CRA CRA Radiation Physics & Safety 2 — Questions and Answers
Question 1: Which regulatory body is responsible for overseeing radiation safety in medical facilities using radioactive materials in the United States?
- OSHA
- EPA
- NRC (Nuclear Regulatory Commission) (Correct answer)
- FDA
Correct answer: NRC (Nuclear Regulatory Commission)
The NRC regulates the civilian use of radioactive materials, including those used in nuclear medicine and radiation therapy.
Question 2: What is the purpose of collimation in diagnostic radiology?
- To increase radiation output from the X-ray tube
- To limit the X-ray beam to the area of clinical interest and reduce patient dose (Correct answer)
- To filter out high-energy photons from the beam
- To reduce the heat generated in the X-ray tube anode
Correct answer: To limit the X-ray beam to the area of clinical interest and reduce patient dose
Collimation restricts the X-ray beam to the area of interest, reducing unnecessary radiation exposure to the patient and improving image quality.
Question 3: Which type of radiation interaction with matter is most responsible for photoelectric effect in diagnostic radiology?
- High-energy photons interacting with outer-shell electrons
- Low-energy photons interacting with inner-shell electrons (Correct answer)
- Neutrons interacting with atomic nuclei
- Alpha particles interacting with tissue
Correct answer: Low-energy photons interacting with inner-shell electrons
The photoelectric effect occurs when a low-energy photon is completely absorbed by and ejects an inner-shell electron from an atom.
Question 4: A lead apron used for radiation protection in diagnostic radiology typically provides an attenuation equivalent of:
- 0.1 mm Pb
- 0.25 mm Pb
- 0.5 mm Pb (Correct answer)
- 1.0 mm Pb
Correct answer: 0.5 mm Pb
Standard lead aprons used in diagnostic radiology are typically equivalent to 0.5 mm of lead, providing approximately 90% attenuation of scatter radiation.
Question 5: Radiation-induced health effects that have a threshold dose below which no harm occurs and increase in severity with dose are called:
- Stochastic effects
- Deterministic (non-stochastic) effects (Correct answer)
- Genetic effects
- Latent effects
Correct answer: Deterministic (non-stochastic) effects
Deterministic effects (e.g., radiation burns, cataracts) occur above a threshold dose and worsen in severity as dose increases.
Question 6: In a radiology department, which area classification requires the MOST stringent radiation shielding design?
- Waiting room adjacent to imaging suite
- Control booth behind protective barrier
- Radiographic room housing the X-ray equipment (Correct answer)
- Staff break room one floor above imaging
Correct answer: Radiographic room housing the X-ray equipment
The radiographic room is the primary radiation area with the highest dose rates, requiring the most robust shielding by design.
CRA CRA Radiation Physics & Safety 2
Which regulatory body is responsible for overseeing radiation safety in medical facilities using radioactive materials in the United States?