Radiography Exam Radiation Protection and Safety 1 — Questions and Answers
Question 1: Which principle of radiation protection is described as keeping radiation exposure As Low As Reasonably Achievable?
- ALARA (Correct answer)
- NCRP
- MPD
- HVL
Correct answer: ALARA
ALARA stands for As Low As Reasonably Achievable and is the foundational principle guiding all radiation protection practices.
ALARA (As Low As Reasonably Achievable) is mandated by the NRC and NCRP as the guiding principle for all radiation workers. It requires using the lowest dose necessary while still obtaining diagnostic-quality images. Practical ALARA measures include collimation, proper exposure factors, shielding, and distance.
Question 2: The recommended annual occupational effective dose limit for radiation workers in the United States is:
- 50 mSv (5 rem) (Correct answer)
- 100 mSv (10 rem)
- 20 mSv (2 rem)
- 150 mSv (15 rem)
Correct answer: 50 mSv (5 rem)
The NCRP recommends a maximum annual occupational effective dose limit of 50 mSv (5 rem) for radiation workers.
Per NCRP Report No. 116, the annual occupational effective dose limit is 50 mSv (5 rem). Additionally, there is a cumulative dose limit of 10 mSv × age in years. For the lens of the eye, the limit is 150 mSv/year, and for the skin and extremities it is 500 mSv/year.
Question 3: Which type of radiation monitoring device uses lithium fluoride crystals to measure accumulated radiation dose?
- TLD badge (Correct answer)
- Film badge
- Pocket dosimeter
- Geiger-Müller counter
Correct answer: TLD badge
Thermoluminescent dosimeters (TLDs) use lithium fluoride crystals that trap electrons when exposed to radiation; heating releases the energy as measurable light.
TLD badges contain lithium fluoride (LiF) crystals. When ionizing radiation passes through, electrons are trapped in the crystal lattice. Upon heating, these electrons release energy as visible light (thermoluminescence), which is measured to calculate dose. TLDs are more accurate than film badges and are not affected by heat or humidity.
Question 4: To reduce occupational radiation exposure, a radiographer should use which combination of protective strategies?
- Time, distance, and shielding (Correct answer)
- Collimation, filtration, and kVp
- mAs, kVp, and SID
- Grids, screens, and cassettes
Correct answer: Time, distance, and shielding
Time, distance, and shielding are the three cardinal principles of radiation protection for workers.
The three cardinal principles of radiation protection are: (1) minimize time of exposure, (2) maximize distance from the source (dose follows inverse square law), and (3) use appropriate shielding such as lead aprons, thyroid shields, and lead barriers. Doubling the distance reduces dose to one-quarter of the original.
Question 5: What is the minimum recommended lead equivalency for protective aprons used in fluoroscopy?
- 0.5 mm Pb (Correct answer)
- 0.25 mm Pb
- 1.0 mm Pb
- 0.1 mm Pb
Correct answer: 0.5 mm Pb
The minimum recommended lead equivalency for protective aprons used during fluoroscopy is 0.5 mm of lead.
NCRP and most regulatory bodies recommend a minimum of 0.5 mm lead equivalent for fluoroscopic protective aprons. Lighter 0.25 mm aprons may be used for lower-energy procedures but are not adequate for fluoroscopy. Wrap-around aprons should be used when the radiographer may be exposed from multiple directions.
Question 6: Which inverse square law calculation correctly determines the new dose rate when a radiographer moves from 1 meter to 3 meters from the radiation source?
- 1/9 of the original dose rate (Correct answer)
- 1/3 of the original dose rate
- 3 times the original dose rate
- 9 times the original dose rate
Correct answer: 1/9 of the original dose rate
The inverse square law states that intensity is inversely proportional to the square of the distance. Tripling the distance reduces dose to 1/9 (1/3² = 1/9).
The inverse square law: I₁/I₂ = D₂²/D₁². Moving from 1 m to 3 m: new intensity = original × (1/3)² = original/9. This demonstrates why increasing distance is highly effective — tripling distance reduces dose by 89%. This principle is fundamental to radiation safety calculations.
Radiography Exam Radiation Protection and Safety 1
Which principle of radiation protection is described as keeping radiation exposure As Low As Reasonably Achievable?