NMTCB Exam 2026/2027 | Nuclear Medicine Technology
Certification Board | Complete Practice Questions, Answers &
Detailed Rationales
DOMAIN I — RADIATION PHYSICS & DETECTION
1. Which type of radioactive decay results in emission of a helium
nucleus?
A. Beta-minus decay
B. Alpha decay
C. Positron emission
D. Electron capture
Correct Answer: B. Alpha decay
Rationale: Alpha decay releases an alpha particle consisting of two
protons and two neutrons, equivalent to a helium-4 nucleus.
2. What is the primary particle emitted during beta-minus decay?
A. Positron
B. Neutron
C. Electron
D. Alpha particle
Correct Answer: C. Electron
Rationale: Beta-minus decay converts a neutron into a proton while
emitting an electron and an antineutrino.
,3. Which decay process converts a proton into a neutron?
A. Beta-minus decay
B. Positron emission
C. Alpha decay
D. Isomeric transition
Correct Answer: B. Positron emission
Rationale: In positron emission, a proton changes into a neutron and a
positron is emitted.
4. What is the principal photon emitted following positron
annihilation?
A. One 140-keV photon
B. Two 511-keV photons
C. Two 140-keV photons
D. One 511-keV photon
Correct Answer: B. Two 511-keV photons
Rationale: A positron annihilates with an electron, producing two 511-
keV photons traveling approximately 180° apart.
5. Which radionuclide is commonly used for routine planar and SPECT
nuclear medicine imaging?
A. Tc-99m
B. I-131
,C. Sr-90
D. Ra-226
Correct Answer: A. Tc-99m
Rationale: Tc-99m has favorable imaging characteristics, including a
140-keV gamma photon and approximately 6-hour physical half-life.
6. What happens to the atomic number during alpha decay?
A. It increases by 2
B. It decreases by 2
C. It decreases by 1
D. It remains unchanged
Correct Answer: B. It decreases by 2
Rationale: An alpha particle contains two protons, so loss of the particle
decreases atomic number by two.
7. What happens to the mass number during beta-minus decay?
A. It decreases by 4
B. It decreases by 1
C. It remains unchanged
D. It increases by 1
Correct Answer: C. It remains unchanged
Rationale: Beta-minus decay changes a neutron into a proton without
changing the total number of nucleons.
, 8. Which interaction involves a photon transferring part of its energy
to an electron and changing direction?
A. Photoelectric effect
B. Compton scattering
C. Pair production
D. Annihilation
Correct Answer: B. Compton scattering
Rationale: Compton scattering transfers part of the photon energy to an
electron while the photon continues with reduced energy in a different
direction.
9. Which interaction results in complete absorption of a photon by an
atom?
A. Compton scattering
B. Coherent scattering
C. Photoelectric effect
D. Pair production
Correct Answer: C. Photoelectric effect
Rationale: In the photoelectric effect, the incident photon transfers all
of its energy to a bound electron and disappears.
10. Which interaction is most important for producing scatter that can
degrade gamma-camera images?
Certification Board | Complete Practice Questions, Answers &
Detailed Rationales
DOMAIN I — RADIATION PHYSICS & DETECTION
1. Which type of radioactive decay results in emission of a helium
nucleus?
A. Beta-minus decay
B. Alpha decay
C. Positron emission
D. Electron capture
Correct Answer: B. Alpha decay
Rationale: Alpha decay releases an alpha particle consisting of two
protons and two neutrons, equivalent to a helium-4 nucleus.
2. What is the primary particle emitted during beta-minus decay?
A. Positron
B. Neutron
C. Electron
D. Alpha particle
Correct Answer: C. Electron
Rationale: Beta-minus decay converts a neutron into a proton while
emitting an electron and an antineutrino.
,3. Which decay process converts a proton into a neutron?
A. Beta-minus decay
B. Positron emission
C. Alpha decay
D. Isomeric transition
Correct Answer: B. Positron emission
Rationale: In positron emission, a proton changes into a neutron and a
positron is emitted.
4. What is the principal photon emitted following positron
annihilation?
A. One 140-keV photon
B. Two 511-keV photons
C. Two 140-keV photons
D. One 511-keV photon
Correct Answer: B. Two 511-keV photons
Rationale: A positron annihilates with an electron, producing two 511-
keV photons traveling approximately 180° apart.
5. Which radionuclide is commonly used for routine planar and SPECT
nuclear medicine imaging?
A. Tc-99m
B. I-131
,C. Sr-90
D. Ra-226
Correct Answer: A. Tc-99m
Rationale: Tc-99m has favorable imaging characteristics, including a
140-keV gamma photon and approximately 6-hour physical half-life.
6. What happens to the atomic number during alpha decay?
A. It increases by 2
B. It decreases by 2
C. It decreases by 1
D. It remains unchanged
Correct Answer: B. It decreases by 2
Rationale: An alpha particle contains two protons, so loss of the particle
decreases atomic number by two.
7. What happens to the mass number during beta-minus decay?
A. It decreases by 4
B. It decreases by 1
C. It remains unchanged
D. It increases by 1
Correct Answer: C. It remains unchanged
Rationale: Beta-minus decay changes a neutron into a proton without
changing the total number of nucleons.
, 8. Which interaction involves a photon transferring part of its energy
to an electron and changing direction?
A. Photoelectric effect
B. Compton scattering
C. Pair production
D. Annihilation
Correct Answer: B. Compton scattering
Rationale: Compton scattering transfers part of the photon energy to an
electron while the photon continues with reduced energy in a different
direction.
9. Which interaction results in complete absorption of a photon by an
atom?
A. Compton scattering
B. Coherent scattering
C. Photoelectric effect
D. Pair production
Correct Answer: C. Photoelectric effect
Rationale: In the photoelectric effect, the incident photon transfers all
of its energy to a bound electron and disappears.
10. Which interaction is most important for producing scatter that can
degrade gamma-camera images?
