      0.05     19          6.82        54.11   1.88     0.17      20         8         48     4
 Elbow LAT      0.05     19          8.34        54.03   1.83     0.17      20         8         49     4
   Foot AP      0.04     47          7.43        48.49   1.61     0.06      21         9         46     3
  Foot LAT      0.06     33          9.26        53.53    1.9     0.08      21         8         48     4
 Foot OBL       0.05     46          7.62        50.04   1.68     0.07      21         8         47     3
 D spine AP     1.91     27          19.56       71.89   39.31    3.29      20         23        73     35
D spine LAT      3.6     27          27.52       78.19   79.83    11.49     20         31        66    139
 C spine AP     0.38     66          12.67       62.26   12.69    0.67      20         14        65     13
C spine LAT     0.39     65          15.49       63.31   12.98    0.996     20         15        65     13
   LSS AP       2.91     82          23.2        73.3    56.3     5.23      20         26        75     42
  LSS LAT        3.9     83          28.25       89.04   46.98     8.9      20         31        86     55
  LSS Spot      7.16     58          34.77       92.6    87.72    17.06     20         34        95     76
  Wrist AP      0.05     27          4.52        47.96   1.51     0.14      20         6         46     3
 Wrist LAT      0.05     33          9.24        50.59   1.92     0.14      20         8         48     3
 Wrist OBL      0.04     25          9.54        48.78   1.71     0.17      20         8         46     3
      Table 5.11: Comparison between the current work and a previous TLD work

In general the mean ESD of the current work was less than that of the
previous TLD work. This may be attributed to the large sample size of the
current work and the less exposure factors found in the current work. Only
for chest PA was the calculated ESD in the current work slightly higher than
that of the previous TLD work. This is clearly due to the higher exposure
factors and higher organ thickness found in the current work.
                                                                                               78


                 with
5.6.2 Comparison with other countries
Table 5.11 compares the results of the current survey with those conducted
in other countries or recommended by different scientific organizations.
                                                 Chest AP

                 Sample size       Mean ESD*                                       Organ thickness
                                                Median ESD   Mean kVp   Mean mAs
                                     (mGy)                                              (cm)
                                       0.19                                            20.77
 Current work        13                            0.15       87.38       3.03
                                    0.09-0.46                                           8-25
  ICRP [66]           ---               ---         ---         ---        ---            ---
   Italy [67]        37                0.36         ---         ---        ---            ---
 Malaysia [29]        ---               ---         ---         ---        ---            ---
   UK [68]           236               0.14        0.14         76          3             ---
   Iran [69]         50                0.74         ---         83         31             ---
 Estonia [70]         ---               ---         ---         ---        ---            ---
  China [71]          ---               ---         ---         ---        ---            ---
 NRPB [22]            ---               ---         ---         ---        ---            ---
                                                 Chest PA

                 Sample size       Mean ESD                                        Organ thickness
                                                Median ESD   Mean kVp   Mean mAs
                                    (mGy)                                               (cm)
                                      0.35                                             22.76
 Current work        309                           0.16       116.96      4.24
                                   0.02-0.94                                           10-42
  ICRP [66]           ---              0.3          ---         ---        ---            ---
   Italy [67]        39               0.20          ---         ---        ---            ---
 Malaysia [29]       131              0.28        0.26         79           9             ---
   UK [68]          5133              0.15        0.12         85           5             ---
   Iran [69]         50               0.67          ---        122         16             ---
 Estonia [70]         ---             0.31          ---         ---        ---            ---
  China [71]          ---             0.34          ---         ---        ---            ---
 NRPB [22]            ---             0.18          ---         ---        ---            ---
                                                Chest LAT

                 Sample size       Mean ESD                                        Organ thickness
                                                Median ESD   Mean kVp   Mean mAs
                                     (mGy)                                              (cm)
                                      1.34                    123.90     13.91         31.77
 Current work        145                           1.97
                                   0.02-11.08                                          10-47
  ICRP [66]           ---              1.5           ---        ---        ---            ---
   Italy [67]        28               0.88           ---        ---        ---            ---
 Malaysia [29]       62               1.40         1.17         88         19             ---
   UK [68]           112              0.85         0.51         98         15             ---
   Iran [69]          ---              ---           ---        ---        ---            ---
 Estonia [70]        241              0.90           ---        ---        ---            ---
  China [71]          ---             1.54           ---        ---        ---            ---
 NRPB [22]            ---             0.99           ---        ---        ---            ---
                                                 Pelvis AP

                 Sample size       Mean ESD                                        Organ thickness
                                                Median ESD   Mean kVp   Mean mAs
                                    (mGy)                                               (cm)
                                      1.28                    70.85      24.82          20.98
 Current work        53                            1.26
                                   0.02-2.53                                           13-115
  ICRP [66]           ---             10.4          ---         ---        ---            ---
   Italy [67]        48               2.65          ---         ---        ---            ---
 Malaysia [29]       70               8.41         5.33         70         40             ---
   UK [68]          2220              3.60          3.0         74         35             ---
   Iran [69]         50               2.93          ---         82         61             ---
 Estonia [70]        108              3.90          ---         ---        ---            ---
  China [71]          ---             2.65          ---         ---        ---            ---
 NRPB [22]            ---              ---          ---         ---        ---            ---
                     Table 5.12: Comparison of ESD with other countries



* Range of current work is given
                                                                                           79

                                             LSS AP

                Sample size   Mean ESD                                         Organ thickness
                                           Median ESD    Mean kVp   Mean mAs
                               (mGy)                                                (cm)
                                 2.91                     73.30      56.30          23.2
Current work        82                        2.81
                              0.18-8.08                                            13-35
 ICRP [66]           ---         10.5          ---          ---        ---            ---
  Italy [67]         ---          ---          ---          ---        ---            ---
Malaysia [29]       88          10.56         9.06          77         51             ---
  UK [68]          2151            5           4.3          77         42             ---
  Iran [69]          ---         4.85          ---          91         72             ---
Estonia [70]        200          6.40          ---          ---        ---            ---
 China [71]          ---         5.18          ---          ---        ---            ---
NRPB [22]            ---         7.68          ---          ---        ---            ---
                                            LSS LAT

                Sample size   Mean ESD                                         Organ thickness
                                           Median ESD    Mean kVp   Mean mAs
                               (mGy)                                                (cm)
                                 3.90                     89.04      46.98         28.25
Current work        83                        3.78
                              0.28-7.25                                            13-37
 ICRP [66]           ---         10.5          ---           ---       ---            ---
  Italy [67]        30           7.41          ---           ---       ---            ---
Malaysia [29]       97          18.60         13.97         89         72             ---
  UK [68]          2690         11.70         10.1          88         72             ---
  Iran [69]         229          5.68          ---          100        84             ---
Estonia [70]         ---        10.70          ---           ---       ---            ---
 China [71]          ---        10.53          ---           ---       ---            ---
NRPB [22]            ---         19.7          ---           ---       ---            ---
                                           Abdomen AP

                Sample size   Mean ESD                                         Organ thickness
                                           Median ESD    Mean kVp   Mean mAs
                                (mGy)                                               (cm)
                                 2.89                     73.09      53.25         25.59
Current work        23                        2.41
                              0.03-14.07                                           15-80
 ICRP [66]          ---          10.5          ---          ---        ---            ---
  Italy [67]        ---            3           ---          ---        ---            ---
Malaysia [29]       99            10          9.22          71         57             ---
  UK [68]          2144          4.70         4.10          74         46             ---
  Iran [69]         50           2.56          ---          80         58             ---
Estonia [70]        ---           ---          ---          ---        ---            ---
 China [71]         ---          3.71          ---          ---        ---            ---
NRPB [22]           ---          6.68          ---          ---        ---            ---
                                           C spine AP

                Sample size   Mean ESD                                         Organ thickness
                                           Median ESD    Mean kVp   Mean mAs
                                (mGy)                                               (cm)
                                 0.38                     62.26      12.69         12.67
Current work        66                        0.31
                               0.09-3.4                                             5-23
 ICRP [66]          ---           ---           ---         ---        ---            ---
  Italy [67]        ---           ---           ---         ---        ---            ---
Malaysia [29]       48           1.02          0.70         66         16             ---
  UK [68]           ---           ---           ---         ---        ---            ---
  Iran [69]         52           1.48           ---         74         35             ---
Estonia [70]        ---           ---           ---         ---        ---            ---
 China [71]         ---          0.28           ---         ---        ---            ---
NRPB [22]           ---           ---           ---         ---        ---            ---
                                           C spine LAT

                Sample size   Mean ESD                                         Organ thickness
                                           Median ESD    Mean Kvp   Mean mAs
                               (mGy)                                                (cm)
                                 0.39                     63.31      12.98         15.49
Current work        65                        0.36
                              0.23-0.72                                             8-29
 ICRP [66]          ---           ---          ---          ---        ---            ---
  Italy [67]        ---           ---          ---          ---        ---            ---
Malaysia [29]       46           1.60         1.49          69         20             ---
  UK [68]           ---           ---          ---          ---        ---            ---
  Iran [69]         37           1.68          ---          79         36             ---
Estonia [70]        ---           ---          ---          ---        ---            ---
 China [71]         ---          0.36          ---          ---        ---            ---
NRPB [22]           ---           ---          ---          ---        ---            ---
                                    Table 5.12: Continued
                                                                                          80

                                            Skull AP

                 Sample size   Mean ESD                                       Organ thickness
                                           Median ESD   Mean kVp   Mean mAs
                                (mGy)                                              (cm)
                                  0.89                   70.16      18.41         19.02
 Current work        22                       0.84
                               0.54-1.45                                          15-24
  ICRP [66]          ---           1.5         ---           ---      ---            ---
   Italy [67]        ---           ---         ---           ---      ---            ---
 Malaysia [29]      103           4.78        4.74           71       38             ---
   UK [68]          329            2.3        1.90           72       32             ---
   Iran [69]         ---           ---         ---           ---      ---            ---
 Estonia [70]        ---           ---         ---           ---      ---            ---
  China [71]         ---           ---         ---           ---      ---            ---
 NRPB [22]           ---           4.2         ---           ---      ---            ---
                                            Skull PA

                 Sample size   Mean ESD                                       Organ thickness
                                           Median ESD   Mean kVp   Mean mAs
                                (mGy)                                              (cm)
                                  0.68                   66.80        16           28.3
 Current work        10                       0.72
                               0.61-0.72                                          14-70
  ICRP [66]          ---            5          ---           ---      ---            ---
   Italy [67]       40            1.91         ---           ---      ---            ---
 Malaysia [29]      103           4.78       4.74            71       38             ---
   UK [68]          329            2.3       1.90            72       32             ---
   Iran [69]        42             ---         ---           74       26             ---
 Estonia [70]        ---           ---         ---           ---      ---            ---
  China [71]         ---           ---         ---           ---      ---            ---
 NRPB [22]           ---           4.2         ---           ---      ---            ---
                                           Skull LAT

                 Sample size   Mean ESD                                       Organ thickness
                                           Median ESD   Mean kVp   Mean mAs
                                (mGy)                                              (cm)
                                  0.58                   64.94      14.39          14.7
 Current work        32                       0.59
                               0.34-0.81                                          12-18
  ICRP [66]          ---           3.1         ---           ---      ---            ---
   Italy [67]       40            1.45         ---           ---      ---            ---
 Malaysia [29]      78            3.34        3.03           68       32             ---
   UK [68]          243            1.2         1.1           66       19             ---
   Iran [69]        40             ---         ---           68       18             ---
 Estonia [70]        ---           ---         ---           ---      ---            ---
  China [71]         ---           ---         ---           ---      ---            ---
 NRPB [22]           ---          2.19         ---           ---      ---            ---
                                     Table 5.12: Continued

        chest
For the chest AP Scan, the average calculated ESD (0.19 mGy) in the
current work was comparable to that measured in UK [68], but was much
less than that measured in Iran [69] and Italy [67]. The high dose found in
Iran survey may be attributed to the high mAs (31 versus 3.03). The ratio of
the maximum to the minimum ESD (0.46/0.09=5.11) could not clearly be
explained by the ratio of the maximum to the minimum organ thickness
(25/8=3.13).


        chest
For the chest PA Scan, the average calculated ESD (0.35 mGy) in the
current work was in close agreement with that measured in Estonia [70] and
China [71], and was less than tat measured in Iran [69], but was higher than
                                                                        81


measured in Italy [67] and Malaysia [29] and UK [68]. The higher ESD
found in the current work compared to Malaysian survey can be attributed to
the high kVp found in the current work compared to that found in
Malaysian survey (116.96 versus 79). Also the higher ESD found in the
current work compared to the UK survey can be attributed to the high kVp
found in the current work compared with that found in the UK survey
(116.96 versus 85). The ratio of the maximum to the minimum ESD
(0.94/0.02=47) could not be explained by the ratio of the maximum to the
minimum organ thickness (42/10=4.2).


        chest
For the chest LAT Scan, the average calculated ESD (1.34 mGy) in the
current work was in close agreement with that measured in Malaysia [29]
and pretty close to that measured in China [71], but was higher than
measured in Italy [67], Estonia [70] and UK [68]. The higher ESD found in
the current work compared to the survey made in UK can be attributed to
the high kVp found in the current work compared with that found in the UK
survey (123.9 versus 98). The ratio of the maximum to the minimum ESD
(11.08/0.02=554) could not be explained by the ratio of the maximum to the
minimum organ thickness (47/10=4.7).


