ARRT Radiation Protection Principles 3 — Questions and Answers
Question 1: What does the acronym ALARA stand for in radiation protection?
- As Low As Reasonably Achievable (Correct answer)
- As Low As Radiation Allows
- Allowable Limit And Radiation Attenuation
- Administered Level And Risk Assessment
Correct answer: As Low As Reasonably Achievable
ALARA stands for 'As Low As Reasonably Achievable' and is the guiding principle for minimizing radiation exposure.
Question 2: Which of the following exposure factors would result in the highest patient dose during a radiographic procedure?
- High kVp, low mAs
- Low kVp, high mAs (Correct answer)
- High kVp, high mAs
- Low kVp, low mAs
Correct answer: Low kVp, high mAs
Low kVp increases photoelectric interactions and beam absorption, and high mAs increases the number of photons, together yielding the highest patient dose.
Question 3: Protective lead aprons used in fluoroscopy are typically equivalent to what lead thickness?
- 0.125 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 provide 0.5 mm Pb equivalency, attenuating approximately 90–95% of scatter radiation at fluoroscopic energies.
Question 4: Which of the following best describes stochastic radiation effects?
- Effects with a threshold dose below which no harm occurs
- Effects whose severity increases with dose
- Effects whose probability increases with dose but have no threshold (Correct answer)
- Deterministic effects occurring at high doses
Correct answer: Effects whose probability increases with dose but have no threshold
Stochastic effects (e.g., cancer, genetic effects) have no established threshold; their probability increases with dose.
Question 5: During fluoroscopy, where should the radiographer stand to minimize scatter exposure?
- At the tube end of the table
- As close to the patient as possible
- At a 90-degree angle to the primary beam, at maximum distance (Correct answer)
- Directly behind the image intensifier
Correct answer: At a 90-degree angle to the primary beam, at maximum distance
Standing at 90 degrees to the primary beam and maximizing distance reduces scatter dose by applying both angular and inverse-square-law benefits.
Question 6: What is the primary purpose of a secondary protective barrier in a radiographic room?
- Attenuate the primary beam
- Shield against scatter and leakage radiation (Correct answer)
- Collimate the X-ray beam
- Filter low-energy photons from the primary beam
Correct answer: Shield against scatter and leakage radiation
Secondary barriers are designed to attenuate scatter and leakage radiation, which travel in all directions from the patient and tube housing.
Question 7: A OSL dosimeter measures occupational radiation dose using which principle?
- Ionization of a gas-filled chamber
- Darkening of photographic film
- Stimulated luminescence from aluminum oxide crystals (Correct answer)
- Thermoluminescence from lithium fluoride crystals
Correct answer: Stimulated luminescence from aluminum oxide crystals
Optically stimulated luminescence (OSL) dosimeters use aluminum oxide crystals that emit light proportional to absorbed dose when stimulated by laser light.
ARRT Radiation Protection Principles 3
What does the acronym ALARA stand for in radiation protection?