100+ Free ABR Nuclear Radiology Practice Questions

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What is the physical half-life and principal gamma energy of Tc-99m, the most widely used radionuclide in nuclear medicine?

6 hours, 140 keV

110 minutes, 511 keV

13 hours, 159 keV

8 days, 364 keV

to track

2026 Statistics

Key Facts: ABR Nuclear Radiology Exam

~200

Total MCQ Items

ABR Nuclear Radiology subspecialty CAQ

0.15

Mo-99 Breakthrough Limit (μCi/mCi)

NRC/USP Tc-99m eluate QC

7 mrem/hr

I-131 Release Dose Rate at 1 m

NRC patient release criteria

$1,950

2026 Exam Fee

ABR Nuclear Radiology CAQ

4 mo

Minimum Nuclear Training

ACGME-accredited (or 1-year fellowship)

Pearson VUE

Test Delivery

Computer-based testing at authorized centers

The ABR Nuclear Radiology CAQ is a 1-day Pearson VUE computer-based exam with ~200 single-best-answer MCQs. The 2026 content outline emphasizes physics and radioisotopes (~12%), instrumentation (~8%), radiation safety (~8%), FDG-PET oncology (~15%), cardiac nuclear (~10%), bone imaging (~8%), GU and hepatobiliary (~6%), thyroid and parathyroid (~8%), pulmonary V/Q (~5%), GI and infection (~5%), neurologic nuclear (~5%), and therapy and theranostics (~10%). Exam fee ~$1,950; requires ABR Diagnostic Radiology certification plus nuclear radiology training (4-month minimum or 1-year fellowship), or ABNM certification.

Sample ABR Nuclear Radiology Practice Questions

Try these sample questions to test your ABR Nuclear Radiology exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1What is the physical half-life and principal gamma energy of Tc-99m, the most widely used radionuclide in nuclear medicine?

A.6 hours, 140 keV

B.110 minutes, 511 keV

C.13 hours, 159 keV

D.8 days, 364 keV

Explanation: Tc-99m has a physical half-life of 6.0 hours and emits a principal gamma photon of 140 keV via isomeric transition. Its combination of short half-life, monoenergetic 140 keV photon (ideal for NaI(Tl) gamma cameras), and chemistry that allows labeling of diverse agents makes it the workhorse SPECT radionuclide. F-18 is 110 min and 511 keV, I-123 is 13 h and 159 keV, and I-131 is 8 d and 364 keV.

2Mo-99 decays to Tc-99m primarily by which decay mode?

A.Beta-minus decay

B.Alpha decay

C.Electron capture

D.Isomeric transition

Explanation: Mo-99 (T1/2 66 h) decays by beta-minus emission to Tc-99m in about 87% of disintegrations (the remainder goes directly to Tc-99 ground state). Tc-99m then decays to Tc-99 by isomeric transition with emission of the diagnostic 140 keV photon. Understanding the parent-daughter relationship is essential for generator elution and eluate QC.

3The NRC/USP limit for Mo-99 radionuclidic breakthrough in a Tc-99m generator eluate at the time of administration is:

A.0.015 μCi Mo-99 per mCi Tc-99m

B.1.5 μCi Mo-99 per mCi Tc-99m

C.15 μCi Mo-99 per mCi Tc-99m

D.0.15 μCi Mo-99 per mCi Tc-99m

Explanation: The limit is 0.15 μCi Mo-99 per mCi Tc-99m at the time of administration. Because Mo-99 (T1/2 66 h) decays more slowly than Tc-99m (T1/2 6 h), the ratio worsens with time, so the eluate must be measured at the time of use. The Al3+ chemical purity limit for fission-based generators is ≤10 μg/mL.

4Which radionuclide used in PET imaging has the shortest physical half-life, making it practical only with an on-site or nearby cyclotron/generator?

A.F-18 (110 min)

B.Ga-68 (68 min)

C.N-13 (10 min)

D.Rb-82 (75 seconds)

Explanation: Rb-82 has the shortest half-life at approximately 75 seconds and is produced from a Sr-82/Rb-82 generator (Sr-82 parent T1/2 25 days) — it is used for cardiac PET perfusion imaging because an on-site cyclotron is not required. N-13 ammonia (10 min) requires an on-site cyclotron. F-18 (110 min) and Ga-68 (68 min, from Ge-68/Ga-68 generator) are longer-lived.

5The biological half-life of a radiopharmaceutical is 12 hours and the physical half-life of its radionuclide is 6 hours. What is the effective half-life?

