NCT 2026 Exam Prep: Nuclear Medicine
Advanced Associate (NMAA) Practice
Questions with Answer Rationales
Advanced Imaging |
Radiopharmaceutical Therapy | Patient
Management | Clinical Procedures
Review
SECTION 1: ADVANCED IMAGING (Questions 1–40)
1. Which PET radiopharmaceutical is most commonly used for myocardial
viability assessment, and what is its mechanism of uptake?
A. Rb-82 chloride; Na⁺/K⁺-ATPase pump
B. F-18 FDG; glucose transporter-mediated uptake and hexokinase
phosphorylation
C. N-13 ammonia; passive diffusion and glutamine synthesis
D. O-15 water; freely diffusible tracer
Rationale: F-18 FDG is the gold standard for myocardial viability assessment. It
enters myocytes via glucose transporters (GLUT-1 and GLUT-4) and is
phosphorylated by hexokinase to FDG-6-phosphate, which becomes trapped
intracellularly. Viable myocardium demonstrates preserved FDG uptake even in
regions of reduced perfusion (perfusion–metabolism mismatch).
2. What is the primary advantage of CZT solid-state detectors over
conventional Anger cameras in SPECT imaging?
A. Lower cost
B. Higher energy resolution and count sensitivity
C. Larger field of view
D. Reduced need for collimators
,Rationale: CZT (cadmium zinc telluride) detectors directly convert gamma
photons to electrical signals, providing significantly higher energy resolution
(approximately 5–6% at 140 keV vs. 10–12% for NaI) and count sensitivity
compared to conventional scintillation cameras.
3. Which reconstruction algorithm is most commonly used in PET/CT
imaging to produce images with high contrast and low noise?
A. Filtered back projection
B. Ordered subset expectation maximization (OSEM)
C. Maximum likelihood expectation maximization (MLEM)
D. Algebraic reconstruction technique (ART)
Rationale: OSEM is the most widely used iterative reconstruction algorithm in
PET/CT. It divides projection data into subsets and performs iterative updates,
achieving convergence faster than MLEM while maintaining image quality.
4. In PET imaging, what is the energy of each annihilation photon produced
when a positron encounters an electron?
A. 140 keV
B. 159 keV
C. 511 keV
D. 662 keV
Rationale: When a positron annihilates with an electron, the combined mass is
converted into two 511 keV photons emitted in opposite directions (180° apart).
This forms the basis of coincidence detection in PET imaging.
5. Which of the following best describes the "partial volume effect" in PET
imaging?
A. Increased tracer uptake in small lesions
B. Underestimation of tracer concentration in structures smaller than
approximately 2–3 times the spatial resolution
C. Artifactual uptake in the bladder
D. Photon attenuation by bone
Rationale: The partial volume effect causes underestimation of activity
concentration in small structures because the signal is spread across multiple
voxels. Structures smaller than 2–3 times the FWHM of the system's spatial
resolution are affected.
,6. What is the standard uptake value (SUV) in PET imaging normalized to?
A. Liver uptake
B. Injected dose and patient body weight
C. Blood glucose level
D. Plasma volume
Rationale: SUV = (tissue activity concentration) / (injected dose / body weight). It
provides a semi-quantitative measure of tracer uptake normalized for injected dose
and patient size.
7. Which radiopharmaceutical is used for PET imaging of prostate-specific
membrane antigen (PSMA) in prostate cancer?
A. F-18 fluciclovine
B. Ga-68 PSMA-11
C. C-11 choline
D. F-18 FDG
Rationale: Ga-68 PSMA-11 binds with high affinity to PSMA, which is
overexpressed on prostate cancer cells. It is highly sensitive for detecting prostate
cancer recurrence and metastases.
8. What is the primary mechanism of F-18 FDG uptake in malignant cells?
A. Increased blood flow
B. Upregulation of glucose transporters and hexokinase activity
C. Receptor-mediated endocytosis
D. Passive diffusion
Rationale: Malignant cells exhibit increased glucose metabolism due to
upregulated GLUT-1 and GLUT-3 transporters and increased hexokinase activity.
