Nuclear Medicine – NMTCB Practice Exam 2026/2027
This study guide covers the five major NMTCB content domains: Radiation Physics and
Detection, Radiation Safety and Regulations, Pharmaceutical and Radiopharmaceutical Agents,
Instrumentation Operation and Quality Control, and Clinical Procedures. Candidates will review
radionuclide characteristics, radiopharmacy calculations, imaging instrumentation, quality
assurance procedures, SPECT/PET imaging principles, patient care, and diagnostic nuclear
medicine protocols commonly encountered in clinical practice. The material is designed to
strengthen technical knowledge, reinforce clinical decision-making skills, and support
comprehensive preparation for the Certified Nuclear Medicine Technologist (CNMT)
certification examination
Question 1
The decay of Molybdenum-99 to Technetium-99m occurs through which type of
radioactive decay?
A) Alpha decay
B) Beta decay followed by isomeric transition
C) Positron emission
D) Electron capture
Answer: B) Beta decay followed by isomeric transition
Rationale: Molybdenum-99 decays by beta emission to Technetium-99m (metastable
state), which then undergoes isomeric transition (gamma emission) to Technetium-99
(ground state). This is the principle behind the Tc-99m generator.
Question 2
The technetium-99m generator is typically eluted how often?
A) Daily
B) Weekly
C) Monthly
D) Every 6 hours
,Answer: A) Daily
Rationale: Tc-99m generators are typically eluted daily (or more frequently if needed, e.g.,
every 6-8 hours). The generator is "milked" to obtain Tc-99m, which has built up from the
decay of Mo-99. Eluting daily maximizes yield and ensures adequate activity for clinical
procedures.
Question 3
What is the "breakthrough" in a Tc-99m generator quality control?
A) Presence of aluminum ions in the eluate
B) Presence of Mo-99 in the eluate
C) Presence of Tc-99 in the eluate
D) Presence of saline in the eluate
Answer: B) Presence of Mo-99 in the eluate
Rationale: Breakthrough refers to the presence of the parent isotope (Mo-99) in the eluate.
Mo-99 breakthrough is strictly limited (<0.15 µCi Mo-99 per mCi of Tc-99m) because Mo-
99 has a longer half-life (66 hours), higher energy, and contributes additional patient
radiation dose.
Question 4
Which of the following is the recommended collimator for imaging I-131?
A) Low-energy, high-resolution collimator
B) Medium-energy collimator
C) High-energy collimator
D) Pinhole collimator
Answer: C) High-energy collimator
Rationale: I-131 emits high-energy gamma photons (364 keV) and requires a high-energy
collimator with thick septa to prevent septal penetration and maintain image quality.
Low- and medium-energy collimators are not suitable for high-energy isotopes.
,Question 5
Which radiopharmaceutical is used for sentinel lymph node mapping?
A) Tc-99m Sulfur Colloid
B) Tc-99m MDP
C) Tc-99m Sestamibi
D) Tc-99m DTPA
Answer: A) Tc-99m Sulfur Colloid
Rationale: Tc-99m sulfur colloid (or filtered sulfur colloid) is the radiopharmaceutical of
choice for sentinel lymph node mapping in breast cancer, melanoma, and other cancers.
The particles are injected peri-tumorally and migrate through the lymphatic system to the
sentinel node.
Question 6
The particle size of Tc-99m sulfur colloid for lymphoscintigraphy is typically:
A) Less than 100 nm (filtered)
B) 100-200 nm (filtered)
C) 200-500 nm (unfiltered)
D) 1-5 microns
Answer: A) Less than 100 nm (filtered)
Rationale: For sentinel lymph node mapping, filtered sulfur colloid (particles less than 100
nm, typically 50-100 nm) is used to allow movement through lymphatic channels while
being trapped in the sentinel node. Larger particles may not migrate as effectively.
Question 7
Which of the following is a common adverse reaction to radiopharmaceuticals?
, A) Anaphylaxis
B) Nausea
C) Rash
D) All of the above
Answer: D) All of the above
Rationale: Adverse reactions to radiopharmaceuticals are rare but can include anaphylaxis
(severe, rare), nausea, rash, flushing, hypotension, and other symptoms. Patients should be
monitored for allergic reactions, especially with certain agents like MAA (albumin).
Question 8
The "blood pool" phase of a three-phase bone scan is obtained at approximately:
A) Immediately after injection (flow phase)
B) 5-10 minutes after injection (blood pool/soft tissue phase)
C) 2-4 hours after injection (delayed bone phase)
D) 24 hours after injection
Answer: B) 5-10 minutes after injection (blood pool/soft tissue phase)
Rationale: The three-phase bone scan includes: Phase 1 (flow/angiographic phase) – 1-2
minutes after injection; Phase 2 (blood pool/soft tissue phase) – 5-10 minutes after
injection; Phase 3 (delayed phase/bone uptake) – 2-4 hours after injection.
Question 9
Which of the following conditions is best evaluated by a three-phase bone scan?