For the Pelvis AP Scan, the average calculated ESD (1.28 mGy) in the
current work was less than measured in other countries. The ratio of the
maximum to the minimum ESD (2.53/0.02=126.5) could not be explained
by the ratio of the maximum to the minimum organ thickness (115/13=8.85).


For the LSS AP Scan, the average calculated ESD (2.91 mGy) in the current
work was much less than that measured in other countries. The ratio of the
maximum to the minimum ESD (8.08/0.18=44.89) could not be explained
by the ratio of the maximum to the minimum organ thickness (35/13=2.69).
                                                                           82




For the LSS LAT Scan, the average calculated ESD (3.9 mGy) in the current
work was much less than that measured in other countries. The ratio of the
maximum to the minimum ESD (7.25/0.28=25.89) could not be explained
by the ratio of the maximum to the minimum organ thickness (37/13=2.85).


For the Abdomen AP Scan, the average calculated ESD (2.89 mGy) in the
current work was close to that measured in Italy [67] and pretty close to that
measured in Iran [69], but less than that measured in China [71], UK [68]
and Malaysia [29]. The ratio of the maximum to the minimum ESD
(14.07/0.03=4.69) was in close agreement with the ratio of the maximum to
the minimum organ thickness (80/15=5.33).


For the C spine AP Scan, the average calculated ESD (0.38 mGy) in the
current work was a slightly higher than that measured in China [71], but as
less than that measured in Malaysia [29] and Iran [69]. The ratio of the
maximum to the minimum ESD (3.4/0.09=37.78) could not be explained by
the ratio of the maximum to the minimum organ thickness (23/5=4.6).


For the C spine LAT Scan, the average calculated ESD (0.39 mGy) in the
current work was close to that measured in China [71], but less than that
measured in Malaysia [29] and Iran [69]. The ratio of the maximum to the
minimum ESD (0.72/0.23=3.13) was in close agreement with the ratio of the
maximum to the minimum organ thickness (29/8=3.63).


For the Skull AP Scan, the average calculated ESD (0.89 mGy) in the
current work was less than that measured in Malaysia [29] and UK [68]. The
ratio of the maximum to the minimum ESD (1.45/0.54=2.69) could not be
                                                                             83


explained by the ratio of the maximum to the minimum organ thickness
(24/15=1.6).


For the Skull PA Scan, the average calculated ESD (0.68 mGy) in the
current work was less than that measured in Italy [67], Malaysia [29] and UK
[68]. The ratio of the maximum to the minimum ESD (0.72/0.61=1.18)
could not be explained by the ratio of the maximum to the minimum organ
thickness (70/14=5).


For the Skull LAT Scan, the average calculated ESD (0.58 mGy) in the
current work was less than that measured in Italy [67], Malaysia [29] and UK
[68]. The ratio of the maximum to the minimum ESD (0.81/0.34=2.38)
could not be explained by the ratio of the maximum to the minimum organ
thickness (18/12=1.5).


               organ
5.7 Results of organ dose survey
For this part of the study, XDOSE software [43] was used to calculate the
internal organ dose (effective equivalent dose) for the available examinations.
Table 5.13 summarizes the results of this experiment.


It is clear from table 5.12 that the highest organ dose occurs when the organ
is located within the scanning field. The ovaries receive the highest dose
from LSS scans (0.52 mSv from AP, and 0.23 mSv from LAT). Ovaries also
receive 0.25 mSv from pelvic AP scans. The other scan have no (or
minimum) dose burden on ovaries. The testes on the other hand, receive the
highest dose from pelvic scan (0.95 mSv). Testes also receive 0.01 mSv from
LSS AP scan; other scans deliver less (no significant dose) to the testes.
                                                                             84


The thyroid receive the highest dose from C-spine (0.25 mSv) and chest
scans (0.04 mSv from AP, 0.03 mSv from PA and 0.01 from LAT). Other
scans deliver variable range of dose to the thyroid.
Bones receive the highest dose from LSS scans (0.12 mSv from AP and 0.11
mSv from LAT). All other scans deliver variable doses to the bones.


Uterus receives the highest dose for LSS scan (0.69 mSv from AP and 0.11
mSv from LAT). The uterus also receives high doses from pelvic scan (0.34
mSv) and KUB AP scan (0.02 mSv). Other scans deliver minimum doses to
the uterus.


The net effect of different scans on the total body is stated in the last row of
table 5.12. It is clear that the maximum radiation burden on the body is from
LSS scans (0.19 mSv from AP and 0.12 mSv from LAT). This dose is well
below the yearly public limit and also of that of radiation workers. The least
radiation burden on the body is from C-spine scans (0.008 mSv from AP
and 0.007 mSv from LAT) and shoulder AP (0.007 mSv) scans. The chest
PA scan which is a very common scan delivers 0.03 mSv for the whole body
which is equal to 1/33 of the yearly public limit and 1/666 of the workers
yearly limit.
                                                                                            85


Source organ                           Chest
                Chest AP   Chest PA              Pelvis AP   KUB* AP   LSS AP     LSS LAT
                                        LAT
                  mSv        mSv                   mSv         mSv      mSv         mSv
 Target organ                           mSv
 Ovaries         0.0003     0.0006     0.0009     0.2531      0.0242   0.5191      0.2273
  Testes            0          0          0       0.9529      0.0004   0.0114      0.0029
  Lungs          0.0529     0.0985     0.1504     0.0006      0.0416   0.0754      0.0229
 Stomach         0.0516     0.0279     0.0133     0.0350      1.0564   1.0911      0.0271
   LLI           0.0003     0.0007     0.0006     0.2908      0.0474   0.3969      0.0218
  RBM            0.0112     0.0317     0.0391     0.0353      0.0440   0.0821      0.1014
 Thyroid         0.0433     0.0125     0.0373        0        0.0005   0.0003      0.0005
  Breasts        0.1069     0.0229     0.1559     0.0009      0.0227   0.0143      0.0033
Esophagus        0.0257     0.0574     0.0677     0.0008      0.0694   0.0965      0.0139
   Liver         0.0447     0.0489     0.1625     0.0217      0.6594   0.6282      0.6353
U bladder        0.0001     0.0001     0.0003     0.6045      0.0051   0.4684      0.0455
   Skin          0.0169     0.0183     0.0534     0.1086      0.0955   0.1230      0.1377
Tot bone         0.0254     0.0564     0.0720     0.0656      0.0955   0.1248      0.1127
  Brain          0.0003     0.0007     0.0013        0           0        0           0
 Thymus          0.1129     0.0215     0.0701     0.0001      0.0060   0.0074      0.0037
 Adrenals        0.0132     0.1128     0.0601     0.0036      0.1301   0.1505      0.1718
 Pancreas        0.0318     0.0530     0.0401     0.0098      0.4267   0.4682      0.0928
  Spleen         0.0196     0.0937     0.0223     0.0093      0.2368   0.2201      0.0255
 Kidneys         0.0071     0.0704     0.0397     0.0188      0.1396   0.1597      0.4280
 Small int       0.0013     0.0029     0.0039     0.3068      0.2171   0.7242      0.2155
   ULI           0.0020     0.0038     0.0058     0.3588      0.4429   0.8782      0.2909
  Uterus         0.0002     0.0006     0.0009     0.3415      0.0239   0.6883      0.1120
  Muscle         0.0138     0.0210     0.0332     0.1261      0.1005   0.1795      0.1019
 Eye lens        0.0006     0.0004     0.0028        0           0        0           0
  Heart          0.0712     0.0430     0.0823     0.0008      0.0653   0.0811      0.0157
G bladder        0.0217     0.0217     0.0438     0.0553      0.8549   0.9539      0.2289
  Head           0.0051     0.0091     0.0120        0           0        0           0
  Trunk          0.0282     0.0445     0.0716     0.1544      0.1966   0.3190      0.1924
   Leg              0          0          0       0.0614         0     0.0018      0.0009
 Average
                 0.0176     0.0280     0.0445     0.1130      0.1193   0.1942      0.1171
total body
                Table 5.13: Average organ doses of different X-ray examinations




* KUB: kidney, ureter and bladder
                                                                                86



Source organ   C spine   C spine      Shoulder                          Skull
                                                 Skull AP   Skull PA
                 AP       LAT            AP                             LAT
                                                   mSv        mSv
Target organ    mSv       mSv           mSv                             mSv
 Ovaries          0         0             0         0          0          0
  Testes          0         0             0         0          0          0
  Lungs        0.0028    0.0017        0.0126    0.0007     0.0004     0.0002
 Stomach          0         0          0.0002       0          0          0
   LLI            0         0             0         0          0          0
  RBM          0.0041    0.0033        0.0033    0.0134     0.0077     0.0081
 Thyroid       0.2505    0.0087        0.0032    0.0512     0.0096     0.0084
  Breasts      0.0004    0.0001        0.0015    0.0005        0          0
Esophagus      0.0087    0.0056        0.0026    0.0019     0.0020     0.0009
   Liver       0.0001    0.0001           0         0          0          0
U bladder         0         0             0      0.0033        0          0
   Skin        0.0098    0.0106        0.0073    0.0353     0.0224     0.0244
Tot bone       0.0205    0.0152        0.0119    0.0873     0.0439     0.0516
  Brain        0.0027    0.0043        0.0001    0.0979     0.0799     0.0900
 Thymus        0.0039    0.0008        0.0027    0.0004     0.0004     0.0002
 Adrenals         0         0          0.0002       0          0          0
 Pancreas         0         0          0.0002       0          0          0
  Spleen       0.0001       0          0.0003       0          0          0
 Kidneys          0         0             0         0          0          0
 Small int        0         0             0         0          0          0
   ULI            0         0             0         0          0          0
  Uterus          0         0             0         0          0          0
  Muscle       0.0060    0.0052        0.0043    0.0063     0.0073     0.0050
 Eye lens      0.0101    0.0004        0.0005    0.8222     0.0037     0.2258
  Heart        0.0004    0.0002        0.0013    0.0001        0          0
G bladder         0         0             0         0          0          0
  Head         0.0604    0.0507        0.0025    0.247      0.1696     0.1666
  Trunk        0.0047    0.0040        0.0084    0.0006     0.0004     0.0003
   Leg            0         0             0         0          0          0
 Average
               0.0078    0.0065        0.0067    0.0205     0.0141     0.0137
total body
                                  Table 5.13: Continued
                                                                          87


                     rgan
                    org           some        X-
5.7.1 Comparison of organ dose of some common X-ray examinations with
that of other countries
Table 5.13 compares the calculated organ doses of the current work with
that of the Iranian and UK populations.


As organ doses depend on the ESDs and since the calculated ESD in the
current work was less than that in many other countries, it is expected that
the calculated organ doses of the current work will be lower than organ doses
in other countries. When comparing the calculated organ doses of different
X-ray examinations with those of Iranian population [69], we found that
almost all examinations yielded organ doses less than those measured in
Iran. Similarly, when comparing the results of the current work with that of
UK population [72], our calculated organ doses were found to be less than
those of the UK population for most X-ray examinations. Only for chest PA
scans that our calculated average ESD and hence organ doses were much
higher than that in UK. In fact our calculated ESD is almost two times higher
than that calculated in UK.
                                                                                         88



                                    Current work        Iran [69] mSv
Examination           Organ                                                    UK [72] mSv
                                        mSv          Female         Male
                                   Female 0.0003
                     Gonads                           0               0            ---
                                      Male 0
                   Bone marrow           ---         0.11            0.12          ---
                      Colon              ---         0.01             0            ---
                      Lungs           0.0529         0.33            0.45          ---
                     Stomach          0.0516         0.17            0.22          ---
                     Bladder          0.0001          0               0            ---
                      Breast          0.1069         0.57             0            ---
                       Liver          0.0447         0.29            0.27          ---
                    Esophagus         0.0257         0.27            0.27          ---
                     Thyroid          0.0433         0.6             0.65          ---
 Chest AP              Skin           0.0169         0.05            0.05          ---
                    b. surface           ---         0.08            0.1           ---
                     Adrenals         0.0132         0.14            0.13          ---
                      Brain           0.0003          0               0            ---
                       ULI            0.0020         0.02            0.02          ---
                   Small intense      0.0013         0.03            0.02          ---
                      Kidney          0.0071         0.08            0.05          ---
                      Muscle          0.0138         0.05            0.05          ---
                     Pancreas         0.0318         0.22            0.14          ---
                      Spleen          0.0196         0.2             0.19          ---
                     Thymus           0.1129         0.67            0.71          ---
                      Uterus          0.0002          0               0            ---
                                   Female 0.0006
                     Gonads                           0               0            ---
                                      Male 0
                   Bone marrow           ---         0.02            0.19         0.02
                      Colon              ---         0.01             0             0
                      Lungs           0.0985         0.55            0.6          0.07
                     Stomach          0.0279         0.15            0.14         0.02
                     Bladder          0.0001          0               0             0
                      Breast          0.0229         0.08             0           0.01
                       Liver          0.0489         0.21            0.19         0.03
                    Esophagus         0.0574         0.35            0.34         0.04
                     Thyroid          0.0125         0.2             0.2          0.01
 Chest PA              Skin           0.0183         0.05            0.05          ---
                    b. surface           ---         0.11            0.11          ---
                     Adrenals         0.1128         0.35            0.34          ---
                      Brain           0.0007         0.01            0.01          ---
                       ULI            0.0029         0.02            0.02          ---
                   Small intense      0.0704         0.03            0.02          ---
                      Kidney          0.0704         0.18            0.16          ---
                      Muscle          0.0210         0.05            0.05          ---
                     Pancreas         0.0530         0.19            0.17          ---
                      Spleen          0.0937         0.31            0.31          ---
                     Thymus           0.0215         0.17            0.14          ---
                      Uterus          0.0006   Tab
                                                       0              0            ---


