ARRT Radiation Protection Principles 5 — Questions and Answers
Question 1: During a portable chest X-ray, the technologist should stand at least how far from the patient if no protective barrier is available?
- 1 foot (30 cm)
- 3 feet (1 meter)
- 6 feet (2 meters) (Correct answer)
- 10 feet (3 meters)
Correct answer: 6 feet (2 meters)
Standing at least 6 feet (2 meters) from the patient and outside the primary beam significantly reduces scatter exposure during portable radiography.
Question 2: What type of radiation exposure effect describes cataracts developing after high-dose exposure to the eye?
- Stochastic effect
- Deterministic (nonstochastic) effect (Correct answer)
- Hereditary effect
- Carcinogenic effect
Correct answer: Deterministic (nonstochastic) effect
Cataracts are a deterministic effect with a dose threshold; severity increases with dose above the threshold.
Question 3: Which of the following best defines the concept of 'workload' (W) in shielding calculations for a radiographic room?
- Number of patients per week
- Weekly total of mA-minutes at a reference kVp (Correct answer)
- Total time the X-ray unit is energized per day
- Number of radiographic exposures per hour
Correct answer: Weekly total of mA-minutes at a reference kVp
Workload (W) is expressed in mA-min per week and represents the total amount of radiation produced, used in NCRP shielding design calculations.
Question 4: A technologist's monthly dosimeter reading shows 5 mSv. Which action is most appropriate?
- No action needed; this is within annual limits
- Immediately notify radiation safety officer as this exceeds monthly limits
- Investigate work practices and potential sources of elevated exposure (Correct answer)
- Discontinue working in radiation areas for the remainder of the year
Correct answer: Investigate work practices and potential sources of elevated exposure
5 mSv in one month is elevated (10% of the annual limit) and warrants investigation of work practices, even though it is not a regulatory violation.
Question 5: Which interaction between X-ray photons and matter is the primary source of occupational scatter radiation in diagnostic imaging?
- Photoelectric effect
- Compton scatter (Correct answer)
- Pair production
- Photonuclear reaction
Correct answer: Compton scatter
Compton scatter is the dominant interaction at diagnostic energies (above ~30 keV) and is the main source of scatter radiation reaching the technologist.
Question 6: The use of gonadal shielding is indicated when the gonads are within how many centimeters of the primary beam edge?
- 1 cm
- 3 cm
- 5 cm (Correct answer)
- 10 cm
Correct answer: 5 cm
Gonadal shielding should be used when the gonads are within 5 cm of the primary beam to protect these radiosensitive reproductive organs.
Question 7: Which of the following correctly describes the use factor (U) in radiation shielding design?
- Fraction of the workweek the X-ray unit is in use
- Fraction of time the primary beam is directed at a particular barrier (Correct answer)
- Number of occupants in adjacent areas
- Ratio of scattered to primary radiation
Correct answer: Fraction of time the primary beam is directed at a particular barrier
The use factor (U) represents the fraction of time the primary beam is directed toward a specific wall, floor, or ceiling during normal operations.
ARRT Radiation Protection Principles 5
During a portable chest X-ray, the technologist should stand at least how far from the patient if no protective barrier is available?