ARRT Radiation and Safety 3 — Questions and Answers
Question 1: What is the recommended minimum distance a radiographer should stand from the patient during a portable radiographic exposure when a protective barrier is unavailable?
- 1 foot (0.3 m)
- 3 feet (0.9 m)
- 6 feet (1.8 m) (Correct answer)
- 10 feet (3 m)
Correct answer: 6 feet (1.8 m)
When no protective barrier is available, the technologist should stand at least 6 feet (1.8 m) from the patient and the primary beam.
Question 2: The dose equivalent limit for the lens of the eye for radiation workers is:
- 15 mSv/year
- 50 mSv/year
- 150 mSv/year (Correct answer)
- 500 mSv/year
Correct answer: 150 mSv/year
NCRP recommends a 150 mSv (15 rem) per year dose equivalent limit for the lens of the eye for occupational workers.
Question 3: Which interaction is primarily responsible for patient dose in diagnostic X-ray imaging?
- Classical (coherent) scattering
- Photoelectric effect (Correct answer)
- Compton scattering
- Pair production
Correct answer: Photoelectric effect
The photoelectric effect results in complete absorption of the X-ray photon by the tissue, contributing most significantly to patient dose in the diagnostic range.
Question 4: A radiation worker receives an extremity dose of 450 mSv in one year. This is:
- Below the annual extremity limit of 500 mSv (Correct answer)
- Above the annual extremity limit of 250 mSv
- Exactly at the extremity limit of 450 mSv
- Above the extremity limit of 100 mSv
Correct answer: Below the annual extremity limit of 500 mSv
The NCRP annual dose equivalent limit for extremities (hands and feet) is 500 mSv (50 rem), so 450 mSv is below the limit.
Question 5: During fluoroscopy, scatter radiation to personnel is greatest:
- At the image intensifier end of the table
- At the X-ray tube end of the table
- Directly beside the patient at the tabletop level (Correct answer)
- Behind a 0.5 mm Pb shield at any location
Correct answer: Directly beside the patient at the tabletop level
Scatter radiation is highest at the patient's tabletop level directly beside the patient, where primary beam interactions with tissue create the most scatter.
Question 6: What term describes the ability of radiation to produce ions as it passes through matter?
- Attenuation
- Ionization (Correct answer)
- Scintillation
- Excitation
Correct answer: Ionization
Ionization is the process by which radiation removes electrons from atoms, producing ion pairs and causing biological damage.
Question 7: Which of the following is NOT a cardinal principle of radiation protection?
- Time
- Distance
- Shielding
- Collimation (Correct answer)
Correct answer: Collimation
The three cardinal principles of radiation protection are time, distance, and shielding; collimation is an image quality and dose reduction technique but not a cardinal principle.
ARRT Radiation and Safety 3
What is the recommended minimum distance a radiographer should stand from the patient during a portable radiographic exposure when a protective barrier is unavailable?