              Table 5.14: Comparison of organ doses with different countries
                                                                                             89



                                        Current work          Iran [69] mSv
    Examination             Organ                                                  UK [72] mSv
                                            mSv          Female           Male
                         Gonads               0            0                  0        ---
                       Bone marrow        0.0041         0.05               0.05      0.07
                          Colon              ---           0                  0         0
                          Lungs           0.0028         0.1                0.11      0.07
                         Stomach              0            0                  0         0
                         Bladder              0            0                  0         0
                          Breast          0.0004         0.01                 0         0
                           Liver          0.0001           0                  0         0
                        Esophagus         0.0087         0.17               0.17      0.12
                         Thyroid          0.2505         1.13               1.16      0.84
                           Skin           0.0098         0.03               0.03       ---
   C spine* AP
                        b. surface                       0.08               0.08       ---
                         Adrenals            0             0                  0        ---
                          Brain           0.0027         0.02               0.01       ---
                           ULI               0             0                  0        ---
                       Small intense         0             0                  0        ---
                          Kidney             0             0                  0        ---
                          Muscle           0.006         0.02               0.03       ---
                         Pancreas            0             0                  0        ---
                          Spleen          0.0001           0                  0        ---
                         Thymus           0.0039         0.56               0.52       ---
                          Uterus             0             0                  0        ---
                         Gonads              0            0                  0         ---
                       Bone marrow        0.0033         0.05               0.05       ---
                          Colon                           0                  0         ---
                          Lungs           0.0017         0.03               0.03       ---
                         Stomach             0            0                  0         ---
                         Bladder             0            0                  0         ---
                          Breast          0.0001          0                  0         ---
                           Liver          0.0001          0                  0         ---
                        Esophagus         0.0056         0.02               0.02       ---
                         Thyroid          0.0087         0.14               0.1        ---
                           Skin           0.0106         0.03               0.03       ---
   C spine LAT
                        b. surface                       0.05               0.05       ---
                         Adrenals            0            0                  0         ---
                          Brain           0.0043         0.02               0.01       ---
                           ULI               0            0                  0         ---
                       Small intense         0            0                  0         ---
                          Kidney             0            0                  0         ---
                          Muscle          0.0052         0.02               0.03       ---
                         Pancreas            0            0                  0         ---
                          Spleen             0            0                  0         ---
                         Thymus           0.0008         0.02               0.01       ---
                          Uterus             0            0                  0         ---
                                       Table 5.14: Continued




* C-spine: cervical spine
                                                                                        90



                                      Current work        Iran [69] mSv
   Examination          Organ                                                 UK [72] mSv
                                          mSv          Female         Male
                                     Female 0.5191
                       Gonads                          1.04            0.01       ---
                                      Male 0.0114
                     Bone marrow        0.0821         0.71            0.39      0.68
                        Colon                          1.49            0.47      2.4
                        Lungs           0.0754         1.57            1.43      0.15
                       Stomach          1.0911         3.74            2.18      1.51
                       Bladder          0.4684         0.38            0.09      2.49
                        Breast          0.0003         2.73              0       0.03
                         Liver          0.6282          27             1.69      2.16
                      Esophagus         0.0965         0.9             0.57      0.02
                       Thyroid          0.0003         0.17            0.07        0
     LSS* AP             Skin            0.123         0.28            0.17       ---
                      b. surface                       0.29            0.15       ---
                       Adrenals         0.1505         1.03            0.6        ---
                        Brain              0             0              0         ---
                         ULI            0.8782         3.73              2        ---
                     Small intense      0.7242         3.02            1.4        ---
                        Kidney          0.1597         0.91            0.53       ---
                        Muscle          0.1795         0.25            0.15       ---
                       Pancreas         0.4682         2.39            1.4        ---
                        Spleen          0.2201         1.32            0.78       ---
                       Thymus           0.0074         0.94            0.42       ---
                        Uterus          0.6883         0.36              0        ---
                                     Female 0.2273
                       Gonads                          0.18            0.01       ---
                                      Male 0.0029
                     Bone marrow        0.0218         0.5             0.43       ---
                        Colon                          0.41            0.31       ---
                        Lungs           0.0229         1.15            1.14       ---
                       Stomach          0.0271         0.3             0.23       ---
                       Bladder          0.0455         0.2             0.1        ---
                        Breast          0.0033         0.1              0         ---
                         Liver          0.6353         1.57            1.34       ---
                      Esophagus         0.0139         0.31            0.28       ---
                       Thyroid          0.0005         0.04            0.05       ---
    LSS LAT              Skin           0.1377         0.2             0.19       ---
                      b. surface                       0.24            0.2        ---
                       Adrenals         0.1718         0.81            0.67       ---
                        Brain              0            0               0         ---
                         ULI            0.2909         1.14            0.92       ---
                     Small intense      0.2155         0.89            0.71       ---
                        Kidney           0.428         1.6             1.38       ---
                        Muscle          0.1019         0.18            0.17       ---
                       Pancreas         0.0928         0.5             0.38       ---
                        Spleen          0.0255         0.29            0.23       ---
                       Thymus           0.0037         0.16            0.11       ---
                        Uterus           0.112         0.26             0         ---
                                     Table 5.14: Continued




* LSS: Lumbo-sacral spine
                                                                                 91

                               Current work        Iran [69] mSv
Examination      Organ                                                 UK [72] mSv
                                   mSv          Female         Male
                              Female 0.2531
                Gonads                          1.069           1.02       ---
                               Male 0.9529
              Bone marrow        0.0353         0.35            0.2       0.25
                 Colon                          2.03            1.6       1.85
                 Lungs           0.0006         0.01            0.01      0.01
                Stomach           0.035         0.14            0.24      0.29
                Bladder          0.6045         2.5             1.4       2.13
                 Breast          0.0009         0.01              0       0.01
                  Liver          0.0217         0.1             0.14      0.13
               Esophagus         0.0008           0               0         0
                Thyroid             0             0               0         0
 Pelvis AP        Skin           0.1086         0.19            0.15       ---
               b. surface                       0.38            0.2        ---
                Adrenals         0.0036         0.04            0.05       ---
                 Brain              0             0               0        ---
                  ULI            0.3588         2.1             1.79       ---
              Small intense      0.3068         1.61            1.29       ---
                 Kidney          0.0188         0.22            0.24       ---
                 Muscle          0.1261         0.18            0.14       ---
                Pancreas         0.0098         0.15            0.2        ---
                 Spleen          0.0093         0.05            0.06       ---
                Thymus           0.0001           0               0        ---
                 Uterus          0.3415         1.35              0        ---
                Gonads              0            0               0         ---
              Bone marrow        0.0077         0.08            0.09      0.12
                 Colon                           0               0          0
                 Lungs           0.0004          0               0        0.01
                Stomach             0            0               0          0
                Bladder             0            0               0          0
                 Breast             0            0               0          0
                  Liver             0            0               0          0
               Esophagus          0.002          0              0.01      0.02
                Thyroid          0.0096         0.03            0.03      0.14
                  Skin           0.0224         0.1             0.1        ---
  Skull PA
               b. surface                       0.1             0.1        ---
                Adrenals            0            0               0         ---
                 Brain           0.0799         0.95            0.94       ---
                  ULI               0            0               0         ---
              Small intense         0            0               0         ---
                 Kidney             0            0               0         ---
                 Muscle          0.0073         0.08            0.09       ---
                Pancreas            0            0               0         ---
                 Spleen             0            0               0         ---
                Thymus           0.0004          0               0         ---
                 Uterus             0            0               0         ---
                Gonads              0             0               0        ---
              Bone marrow        0.0081         0.07            0.07       ---
                 Colon                            0               0        ---
                 Lungs           0.0002           0               0        ---
                Stomach             0             0               0        ---
                Bladder             0             0               0        ---
                 Breast             0             0               0        ---
                  Liver             0             0               0        ---
               Esophagus         0.0009           0               0        ---
                Thyroid          0.0084         0.07            0.07       ---
                  Skin           0.0244         0.06            0.06       ---
 Skull LAT
               b. surface                       0.08            0.08       ---
                Adrenals            0             0               0        ---
                 Brain            0.09          0.82            0.77       ---
                  ULI               0             0               0        ---
              Small intense         0             0               0        ---
                 Kidney             0             0               0        ---
                 Muscle           0.005         0.06            0.06       ---
                Pancreas            0             0               0        ---
                 Spleen             0             0               0        ---
                Thymus           0.0002           0               0        ---
                 Uterus             0             0               0        ---
                              Table 5.14: Continued
                                                                      92


5.8 X-ray dose calculator
In order to facilitate the calculation of ESD and internal organ doses, a
software was developed based on visual basic. This program uses the newly
developed ESD method (see section 5.1.1) to calculate ESD. The program
also uses the tabulated dose conversion coefficients based on Monte Carlo
computation method (a complete listing of those tabulations are available
with XDOSE computer program) in order to calculate internal organ doses.
A copy of this program is attached to the thesis.


It is very important to note that the newly developed ESD calculation
method requires further assessment of its performance in comparison with
direct TLD and output methods.
                                                                       93


                             Chapter 6
                             Conclusion


1- A new ESD calculation method was developed empirically from an
   existing method, The newly developed method estimates the ESD of
   patients even before they are scanned. The new method compared
   very well with method2.


2- The newly developed ESD calculation method requires further
   experimental assessment of its performance.


3- A new computer program (X-ray dose calculator) was developed using
   visual basic, the computer program uses the newly modeled HVL and
   BSF formulas to calculate the HVL and BSF and uses the newly
   developed ESD calculation method, It also uses the tabulated Monte
   Carlo computation method from XDOSE computer program.


4- All ESD calculation methods compare well with method 2 which
   depends on direct measurements of machines output. There was a
   topographic error in method 1, this was corrected and the corrected
   method compared well with method 2.


5- The current survey was conducted using method 2 and was compared
   with previous TLD measurement and surveys in other countries.




6- It was noted that the ratio of the maximum to minimum ESD (for
   most scans) could not be explained by the variation in organ thickness,
   this may be due to the fact that the technologists did not use the
                                                                       94


   automatic exposure control system during this work and indeed
   during most of their clinical practice.


7- The high ESD for chest examinations compared to that in UK and
   other countries may be attributed to the high exposure parameters
   found in the current survey. This must be conveyed to the radiology
   technologists and corrective action must be taken.


8- It is clear from the calculated uterus dose that apart from LSS, pelvic
   and KUB scans, no significant dose is delivered to the uterus and this
   indicates that scans other than those mentioned can safely be
   preformed on pregnant women with no appreciable risk to the fetus.
   When LSS, KUB and pelvic scans are preformed on pregnant women
   shields of the gonads and uterus must be used.
                                                                                      95


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46-                                                      X-
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47-                                  Carlo
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54-   Wu X, Gingold El, Barnes GT and Tucker DM: Normalized
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56-   XDOSE Computer program produced by National Radiation
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57-   PCXMC.
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61-   <http://learntech.uwe.ac.uk/radscience/detection1/detection_p5.htm>
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                                                                                                                102



Appendix A:
   Patients related information and exposure factors are available in the attached CD.



