Radiation biology Flashcards
What units is exposure measured in?
Roentgens (R)
What unit is absorbed dose in?
Gray or Rads (1 Gy = 100 rads) Energy absorbed - a physical quantity
How is Equivalent dose calculated and what unit is it in?
Absorbed dose x weighting factor (x-rays = 1, alpha particles = 20) Sievert (Biologic effect - corrected for type of radiation)
How is Effective dose calculated and what unit is it in?
Effective dose = Eq dose x tissue weighting factor Sievert Biologic effect on tissue type (if whole body then equal to equivalent dose)
Most sensitive phase of cell cycle
M-phase > G2 > G1 > S
Law of Bergonie and Tribondeau
Cell sensitivity is directly related to reproductive activity and inversely related to differentiation
Acut Radiation Syndromes
(1) Organ systems
(2) Doses
(3) Latent Period
Some perspective mGy is a diagnostic dose (30 mGy for CT AP)
Gy is a dose that makes you sick
What symptom is a marker for severity and prognosis in cases of possible acute radiation syndrome?
Vomiting
LD 50/30 for a person
3-4 Gy without treatment
Up to 8.5 Gy with treatment
Dose and onset of: Early Transient Erythema
2 Gy skin dose; hours
Dose and onset of: Severe “Robust” Erythema
6 Gy skin dose; 1 week
Dose and onset of: Telangiectasia
10 Gy skin dose; 52 weeks
Dose and onset of: Dry desquamation
13 Gy skin dose; 4 weeks
Dose and onset of: Moist desquamation / ulceration
18 Gy skin dose; 4 weeks
Dose and onset of: Secondary ulceration
24 Gy skin dose; > 6 weeks
Dose and onset of: Temporary epilation
3 Gy; 21 days
Dose and onset of: Permanent epilation
7 Gy; 21 days
Acute exposrure threshold to cause cataract
0.5 - 2.5 Gy
Annual Dose Rate Limit for cataracts
150 m Sv
Senile cataracts affect the anterior lens; radiation induced cataracts tend to involve the posterior lens
Temporary and Permanent Sterility/Infertility
- Male Temporary: 0.15 - 2.5 Gy
- Male Permanent: 5 Gy
- Female at age 12: 10 Gy
- Female at age 45: 2 Gy
- Female of unknown age: 6 Gy
Dose to cause symptom: Nausea (30% of people)
0.75 - 1.25 Gy WB
Dose to cause symptom: Depress circulating lymphocytes
0.25 Gy WB
Dose to cause symptom: LD 50/60 (Marrow)
3-4 Gy WB
Dose to cause symptom: LD 50/4 (GI)
8-10 Gy WB
Dose to cause symptom: LD for CNS
>20 Gy (20 -100) WB
Dose to cause symptom: Double the natural or spontaneous mutation rate
1 Gy
Dose to cause symptom: Effective dose from background radiation in the US
3 mSV per year
Sentinal event dose
15 Gy
Occupation exposure limits to lens, radiation worker and extremity (mSv/year)
150, 50, 500
Public exposure limit
1 mSv/year (continuous)
5 mSv/year (infrequent)
Public exposure limit: Embryo/fetus via mother
5 mSv/year (1mSv to fetus directly)
Public exposure limit: Embryo fetus (post declared pregnancy)
0.5 mSv/month
Public exposure limit: Controlled Areas
50 mSv/month
Public exposure limit: Uncontrolled areas
5 mSv/year
Genetically significant dose
0.25 mSv
Effective dose from background radiation in the US
3 mSv per year