FDG is phosphorylated and trapped intracellularly, reflecting metabolic activity.
9. Which of the following is the correct energy window for PET imaging with
F-18 FDG?
A. 140 keV ± 10%
B. 511 keV ± 20%
C. 159 keV ± 10%
D. 662 keV ± 10%
, Rationale: PET imaging detects 511 keV annihilation photons. The energy
window is typically set at 511 keV ± 20% (approximately 409–613 keV) to capture
the photopeak while excluding scatter.
10. Which PET radiopharmaceutical is used for imaging of neuroendocrine
tumors?
A. F-18 FDG
B. Ga-68 DOTATATE
C. F-18 florbetapir
D. C-11 choline
Rationale: Ga-68 DOTATATE binds to somatostatin receptor subtype 2 (SSTR2),
which is overexpressed on well-differentiated neuroendocrine tumors. It is highly
sensitive for staging and restaging NETs.
11. What is the purpose of time-of-flight (TOF) capability in PET/CT
imaging?
A. To reduce radiation dose
B. To improve image contrast and reduce noise by localizing the annihilation
event along the line of response
C. To shorten acquisition time
D. To eliminate the need for attenuation correction
Rationale: TOF PET measures the difference in arrival times of the two
annihilation photons, allowing localization of the annihilation event along the line
of response. This improves signal-to-noise ratio and image quality.
12. Which of the following is a limitation of F-18 FDG PET for brain tumor
imaging?
A. Low tracer uptake in normal brain
B. High background uptake in normal gray matter
C. Poor spatial resolution
D. Rapid tracer clearance
Rationale: Normal brain tissue has high glucose metabolism, resulting in high
background FDG uptake that can obscure tumor visualization. Amino acid tracers
such as F-18 FDOPA or C-11 methionine are often preferred for brain tumor
imaging.
Advanced Associate (NMAA) Practice
Questions with Answer Rationales
Advanced Imaging |
Radiopharmaceutical Therapy | Patient
Management | Clinical Procedures
Review
SECTION 1: ADVANCED IMAGING (Questions 1–40)
1. Which PET radiopharmaceutical is most commonly used for myocardial
viability assessment, and what is its mechanism of uptake?
A. Rb-82 chloride; Na⁺/K⁺-ATPase pump
B. F-18 FDG; glucose transporter-mediated uptake and hexokinase
phosphorylation
C. N-13 ammonia; passive diffusion and glutamine synthesis
D. O-15 water; freely diffusible tracer
Rationale: F-18 FDG is the gold standard for myocardial viability assessment. It
enters myocytes via glucose transporters (GLUT-1 and GLUT-4) and is
phosphorylated by hexokinase to FDG-6-phosphate, which becomes trapped
intracellularly. Viable myocardium demonstrates preserved FDG uptake even in
regions of reduced perfusion (perfusion–metabolism mismatch).
2. What is the primary advantage of CZT solid-state detectors over
conventional Anger cameras in SPECT imaging?
A. Lower cost
B. Higher energy resolution and count sensitivity
C. Larger field of view
D. Reduced need for collimators
,Rationale: CZT (cadmium zinc telluride) detectors directly convert gamma
photons to electrical signals, providing significantly higher energy resolution
(approximately 5–6% at 140 keV vs. 10–12% for NaI) and count sensitivity
compared to conventional scintillation cameras.
3. Which reconstruction algorithm is most commonly used in PET/CT
imaging to produce images with high contrast and low noise?
A. Filtered back projection
B. Ordered subset expectation maximization (OSEM)
C. Maximum likelihood expectation maximization (MLEM)
D. Algebraic reconstruction technique (ART)
Rationale: OSEM is the most widely used iterative reconstruction algorithm in
PET/CT. It divides projection data into subsets and performs iterative updates,
achieving convergence faster than MLEM while maintaining image quality.