A.18 hours

B.9 hours

C.6 hours

D.4 hours

Explanation: Effective half-life combines biological and physical clearance: 1/Teff = 1/Tp + 1/Tb = 1/6 + 1/12 = 3/12, so Teff = 4 hours. Teff is always shorter than either Tp or Tb individually. When Tb >> Tp, Teff approaches Tp (as with most Tc-99m agents). When Tp >> Tb, Teff approaches Tb.

6Positron emission results in two 511 keV annihilation photons emitted at approximately what angle to each other?

A.90 degrees

B.140 degrees

C.360 degrees

D.180 degrees

Explanation: When a positron annihilates with an electron, conservation of momentum produces two 511 keV photons traveling at approximately 180 degrees (antiparallel). PET detector rings exploit this by requiring coincidence detection of two 511 keV photons within a narrow timing window (~6-12 ns, or <1 ns with time-of-flight PET) along a line of response.

7Which of the following radionuclides decays by alpha emission and is used therapeutically for castration-resistant prostate cancer with symptomatic bone metastases?

A.Lu-177

B.Y-90

C.Sm-153

D.Ra-223

Explanation: Ra-223 dichloride (Xofigo) is an alpha emitter with physical half-life 11.4 days. It mimics calcium and localizes to areas of increased bone turnover (metastases). The ALSYMPCA trial demonstrated an overall survival benefit in men with mCRPC with symptomatic bone metastases and without visceral disease. Alpha particles deliver high linear energy transfer (LET) with short path length (<100 μm), sparing bone marrow.

8What is the principal decay mode of F-18 used for FDG-PET imaging?

A.Beta-plus (positron) emission

B.Beta-minus emission

C.Alpha emission

D.Isomeric transition

Explanation: F-18 decays by beta-plus (positron) emission in ~97% of disintegrations (remainder by electron capture). Maximum positron energy is 633 keV; mean range in tissue is ~0.6 mm, giving F-18 excellent spatial resolution for PET. Physical half-life is 109.8 minutes, allowing regional distribution of unit doses from a central cyclotron.

9Which radionuclide is produced from a Ge-68/Ga-68 generator and used in DOTATATE PET imaging for neuroendocrine tumors?

A.F-18

B.Cu-64

C.Zr-89

D.Ga-68

Explanation: Ga-68 (T1/2 68 min) is eluted from a Ge-68/Ga-68 generator (Ge-68 parent T1/2 271 days). Ga-68 DOTATATE binds somatostatin receptor type 2 (SSTR2) overexpressed on well-differentiated neuroendocrine tumors. Therapeutic counterpart is Lu-177 DOTATATE (LUTATHERA), used in peptide receptor radionuclide therapy (PRRT) — a landmark theranostic pair.

10Which decay mode does I-123 (13 h, 159 keV) undergo?

A.Beta-minus

B.Beta-plus

C.Isomeric transition

D.Electron capture

Explanation: I-123 decays by electron capture to Te-123, emitting a 159 keV gamma photon ideal for gamma camera imaging. It is used for thyroid imaging/uptake (lower radiation dose than I-131), DaT scans (I-123 ioflupane), MIBG imaging (I-123 MIBG for pheochromocytoma and neuroblastoma diagnosis), and thyroid cancer imaging. I-131 (8 d) decays by beta-minus + gamma and is used therapeutically.

About the ABR Nuclear Radiology Exam

The ABR Nuclear Radiology Subspecialty CAQ is a 1-day computer-based examination for diagnostic radiologists who have completed at least 4 months of ACGME-accredited Nuclear Radiology training during residency or a 1-year Nuclear Radiology fellowship following ABR Diagnostic Radiology primary certification (ABNM-certified physicians may also qualify). The exam contains approximately 200 single-best-answer MCQs covering radioactive decay physics, Mo-99/Tc-99m generator radiopharmacy and QC, Anger camera and SPECT/PET instrumentation, NRC radiation safety and release criteria, FDG-PET oncology (Deauville lymphoma scoring, lung, H&N, melanoma, colorectal), cardiac MPI (SPECT and Rb-82/N-13 ammonia PET, pharmacologic stress, amyloid PYP), Tc-99m MDP bone imaging, renal scans (MAG3, DTPA, DMSA, captopril), HIDA hepatobiliary, I-123/I-131 thyroid imaging and therapy, Tc-99m sestamibi parathyroid, V/Q PIOPED criteria for PE, DaT scan, amyloid PET, and theranostics (Lu-177 DOTATATE, Lu-177 PSMA-617, Y-90 TARE, Ra-223, I-131 MIBG).

