Physics Ch 11 Rad Biology

Question 1

what is linear energy transfer (LET)?

Answer 1

avg amt energy deposited per unit path length

Question 2

which synd is most sensitive to xrays?

Answer 2

ataxia telangiectasia

Question 3

cells are most sensitive during cell cycle phase –> order the parts of the cell cycle phase from most to least sensitive

Answer 3

M > G2 > G1 > S

Question 4

which part of GI tract is most radiosensitive?

Answer 4

small bowel

Question 5

acute radiation synd (ARS) –> what sx is a marker of severity/poor prognosis?

Answer 5

early vomiting

Question 6

what is LD 50/30? what is the typical LD 50/30 dose?

Answer 6

3-4Gy w/o tx –> kill 50% of ppl w/in 30 days

Question 7

rad effect on fetus –> most vulnerable time?

Answer 7

8-15wk

Question 8

fetus –> 8-15wk –> rad dose of 100-200 mGy –> assoc comp?

Answer 8

mental retard

Question 9

occupational worker –> exposure limit –> lens?

Answer 9

150 mSv/yr

Question 10

occupational worker –> exposure limit –> radiation worker?

Answer 10

50 mSv/yr

Question 11

occupational worker –> exposure limit –> extremity?

Answer 11

500 mSv/yr

Question 12

public –> exposure limit –> eff dose from background rad in USA?

Answer 12

3 mSv/yr

Question 13

public –> exposure limit –> preg?

Answer 13

0.5 mSv/mo

Question 14

MRI –> specific absorption ratio (RF power absorbed per unit mass) –> limit for whole body?

Answer 14

4 W/kg for whole body for 15min

Question 15

bone marrow synd –> estimated threshold?

Answer 15

2Gy

Question 16

GI synd –> estimated threshold?

Answer 16

8 Gy

Question 17

CNS synd –> estimated threshold?

Answer 17

20Gy

Question 18

general public –> risk of radiation-induced cancer (%/Sv)?

Answer 18

4-5% / Sv

Question 19

male –> temporary sterility –> estimated threshold?

Answer 19

0.15-2.5 Gy

Question 20

male –> permanent sterility –> estimated threshold?

Answer 20

5 Gy

Question 21

female –> sterility –> estimated threshold?

Answer 21

6 Gy (2-10 Gy)

Question 22

depress circulating lymphocytes –> estimated threshold?

Answer 22

0.25 Gy

Question 23

USA pop –> #1 contributor to effective dose?

Answer 23

55% –> radon

Question 24

permanent sterility –> M vs F?

Answer 24

6 Gy (M) vs 3 Gy (F)

Question 25

Dose?

• LD50/60 (BM)
• LD50/4 (GI)
• LD for CNS

Answer 25

• LD50/60 (BM): 5Gy
• LD50/4 (GI): 10
• LD for CNS: 20

Question 26

Xray generation –> leakage radiation –> should NOT exceed what dose at 1m from source?

Answer 26

1.0mGy/hr at 1m from source

Question 27

Diagnostic radiography unit operated at >70kVp –> must contain total filtration of how much Aluminum equivalent?

Answer 27

2.5mm

Question 28

USA –> avg person –> avg total effective dose annual?

Answer 28

6mSv

Question 29

Which tissue weighting factor is lowest? Lung, red BM, skin, breast, stomach?

Answer 29

Skin

Question 30

Gamma rays can be shielded using what materials? (2)

Answer 30

lead or concrete

Question 31

BEIR report VII –> gen pop –> radiation-induced CA –> avg risk of mortality?

Answer 31

5% per Sv

Question 32

fetal dosimetry –> dose?

• no risk of birth defect/intell disability/fetal death
• “gray zone” –> risk is uncertain but likely clinically too low to detect
• inc risk

Answer 32

• <50 mGy
• 50-100
• > 100

Question 33

fetal dosimetry –> inc risk of what in each gestational age?

• preimplantation (1-2wk)
• organogenesis (3-8wk)
• 9-15wk

Answer 33

• fetal death
• birth defect
• growth/intell disability

Question 34

fetal dosimetry –> risk of childhood cancer –> 2x inc –> at what rad dose?

Answer 34

25mGy