4. In PET imaging, what is the energy of each annihilation photon produced
when a positron encounters an electron?
A. 140 keV
B. 159 keV
C. 511 keV
D. 662 keV
Rationale: When a positron annihilates with an electron, the combined mass is
converted into two 511 keV photons emitted in opposite directions (180° apart).
This forms the basis of coincidence detection in PET imaging.
5. Which of the following best describes the "partial volume effect" in PET
imaging?
A. Increased tracer uptake in small lesions
B. Underestimation of tracer concentration in structures smaller than
approximately 2–3 times the spatial resolution
C. Artifactual uptake in the bladder
D. Photon attenuation by bone
Rationale: The partial volume effect causes underestimation of activity
concentration in small structures because the signal is spread across multiple
voxels. Structures smaller than 2–3 times the FWHM of the system's spatial
resolution are affected.
,6. What is the standard uptake value (SUV) in PET imaging normalized to?
A. Liver uptake
B. Injected dose and patient body weight
C. Blood glucose level
D. Plasma volume
Rationale: SUV = (tissue activity concentration) / (injected dose / body weight). It
provides a semi-quantitative measure of tracer uptake normalized for injected dose
and patient size.
7. Which radiopharmaceutical is used for PET imaging of prostate-specific
membrane antigen (PSMA) in prostate cancer?
A. F-18 fluciclovine
B. Ga-68 PSMA-11
C. C-11 choline
D. F-18 FDG
Rationale: Ga-68 PSMA-11 binds with high affinity to PSMA, which is
overexpressed on prostate cancer cells. It is highly sensitive for detecting prostate
cancer recurrence and metastases.
8. What is the primary mechanism of F-18 FDG uptake in malignant cells?
A. Increased blood flow
B. Upregulation of glucose transporters and hexokinase activity
C. Receptor-mediated endocytosis
D. Passive diffusion
Rationale: Malignant cells exhibit increased glucose metabolism due to
upregulated GLUT-1 and GLUT-3 transporters and increased hexokinase activity.
FDG is phosphorylated and trapped intracellularly, reflecting metabolic activity.
9. Which of the following is the correct energy window for PET imaging with
F-18 FDG?
A. 140 keV ± 10%
B. 511 keV ± 20%
C. 159 keV ± 10%
D. 662 keV ± 10%
, Rationale: PET imaging detects 511 keV annihilation photons. The energy
window is typically set at 511 keV ± 20% (approximately 409–613 keV) to capture
the photopeak while excluding scatter.
10. Which PET radiopharmaceutical is used for imaging of neuroendocrine
tumors?
A. F-18 FDG
B. Ga-68 DOTATATE
C. F-18 florbetapir
D. C-11 choline
Rationale: Ga-68 DOTATATE binds to somatostatin receptor subtype 2 (SSTR2),
which is overexpressed on well-differentiated neuroendocrine tumors. It is highly
sensitive for staging and restaging NETs.
11. What is the purpose of time-of-flight (TOF) capability in PET/CT
imaging?
A. To reduce radiation dose
B. To improve image contrast and reduce noise by localizing the annihilation
event along the line of response
C. To shorten acquisition time
D. To eliminate the need for attenuation correction
Rationale: TOF PET measures the difference in arrival times of the two
annihilation photons, allowing localization of the annihilation event along the line
of response. This improves signal-to-noise ratio and image quality.
12. Which of the following is a limitation of F-18 FDG PET for brain tumor
imaging?
A. Low tracer uptake in normal brain
B. High background uptake in normal gray matter
C. Poor spatial resolution
D. Rapid tracer clearance
Rationale: Normal brain tissue has high glucose metabolism, resulting in high
background FDG uptake that can obscure tumor visualization. Amino acid tracers
such as F-18 FDOPA or C-11 methionine are often preferred for brain tumor
imaging.
