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NMTCB-Style Radiation Safety Practice Exam Original Questions
with Answers & Rationales
High-Yield Review Outline: Radiation Safety
1. Basic Radiation Physics
• Ionizing radiation: radiation with enough energy to remove electrons from atoms (alpha, beta, gamma, X-rays)
• Non-ionizing radiation: ultraviolet, visible light, microwaves
• Radioactive decay: unstable nucleus emits particles/energy
o Alpha (α): heavy, 2+ charge, low penetration (stopped by paper, skin)
o Beta (β): electron, negative charge, moderate penetration (stopped by plastic)
o Gamma (γ): electromagnetic, no charge, high penetration (lead shielding)
• Half-life (T½): time for half of radioactive atoms to decay
• Decay modes: beta minus, beta plus (positron), electron capture, isomeric transition
2. Units of Measurement
• Exposure: roentgen (R) – ionization in air
• Absorbed dose: rad or gray (Gy); 1 Gy = 100 rad
• Dose equivalent: rem or sievert (Sv); 1 Sv = 100 rem
• Effective dose: accounts for tissue sensitivity; also rem/Sv
• Activity: curie (Ci) or becquerel (Bq); 1 Ci = 3.7 × 10¹⁰ Bq
• Conversion: 1 mCi = 37 MBq; 1 mSv = 100 mrem
3. Radiation Protection Principles
• ALARA: As Low As Reasonably Achievable
• Time, Distance, Shielding:
o Time: minimize exposure duration
o Distance: inverse square law (doubling distance reduces exposure to ¼)
o Shielding: lead, concrete, tungsten; beta emitters need plastic (low Z) to avoid bremsstrahlung
• Personal dosimeters: film badges, thermoluminescent dosimeters (TLD), optically stimulated luminescence (OSL),
pocket ionization chambers
• Dose limits (typical U.S. NRC):
o Occupational: 50 mSv (5 rem) whole body per year
,https://www.stuvia.com/user/performance
o Pregnant worker: 5 mSv (0.5 rem) over gestation, 0.5 mSv/month
o General public: 1 mSv (100 mrem) per year
4. Nuclear Medicine Specifics
• Radiopharmaceuticals: technetium-99m (most common), iodine-131, fluorine-18 (PET), gallium-67, indium-111
• Tc-99m half-life: 6 hours; gamma energy 140 keV (ideal for gamma camera)
• F-18 half-life: 110 minutes; positron emitter; used in PET
• I-131 half-life: 8 days; beta and gamma; used for thyroid therapy; requires isolation
• Radiation detection instruments:
o Geiger-Müller (GM) counter: high sensitivity, detects presence of radiation
o Ionization chamber: measures exposure rates
o Scintillation detector: gamma camera, well counter
o Dose calibrator: measures activity of radiopharmaceuticals
• Contamination control: wipe tests, surveys, decontamination, radioactive waste disposal
• Patient preparation and post-procedure instructions: hydration, voiding, avoiding close contact with pregnant
women/children for certain studies/therapies
5. Regulations and Agencies
• NRC (Nuclear Regulatory Commission): regulates byproduct nuclear material
• Agreement states: assume regulatory authority from NRC
• FDA: approves radiopharmaceuticals
• DOT: regulates transport of radioactive materials
• OSHA: worker safety, including radiation hazards communication
6. Biological Effects
• Deterministic effects: threshold dose; severity increases with dose (e.g., skin erythema, cataracts, sterility)
• Stochastic effects: no threshold; probability increases with dose (e.g., cancer, genetic effects)
• Acute radiation syndrome: occurs at high doses (>1 Gy whole body); stages: prodromal, latent, manifest illness,
recovery or death
• Radiation sensitivity: rapidly dividing cells most sensitive (bone marrow, GI mucosa, gonads, skin)
7. Shielding Calculations
• Half-value layer (HVL): thickness of material that reduces radiation intensity by half
• Tenth-value layer (TVL): reduces to one-tenth
• Inverse square law: I₁/I₂ = (D₂/D₁)²
, https://www.stuvia.com/user/performance
• Decay calculations: A = A₀ × e^(-0.693t/T½)
Original Practice Questions (50 Questions)
Choose the best answer for each question.
1. A nuclear medicine technologist is working with a 10 mCi
Tc-99m source at a distance of 2 feet. If the technologist
moves to a distance of 6 feet, what is the new exposure
rate?
A. Same
B. One-third
C. One-ninth
D. One-sixth
Answer: C
Rationale: Inverse square law: doubling distance reduces
exposure to ¼, tripling distance reduces to 1/9. From 2 ft
to 6 ft is triple distance, so exposure is 1/9 of original.
2. Which type of radiation is most penetrating and requires
lead shielding?