Appendix B :
                                              Patients' survey

                                                                 Organ                 Tube
                      Num. Patient age               Height
X-ray exam   View                      Weight (kg)             thickness   FSD (cm)   potential    mAs       ESD (mGy)
                    of patients (year)                (cm)
                                                                  (cm)                 (kVp)
                                58.77       72.92     116.85    20.77       124.77     87.38       3.03         0.19
             AP        13
                                45-75      40-100    106-136    8-25       105-150    61-113      1.6-12     0.09-0.46
  Chest                         49.49       73.06    118.23     22.76       176.99    116.96       4.24         0.35
             PA       309
                               18-102      32-152    13-188     10-42      105-200    44-173      1.4-32      0.02-.94
                                49.58       71.47    119.54     31.77       176.77     123         13.92        1.34
             LAT      145
                                18-98      32-145    91-188     3-47       105-300    44-200      1.4-92.5   0.02-11.08
                                45.83       70.4      120.4      20.98      112.83     70.82       24.6         1.28
             AP        53
                                20-95      50-94     93-189     13-115     105-120     43-75      1.4-50     0.02-2.53
  Pelvis
                                 50        77.19      116.75    17.56       113.75      73         22.06        1.22
             LAT       16
                                24-95      57-94     102-135    13-25      110-115     70-75       14-53     0.68-2.53
                                42.52       79.29    120.14     21.84       113.78     70.29       54.65        2.76
  KUB        AP       185
                                19-81      40-134    71-177     4-35       105-115    14.5-85     6.3-404    0.02-18.03
                                47.06       82.66    121.31      23.2       113.78      73.3        56.3        2.91
             AP        82
                                22-87      49-132    94-181     13-35      110-150     37-90      2.8-163    0.18-8.08
                                51.33      70.33       115       21         111.67     77.67       29.17        1.95
             OBL       6
                                34-60      55-78     115-115    19-25      110-115    71.5-90     15.5-36     1.1-2.37
   LSS
                                47.07       82.42     120.9     28.25       113.7      89.04       46.98        3.9
             LAT       83
                                22-87      49-132    94-181     13-37      110-150     38-96      14-102     0.28-7.25
                                46.35       84.18    123.72     34.77       113.25      92.6       87.72        7.16
             Spot      58
                                24-87      49-132    94-181     28-45      110-115     90-96      32-249     2.61-20.36
                                 34.9       82.76     119.67      17        113.81      61.5        4.39        0.17
             AP        21
                                18-68      50-120    102-147     7-24      110-115     58-66      1.6-12.5   0.05-0.57
Humerus
                                32.22       83.56     115.83    11.94       114.28     61.08        3.25        0.11
             LAT       18
                                18-49      50-120    102-134    7-18       110-122    58.5-63     1.6-12.5   0.05-0.43
                                45.87       77.38     15.88     25.59       126.3      73.09       53.25        2.89
Abdomen      AP       123
                                18-90      40-120    93-172     15-80      110-170     44-93      1.8-320    0.03-14.07
                                44.15        76.4    121.91     12.67       121.62     62.26       12.69        0.38
             AP        66
                                18-88      41-130    98-181     5-23       105-150     43-71      2.5-110     0.09-3.4
 C spine
                                44.03       76.95    121-68     15.49       123.49     63.31       12.98        0.39
             LAT       65
                                9-88       52-130    98-181     8-29       114-150     60-66       8.5-18    0.23-0.72


                                        Table B1: Patients' survey
                                                                                                                    103




                                                                     Organ                 Tube
                          Num. Patient age               Height
X-ray exam     View                        Weight (kg)             thickness   FSD (cm)   potential    mAs       ESD (mGy)
                        of patients (year)                (cm)
                                                                      (cm)                 (kVp)
                                    43.69      82.44     118.62     14.32       112.95     62.02        4.91        0.19
                AP         61
                                    18-87     50-125     95-157     7-25       100-120     58-73      1.25-40    0.04-1.75
   Knee
                                    40.62      80.9      119.62     11.88       113.17     62.09       3.35         0.13
               LAT         52
                                    18-76     50-125     95-157     7-16       105-120    58-85.5     1.4-16     0.04-0.59
                Cald                 29       72.33       114.33     17          122       73.67        23          0.9
                           3
                well                18-49     55-92      106-127    15-20      122-122     73-75       22-25     0.84-1.02
                                    40.29      83.21      117.5     20.71       121.14     73.86        21           0.9
                PA         14
   Parsal                           24-51     62-125     106-165    18-22      110-122     70-75       16-22      0.56-1.3
  sinuses                           38.52      80.24      116.81    13.71       121.43     62.33        11.5        0.32
               LAT         21
                                    18-51     55-125     106-165    10-16      110-122    60-64.5      10-14     0.24-0.51
                                    38.15      80.45      117.2      21.2       121.4       74.6        25          1.07
               Waters      20
                                    18-51     55-125     106-165    15-25      110-122     73-75       22-28     0.84-1.48
                                    39.09      84.4       132.49     7.43       110.74     48.49       1.61         0.04
                AP         47
                                    20-84     55-135     101-189     4-10       95-115     44-55      0.6-2.5    0.01-0.08
                                    46.83      82         170.83     7.42        110        53          1.4         0.05
                PA         6
                                    31-70     71-99      154-185    3.5-9.5    110-110     49-55      1.4-1.4    0.04-0.05
   Foot
                                    41.82      78.39      136.18     9.26       110.45     53.53        1.9         0.06
               LAT         33
                                    20-70     55-101     101-185    2-12.5     105-115    44-58.5     1.4-2.6    0.02-0.09
                                    40.52      85.65      138.13     7.62       110.98     50.04       1.68         0.05
               OBL         46
                                    20-84     55-135     101-189     2-12      105-115     44-78      1.4-2.5    0.02-0.14
                                    40.88     66.71      117.17     16.04       114.38      69.6      17.07         0.83
                AP         24
                                    21-95     45-91      88-175     9-22       110-120     63-80      3.2-32     0.14-2.03
  Femur
                                    40.88     66.71      117.17     14.29       113.96     70.48      18.05         1.02
               LAT         24
                                    21-95     45-91      88-175     9-18       100-120     63-87      3.2-83     0.14-7.66
                                    38.22     66.85      115.67     19.56       113.52     71.89       39.31        1.91
                AP         27
                                    20-80     51-99      99-155     12-27      110-115     66-73       18-89      0.87-3.9
Dorsal spine                        38.22     66.85      115.67     27.52       113.52     78.19       79.83         3.6
               LAT         27
                                    20-80     51-99      99-155     22-37      110-115     55-90      10-250     0.63-13.23
                                    33.91        69       125.27    30.36       113.64     57.09       189.29       5.27
                Spot       11
                                    20-49      55-99     109-155    26-35      11-115      55-60      2.2-220    0.07-7.37
                                     37.5      77.77      119.46     1.71       111.35     44.62        1.36        0.03
                AP         26
                                    18-70     54-135     75-167      1-5       105-115     41-52       0.8-1.6   0.01-0.04
                                    40.04      74.43      118.64     2.46       112.5      44.27        1.35        0.02
  Finger       LAT         28
                                    18-70     54-115     75-167      1-7       105-150     41-52       0.8-1.8   0.01-0.04
                                    41.65      79.65      110.4      1.95       111.25      43.5        1.44        0.03
               OBL         20
                                    20-70     54-135     75-128      1-5       105-115     41-47      1.25-1.8   0.01-0.04
                                     42.6      80.47      119.86     15.3       122.85     63.13       12.55        0.41
 Shoulder       AP         87
                                    18-81     42-120     97-177     8-23       75-150      58-70       2.5-20    0.12-0.96
                                    29.67       88.3      123.3      4.52       112.96     47.96        1.51        0.05
                AP         27
                                    19-59     62-135     106-178     2-8       110-120     45-55       1.4-18    0.02-0.25
                                    37.22        81       115.33    15.89       111.67     49.72        1.74        0.05
                PA         9
                                    18-61     42-102     99-137     3-105      105-115    44-53.5      1.25-2    0.03-0.06
   Wrist
                                    31.45      85.27      120.55     9.24       113.79     50.59        1.92        0.05
               LAT         33
                                    18-61     42-135     99-178     4-105      105-155     46-55       1.6-2.2   0.02-0.07
                                    31.36      87.64      124.12     9.54       112.6      48.78        1.71        0.04
               OBL         25
                                    19-61     59-135     99-178     4-105      105-120     44-55       1.25-2    0.02-0.07
                                    29.14      70.64      120.36    12.29       113.93     60.68        2.03        0.08
                AP         14
   Tibia                            18-55     53-115     106-130    9-17       110-120     55-63       1.6-2.5   0.03-0.11
   fibula                           29.14      70.64      120.36     8.86       113.93     58.75         1.8        0.07
               LAT         14
                                    18-55     53-115     106-130    3-18       110-120     42-63      1.25-2.2   0.03-0.09


                                             Table B1: continued
                                                                                                                   104




                                                                    Organ                 Tube
                         Num. Patient age               Height
X-ray exam    View                        Weight (kg)             thickness   FSD (cm)   potential    mAs       ESD (mGy)
                       of patients (year)                (cm)
                                                                     (cm)                 (kVp)
                                   30.09      75.68      127.36    19.02       118.91     70.16       18.41        0.89
              AP          22
                                   18-72     40-130     104-182    15-24      110-122     68-73       16-25     0.54-1.45
                                    26.1      71.4       127.8      28.3       121.3       66.8        16          0.68
              PA          10
                                   18-48     50-103     108-174    14-70      115-122     66-70       14-18     0.61-0.72
  Skull
                                   28.84      74.34      127.69     14.7       119.66     64.94       14.39        0.58
              LAT         32
                                   18-72     40-130     104-182    12-18      110-122     63-70       12-18     0.34-0.81
                                   28.94     63.81       128.06    26.25       113.19     68.31        18          0.99
             Townes       16
                                   18-72     50-75      108-182    14-70       70-122     63-73       11-22     0.69-1.52
                                   35.27      81.78     116.76      4.27       109.66     44.63        1.45        0.03
              AP          41
                                   18-68     34-135     96-160      1-12       91-115     42-48      1.25-1.8   0.01-0.05
                                    32        83.9       118.6       3.9        115       45.35        1.48        0.03
              PA          10
                                   23-51     55-128     85-138      2.5-7     115-115    42-48.5     1.25-1.6   0.02-0.04
  Hand                             32.24      80.28     117.48      9.28       111.6      50.64       1.82         0.05
              LAT         25
                                   18-60     48-128     85-138      5-12      105-115     44-58       1.4-2     0.02-0.07
                                   31.56      86.56      121.93     6.26       110.93     45.41        1.51        0.03
             OBL          27
                                   19-60     48-135     100-160     2-12       95-115     42-48      1.25-1.6   0.01-0.05
              Ball                  53.3      71.4       108.5      6.35        108.6      45         1.46         0.02
                          10
             catcher               43-68     34-101     96-120      4.5-9      91-115     43-48      1.4-1.6    0.02-0.05
                                   29.82      73.82      118.1     10.02       111.8      55.8          2          0.07
              AP          50
                                   18-80     40-127     103-132    4-15       105-115    50-61.5     1.6-3.6    0.03-0.13
  Ankle                            30.58      71.47      118.61     7.43       111.25     53.81        2.01        0.06
              LAT         36
                                   18-80     40-125     107-132     4-12      105-115     52-58      1.25-3.2   0.04-0.11
                                   30.55      72.42      117.71     9.08       112.26     55.73       1.83         0.06
             OBL          31
                                   18-80     40-127     103-132    4.5-12     105-115    50-61.5     1.6-2.2    0.03-0.09
                                   29.48      81.04     125.44      5.62       112.8      53.32        1.81        0.05
              AP          25
                                   19-52     50-135     98-172      2.6-9     110-115     49-57      1.25-25    0.03-0.07
 Forearm
                                   29.46      82.33     125.75      9.07       112.71     55.67       1.95         0.06
              LAT         24
                                   19-52     52-135     98-172     2.6-65     110-115     49-95      0.6-2.5    0.02-0.17
                                   34.11       81        123.16     6.82       112.11     54.11       1.88         0.05
              AP          19
                                   18-73     45-133     106-158     3-9.5     110-115     48-63      1.6-2.5    0.03-0.08
  Elbow
                                   34.11       81        123.16     8.34       112.11     54.03       1.83         0.05
              LAT         19
                                   18-73     45-133     106-158    6-10.5     110-115     50-63      1.6-2.5    0.03-0.08
              Cald                 38.14       74       115.14     15.86        122       73.29        22          0.91
                          7
              well                 18-65     49-108     96-149     15-19      122-122     73-75       22-22     0.84-1.23
 Sinuses                            36.7      76.9       120        12.5       120.8       61.9       11.19        0.35
              LAT         10
                                   18-65     49-108     96-165      8-16      110-122     60-64       9-14      0.23-0.57
                                    36.7      76.9        111       16.8       120.8       74          24.1        1.13
             Waters       10
                                   18-65     49-108      6-165     15-21      110-122     73-75       22-25     0.84-1.89
              Cald                 36.94      77.63      113.88     17.5       120.56     72.25       30.81        1.17
                          16
              well                 21-70     55-115     104-135    14-21      114-122     70-75       22-75     0.84-2.87
  PNS                              37.06      77.63      113.88    18.94       120.56     73.88      29.59         1.19
             Waters       16
                                   21-70     55-115     104-135    13-23      114-122     73-75      7.5-75     0.31-3.06
                                   37.21      77.86     106.93     13.64       120.36     60.29      10.18         0.26
              LAT         14
                                   21-70     55-115     11-135     8-19       114-122     60-62      8.5-12      0.2-0.37
                                   38.86     79.17      118.43     15.29       118.29     64.86      11.14         0.48
 Clavicle     AP          7
                                   21-63     60-94      97-146     7-22       105-122    61.5-71     2.5-16     0.12-0.72
                                   37.43      83.57      123.71    11.86       110.71     61.57        2.3         0.09
              AP          7
                                   20-66     68-114     109-170    9-19       100-120     57-68       2-2.5     0.07-0.13
   Leg
                                   37.43      83.57      123.71    11.14       112.14     62.29        2.3         0.09
              LAT         7
                                   20-66     68-114     109-170    6-16       110-120     57-68       2-2.5     0.07-0.13


