CHP Biological Effects of Radiation 3

Question 1

The oxygen enhancement ratio (OER) for low-LET radiation is approximately:

Accepted Answer

2.5–3.0

Answer

For low-LET radiation such as X-rays and gamma rays, the OER is approximately 2.5–3.0, meaning hypoxic cells require 2.5–3 times more dose to achieve the same level of killing as well-oxygenated cells.

Question 2

Which of the following radiation-induced chromosome aberrations is considered an 'unstable' aberration that is eliminated from the dividing cell population over time?

Accepted Answer

Dicentic chromosome

Answer

Dicentric chromosomes are unstable aberrations because they cause problems during cell division (bridge-breakage-fusion cycles), leading to cell death and their loss from the proliferating population over time.

Question 3

The latency period for radiation-induced solid tumors in humans is typically:

Accepted Answer

5–10 years or more

Answer

Radiation-induced solid tumors typically have a latency period of at least 5–10 years, with many tumors appearing decades after exposure, as seen in atomic bomb survivor data.

Question 4

Which model best describes the relationship between radiation dose and cancer risk at low doses used in current radiation protection?

Accepted Answer

Linear-quadratic model extrapolated to zero (LNT)

Answer

The linear no-threshold (LNT) model, derived from the linear-quadratic fit at high doses, is the basis of current radiation protection and assumes cancer risk is proportional to dose with no safe threshold.

Question 5

Radiation-induced cataracts are classified as:

Accepted Answer

Deterministic effects occurring at doses above a threshold, now revised downward to ~0.5 Gy

Answer

Cataracts are deterministic effects; ICRP now recognizes a threshold of approximately 0.5 Gy acute dose (or equivalent fractionated dose), revised downward from the previously assumed 2–10 Gy.

(CHP) Certified Health Physicist Practice Test

(CHP) Certified Health Physicist Practice Test

CHP Biological Effects of Radiation 3