Radiation Biology

Document Sample
Radiation Biology Powered By Docstoc
					Radiation Biology
 Cellular Level
           Cell Sensitivity
           Radiolysis of Water
           Direct Effect/Indirect Effect
           Target Theory
 Radiation Effect
           Early Effects
                      Prodromal/Latent period/Manifest Illness

   {                  Hematopoietic Syndrome
                      GI Syndrome
                      CNS Syndrome
                      Local tissue damage
           Late Effects
                      Local Tissue Effect
                      Life Span shortening
 Radiation Protection
                      Time Distance Shielding
                      Shield Types
                      ALARA
                    Radiation Biology History


          1895-Roentgen announces discovery of X-rays

       1896-(4 months later) Reports of skin effects in x-ray
                           researchers
        1902-First cases of radiation induced skin cancer
                             reported
      1906-Pattern for differential radiosensitivity of tissues
                         was discovered.




Radiation Biology
Largest
sources of
man-made
radiation are
medical and
dental x-
rays.
THE EARLY YEARS
                   Radiation can cause
                   biological changes




             Technologists should have an
             understanding of:
             • Cellular biology
             • How radiation interacts with cells
               in order to protect oneself and the
               patient.




Radiation Biology
Cellular Level
                           •Radiation passes thru individual without any damage to
     No damage              cells

                           •Radiation causes injury to cell but cell is able to repair
    Injury/damage           damage


Cells incorrectly repair   •Cells repair but incorrectly causing deformity



       Cells die           •Radiation causes cell to die



                                        {    Cellular Levels
     Cell Sensitivity
Early Effect:

        radiation response occurs within minutes/days after exposure
        acute radiation syndrome
        local tissue damage

 Late Effect:

        radiation response not observable for months or years
        leukemia
         cataracts
        other cancers
        local tissue damage
        Life span shortening
        genetic damage
             • 1. Stem cells are radiosensitive.
  Law of     • 2. The younger the tissues and organs, the
               more radiosensitive
 Bergonie    • 3. When level of metabolic activity is high,
               radiosensitivity is high
    and      • 4. As proliferation rate for cells and growth
Tribondeau     rate for tissues increases, the radiosensitivity
               increases.




 Cell Sensitivity
Radiosensitivity   High                Intermediate      Low

                                          Endothelial
                    Lymphocytes                           Muscle cells
                                             cells




                    Spermatogonia         osteoblasts      Nerve cells




                    Erythroblasts         spermatids      Chondrocytes




                    Intestinal crypt
                                           fibroblasts
                          cells




Cell Sensitivity
                                                  Linear Response to
                                                        radiation:
                                            1. Non-threshold
                                                • Assumes no dose is
                                                  safe
                                            2. Threshold assumes
                                                • Minimum dose needed
                                                  to produce a response


A dose response relationship is produced by extrapolating high dose experimental
data to low doses.
Table 2-3: Groups Studied for Radiation Effects

Scott Sorenson, 2000.

Groups Studied for Health Effects
American Radiologists
Nuclear weapon survivors
Radiation-accident victims
Radiation-accident victims
Marshall Islanders (Atomic bomb fallout)
Residents with high levels of environmental radiation
Uranium miners
Radium watch-dial painters
Radioiodine patients
Ankylosing spondylitis patients (radiation therapy)
Thorotrast patients (radioactive contrast material)
Diagnostic irradiation in-utero
Cyclotron workers
     Diagnostic radiology is almost exclusively
   concerned with the late of effects for radiation
exposure. This assumes a linear non-threshold dose-
    response relationship. However, no dose is
                  considered safe.




Cell Sensitivity
     Basic Cell Structure
1.        Two parts:
     1.     Nucleus- contains
            DNA
     2.     Cytoplasm is 80%
            water

2.        DNA is at risk when
          a cell is exposed to
          ionizing radiation
     Genetic:     Somatic: All other
   Reproductive       cells, non-
      Cells       reproductive cells


Cell Structure
Ionization radiation interacts with a water (H2O). Water dissociates into
2 ions. This process creates free radicals. These are uncharged molecules
containing as single unpaired electron in outer shell.
1.   H 2 O molecules -
2.   Ejection of electron
     = free radical
3.   H2 0 2 = hydrogen
     peroxide

        Radiolysis of Water
HOH+   recombine to   H2O
Let’s Play Jenga !!
       Target theory suggests that a key molecule must be
       inactivated. The key molecule is assumed to be DNA.
• When interaction occurs between radiation and target molecule, it is
  considered a “hit”