                                            Table B1: continued
                                                                                                              105

                        Histograms and box charts of ESD per radiograph for X-ray projections.
B-1 Chest AP:

                    8
                                                                                                 0.5

                    7

                                                                                                 0.4
                    6


                    5
     Frequency




                                                                                                 0.3




                                                                                      Chest AP
                    4


                    3                                                                            0.2


                    2
                                                                                                 0.1
                    1


                 0                                                                               0.0
                 0.0          0.1       0.2            0.3         0.4         0.5
                                          Chest AP




B-2 Chest PA:

                    200                                                                                 2.0

                    180

                    160
                                                                                                        1.5
                    140

                    120
        Frequency




                                                                                                        1.0
                                                                                          Chest PA




                    100

                        80

                        60
                                                                                                        0.5
                        40

                        20

                                                                                                        0.0
                        0
                        0.0   0.5   1.0          1.5         2.0         2.5    3.0
                                              Chest PA




B-3 Chest LAT:

                 100
                                                                                                        8


                    80
                                                                                                        6
     Frequency




                    60
                                                                                            Chest LAT




                                                                                                        4

                    40


                                                                                                        2
                    20



                        0                                                                               0
                              2     4            6           8           10      12
                                              Chest LAT
                                                                                                                     106

B-4 Pelvis AP:

                    11                                                                                     2.5
                    10

                        9
                                                                                                           2.0
                        8

                        7
                                                                                                           1.5
      Frequency



                        6




                                                                                              Pelvis AP
                        5
                                                                                                           1.0
                        4

                        3

                        2                                                                                  0.5

                        1

                        00.0              0.5         1.0           1.5         2.0    2.5
                                                                                                           0.0

                                                        Pelvis AP




B-5 Pelvis LAT:

                                                                                                           3.0
                    8


                    7
                                                                                                           2.5

                    6


                    5
                                                                                                           2.0
      Frequency




                                                                                              Pelvis LAT




                    4
                                                                                                           1.5
                    3


                    2                                                                                      1.0

                    1
                                                                                                           0.5
                  0
                  0.0               0.5         1.0         1.5           2.0    2.5   3.0
                                                      Pelvis LAT




B-6 KUB AP:

                    100

                                                                                                            20


                        80
                                                                                                            15


                        60
        Frequency




                                                                                                            10
                                                                                                   KUB AP




                        40
                                                                                                             5


                        20
                                                                                                             0


                            0
                                0                 5               10            15       20
                                                                                                            -5
                                                            KUB AP                                               B
                                                                                                                107

B-7 LSS AP:

                   20
                                                                                                          6



                   15

                                                                                                          4
      Frequency




                                                                                               LSS AP
                   10


                                                                                                          2

                      5




                                                                                                          0
                      0
                               1       2       3       4        5       6    7   8    9
                                                       LSS AP




B-8 LSS LAT:

                          25                                                                                8

                                                                                                            7
                          20
                                                                                                            6

                                                                                                            5
                          15
              Frequency




                                                                                                            4
                                                                                                LSS LAT




                          10                                                                                3

                                                                                                            2

                          5
                                                                                                            1

                                                                                                            0
                          00       1       2       3        4       5        6   7    8
                                                        LSS LAT                                           -1




B-9 LSS Spot:

                   18
                   17
                   16
                   15                                                                                10
                   14
                   13
                   12
                   11
       Frequency




                   10
                                                                                          LSS Spot




                    9
                    8                                                                                   5
                    7
                    6
                    5
                    4
                    3
                    2
                                                                                                        0
                    1
                    0
                                       5               10               15       20
                                                       LSS Spot
                                                                                                     108

B-10 Humerus AP:

                     15
                     14
                     13
                     12
                     11                                                                        0.5
                     10
                             9
        Frequency




                                                                              Humerus AP
                             8
                             7
                             6
                             5
                             4
                             3                                                                 0.0
                             2
                             1
                        0
                        0.0                                      0.5
                                             Humerus AP




B-11 Humerus LAT:

                  15
                  14
                  13
                  12
                  11                                                                           0.5
                  10
                      9
                                                                                 Humerus LAT
     Frequency




                      8
                      7
                      6
                      5
                      4
                      3                                                                        0.0
                      2
                      1
                     0
                     0.0                                                0.5
                                             Humerus LAT




B-12 Abdomen AP:

                             60                                                                  8
                             55

                             50

                             45                                                                  6
                             40

                             35
                 Frequency




                                                                                    Abdomen AP




                             30                                                                  4

                             25

                             20

                             15                                                                  2

                             10

                                 5
                                                                                                 0
                                 0
                                 0   2   4     6     8      10   12    14
                                               Abdomen AP
                                                                                                                                109

B-13 C Spine AP:

                        65                                                                                               0.7
                        60

                        55                                                                                               0.6
                        50

                        45                                                                                               0.5

                        40
            Frequency



                        35                                                                                               0.4




                                                                                                            C spine AP
                        30
                                                                                                                         0.3
                        25

                        20
                                                                                                                         0.2
                        15

                        10
                                                                                                                         0.1
                            5

                            0
                             0                                         2                                                 0.0
                                                             C spine AP




B-14 C Spine LAT:

                        25
                                                                                                                         0.7


                                                                                                                         0.6
                        20

                                                                                                                         0.5

                        15
           Frequency




                                                                                                                         0.4
                                                                                                           C spine LAT




                                                                                                                         0.3
                        10

                                                                                                                         0.2

                            5                                                                                            0.1


                                                                                                                         0.0
                            0
                            0.1         0.2      0.3          0.4          0.5         0.6     0.7
                                                         C spine LAT                                                     -0.1




B-15 Knee AP:

                 40
                                                                                                                         0.5
                 35


                 30                                                                                                      0.4


                 25
     Frequency




                                                                                                                         0.3
                                                                                                             Knee AP




                 20


                 15                                                                                                      0.2

                 10
                                                                                                                         0.1
                        5


                       0                                                                                                 0.0
                       0.0        0.2    0.4   0.6     0.8     1.0     1.2       1.4   1.6   1.8     2.0
                                                             Knee AP
                                                                                                                                           110

B-16 Knee LAT:

                 30
                                                                                                                                     0.5

                 25
                                                                                                                                     0.4

                 20
     Frequency




                                                                                                                                     0.3




                                                                                                            Knee LAT
                 15


                                                                                                                                     0.2
                 10



                       5
                                                                                                                                     0.1



                   0                                                                                                                 0.0
                   0.0             0.1         0.2          0.3          0.4    0.5   0.6
                                                       Knee LAT




B-17 Parsal Sinuses AP:

                             8                                                                                                       1.5

                                                                                                                                     1.4
                             7

                                                                                                                                     1.3
                             6
                                                                                                                                     1.2
                             5
                                                                                                                 Parsal Sinuses AP




                                                                                                                                     1.1
                 Frequency




                             4                                                                                                       1.0

                                                                                                                                     0.9
                             3
                                                                                                                                     0.8
                             2
                                                                                                                                     0.7

                             1                                                                                                       0.6

                                                                                                                                     0.5
                             0
                             0.4         0.6          0.8          1.0         1.2    1.4
                                                     Parsal Sinuses AP                                                               0.4




B-18 Parsal Sinuses LAT:

                       4
                                                                                                                      0.6


                                                                                                                      0.5
                       3
                                                                                            Parsal Sinuses LAT




                                                                                                                      0.4
           Frequency




                       2
                                                                                                                      0.3


                                                                                                                      0.2
                       1

                                                                                                                      0.1


                       0
                       0.2                                        0.4                                                 0.0
                                                Parsal Sinuses LAT
                                                                                                                              111

B-19 Parsal Sinuses Waters:

                        14                                                                                              1.5
                        13
                        12                                                                                              1.4
                        11
                        10                                                                                              1.3




                                                                                                Parsal Sinuses Waters
                         9
                         8
          Frequency



                                                                                                                        1.2
                         7
                         6                                                                                              1.1
                         5
                         4
                                                                                                                        1.0
                         3
                         2
                                                                                                                        0.9
                         1
                        0
                        0.8            1.0                     1.2                  1.4                                 0.8
                                             Parsal Sinuses Waters




B-20 Foot AP:

                  20
                  19
                  18
                  17
                  16
                  15                                                                                               0.1
                  14
                  13
                  12
      Frequency




                  11
                                                                                              Foot AP




                  10
                   9
                   8
                   7
                   6
                   5
                   4                                                                                               0.0
                   3
                   2
                   1
                   0
                  0.00          0.02                 0.04            0.06           0.08
                                                      Foot AP




B-21 Foot PA:

                        4                                                                                               0.1




                        3
            Frequency




                        2
                                                                                               Foot PA




                        1                                                                                               0.0




                    0
                  0.040       0.042          0.044          0.046           0.048     0.050
                                                      Foot PA
                                                                                                                                      112

B-22 Foot LAT:

                    10

                         9

                         8
                                                                                                                                0.1
                         7

                         6
       Frequency




                                                                                                                   Foot LAT
                         5

                         4

                         3

                         2                                                                                                      0.0
                         1

                      0
                     0.00                 0.02          0.04             0.06               0.08            0.10
                                                              Foot LAT




B-23 Foot OBL:

                   25




                   20
                                                                                                                                0.1


                   15
     Frequency




                                                                                                                     Foot OBL




                   10




                       5                                                                                                        0.0



                    0
                   0.00            0.02      0.04      0.06     0.08         0.10     0.12         0.14     0.16
                                                              Foot OBL




B-24 Femur AP:

                             8                                                                                                  1.5

                             7


                             6
                                                                                                                                1.0
                             5
                 Frequency




                                                                                                                   Femur AP




                             4


                             3                                                                                                  0.5

                             2


                             1
                                                                                                                                0.0
                             0
                             0.0   0.2    0.4    0.6   0.8     1.0     1.2      1.4   1.6     1.8     2.0    2.2
                                                               Femur AP
                                                                                                                         113

B-25 Femur LAT:

                  16
                  15
                  14
                  13
                  12                                                                                             1
                  11
                  10
                   9
      Frequency




                                                                                           Femur LAT
                   8
                   7
                   6
                   5
                   4
                   3                                                                                             0
                   2
                   1
                   00    1         2         3         4         5         6    7     8
                                                  Femur LAT




B-26 Dorsal Spine AP:

                  8                                                                                          3.0

                  7
                                                                                                             2.5
                  6


                  5                                                                                          2.0
      Frequency




                                                                                           C spine LAT




                  4
                                                                                                             1.5

                  3

                                                                                                             1.0
                  2


                  1                                                                                          0.5

                  0
                  0.5   1.0       1.5       2.0       2.5       3.0   3.5      4.0   4.5
                                            Dorsal Spine AP                                                  0.0




B-27 Dorsal Spine LAT:

                  12                                                                                             12
                  11

                  10                                                                                             10
                   9

                   8                                                                                                 8
                                                                                              Dorsal Spine LAT




                   7
      Frequency




                   6                                                                                                 6
                   5

                   4                                                                                                 4
                   3

                   2                                                                                                 2
                   1

                   0                                                                                                 0
                   0          2         4         6         8         10       12     14
                                             Dorsal Spine LAT
                                                                                                       114

B-28 Dorsal Spine Spot:

                    4

                                                                                                 8


                    3
                                                                                                 6




                                                                             Dorsal Spine Spot
      Frequency




                    2
                                                                                                 4




                    1                                                                            2




                    0                                                                            0
                    0         2               4               6          8
                                   Dorsal Spine Spot




B-29 Finger AP:

                    9                                                                            0.1

                    8

                    7

                    6
        Frequency




                    5
                                                                             Finger AP




                    4

                    3
                                                                                                 0.0
                    2

                    1

                   0
                  0.00      0.01       0.02         0.03          0.04
                                       Finger AP




B-30 Finger LAT:

                    12                                                                           0.1
                    11

                    10

                        9

                        8

                        7
      Frequency




                                                                               Finger LAT




                        6

                        5

                        4

                        3                                                                        0.0

                        2

                        1

                     0
                    0.00    0.01       0.02            0.03       0.04
                                       Finger LAT
                                                                                                                             115

B-31 Finger OBL:

                             8                                                                                 0.1

                             7


                             6


                             5
                 Frequency




                                                                                                  Finger OBL
                             4


                             3


                             2                                                                                 0.0


                             1


                          0
                         0.00         0.01           0.02            0.03            0.04
                                                    Finger OBL




B-32 Shoulder AP:

                                                                                                                       0.7
                   25

                                                                                                                       0.6

                   20
                                                                                                                       0.5
     Frequency




                                                                                                                       0.4
                                                                                                        Shoulder AP




                   15

                                                                                                                       0.3
                   10
                                                                                                                       0.2


                       5                                                                                               0.1


                                                                                                                       0.0
                      0
                      0.0           0.2        0.4             0.6             0.8          1.0
                                                Shoulder AP                                                           -0.1




B-33 Wrist AP:

                         16                                                                                           0.25
                         15
                         14
                         13                                                                                           0.20
                         12
                         11
                         10                                                                                           0.15
                             9
           Frequency