A) Osteomyelitis vs. cellulitis
B) Bone metastasis
C) Fracture
D) Arthritis
Answer: A) Osteomyelitis vs. cellulitis
Rationale: The three-phase bone scan is particularly useful for differentiating osteomyelitis
This study guide covers the five major NMTCB content domains: Radiation Physics and
Detection, Radiation Safety and Regulations, Pharmaceutical and Radiopharmaceutical Agents,
Instrumentation Operation and Quality Control, and Clinical Procedures. Candidates will review
radionuclide characteristics, radiopharmacy calculations, imaging instrumentation, quality
assurance procedures, SPECT/PET imaging principles, patient care, and diagnostic nuclear
medicine protocols commonly encountered in clinical practice. The material is designed to
strengthen technical knowledge, reinforce clinical decision-making skills, and support
comprehensive preparation for the Certified Nuclear Medicine Technologist (CNMT)
certification examination
Question 1
The decay of Molybdenum-99 to Technetium-99m occurs through which type of
radioactive decay?
A) Alpha decay
B) Beta decay followed by isomeric transition
C) Positron emission
D) Electron capture
Answer: B) Beta decay followed by isomeric transition
Rationale: Molybdenum-99 decays by beta emission to Technetium-99m (metastable
state), which then undergoes isomeric transition (gamma emission) to Technetium-99
(ground state). This is the principle behind the Tc-99m generator.
Question 2
The technetium-99m generator is typically eluted how often?
A) Daily
B) Weekly
C) Monthly
D) Every 6 hours
,Answer: A) Daily
Rationale: Tc-99m generators are typically eluted daily (or more frequently if needed, e.g.,
every 6-8 hours). The generator is "milked" to obtain Tc-99m, which has built up from the
decay of Mo-99. Eluting daily maximizes yield and ensures adequate activity for clinical
procedures.
Question 3
What is the "breakthrough" in a Tc-99m generator quality control?
A) Presence of aluminum ions in the eluate
B) Presence of Mo-99 in the eluate
C) Presence of Tc-99 in the eluate
D) Presence of saline in the eluate
Answer: B) Presence of Mo-99 in the eluate
Rationale: Breakthrough refers to the presence of the parent isotope (Mo-99) in the eluate.
Mo-99 breakthrough is strictly limited (<0.15 µCi Mo-99 per mCi of Tc-99m) because Mo-
99 has a longer half-life (66 hours), higher energy, and contributes additional patient
radiation dose.
Question 4
Which of the following is the recommended collimator for imaging I-131?
A) Low-energy, high-resolution collimator
B) Medium-energy collimator
C) High-energy collimator
D) Pinhole collimator
Answer: C) High-energy collimator
Rationale: I-131 emits high-energy gamma photons (364 keV) and requires a high-energy
collimator with thick septa to prevent septal penetration and maintain image quality.
Low- and medium-energy collimators are not suitable for high-energy isotopes.
,Question 5
Which radiopharmaceutical is used for sentinel lymph node mapping?
A) Tc-99m Sulfur Colloid
B) Tc-99m MDP
C) Tc-99m Sestamibi
D) Tc-99m DTPA
Answer: A) Tc-99m Sulfur Colloid
Rationale: Tc-99m sulfur colloid (or filtered sulfur colloid) is the radiopharmaceutical of
choice for sentinel lymph node mapping in breast cancer, melanoma, and other cancers.
The particles are injected peri-tumorally and migrate through the lymphatic system to the
sentinel node.
Question 6
The particle size of Tc-99m sulfur colloid for lymphoscintigraphy is typically:
A) Less than 100 nm (filtered)
B) 100-200 nm (filtered)
C) 200-500 nm (unfiltered)
D) 1-5 microns
Answer: A) Less than 100 nm (filtered)
Rationale: For sentinel lymph node mapping, filtered sulfur colloid (particles less than 100
nm, typically 50-100 nm) is used to allow movement through lymphatic channels while
being trapped in the sentinel node. Larger particles may not migrate as effectively.
Question 7
Which of the following is a common adverse reaction to radiopharmaceuticals?
, A) Anaphylaxis
B) Nausea
C) Rash
D) All of the above
Answer: D) All of the above
Rationale: Adverse reactions to radiopharmaceuticals are rare but can include anaphylaxis
(severe, rare), nausea, rash, flushing, hypotension, and other symptoms. Patients should be
monitored for allergic reactions, especially with certain agents like MAA (albumin).
Question 8
The "blood pool" phase of a three-phase bone scan is obtained at approximately:
A) Immediately after injection (flow phase)
B) 5-10 minutes after injection (blood pool/soft tissue phase)
C) 2-4 hours after injection (delayed bone phase)
D) 24 hours after injection
Answer: B) 5-10 minutes after injection (blood pool/soft tissue phase)
Rationale: The three-phase bone scan includes: Phase 1 (flow/angiographic phase) – 1-2
minutes after injection; Phase 2 (blood pool/soft tissue phase) – 5-10 minutes after
injection; Phase 3 (delayed phase/bone uptake) – 2-4 hours after injection.
Question 9
Which of the following conditions is best evaluated by a three-phase bone scan?
A) Osteomyelitis vs. cellulitis
B) Bone metastasis
C) Fracture
D) Arthritis
Answer: A) Osteomyelitis vs. cellulitis
Rationale: The three-phase bone scan is particularly useful for differentiating osteomyelitis
