ARRT Radiation Protection Principles 2 — Questions and Answers
Question 1: Which quantity is used to express the effective dose received by a radiation worker and accounts for tissue sensitivity?
- Absorbed dose (Gy)
- Equivalent dose (Sv)
- Effective dose (Sv) (Correct answer)
- Exposure (C/kg)
Correct answer: Effective dose (Sv)
Effective dose (Sv) weights equivalent doses by tissue weighting factors to reflect overall biological risk to the whole body.
Question 2: A radiographer doubles the distance from a fluoroscopy unit. By what factor does the radiation intensity change?
- Decreases by half
- Decreases by one-fourth (Correct answer)
- Decreases by one-third
- Remains the same
Correct answer: Decreases by one-fourth
According to the inverse square law, doubling the distance reduces intensity to 1/4 of the original value.
Question 3: Which type of radiation interaction is primarily responsible for photoelectric absorption in diagnostic radiology?
- Compton scatter
- Pair production
- Coherent scatter
- Photoelectric effect (Correct answer)
Correct answer: Photoelectric effect
The photoelectric effect dominates at lower kVp ranges used in diagnostic radiology, where the photon is completely absorbed by an inner-shell electron.
Question 4: What is the recommended annual occupational effective dose limit for radiation workers in the US according to NCRP?
- 10 mSv
- 20 mSv
- 50 mSv (Correct answer)
- 100 mSv
Correct answer: 50 mSv
NCRP Report No. 116 sets the annual occupational effective dose limit at 50 mSv (5 rem).
Question 5: Which material provides the most effective shielding against scatter radiation in a radiographic suite?
- Aluminum
- Concrete or lead (Correct answer)
- Plastic
- Wood
Correct answer: Concrete or lead
Lead and concrete are used for primary and secondary barriers because of their high atomic number and density, which attenuate X-rays effectively.
Question 6: A pregnant technologist should limit fetal dose to no more than how much over the entire gestational period, per NCRP?
- 1 mSv (0.1 rem)
- 5 mSv (0.5 rem) (Correct answer)
- 10 mSv (1 rem)
- 50 mSv (5 rem)
Correct answer: 5 mSv (0.5 rem)
NCRP recommends the fetal dose not exceed 5 mSv (0.5 rem) over the entire gestation once pregnancy is declared.
Question 7: Which beam-limiting device is most effective at reducing patient dose and improving image contrast?
- Heel effect compensator
- Collimator (Correct answer)
- Compensating filter
- Anti-scatter grid
Correct answer: Collimator
Collimation restricts the primary beam to the area of clinical interest, reducing scatter production and patient dose.
ARRT Radiation Protection Principles 2
Which quantity is used to express the effective dose received by a radiation worker and accounts for tissue sensitivity?