RSO Radiation Biology and Health Effects 1 — Questions and Answers
Question 1: What term describes the ability of ionizing radiation to cause biological damage by directly breaking chemical bonds in DNA?
- Direct action (Correct answer)
- Indirect action
- Linear energy transfer
- Relative biological effectiveness
Correct answer: Direct action
Direct action occurs when ionizing radiation interacts directly with critical biomolecules such as DNA, breaking chemical bonds without involving intermediate water radicals.
Question 2: Which type of radiation has the highest relative biological effectiveness (RBE) for causing biological damage?
- X-rays
- Gamma rays
- Alpha particles (Correct answer)
- Beta particles
Correct answer: Alpha particles
Alpha particles have the highest RBE because their dense ionization tracks cause clustered DNA damage that is difficult for cells to repair.
Question 3: The linear no-threshold (LNT) model assumes that radiation risk is:
- Zero below a threshold dose
- Proportional to dose at all levels with no safe threshold (Correct answer)
- Inversely proportional to dose rate
- Constant regardless of dose
Correct answer: Proportional to dose at all levels with no safe threshold
The LNT model postulates that any dose of radiation, no matter how small, carries a proportional cancer risk with no completely safe threshold.
Question 4: Acute radiation syndrome (ARS) typically requires a whole-body dose of at least:
- 10 mSv
- 100 mSv
- 1 Sv (Correct answer)
- 0.1 mSv
Correct answer: 1 Sv
ARS generally requires a whole-body absorbed dose of approximately 1 Sv (100 rem) delivered over a short period to produce clinically significant symptoms.
Question 5: Which organ system is most sensitive to radiation-induced damage in adults, making it the primary determinant of survival after high acute doses?
- Cardiovascular system
- Respiratory system
- Hematopoietic (bone marrow) system (Correct answer)
- Nervous system
Correct answer: Hematopoietic (bone marrow) system
The hematopoietic system is most radiosensitive in adults; bone marrow suppression leading to infection and hemorrhage is the dominant cause of death at moderate acute doses.
Question 6: Stochastic radiation effects such as cancer are characterized by:
- A threshold dose below which they cannot occur
- Severity increasing with dose
- Probability increasing with dose but severity independent of dose (Correct answer)
- Occurrence only after acute exposures
Correct answer: Probability increasing with dose but severity independent of dose
Stochastic effects have a probability of occurrence that increases with dose, but if the effect occurs, its severity does not depend on the dose received.
RSO Radiation Biology and Health Effects 1
What term describes the ability of ionizing radiation to cause biological damage by directly breaking chemical bonds in DNA?