Radiation Effects

Question 1

Gy

Answer 1

Joules per kg

Question 2

Relative Biological Effectiveness (RBE)

Answer 2

ratio of the dose of 250 keV x-rays to the dose of the test radiation that produce an equivalent biological effect.

Question 3

Dose Equivalent

Answer 3

Dose times quality factor (QF), arbitrarily assigned

Question 4

Effective Dose Equivalent

Answer 4

Dose equivalent multiplied by a weighting function depending on the tissue that is irradiated.

Question 5

Direct and Indirect Mechanisms of Cellular Damage

Answer 5

Particle damages the cells directly in DNA or other components, or for indirect, cytoplasm has ionization that produces free radical species

Question 6

Direct cellular damage can result in:

Answer 6

cell death or point mutation, or fatal mutation for the next generation

Question 7

Indirect cellular damage can result in:

Answer 7

membrane instability, DNA damage in cytoplasm, radical species

Question 8

Reactive Species Formed by Ionization

Answer 8

Free Radicals, Hydrogen Peroxide, Superoxide, Ozone

Question 9

Radiation effect during different cell cycles

Answer 9

Most sensitive in mitosis, least sensitive during S phase (where endonuclease is working the hardest)

Question 10

Apoptosis and p53

Answer 10

p53 gene regulates mitosis, and can lead to cell death from radiation. Mutation in p53 will lead to cancer.

Question 11

Mean lethal dose

Answer 11

Dose at which survival is 1/e (37%)

Question 12

Deterministic effects of radiation

Answer 12

Threshold radiation at which no effect is seen exists. Severity of damage due to radiation.

Question 13

Stochastic effects of radiation

Answer 13

Probability of cancer occurrence is stochastic. No threshold is reported for cancer occurrence.

Question 14

Skin Dose and Effects

Answer 14

2 Gy: temporary erythema, 3 Gy: epilation, 10 Gy: desquamation, 18 Gy: necrosis

Question 15

Hematopoietic Dose and Effects

Answer 15

0.1 Gy: chromosomal abnormalities in lymphocytes, 0.3 Gy: Lymphocytes lowered, 1 Gy: Granulocytes lowered, 4-6 Gy: increase in granulocyte count followed by total collapse

Question 16

Acute Radiation Syndrome

Answer 16

Prodromal, 10 Gy: fever, apathy, diarrhea; Cerebrovascular, 100 Gy: death, seizure, coma; Hematopoietic, 3-8 Gy: PANcytopenia

Question 17

LD-50/30 and LD-50/60

Answer 17

Dose to kill 50% of population in 30 or 60 days

Question 18

Effect of Radiation on Fetus

Answer 18

Neurological system affected the most. Malformations and mental retardation possible in first and second trimester. Possible childhood cancer correlation if irradiated late in fetal development.

Question 19

Absolute Risk

Answer 19

Incidence in EXPOSED group

Question 20

Relative Risk

Answer 20

Incidence in exposed group / incidence in unexposed group

Question 21

Excess Relative Risk

Answer 21

“Excess” risk caused by exposure, specifically Relative risk minus 1.

Question 22

Attributable Risk

Answer 22

1-1/(Relative Risk)

Question 23

Cancer Risk Models: BEIR VII Phase 2 (2006)

Answer 23

models of cancer risk based upon dose, age at exposure and attained age, linear-no threshold model assumed for all solid tumors; linear-quadratic for leukemia

Question 24

Radioresistance

Answer 24

p53 can mutate to develop resistance to radiation for cancer cells. Also radiation increases hypoxic population to increase (since oxygen radicalizes to kill cancer)