RSO Radiation Biology and Health Effects 2 — Questions and Answers
Question 1: The term 'effective dose' accounts for which two factors beyond absorbed dose?
- Energy and time
- Radiation weighting factor and tissue weighting factor (Correct answer)
- Distance and shielding
- Dose rate and exposure duration
Correct answer: Radiation weighting factor and tissue weighting factor
Effective dose is calculated by multiplying absorbed dose by a radiation weighting factor (for radiation type) and then by tissue weighting factors (for organ sensitivity) to give a single risk estimate.
Question 2: Which of the following is a deterministic radiation effect?
- Leukemia
- Thyroid cancer
- Cataract of the eye lens (Correct answer)
- Hereditary mutations
Correct answer: Cataract of the eye lens
Cataracts are a deterministic effect with a threshold dose, meaning they only occur above a certain dose level, and severity increases with dose above that threshold.
Question 3: In radiobiology, the 'four Rs' of radiobiology include repair, reoxygenation, redistribution, and:
- Reproduction
- Repopulation (Correct answer)
- Resistance
- Regulation
Correct answer: Repopulation
The four Rs of radiobiology are repair of sublethal damage, reoxygenation of hypoxic cells, redistribution of cells through the cell cycle, and repopulation of surviving cells.
Question 4: The tissue weighting factor (wT) for the gonads in ICRP Publication 103 is:
- 0.20
- 0.08 (Correct answer)
- 0.12
- 0.05
Correct answer: 0.08
ICRP Publication 103 assigns gonads a tissue weighting factor of 0.08, reflecting their contribution to total detriment-adjusted risk from uniform whole-body irradiation.
Question 5: Which radiation-induced DNA lesion is considered the most biologically significant for cell killing and carcinogenesis?
- Single-strand break
- Base damage
- Double-strand break (Correct answer)
- Cross-link with protein
Correct answer: Double-strand break
Double-strand breaks (DSBs) are the most critical DNA lesions because both strands are severed, making faithful repair difficult and increasing the risk of chromosomal aberrations.
Question 6: A radiation worker receives an equivalent dose of 50 mSv to the lens of the eye in one year. According to current ICRP guidance, this:
- Exceeds the annual occupational lens dose limit of 20 mSv (Correct answer)
- Is below all occupational limits and requires no action
- Exceeds the annual whole-body limit but not the lens limit
- Triggers mandatory medical removal from work
Correct answer: Exceeds the annual occupational lens dose limit of 20 mSv
The current ICRP and NRC occupational lens dose limit is 20 mSv/year (averaged over 5 years, with no single year exceeding 50 mSv), and 50 mSv in one year approaches or exceeds this limit depending on the averaging approach.