                                                                                                   Wrist AP




                             8
                                                                                                                      0.10
                             7
                             6
                             5
                                                                                                                      0.05
                             4
                             3
                             2
                                                                                                                      0.00
                             1
                              0
                             0.00   0.05     0.10           0.15        0.20         0.25
                                                      Wrist AP                                                  -0.05
                                                                                   116

B-34 Wrist LAT:

                    12                                                      0.15
                    11

                    10

                    9
                                                                            0.10
                    8

                    7
      Frequency




                                                             Wrist LAT
                    6
                                                                            0.05
                    5

                    4

                    3
                                                                            0.00
                    2

                    1

                    0
                                      0.05
                                   Wrist LAT                               -0.05




B-35 Wrist OBL:

                    7                                                      0.15


                    6


                    5                                                      0.10


                    4
        Frequency




                                                          Wrist OBL




                                                                           0.05
                    3


                    2

                                                                           0.00
                    1


                    0                0.05
                                  Wrist OBL                                -0.05




B-36 Tibia Fibula AP:

                    7                                                      0.15


                    6


                    5                                                      0.10
                                                         Tibia Fibula AP




                    4
       Frequency




                                                                           0.05
                    3


                    2

                                                                           0.00
                    1


                    0    0.05                     0.10
                                Tibia Fibula AP                            -0.05
                                                                                                                                117

B-37 Tibia Fibula LAT:

                      5                                                                                                  0.15



                      4
                                                                                                                         0.10


                      3




                                                                                                     Tibia Fibula LAT
         Frequency




                                                                                                                         0.05
                      2




                      1                                                                                                  0.00



                      0                    0.05                                           0.10
                                            Tibia Fibula LAT                                                            -0.05




B-38 Skull AP:

                      5
                                                                                                                1.2


                      4
                                                                                                                1.0



                      3                                                                                         0.8
          Frequency




                                                                                                 Skull AP




                                                                                                                0.6
                      2

                                                                                                                0.4

                      1
                                                                                                                0.2


                      0
                      0.4          0.6     0.8          1.0           1.2          1.4                          0.0
                                                   Skull AP




B-39 Skull PA:

                  6


                                                                                                                        1.0
                  5



                  4
                                                                                                                        0.8
      Frequency




                                                                                                   Skull PA




                  3
                                                                                                                        0.6

                  2

                                                                                                                        0.4
                  1



                  0                                                                                                     0.2
                            0.62    0.64   0.66       0.68     0.70         0.72         0.74
                                                  Skull PA
                                                                                                                                        118

B-40 Skull LAT:

                   7

                                                                                                                      0.8
                   6


                   5
                                                                                                                      0.6

                   4
       Frequency




                                                                                                       Skull LAT
                                                                                                                      0.4
                   3


                   2
                                                                                                                      0.2

                   1


                   0                                                                                                  0.0
                   0.3              0.4            0.5          0.6            0.7         0.8
                                                          Skull LAT




B-41 Skull Townies:

                        7                                                                                                         1.7
                                                                                                                                  1.6
                        6                                                                                                         1.5
                                                                                                                                  1.4
                        5                                                                                                         1.3
                                                                                                                                  1.2
                                                                                                                                  1.1
                        4
            Frequency




                                                                                                                   Skull Townes




                                                                                                                                  1.0
                                                                                                                                  0.9
                        3
                                                                                                                                  0.8
                                                                                                                                  0.7
                        2
                                                                                                                                  0.6
                                                                                                                                  0.5
                        1                                                                                                         0.4
                                                                                                                                  0.3
                        0                                                                                                         0.2
                        0.6   0.7     0.8    0.9         1.0   1.1    1.2      1.3   1.4   1.5   1.6
                                                         Skull Townes                                                             0.1




B-42 Hand AP:

                   14
                   13
                   12
                   11
                                                                                                                          0.1
                   10
                        9
                        8
      Frequency




                                                                                                         Hand AP




                        7
                        6
                        5
                        4
                        3
                                                                                                                          0.0
                        2
                        1
                        0
                                      0.02                                  0.04
                                                           Hand AP
                                                                                              119

B-43 Hand PA:

                        4                                                               0.1




            Frequency   3




                        2




                                                                            Hand PA
                        1                                                               0.0




                        0   0.02                                  0.04
                                             Hand PA




B-44 Hand LAT:

                   12

                   11

                   10

                        9                                                               0.1
                        8

                        7
       Frequency




                                                                            Hand LAT




                        6

                        5

                        4

                        3

                        2                                                               0.0

                        1

                        0
                                   0.02      0.04          0.06
                                            Hand LAT




B-45 Hand OBL:

                   16
                   15
                   14
                   13
                   12                                                                   0.1
                   11
                   10
                        9
     Frequency




                                                                             Hand OBL




                        8
                        7
                        6
                        5
                        4
                        3                                                               0.0
                        2
                        1
                        0            0.02           0.04             0.06
                                            Hand OBL
                                                                                                                        120

B-46 Hand Ball Catcher:

                             7                                                                                    0.1


                             6


                             5




                                                                                              Hand Ball Catcher
                             4
                 Frequency




                             3


                             2
                                                                                                                  0.0

                             1


                             0      0.02                        0.04                   0.06
                                                  Hand Ball Catcher




B-47 Ankle AP:

                    14
                    13
                    12
                    11
                                                                                                                  0.1
                    10
                        9
                        8
      Frequency




                                                                                              Ankle AP




                        7
                        6
                        5
                        4
                        3
                                                                                                                  0.0
                        2
                        1
                      0
                     0.02        0.04      0.06          0.08          0.10     0.12   0.14
                                                     Ankle AP




B-48 Ankle LAT:

                   10

                       9

                       8
                                                                                                                  0.1
                       7

                       6
     Frequency




                                                                                              Ankle LAT




                       5

                       4

                       3

                       2                                                                                          0.0
                       1

                     0
                    0.02          0.04            0.06          0.08          0.10     0.12
                                                    Ankle LAT
                                                                                                      121

B-49 Ankle OBL:

                 12

                 11

                 10

                    9                                                                           0.1
                    8

                    7
     Frequency




                                                                                    Ankle OBL
                    6

                    5

                    4

                    3

                    2                                                                           0.0

                    1

                     0
                    0.02   0.04          0.06          0.08   0.10      0.12
                                           Ankle OBL




B-50 Forearm AP:

                    12

                    11

                    10

                     9                                                                       0.1
                     8

                     7
        Frequency




                                                                               Forearm AP




                     6

                     5

                     4

                     3

                     2                                                                       0.0

                     1

                     0
                                                0.05
                                           Forearm AP




B-51 Forearm LAT:

                    16
                    15
                    14
                    13
                    12                                                                       0.1
                    11
                    10
                     9
        Frequency




                                                                               Forearm LAT




                     8
                     7
                     6
                     5
                     4
                     3                                                                       0.0
                     2
                     1
                     0
                    0.00          0.05             0.10          0.15
                                           Forearm LAT
                                                                                           122

B-52 Elbow AP:

                      8


                      7


                      6                                                         0.1

                      5
          Frequency




                                                                  Elbow AP
                      4


                      3


                      2
                                                                                0.0
                      1


                      0           0.05
                                          Ebow AP




B-53 Elbow LAT:

                      8


                      7


                      6                                                         0.1

                      5
          Frequency




                                                                  Elbow LAT




                      4


                      3


                      2
                                                                                0.0
                      1


                      0           0.05
                                         Ebow LAT




B-54 PNS Caldwell:

                 12

                 11                                                                  3.0

                 10
                                                                                     2.5
                      9

                      8
                                                                                     2.0
                      7
                                                                      PNS Caldwell
     Frequency




                      6
                                                                                     1.5
                      5

                      4
                                                                                     1.0
                      3

                      2
                                                                                     0.5
                      1

                      0
                      0.5   1.0     1.5         2.0   2.5   3.0                      0.0
                                     PNS Caldwell
                                                                                                      123

B-55 PNS Waters:

                       12                                                                       3.5
                       11

                       10                                                                       3.0

                       9
                                                                                                2.5
                       8

                       7
           Frequency



                                                                                                2.0




                                                                                   PNS Waters
                       6

                       5                                                                        1.5
                       4

                       3                                                                        1.0

                       2
                                                                                                0.5
                       1

                       0
                       0.0   0.5          1.0     1.5     2.0      2.5   3.0                    0.0
                                                PNS Waters




B-56 PNS LAT:

                 9

                 8

                 7

                 6
                                                                                                0.5
     Frequency




                 5
                                                                                  PNS LAT




                 4

                 3

                 2
                                                                                                0.0
                 1

              0
             0.20                  0.25           0.30          0.35       0.40
                                                PNS LAT
                                                                                                       ‫421‬


                                           ‫ﻣﻠﺨﺺ ﺍﻟﺒﺤﺚ‬

                                                                                                   ‫ﻣﻘﺪﻣﺔ :‬
                                                                           ‫ﹰ‬
‫ﺗﻠﻌﺐ ﺍﻷﺷﻌﺔ ﺍﻟﺴﻴﻨﻴﺔ ﺩﻭﺭﹰﺍ ﻣﻬﻤﺎ ﰲ ﺗﺸﺨﻴﺺ ﻭ ﻋﻼﺝ ﺍﻟﻜﺜﲑ ﻣﻦ ﺍﻷﻣﺮﺍﺽ . ﻭ ﻳﺼﺎﺣﺐ ﺍﻟﺪﻭﺭ ﺍﳍﺎﻡ ﺍﻟﻄـﱯ ﻟﻸﺷـﻌﺔ‬
‫ﺍﻟﺴﻴﻨﻴﺔ ﺗﺄﺛﲑﺍﺕ ﺑﻴﻮﻟﻮﺟﻴﺔ ﻭ ﺃﺧﻄﺎﺭ ﻋﻠﻰ ﺍﳌﺮﻳﺾ ﻭ ﺍﻟﻔﺮﻳﻖ ﺍﻟﻄﱯ . ﻧﺘﺞ ﻋﻦ ﺍﻻﻫﺘﻤﺎﻡ ﺍﻟﻨﺎﻣﻲ ﺑﺎﻷﺷﻌﺔ ﺍﻟﺴﻴﻨﻴﺔ ﺍﻟﻄﺒﻴـﺔ ﻭ‬
‫ﺍﻷﺧﻄﺎﺭ ﺍﳌﻤﻜﻨﺔ ﺍﳌﺼﺎﺣﺒﺔ ﳍﺎ ﺇﻧﺸﺎﺀ ﺑﺮﺍﻣﺞ ﲢﻜﻢ ﰲ ﺟﻮﺩﺓ ﺍﻷﺷﻌﺔ ﺍﻟﺴﻴﻨﻴﺔ ﻭ ﺍﺳﺘﺒﻴﺎﻥ ﻭ ﺗﻘﻴﻴﻢ ﺟﺮﻋﺎﺕ ﺍﳌﺮﺿﻰ ﰲ ﺍﻟﻜﺜﲑ‬
                                                                                             ‫ﻣﻦ ﺍﻟﺪﻭﻝ .‬
                                                                               ‫ﹰ‬
‫ﺗﻘﺎﺱ ﺟﺮﻋﺎﺕ ﺍﳌﺮﺿﻰ ﺩﻭﻣﺎ ﺑﺎﺳﺘﺨﺪﺍﻡ ﺟﻬﺎﺯ ﻣﻘﻴﺎﺱ ﺍﳉﺮﻋﺔ ﺍﳊﺮﺍﺭﻱ ﺍﻟﻮﻣﺎﺽ ﺃﻭ ﺃﺟﻬﺰﺓ ﻏﺮﻑ ﺍﻟﺘﺄﻳﻦ . ﻋﻠﻰ ﺍﻟﺮﻏﻢ ﻣﻦ‬
‫ﺩﻗﺔ ﺍﳉﻬﺎﺯﻳﻦ ﺇﻻ ﺃ‪‬ﻤﺎ ﺑﺎﻫﻈﻲ ﺍﻟﺜﻤﻦ ﻭ ﻣﻀﻴﻌﲔ ﻟﻠﻮﻗﺖ ﻭ ﻗﺪ ﻳﺆﺛﺮﺍ ﻋﻠﻰ ﺍﻟﺘﻌﺮﺽ ﺍﻹﺷﻌﺎﻋﻲ ﻟﻠﻤﺮﻳﺾ . ﻭ ﳝﻜﻦ ﻗﻴـﺎﺱ‬
                                             ‫ﺍﳉﺮﻋﺔ ﺑﺴﻬﻮﻟﺔ ﻭ ﺑﺪﻭﻥ ﺗﻜﻠﻔﺔ ﻋﻦ ﻃﺮﻳﻖ ﺍﺳﺘﺨﺪﺍﻡ ﺍﻟﻄﺮﻕ ﺍﳊﺴﺎﺑﻴﺔ .‬