Questions

200 scored questions

Time Limit

1-day CBT

Passing Score

Criterion-referenced scaled score set by ABR

Exam Fee

~$1,950 ABR Nuclear Radiology CAQ exam fee (2026) (American Board of Radiology (ABR) / Pearson VUE)

ABR Nuclear Radiology Exam Content Outline

~12%

Physics & Radioisotopes

Radioactive decay — alpha (Ra-223), beta-minus (I-131, Y-90, Lu-177), beta-plus positron emission (F-18, Ga-68, Rb-82, N-13), electron capture (Tl-201, I-123, In-111), isomeric transition (Tc-99m 140 keV). Half-life — physical, biological, effective (1/Teff = 1/Tp + 1/Tb). Mo-99/Tc-99m generator elution and eluate QC — Mo-99 breakthrough ≤0.15 μCi/mCi Tc-99m, Al3+ chemical impurity, pH. Common isotopes and keV energies for imaging.

~8%

Instrumentation

Anger gamma camera (NaI(Tl) crystal, PMTs), collimators (parallel hole general-purpose, pinhole for thyroid/parathyroid, converging/diverging), SPECT reconstruction (OSEM, FBP), SPECT/CT attenuation correction and localization, PET coincidence detection of 511 keV photons from positron annihilation, TOF-PET (time-of-flight improves effective sensitivity), PET/CT, PET/MR. QC — extrinsic/intrinsic uniformity flood, COR, spatial resolution FWHM, sensitivity.

~8%

Radiation Safety & Regulations

NRC (federal) vs Agreement State regulation, ALARA. Occupational dose limits — 5 rem/yr TEDE whole-body, 50 rem extremities, 15 rem lens, 0.5 rem gestational for declared pregnant worker. RSO duties, sealed vs unsealed sources, minor vs major spills. I-131 patient release criteria — dose rate ≤7 mrem/hr at 1 m or TEDE to individuals <5 mSv. Breastfeeding interruption (Tc-99m 12-24 h; I-131 cease). Pediatric weight-based dose adjustments.

~15%

Oncology & FDG-PET

FDG glucose analog mechanism (hexokinase trapping). Patient prep — fasting 4-6 h, blood glucose <200 mg/dL, avoid exercise 24 h, warm blanket for brown fat. Staging — NSCLC (SUV, mediastinal N2/N3), lymphoma Deauville 5-point scale (scores 1-3 favorable), melanoma, head and neck (delay 12 wk post-RT), colorectal, esophageal. False positives — inflammation, sarcoid, TB, histoplasmosis, Warthin, post-op. False negatives — low-grade NHL, BAC, carcinoid, prostate (use PSMA-PET). Ga-68 DOTATATE for NET; F-18/Ga-68 PSMA for prostate (piflufolastat FDA-approved).

~10%

Cardiac Nuclear

MPI SPECT — Tc-99m sestamibi/tetrofosmin (preferred — higher-energy 140 keV, less attenuation) vs Tl-201 (redistribution imaging for viability). Pharmacologic stress — vasodilators (dipyridamole, adenosine, regadenoson; aminophylline reverses, hold caffeine 12-24 h, contraindicated in bronchospasm for adenosine/dipyridamole); dobutamine. PET — Rb-82 (82 s T1/2, generator-produced) and N-13 ammonia for quantitative MBF and CFR. Gated SPECT for EF/wall motion. Amyloid PYP — H/CL >1.5 at 1 h (or visual grade 2-3) suggests ATTR.

~8%

Bone & Musculoskeletal

Tc-99m MDP/HDP three-phase (flow, blood pool, delayed 2-3 h) — osteoblastic activity. Mets, fracture, infection, Paget show increased uptake. Superscan — diffuse uptake with poor renal/soft-tissue activity (extensive metastatic disease or metabolic bone). Cold (photopenic) lesions — multiple myeloma, RCC lytic mets, early AVN, bone infarct. Paget disease — expanded bone, characteristic pelvis/spine/femur distribution. Bone SPECT/CT improves specificity, especially for spine lesions.

