RADIATION PROTECTION - PowerPoint

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					RADIATION PROTECTION
Presented by Rose Aehle RT (R,M) MS
Program Coordinator, Montgomery College
             REFERENCES
• Bushong Radiologic Science for
    Technologists, Eighth Edition
•   Ehrlich, Patient Care in Radiography, Sixth
    Edition
•   Callaway, Mosby’s Comprehensive Review of
    Radiography
•   Saia, Lange Q & A Radiography Examination,
    6th Edition
•   Sherer, Radiation Protection in Medical
    Radiography, Fifth Edition
•   2007 ARRT REGISTRATION HANDBOOK
• The College of St. Catherine, Development
  Testing Program for Radiography
•
PLEASE TURN ALL CELL PHONES
TO VIBRATE MODE
LD   50


 LD 50/60


 THE AMOUNT OF
 RADIATIONTHAT WILL
 CAUSE 50% OF EXPOSED
 INDIVIDUALS TO DIE
 WITHIN 60 DAYS
WHAT THE REGISTRY WANTS YOU
TO KNOW (2007 ARRT handbook)
BIOLOGIC ASPECTS OF RADIATION

Dose response curves (Sherer)
                Line 1
No level of radiation can be considered
   safe.
Response to exposure is directly
   proportional
                Line 2
Threshold is assumed, response
   expected at lower doses
Response to exposure is directly
   proportional
Cataractogenesis
BIOLOGIC ASPECTS OF RADIATION

Dose response curves (Sherer)
                Line 3
Non linear (sigmoid or hypothetical
   sigmoid) dose response
             DIAGRAM B
Non linear, threshold dose response
   used in radiation therapy
BIOLOGIC ASPECTS OF RADIATION

FRACTIONATION     How to read a nonlinear
                  threshold dose response
                  curve



 PROTRACTED
 DOSE                                       Death/ Repair


                Damage/eradication of
                abnormal cells




                               Repair
•Linear quadratic
nonthreshold dose
response curve
•Risks associated with
low dose levels of low
LET radiations
•Stochastic somatic
and genetic effects
• “Leukemia, breast
cancer and heritiable
damage assumed to
follow this curve”
•            Sherer
????????????????????????????




                College of St. Catherine
ANSWERS
D
C
LET, RBE, QF
• Which comes first?




• LET?
  RBE?
  QF?
• LET – AMOUNT OF ENERGY DEPOSITED
  BY RADIATION PER UNIT LENGTH OF
  TISSUE TRAVERSED calloway

• RBE- QUANTITATIVE MEASUREMENT
  OF BIOLOGIC EFFECT

• QF – NUMERIC UNIT GIVEN TO
  RADIATION BASED ON RBE TO
  DETERMINE REM
Facts about LET
• LET - SPARSELY IONIZING RADIATION
• GAMMA AND X-RAY
• LOW LET OF 3 KEV OR LESS
  – ARE PENETRATING
  – INTERACT RANDOMLY ALONG ITS TRACK
    (STOCHASTIC)
• AS LET INCREASES SO DOES RBE
• HIGH LET
  – LOW PENETRATION
  – SLOW MOVING
  – Direct Effect
Effective dose (E)=Wr X Wt x
absorbed dose
•Wr -Radiation          •number assigned to
weighting factor        different types of
                        ionizing radiation.
                        Dependent of the LET
                        of particular radiation

•Wt –Tissue weighting
factor                  •Tissue radiosensitivity
                        of irradiated material
FACTS ABOUT RBE
   • DOSE OF STANDARD RADIATION NECESSARY TO PRODUCE A
                               GENETIC EFFECT
     --------------------------------------------------------------------
DOSE OF TEST RADATION NECESSARY TO PRODUCE THE SAME EFFECT


• STANDARD RADIATION IS TYPICALLY 250
  kVp (Bushong has a range of 200 – 250 kVp)

• Test radiation can range for x-rays to other
  types of ionizing radiation

• RBE for x-rays is one
• Higher LET’s have Higher RBE = Higher QF
          Radiosensitivity
        based on Wt factors
What is more radiosensitive?
• CNS or GI?
• Rectum or Small bowel?
• Erythoblasts or Myelocytes?
• red bone marrow or gonads?
• Adult or elderly?
• Lung or thyroid?
FACTS ABOUT QF
• REM IS CALCULATED BY MULTIPLYING
  THE QF OF A PARTICULAR TYPE OF
  RADIATION X RAD
• QF FOR X-RAYS IS 1
• THEREFORE ONE RAD OF EXPOSURE TO
  X-RAY = ONE REM
• QF FOR ALPA IS 20
  – HIGH LET
  – SLOW MOVING
  – LOW PENETRATION
• THEREFORE ONE RAD OF EXPOSURE TO
  ALPHA = 20 REMS
WHAT DOES THE LAW OF BERGONIE AND
TRIBONDEAU SAY Re RADIOSENSITIVITY?