                                                                                         ‫ﺃﻫﺪﺍﻑ ﺍﻟﺒﺤﺚ :‬
‫ﺍﳍﺪﻑ ﻣﻦ ﺍﻟﺒﺤﺚ ﺍﳊﺎﱄ ﻫﻮ ﺗﻘﻴﻴﻢ ﺩﻗﺔ ﺍﻟﻄﺮﻕ ﺍﳊﺴﺎﺑﻴﺔ ﻭ ﻣﻦ ﰒ ﺍﺳﺘﺨﺪﺍﻡ ﺃﺩﻕ ﻃﺮﻳﻘﺔ ﺣﺴﺎﺑﻴﺔ ﻟﺘﻘﻴﻴﻢ ﺟﺮﻋﺔ ﺍﳌـﺮﻳﺾ‬
‫ﻟﺒﻌﺾ ﺍﺧﺘﺒﺎﺭﺍﺕ ﺍﻷﺷﻌﺔ ﺍﻟﺴﻴﻨﻴﺔ ﳌﺮﺿﻰ ﻣﺴﺘﺸﻔﻰ ﻗﻮﻯ ﺍﻷﻣﻦ ﰲ ﺍﻟﺮﻳﺎﺽ . ﻭ ﺳﻮﻑ ﻳﺘﻢ ﺑﻌﺪ ﺫﻟﻚ ﺣـﺴﺎﺏ ﻭ ﺗﻘﻴـﻴﻢ‬
                                                                  ‫ﺟﺮﻋﺎﺕ ﺍﻷﻋﻀﺎﺀ ﻭ ﺍﳉﺮﻋﺎﺕ ﺍﻟﻔﻌﺎﻟﺔ .‬


                                                                                                  ‫ﺍﻟﻄﺮﻕ :‬
                                             ‫ﲤﺖ ﺍﻟﺪﺭﺍﺳﺔ ﰲ ﻣﺴﺘﺸﻔﻰ ﻗﻮﻯ ﺍﻷﻣﻦ ﻭ ﺍﻧﻘﺴﻤﺖ ﺇﱃ ﺛﻼﺛﺔ ﻣﺮﺍﺣﻞ :‬
‫ﺍﳌﺮﺣﻠﺔ ﺍﻷﻭﱃ : ﰲ ﻫﺬﻩ ﺍﳌﺮﺣﻠﺔ ﲤﺖ ﺩﺭﺍﺳﺔ ﲨﻴﻊ ﺍﻟﻄﺮﻕ ﺍﳌﺨﺘﻠﻔﺔ ﺍﳌﺴﺘﺨﺪﻣﺔ ﳊﺴﺎﺏ ﺟﺮﻋﺔ ﺍﳉﻠﺪ ﻭ ﺣﺎﺻﻞ ﺿـﺮﺏ‬
‫ﺍﳉﺮﻋﺔ ﰲ ﺍﳌﺴﺎﺣﺔ . ﻭ ﻗﻮﺭﻧﺖ ﺩﻗﺔ ﻛﻞ ﻃﺮﻳﻘﺔ ﺑﺎﻟﻄﺮﻳﻘﺔ ﺍﻟﺜﺎﻧﻴﺔ ﻭ ﺍﻟﱵ ﺗﻌﺘﻤﺪ ﻋﻠﻰ ﺍﻟﻘﻴﺎﺱ ﺍﳌﺒﺎﺷﺮ ﻟﻸﺟﻬﺰﺓ ﺍﻟﺴﻴﻨﻴﺔ . ﻭ ﻗﺪ‬
‫ﲤﻜﻨﺎ ﻣﻦ ﺍﻗﺘﺮﺍﺡ ﻃﺮﻳﻘﺔ ﺃﻓﻀﻞ ﳊﺴﺎﺏ ﺍﳉﺮﻋﺎﺕ . ﻭ ﰲ ﻫﺬﻩ ﺍﳌﺮﺣﻠﺔ ﲤﺖ ﻛﺬﻟﻚ ﺇﳚﺎﺩ ﻣﻌﺎﺩﻻﺕ ﻟﺒﻌﺾ ﻣﺘﻐﲑﺍﺕ ﺍﻷﺷﻌﺔ‬
                                                                                                   ‫ﺍﻟﺴﻴﻨﻴﺔ .‬
‫ﺍﳌﺮﺣﻠﺔ ﺍﻟﺜﺎﻧﻴﺔ : ﺍﺳﺘﺨﺪﻣﺖ ﰲ ﻫﺬﻩ ﺍﳌﺮﺣﻠﺔ ﺃﺩﻕ ﻃﺮﻳﻘﺔ ﺣﺴﺎﺑﻴﺔ ﳌﻌﺮﻓﺔ ﺟﺮﻋﺎﺕ ﺍﳉﻠﺪ ﻟﻠﻤﺮﺿﻰ ﻟﺒﻌﺾ ﺇﺧﺘﺒﺎﺭﺍﺕ ﺍﻷﺷﻌﺔ‬
‫ﺍﻟﺴﻴﻨﻴﺔ ﺍﻟﺘﺸﺨﻴﺼﻴﺔ ﺍﳌﺨﺘﺎﺭﺓ ﰲ ﻣﺴﺘﺸﻔﻰ ﻗﻮﻯ ﺍﻷﻣﻦ . ﲤﺖ ﺍﻟﺪﺭﺍﺳﺔ ﺑﺘﻮﺯﻳﻊ ﳕﻮﺫﺝ ﻟﻴﻘﻮﻡ ﺑﺘﻌﺒﺌﺘﻪ ﺍﻟﺘﻘﻨﻴﲔ ﻳﺘﻀﻤﻦ ﲨﻴﻊ‬
‫ﺍﳌﺘﻐﲑﺍﺕ ﺍﻟﱵ ﺗﺆﺛﺮ ﻋﻠﻰ ﺟﺮﻋﺔ ﺍﳌﺮﻳﺾ . ﻭ ﻗﺪ ﻃﺒﻘﺖ ﺃﻓﻀﻞ ﻃﺮﻳﻘﺔ ﺣﺴﺎﺑﻴﺔ ﻋﻠﻰ ﻫﺬﻩ ﺍﻟﻨﻤﺎﺫﺝ ﻟﻠﺘﻨﺒﺆ ﲜﺮﻋﺔ ﻛﻞ ﻣﺮﻳﺾ .‬
‫ﺍﳌﺮﺣﻠﺔ ﺍﻟﺜﺎﻟﺜﺔ : ﲤﺖ ﰲ ﻫﺬﻩ ﺍﳌﺮﺣﻠﺔ ﺩﺭﺍﺳﺔ ﻭ ﺣﺴﺎﺏ ﺟﺮﺍﺕ ﺍﻷﻋﻀﺎﺀ ﻭ ﺍﳉﺮﻋﺔ ﺍﻟﻔﻌﺎﻟﺔ ﻹﺧﺘﺒﺎﺭﺍﺕ ﺃﺷﻌﺔ ﺳﻴﻨﻴﺔ ﳐﺘﻠﻔﺔ‬
      ‫ﺑﺎﺳﺘﺨﺪﺍﻡ ﺑﺮﻧﺎﻣﺞ ) ‪ ( XDOSE‬ﻭ ﺍﻟﺬﻱ ﳛﺴﺐ ﺍﳉﺮﻋﺔ ﺍﻟﺪﺍﺧﻠﻴﺔ ﻟﻠﻤﺮﺿﻰ ﺍﻋﺘﻤﺎﺩﹰﺍ ﻋﻠﻰ ﺟﺮﻋﺔ ﺍﳉﻠﺪ ﺍﶈﺴﻮﺑﺔ.‬


                                                                                     ‫ﺍﻟﻨﺘﺎﺋﺞ ﻭ ﺍﳌﻨﺎﻗﺸﺎﺕ :‬
‫ﰎ ﺍﻟﺘﻮﺻﻞ ﺑﺎﻻﻋﺘﻤﺎﺩ ﻋﻠﻰ ﺍﻟﺪﺭﺍﺳﺎﺕ ﺍﻟﺴﺎﺑﻘﺔ ﺇﱃ ﺳﺒﻊ ﻣﻌﺎﺩﻻﺕ ﳊﺴﺎﺏ ﺟﺮﻋﺔ ﺍﳌﺮﺿﻰ . ﲬﺴﺔ ﻣﻦ ﻫـﺬﻩ ﺍﳌﻌـﺎﺩﻻﺕ‬
                                        ‫‪‬‬          ‫ﻟ‬
‫ﹸﺳﺘﺨﺪﻣﺖ ﰲ ﻫﺬﺍ ﺍﻟﻌﻤﻞ ﻻﻋﺘﻤﺎﺩﻫﺎ ﻋﻠﻰ ﺍﳌﺘﻐﲑﺍﺕ ﺍﹼﱵ ﳝﻜﻦ ﺃﻥ ‪‬ﺗﻌﺮ‪‬ﻑ ﻣﻦ ﺃﺧﺼﺎﺋﻴﻲ ﺍﻷﺷﻌﺔ . ﻛﻤﺎ ﲤﺖ ﻣﻘﺎﺭﻧﺔ ﻛﻞ‬   ‫ﺍ‬
          ‫ﹼ ﻄ‬
‫ﺍﻟﻄﺮﻕ ﻣﻊ ﺍﻟﻄﺮﻳﻘﺔ ﺍﻟﺜﺎﻧﻴﺔ ﺣﻴﺚ ﰎ ﺍﻟﺘﻘﻴﻴﻢ ﻟﻌﺪﺩ 0742 ﻣﺮﻳﺾ ﻭ ﲟﺎ ﻋﺪﺍ ﺍﻟﻄﺮﻳﻘﺔ ﺍﻷﻭﱃ ﻭﺟﺪ ﺃﻥ ﻛﻞ ﺍﻟ ﹼﺮﻕ ﺍﻷﺧﺮﻯ‬
                                                                                                          ‫521‬