A. Alpha
B. Beta
C. Gamma
D. Positron (before annihilation)
Answer: C
Rationale: Gamma rays are high-energy electromagnetic
NMTCB-Style Radiation Safety Practice Exam Original Questions
with Answers & Rationales
High-Yield Review Outline: Radiation Safety
1. Basic Radiation Physics
• Ionizing radiation: radiation with enough energy to remove electrons from atoms (alpha, beta, gamma, X-rays)
• Non-ionizing radiation: ultraviolet, visible light, microwaves
• Radioactive decay: unstable nucleus emits particles/energy
o Alpha (α): heavy, 2+ charge, low penetration (stopped by paper, skin)
o Beta (β): electron, negative charge, moderate penetration (stopped by plastic)
o Gamma (γ): electromagnetic, no charge, high penetration (lead shielding)
• Half-life (T½): time for half of radioactive atoms to decay
• Decay modes: beta minus, beta plus (positron), electron capture, isomeric transition
2. Units of Measurement
• Exposure: roentgen (R) – ionization in air
• Absorbed dose: rad or gray (Gy); 1 Gy = 100 rad
• Dose equivalent: rem or sievert (Sv); 1 Sv = 100 rem
• Effective dose: accounts for tissue sensitivity; also rem/Sv
• Activity: curie (Ci) or becquerel (Bq); 1 Ci = 3.7 × 10¹⁰ Bq
• Conversion: 1 mCi = 37 MBq; 1 mSv = 100 mrem
3. Radiation Protection Principles
• ALARA: As Low As Reasonably Achievable
• Time, Distance, Shielding:
o Time: minimize exposure duration
o Distance: inverse square law (doubling distance reduces exposure to ¼)
o Shielding: lead, concrete, tungsten; beta emitters need plastic (low Z) to avoid bremsstrahlung
• Personal dosimeters: film badges, thermoluminescent dosimeters (TLD), optically stimulated luminescence (OSL),
pocket ionization chambers
• Dose limits (typical U.S. NRC):
o Occupational: 50 mSv (5 rem) whole body per year
,https://www.stuvia.com/user/performance
o Pregnant worker: 5 mSv (0.5 rem) over gestation, 0.5 mSv/month
o General public: 1 mSv (100 mrem) per year
4. Nuclear Medicine Specifics
• Radiopharmaceuticals: technetium-99m (most common), iodine-131, fluorine-18 (PET), gallium-67, indium-111
• Tc-99m half-life: 6 hours; gamma energy 140 keV (ideal for gamma camera)
• F-18 half-life: 110 minutes; positron emitter; used in PET
• I-131 half-life: 8 days; beta and gamma; used for thyroid therapy; requires isolation
• Radiation detection instruments:
o Geiger-Müller (GM) counter: high sensitivity, detects presence of radiation
o Ionization chamber: measures exposure rates
o Scintillation detector: gamma camera, well counter
o Dose calibrator: measures activity of radiopharmaceuticals
• Contamination control: wipe tests, surveys, decontamination, radioactive waste disposal
• Patient preparation and post-procedure instructions: hydration, voiding, avoiding close contact with pregnant
women/children for certain studies/therapies
5. Regulations and Agencies
• NRC (Nuclear Regulatory Commission): regulates byproduct nuclear material
• Agreement states: assume regulatory authority from NRC
• FDA: approves radiopharmaceuticals
• DOT: regulates transport of radioactive materials
• OSHA: worker safety, including radiation hazards communication
6. Biological Effects
• Deterministic effects: threshold dose; severity increases with dose (e.g., skin erythema, cataracts, sterility)
• Stochastic effects: no threshold; probability increases with dose (e.g., cancer, genetic effects)
• Acute radiation syndrome: occurs at high doses (>1 Gy whole body); stages: prodromal, latent, manifest illness,
recovery or death
• Radiation sensitivity: rapidly dividing cells most sensitive (bone marrow, GI mucosa, gonads, skin)
7. Shielding Calculations
• Half-value layer (HVL): thickness of material that reduces radiation intensity by half
• Tenth-value layer (TVL): reduces to one-tenth
• Inverse square law: I₁/I₂ = (D₂/D₁)²
, https://www.stuvia.com/user/performance
• Decay calculations: A = A₀ × e^(-0.693t/T½)
Original Practice Questions (50 Questions)
Choose the best answer for each question.
1. A nuclear medicine technologist is working with a 10 mCi
Tc-99m source at a distance of 2 feet. If the technologist
moves to a distance of 6 feet, what is the new exposure
rate?
A. Same
B. One-third
C. One-ninth
D. One-sixth
Answer: C
Rationale: Inverse square law: doubling distance reduces
exposure to ¼, tripling distance reduces to 1/9. From 2 ft
to 6 ft is triple distance, so exposure is 1/9 of original.
2. Which type of radiation is most penetrating and requires
lead shielding?
A. Alpha
B. Beta
C. Gamma
D. Positron (before annihilation)
Answer: C
Rationale: Gamma rays are high-energy electromagnetic