• Stem cells are_____________
• Mature cells are ____________
• Cells with ___________metabolic and
  ___________mitotic activity are
  radiosensitive
• Cells which are differentiated are
  _____________
SOMATIC EFFECTS
• STOCHASTIC
  aka PROBALISTIC effect




• NONSTOCHASTIC
  aka Deterministic Effect
•
                  SOMATIC
       •Short Term                    •LONG TERM
•ARS                         •THOSE EFFECTS THAT CAN
   –Hemopoietic (BONE        BE DIRECTLY RELATED TO
   MARROW SYNDROME)          HIGH DOSE OF RADIATION
   100-1000 RAD              ARE CLASSIFIED AS
   –25 RADS CAN DEPRESS      NONSTOCHASTIC
   BLOOD COUNT               •Cataract
   –Gastointestinal (600-
                             •Reduced fertility
   1000 RADS)
   –CNS (5000 RADS           •Fibrosis
           Locally           •Organ atrophy
•Erythema 300-1000 RADS      •Sterility
•Epilation                    •LONG TERM STOCHASTIC
•Delay/suppress                         CANCER
menstruation 10 RADS           EMBRYOLOGIC EFFECTS
•Temporary sterility (both
sexes – 200 RADS
         CARCINOGENESIS
• The cancer that can be ALMOST classified as
  radiounique is leukemia
• Has a short latency period
• Has a linear nonthreshold dose response
  curve
• Epidemiologic studies indicate a higher
  incidences in leukemia after large exposures
• Radium watch dial workers –bone ca
• Uranium miners – lung ca
• Early medical radiation workers – leukemia
• Thymus gland treatment – thyroid ca
• Children of Marshal Island – thyroid ca
• Atomic bomb survivors – leukemia/breast,
  lung and bone
WHAT CAN HAPPEN WHEN IONIZING
RADIATION HITS THE CELL?
a) Nothing
b) Direct effect
c) Indirect effect
d) All of the above
HIGH LET is associated with which
effect?
a)   No effect
b)   Direct effect
c)   Indirect effect
d)   Radiolysis of water
The following is true regarding
indirect effect
I) DNA is impacted by free radicals
II) Some free radicals may chemically
    combine to form hydrogen peroxide
III) DNA is directly struck by radiation
IV) The minority of the damage to body is
    caused by indirect effect
a) I only
b) I and II only
c) I, II and III only
d) All of the above
TARGET THEORY
A) THE DNA IS DIRECTLY HIT
B) ONLY SOME CELLS HAVE MASTER
   MOLECULES THAT DIRECT CELL
   ACTIVITY
C) ONE CANNOT DETERMINE IN ANY
   CELL DEATH IF THE DEATH WAS
   RESULT OF DIRECT OR INDIRECT
   EFFECT
EMBRYONIC AND FETAL RISKS
• Spontaneous abortions during first 2
  weeks of pregnancy-- 25 RAD or higher
• 2nd week to 10th week – major
  organogenesis –IF radiation is high
  enough can cause congenital
  abnormalities
• Principle response after that may be
  malignant disease in childhood
PREVENTING ACCIDENTAL
IRRADITATION TO PATIENT
•   FIRST TWO MONTHS, CRITICAL
•   10 DAY RULE
•   ELECTIVE BOOKING
•   QUESTIONAIRE
•   POSTING
IF A PREGNANT PATIENT MUST BE
X-RAYED
•   TIGHT COLLIMATION
•   HIGH KVP
•   SHIELDING
•   REDUCED # OF IMAGES
•   MAKE SURE TO CHECK WITH YOUR
    SUPERVISOR AND BE AWARE OF THE
    SITE’S PROTOCOL
               GSD
• GENETICALLY SIGNIFICANT DOSE
• 20 mrem estimated dose
• Equivalent dose to the reproductive
  organs received by every human would
  cause the same genetic injury as the
  actual dose received by individual
  population members
The pregnant radiographer
    •WHICH OF THE
 FOLLOWING IS (ARE)
        TRUE?           •TRUE
•5 mSv for the period
of pregnancy
•500 mrem for the
period of pregnancy     •TRUE
•0.5 mSv per month
•0.05 mrem per month    •TRUE
•Two badges             •TRUE
LET’S PICK UP THE PACE NOW!
KEEP THE PATIENTS SAFE!!!
WHAT KIND OF EXPOSURE FACTORS ARE BEST
FOR PATIENTS?

• NAME FACTORS TO KEEP PT DOSE DOWN
• AS SID increases, what happens to the
  intensity? What do we adjust and do we
  increase or decrease this adjustment?
• Which of the following impacts PT dose?
  –   Inherent filtration?
  –   Added filtration?
  –   SID?
  –   Focal spot size?
  –   Screen speed?
WHAT GIVES HIGHEST CONTRAST BUT
INCREASES PATIENT DOSE?