• An indirect hit has a larger target area because of the mobility
  of the free radicals

• Radiation acts randomly.
B3…..miss……..A4…..hit…….You sunk my Battleship!!!
      ◊ Three different levels of exposure
        effects:

      ◊ Hematologic syndrome
      ◊ GI syndrome
      ◊ CNS syndrome



ACUTE RADIATION
SYNDROME
 Acute Radiation Syndrome – full body
 exposure given in a few minutes.
Each syndrome has 3 main sub-stages

      prodromal stage

      latent stage

      manifest illness

      cell death/repair



Early Effects
   Acute Radiation Syndromes – full body
    exposure given in a few minutes.


   3 stages of response:
         1. Prodromal -NVD stage
         (nausea, vomiting, diarrhea)

        2. Latent Period-Feels well while
    undergoing biological changes

         3. Manifest Illness-Full effects felt,
    leads to recovery or death

         Total Body Response to
         Radiation
1.   Hematologic : results in infection, hemorrhage
     & anemia

2.   Gastrointestinal : results in diarrhea, nausea &
     vomiting, fever

3.   Central Nervous System : results in convulsions,
     coma, & eventual death from increased
     intracranial pressure.
               CNS least sensitive in ADULTS –
                 MOST sensitive in the FETUS

        3 Radiation Syndromes
Cherynobyl Fall out
For Chernobyl:

o   11,000 mrem- current
    background in red zones
o   12 mrem is your average
    background radiation.
o    This is a thousand times greater
    than the normal background
    level of radiation
o   Approximately 15-20% of babies
    are born healthy.


      Exposure in soil & water
 ◊Late Effects
  ◊Local Tissue Effect
    ◊Erythema
    ◊Cataracts
  ◊Life Span Shortening
  ◊Cancers/Malignancies
  ◊Genetic Effects


Late Effects
     1.    Somatic Effects: develop in the
           individual who is exposed
            Most common:
              Skin Damage, Cataract
                formation & Carcinogenesis

     2.   Genetic Effects: develop in future
          generations as a result of damage to
          germ cells.



Late Effects of Radiation
      Fukushima 50 occupational
      exposure due to rescue work


After reading this article, write your thoughts on the rescue workers in Japan.
Include allowable exposures to workers, possible acute affects, their prognosis
for long term health.




Fukushima, Japan
       Cardinal Principles of Radiation Protection
             Time
             Distance
             Shielding

       ALARA




Radiation Protection
Cardinal Principles of
Radiation Protection
    {   Time Distance and Shielding
        Triad of Radiation Safety

                      1. Time
                      2. Distance
                      3. Shielding

     *Apply to the patient & Technologist



Cardinal Principles of
Protection
                 Skin
                 burns
                 from 30
                 min of
                 beam on
                 time




Over Radiation
       to Skin
Too much time
  under beam
Acute Localized Radiation Effects
The Table 2-2 provides examples of possible radiation effects to skin caused
by typical fluoroscopy exposures. Note that patient and technique factors can
substantially increase exposure rates, significantly reducing the time
necessary for the subsequent effect.
Table 2-2: Dose and Time to Initiate Localized Radiation Effects




                                                                          approximately 42 miutes
                                                                          .7 of an hour is
This is an actual arm tatoo. Now that’s dedication !




l
                              I




      r
                              r



      s
                              s




      e
                              e
                              e
                              v
                              n




      u




a
      a
      q




w
l
                             I




    r
                             r



    s
                             s




    e
                             e
                             e
                             v
                             n




    u




a
    a
    q




w
l
                                I




        r
                                r



        s
                                s




        e
                                e
                                v



                                e
                                n




        u




a
        a
        q




w
       Shielding


A lead protective shield is placed

       Between the x-ray tube and the
        individuals exposed
       Absorbs unnecessary radiation
1.   Contact
2.   Shaped
3.   Shadow

TYPES OF SHIELDING
S
H
I
E
L
D

T
Y
P
E
S
Breast Shield
Shadow shields
SHIELDING
1. TECHNOLOGIST . 25 mm LEAD
    Lead apron
    Gloves
    Thyroid shield
    Glasses

2. PATIENT – . 5 mm LEAD
   Gondal Shielding
As Low As Reasonably Achievable
Primary Barriers
Stay out of primary beam
  Image Wisely website




Image Wisely
PROTECTING THE
PATIENT


   RISK

   VS.

  REWARD

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:0
posted:3/9/2013
language:English
pages:55