                          ‫ﻄ‬                       ‫ﻄ‬                                               ‫ﻴ‬
‫ﺗﻌﻄﻲ ﻧﺘﺎﺋﺞ ﺟ‪‬ﺪﺓ ﺑﺎﳌﻘﺎﺭﻧﺔ ﻣﻊ ﺍﻟﻄﺮﻳﻘﺔ ﺍﻟﺜﺎﻧﻴﺔ . ﻛﺎﻧﺖ ﻧﺘﺎﺋﺞ ﺍﻟ ﹼﺮﻳﻘﺔ ﺍﻟﺜﺎﻟﺜﺔ ﺃﻓﻀﻞ ﻣﻦ ﺍﻟ ﹼﺮﻕ ﺍﻟﺮﺍﺑﻌﺔ ﻭ ﺍﳋﺎﻣﺴﺔ . ﻭ ﰎ‬
                                                          ‫ﻄ‬
‫ﺍﺑﺘﻜﺎﺭ ﻃﺮﻳﻘﺔ ﺟﺪﻳﺪﺓ ﻭ ﻛﺎﻧﺖ ﺃﻓﻀﻞ ﻣﻘﺎﺭﻧﺔ ﻣﻊ ﻛﻞ ﺍﻟ ﹼﺮﻕ ﺍﻷﺧﺮﻯ . ﻭ ﻟﻮﺣﻆ ﺃﻳﻀ‪‬ﺎ ﺃﻥ ﺟﺮﻋﺎﺕ ﺍﳌﺮﺿـﻰ ﳌﻌﻈـﻢ‬
                                                                    ‫ﺃ‬
‫ﺍﻟﻔﺤﻮﺹ ﺑﺎﻷﺷﻌﺔ ﺍﻟﺴﻴﻨﻴﺔ ﺃﻗﻞ ﳑﺎ ﻧﺸﺮ ﺃﻭ ﹸﻭﺻﻲ ﺑﻪ ﰲ ﺍﻟﺒﻼﺩ ﺍﻷﺧﺮﻯ . ﺑﺎﻟﺮﻏﻢ ﻣﻦ ﺫﻟﻚ ﻓﻘﺪ ﻟﻮﺣﻆ ﺃﻥ ) ﳌﻌﻈﻢ‬
   ‫ﺮ‬                                                                           ‫ﺘﻴ‬
‫ﺍﻟﻔﺤﻮﺹ ( ﻻ ﳝﻜﻦ ﺃﻥ ﻳﺸﺮﺡ ﺍﻟ‪‬ﻐ‪‬ﺮ ﰲ ﺍﳉﺮﻋﺔ ﺑﺎﻟﺘﻐﲑ ﰲ ﲰﻚ ﺍﻟﻌﻀﻮ ﻭ ﻫﺬﺍ ﻗﺪ ﻳﻨﺴﺐ ﺇﱃ ﺣﻘﻴﻘﺔ ﺃﻥ ﺳﻴﻄﺮﺓ ﺍﻟﺘﻌ ‪‬ﺽ‬
                           ‫‪‬‬                                                               ‫‪‬‬
‫ﺍﻷﻭﺗﻮﻣﺎﺗﻴﻜ‪‬ﺔ ﻻ ﺗﺴﺘﺨﺪﻡ ﻣﻦ ﻗﺒﻞ ﺍﻟﺘﻘﻨﻴﲔ . ﻭ ﻫﺬﺍ ﺍﻧﻌﻜﺲ ﺃﻳﻀ‪‬ﺎ ﻋﻠﻰ ﺍﻟﺘﻮﺯﻳﻊ ﺍﻹﺣﺼﺎﺋﻲ ﳉﺮﻉ ﺍﳌﺮﺿﻰ . ﻭ ﺗﺘﺒﻊ ﻧﺘﺎﺋﺞ‬‫ﻴ‬
               ‫ﻟ ﻘ‬
‫ﺟﺮﻋﺎﺕ ﺍﻷﻋﻀﺎﺀ ﻧﻔﺲ ﺃﳕﺎﻁ ﺟﺮﻋﺎﺕ ﺍﳉﻠﺪ . ﻭﺟﺪ ﺃﻥ ﺍﻷﻋﻀﺎﺀ ﺍﻟﱵ ﺗﻘﻊ ﰲ ﳎﺎﻝ ﺍﻟﺘﺼﻮﻳﺮ ﻫﻲ ﺍﹼﱵ ﺗﺘﻠ ﹼﻰ ﺃﻋﻠﻰ ﺟﺮﻋﺔ .‬
‫ﺇﺫ ﺗﺘﻠ ﹼﻰ ﺍﳌﺒﺎﻳﺾ ﺃﻋﻠﻰ ﺟﺮﻋﺔ ﻣﻦ ﺗﺼﻮﻳﺮ ﺍﳊﺒﻞ ﺍﻟﺸﻮﻛﻲ )‪ (0.52 mSv‬ﻭ )‪ (0.25 mSv‬ﻣﻦ ﺗﺼﻮﻳﺮ ﺍﳊﻮﺽ . ﻻ‬                 ‫ﻘ‬
‫ﺗﺆﺛﺮ ﺑﻘﻴﺔ ﺃﻧﻮﺍﻉ ﺍﻟﺘﺼﻮﻳﺮ ﻋﻠﻰ ﺍﳌﺒﺎﻳﺾ . ﻳﺘﻠﻘﻰ ﺍﳋﺼﻰ ﻣﻦ ﻧﺎﺣﻴﺔ ﺃﺧﺮﻯ، ﺃﻋﻠﻰ ﺟﺮﻋﺔ ﻣﻦ ﺗـﺼﻮﻳﺮ ﺍﳊـﻮﺽ )‪mSv‬‬
             ‫ﻘ‬
‫59.0( ﻭ ﺗﺼﻮﻳﺮ ﺍﳊﺒﻞ ﺍﻟﺸﻮﻛﻲ )‪ .(0.1 mSv‬ﻭ ﻻ ﺗﺴﺒﺐ ﺍﻟﻔﺤﻮﺹ ﺍﻷﺧﺮﻯ ﺟﺮﻉ ﺇﱃ ﺍﳋﺼﻰ . ﺗﺘﻠ ﹼـﻰ ﺍﻟﻐـﺪﺓ‬
‫ﺍﻟ ‪‬ﺭﻗ‪‬ﺔ ﺃﻋﻠﻰ ﺟﺮﻋﺔ ﻣﻦ ﺗﺼﻮﻳﺮ ﺍﳉﺰﺀ ﺍﻟﻌﻠﻮﻱ ﻣﻦ ﺍﳊﺒﻞ ﺍﻟﺸﻮﻛﻲ )‪ (0.25 mSv‬ﻭ ﺃﺷﻌﺔ ﺍﻟﺼﺪﺭ )‪.(0.04 mSv‬‬                 ‫ﺪ ﻴ‬
                                            ‫ﻘ‬
‫ﺃﻣﺎ ﺑﻘﻴﺔ ﺃﻧﻮﺍﻉ ﺍﻟﺘﺼﻮﻳﺮ ﻓﺘﻌﺮﺽ ﺍﻟﻐﺪﺓ ﺍﻟﺪﺭﻗﻴﺔ ﳉﺮﻉ ﻣﺘﻐﲑﺓ ﺍﳌﺪﻯ . ﺗﺘﻠ ﹼﻰ ﺍﻟﻌﻈﺎﻡ ﺃﻋﻠﻰ ﺟﺮﻋﺔ ﻣـﻦ ﺗـﺼﻮﻳﺮ ﺍﳊﺒـﻞ‬
                        ‫ﻘ ﺮ‬
‫ﺍﻟﺸﻮﻛﻲ )‪ (0.12 mSv‬ﺑﻘﻴﺔ ﺃﻧﻮﺍﻉ ﺍﻟﺘﺼﻮﻳﺮ ﺗﺘﺴﺒﺐ ﰲ ﺟﺮﻋﺎﺕ ﳐﺘﻠﻔﺔ ﻟﻠﻌﻈﺎﻡ . ﻳﺘﻠ ﹼﻰ ﺍﻟ ‪‬ﺣﻢ ﺃﻋﻠﻰ ﺟﺮﻋﺔ ﻣﻦ ﺗﺼﻮﻳﺮ‬
‫ﺍﳊﺒﻞ ﺍﻟﺸﻮﻛﻲ ) ‪ ،(0.69 mSv‬ﻭ ﻣﻦ ﺗﺼﻮﻳﺮ ﺍﳊﻮﺽ )‪ (0.34 mSv‬ﻭ ﻣﻦ ﺗـﺼﻮﻳﺮ ﺍﳉﻬـﺎﺯ ﺍﻟﺒـﻮﱄ )‪mSv‬‬
                                                    ‫ﺮ‬
‫20.0( . ﺑﻴﻨﻤﺎ ﺗﺴﺒﺐ ﺑﻘﻴﺔ ﺃﻧﻮﺍﻉ ﺍﻟﺘﺼﻮﻳﺮ ﺟﺮﻋﺎﺕ ﺻﻐﲑﺓ ﻟﻠ ‪‬ﺣﻢ . ﻛﺎﻧﺖ ﺃﻛﱪ ﺟﺮﻋﺔ ﻳﺘﻌﺮﺽ ﳍﺎ ﺍﳉﺴﻢ ﺑﺎﻟﻜﺎﻣﻞ ﻣﻦ‬
                                                                        ‫ﺗﺼﻮﻳﺮ ﺍﳊﺒﻞ ﺍﻟﺸﻮﻛﻲ )‪. (0.19 mSv‬‬


                                                                                                   ‫ﺍﳋﻼﺻﺔ :‬
                        ‫ﹰ‬                                                              ‫ﹼ‬
‫ﻛﺎﻧﺖ ﻛﻞ ﻃﺮﻕ ﺣﺴﺎﺏ ﺟﺮﻋﺔ ﺍﳌﺮﺿﻰ ﺍﳌﺪﺭﻭﺳﺔ ﻣﺸﺎ‪‬ﺔ . ﺃﻋﻄﺖ ﺍﻟﻄﺮﻳﻘﺔ ﺍﳌﻄﻮﺭﺓ ﻧﺘﺎﺋﺠﺎ ﺃﻓﻀﻞ ﺑﺎﳌﻘﺎﺭﻧﺔ ﻣـﻊ ﺑﻘﻴـﺔ‬
‫ﺍﻟﻄﺮﻕ . ﻭ ﻗﺪ ﻭﺟﺪ ﺃﻥ ﺟﺮﻋﺎﺕ ﺍﳌﺮﺿﻰ ﰲ ﺍﻟﻌﻤﻞ ﺍﳊﺎﱄ ) ﺑﺼﻔﺔ ﻋﺎﻣﺔ ( ﺃﻗﻞ ﳑﺎ ﻧﺸﺮ ﰲ ﺍﻟﺒﻼﺩ ﺍﻷﺧﺮﻯ . ﺑﻴﻨﻤﺎ ﲢﺘﺎﺝ‬
                                                                    ‫ﺼ‬
‫ﺍﳉﺮﻋﺔ ﺍﻟﻌﺎﻟﻴﺔ ﺍﳌﻮﺟﻮﺩﺓ ﰲ ﻓﺤﺺ ﺍﻟ ‪‬ﺪﺭ ﻟﻼﻧﺘﺒﺎﻩ ﻣﻦ ﺗﻘﻨﻴﻲ ﺍﻟﻄﺐ ﺍﻹﺷﻌﺎﻋﻲ . ﻭ ﺗﺴﺒﺐ ﻋﺪﻡ ﺍﺳﺘﺨﺪﺍﻡ ﻧﻈﺎﻡ ﺳـﻴﻄﺮﺓ‬
                                                                                 ‫ﻴ‬
‫ﺍﻟﺘﻌﺮﺽ ﺍﻷﻭﺗﻮﻣﺎﺗﻴﻜ‪‬ﺔ ﰲ ﺍﻟﺘﻮﺯﻳﻊ ﺍﻟﺴﻴﺊ ﳉﺮﻋﺎﺕ ﺍﳌﺮﺿﻰ ﻭ ﺍﻟﺬﻱ ﻻ ﳝﻜﻦ ﺃﻥ ﻳﺸﺮﺡ ﺑﺎﻟﺘﻐﲑ ﰲ ﲰﻚ ﺍﻟﻌﻀﻮ ﰲ ﻣﻌﻈﻢ‬
‫ﺍﻟﻔﺤﻮﺹ ﺍﳌﺪﺭﻭﺳﺔ . ﰎ ﺍﻗﺘﺮﺍﺡ ﻃﺮﻳﻘﺔ ﺟﺪﻳﺪﺓ ﳊﺴﺎﺏ ﺟﺮﻉ ﺍﳌﺮﺿﻰ ﻭ ﻭﺟﺪ ﺃﻥ ﻧﺘﺎﺋﺠﻬﺎ ﺟﻴﺪﺓ ﺑﺎﳌﻘﺎﺭﻧﺔ ﻣـﻊ ﻃـﺮﻕ‬
‫ﺍﳊﺴﺎﺏ ﺍﻷﺧﺮﻯ ﻭ ﰎ ﺗﻄﻮﻳﺮ ﺑﺮﻧﺎﻣﺞ ﻓﻴﺠﻮﻝ ﺑﻴﺴﻚ ﳊﺴﺎﺏ ﺟﺮﻋﺎﺕ ﺍﳌﺮﺿﻰ ﺑﺎﺳﺘﺨﺪﺍﻡ ﺍﻟﻄﺮﻳﻘﺔ ﺍﳉﺪﻳﺪﺓ ﻭ ﺣﺴﺎﺏ‬
                    ‫ﺟﺮﻋﺎﺕ ﺍﻷﻋﻀﺎﺀ ﺑﺎﻻﻋﺘﻤﺎﺩ ﻋﻠﻰ ﺟﺪﺍﻭﻝ ﳏﺎﻛﺎﺓ ﻣﻮﻧﱵ ﻛﺎﺭﻟﻮ ﺍﳌﺮﻓﻘﺔ ﻣﻊ ﺑﺮﻧﺎﻣﺞ ‪.XDOSE‬‬
                                                                                  ‫621‬




                                  ‫ﺟﺎﻣﻌﺔ ﺍﳌﻠﻚ ﺳﻌﻮﺩ‬
                                     ‫ﻛﻠﻴﺔ ﺍﻟﻌﻠﻮﻡ‬
                                 ‫ﻗﺴﻢ ﺍﻟﻔﻴﺰﻳﺎﺀ ﻭ ﺍﻟﻔﻠﻚ‬



‫ﺗﻘﻴﻴﻢ ﺟﺮﻋﺎﺕ ﺍﳉﻠﺪ ﻭ ﺍﳉﺮﻋﺎﺕ ﺍﳌﺆﺛﺮﺓ ﻟﺒﻌﺾ ﺍﺧﺘﺒﺎﺭﺍﺕ ﺍﻷﺷﻌﺔ‬
             ‫ﺍﻟﺴﻴﻨﺔ ﺍﻟﺮﻭﺗﻴﻨﻴﺔ ﺑﺎﺳﺘﺨﺪﺍﻡ ﺍﻟﻄﺮﻕ ﺍﳊﺴﺎﺑﻴﺔ‬

                                                            ‫ﹰ‬
 ‫ﻗﺪﻣﺖ ﻫﺬﻩ ﺍﻟﺮﺳﺎﻟﺔ ﺍﺳﺘﻜﻤﺎﻻ ﳌﺘﻄﻠﺒﺎﺕ ﺍﳊﺼﻮﻝ ﻋﻠﻰ ﺩﺭﺟﺔ ﺍﳌﺎﺟﺴﺘﲑ ﰲ ﻗﺴﻢ ﺍﻟﻔﻴﺰﻳﺎﺀ ﺑﻜﻠﻴﺔ ﺍﻟﻌﻠﻮﻡ‬
                                      ‫ﲜﺎﻣﻌﺔ ﺍﳌﻠﻚ ﺳﻌﻮﺩ‬



                                        ‫ﺇﻋﺪﺍﺩ‬
                             ‫ﺣﻨﺎﻥ ﻓﻮﺍﺯ ﳏﻤﺪ ﺃﺧﻀﺮ‬


                                       ‫ﺑﺈﺷﺮﺍﻑ‬
                              ‫ﺩ. ﻣـﻬﺎ ﺗـﺮﲨـﺎﻥ‬
                              ‫ﺩ. ﺃﲪـﺪ ﻋـﻄـﻴﻒ‬
                              ‫ﺩ. ﻋـﺒﺪﺍﷲ ﺍﳉﻔـﺎﱄ‬

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