•   COMPTON?
•   CHARACTERITIC?
•   BREMSSTRAHLUNG?
•   PHOTOELECTRIC?
DO GRIDS DECREASE PATIENT
EXPOSURE?
MINIMIZING PATIENT EXPOSUER

• SHIELDING
  – Gonadal shielding females reduces gonad
    dose by 50%
  – Gonadal shielding males reduces gonad
    dose by 95%
  – Flat, shadow shields


• COLLIMATION
  – DID YOU KNOW THAT THERE ARE A
    HIGHER SET OF LEAD SHUTTERS PLACED
    NEAR THE X-RAY TUBE WINDOW TO
    ABSORB OFF-FOCUS RADIATION?
• FILTRATION
  – INCREASED FILTRATION (HVL) INCREASES
    THE AVERAGE BEAM ENERGY

  – No filtration on a 70 kVp tube (0-70) would
    produce an average energy of 35 kVp
  – However, if you filter out the lower
    energies (30-70 kVp) is 50 kVp
  – Inherent
  – Added
  – _________is required for machines
    operating at 70 kVp
                HVL
• How many HVL’s are required to reduce
  the intensity of the beam to less that
  15% of its original value

•   A) 2
•   B)3
•   C)4
•   D)5
FLUOROSCOPY
WHERE SCATTER ALWAYS MATTERS!
READING NOMOGRAMS
•What kind of info do
you need?

•From Appleton and
Lange
•What is the
approximate patient
ESE from an AP
projection of the abd.
made at 105 cm, 70
kVp, 300 mA, 0.2 sec
(60 mAs)and 2.5 mm
AL total filtration
SCATTER STATS
• Each time the x-ray beam scatters, its
  intensity at 1 meter from the scattering
  object is one thousandth of its original
  intensity
• or it decreases 1000 times!!!!
• Or 1/1000 or
• 0.1%
         FLUOROSCOPY
• PULSED (DF)
• X-RAY TUBE OPERATES IN RADIOGRAPHIC
  MODE WHICH MEANS USING TECHNICAL
  FACTORS THAT ARE USED FOR OVERHEAD
  EXAMS
• HOWEVER
• THE TIME REQUIRED TO REACH THE
  SELECTED MA AND KV (INTERROGATION
  TIME) AND THE TIME FOR THE X-RAY TUBE TO
  BE SWITCHED OFF (EXTINCTION TIME) IS
  LESS THAN 1 MS
• THEREFORE IN DR FLUORO A 5 MINUTE
  STUDY WILL RESULT IN A PATIENT DOSE OF
  10 RAD VS 20 RAD FOR A CONVENTIONAL
  FLUOROSCOPY STUDY
Conventional fluoroscopy
• mA less than 5
• Use of magnification mode increases
  patient exposure
All types of fluoro
• Intermittent fluoro
• Field size
• Focus to table distance (15” stationary,
  12” mobile
PERSONNEL PROTECTION
Let’s keep safe!
THE ENVIRONMENT
•CONTROLLED AREA    •Badged personnel

•OCCUPANCY FACTOR   •Who,what is where

•UNCONTROLLED       •Everyone else!
AREA

•USE FACTOR         •% of time primary
                    beam is directed at a
                    particular wall
•WORKLOAD           •# of x-ray exams per
                    week
• Primary barrier
• 7 feet, 1/16 inch of lead



• Secondary barrier
• Extend to ceiling
• 1/32 inch of lead
Which of these regulations are
accurate?
• DL for eye is 50 mSv?
• Cumulative whole body is 10mSv x age?
• Leakage radiation – 100 mR/hr at 2 meters?
• Lead aprons at 0 .25 mm pB equivalent?
• ESE in 10R/min in fluoro?
• Exposure cord on portable must be 1 meter
  long?
• Pregnant radiographer DL for fetus is 500
  mrem for period of pregnancy?
• The public exposure DL is 100 mrem per year?
• Bucky slot cover and protective curtain,
  minimum of 0.5 pB equivalent?
FINALLY!!!
• ALARA
• CARDINAL RULES OF PROTECTION
• PERSONNEL MONITORS
  – TLD’S VS OSL VS. FILM BADGES VS
    DOSIMETERS
  – Lithium fluoride vs aluminum oxide vs x-ray
    film vs.gas
• INVERSE SQUARE LAW WITH
  EXPOSURE RATE
• If a radiographer receives 25 mR standing 3
  feet from the source for one hour how much
  would he receive if he stands 2 feet from the
  source at 20 minutes?
• 25mR            2 feet squared
   X              3 feet squared
• 25 mR         4 feet
   x               9 feet
• 4 x = 225
• X = 56 mR per hour
• 20 minutes/60 minutes = .33
• 56 mR x .33 = 18.48 mR at two feet for 20
  minutes
SEE YA!!! GOOD LUCK TO ALL THE
GRADUATES OF 2007!!!!!

				
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