~6%

Genitourinary & Hepatobiliary

Renal — Tc-99m DTPA (GFR), Tc-99m MAG3 (tubular secretion, preferred in renal insufficiency). Furosemide-stimulated diuresis renogram (T1/2 <10 min normal; >20 min obstruction). Captopril renogram for renovascular hypertension. DMSA cortical for pyelonephritis scarring. HIDA — no gallbladder fill at 1 h (or 30 min after morphine) diagnoses acute cholecystitis; CCK-EF <35% suggests chronic cholecystitis/biliary dyskinesia; absent bowel activity by 24 h on phenobarbital-primed neonate scan suggests biliary atresia.

~8%

Thyroid & Parathyroid

I-123 thyroid scan with 24-h RAIU — normal 10-30%. Increased RAIU in Graves (diffuse) and toxic nodule(s); decreased in thyroiditis, iodine load, exogenous thyroxine, factitious. Cold solitary nodule carries ~15-20% malignancy risk. I-131 therapy — hyperthyroidism 10-15 mCi outpatient (Graves); DTC ablation/adjuvant 30-150 mCi (release criteria apply). Tc-99m pertechnetate is trapped but not organified (not for RAIU calculation). Parathyroid Tc-99m sestamibi dual-phase — persistent uptake after thyroid washout localizes adenoma; SPECT/CT + US + 4D-CT correlation.

~5%

Pulmonary (V/Q)

V/Q scan for PE — Tc-99m MAA (80-100 μm particles, ≥90% lodge on first-pass capillary passage; typically 200,000-500,000 particles; reduce in known right-to-left shunt or severe pulmonary hypertension) + Xe-133 or Tc-99m DTPA aerosol for ventilation. PIOPED criteria — segmental perfusion defect with normal ventilation (mismatch) = high probability. Preferred over CTPA in pregnancy with normal CXR (lower fetal and maternal breast dose). Matched defects suggest COPD.

~5%

GI, Infection & Miscellaneous

Meckel scan — Tc-99m pertechnetate for ectopic gastric mucosa (pentagastrin augmentation, H2 blocker pre-scan). GI bleed scan — Tc-99m RBC detects 0.1-0.5 mL/min bleeding over 24 h (superior to sulfur colloid for intermittent bleeding). Gastric emptying — standardized solid meal, <10% retention at 4 h normal. Hepatic hemangioma — Tc-99m RBC perfusion defect with delayed fill-in. Infection — In-111 or Tc-99m HMPAO WBC for osteomyelitis, FUO, prosthesis infection; Ga-67 largely replaced.

~5%

Neurologic Nuclear

DaT scan (I-123 ioflupane) — SPECT of dopamine transporter; asymmetric decreased putaminal uptake (loss of comma/tail shape, dot/period appearance) confirms presynaptic deficit in PD/DLB/MSA/PSP; normal in essential tremor and drug-induced parkinsonism. Brain perfusion SPECT with Tc-99m HMPAO/ECD. Amyloid PET agents (florbetapir, florbetaben, flutemetamol) for AD workup. Tau PET (flortaucipir FDA-approved 2020). FDG-PET — AD (temporoparietal hypometabolism), FTD (frontal), DLB (occipital + cingulate island sign).

~10%

Therapy & Theranostics

I-131 Graves 10-15 mCi, DTC 30-150 mCi. Y-90 microsphere TARE — pre-therapy Tc-99m MAA mapping; hepatopulmonary shunt <15% acceptable; resin SIR-Spheres vs glass TheraSphere. Lu-177 DOTATATE (LUTATHERA) PRRT for progressive well-differentiated midgut NET (NETTER-1 trial). Lu-177 PSMA-617 (Pluvicto, FDA 2022) for PSMA-positive mCRPC post-chemo/ARAT (VISION trial). Ra-223 dichloride (Xofigo) alpha emitter — CRPC bone mets without visceral disease (ALSYMPCA). I-131 MIBG for neuroblastoma and pheo/paraganglioma. Sm-153/Sr-89 bone palliation.

How to Pass the ABR Nuclear Radiology Exam

What You Need to Know

Passing score: Criterion-referenced scaled score set by ABR
Exam length: 200 questions
Time limit: 1-day CBT
Exam fee: ~$1,950 ABR Nuclear Radiology CAQ exam fee (2026)

Keys to Passing

Complete 500+ practice questions
Score 80%+ consistently before scheduling
Focus on highest-weighted sections
Use our AI tutor for tough concepts

ABR Nuclear Radiology Study Tips from Top Performers

1Mo-99/Tc-99m generator radiopharmacy QC — the three must-know eluate limits are: (1) Mo-99 breakthrough ≤0.15 μCi Mo-99 per mCi Tc-99m at time of administration (radionuclidic purity, measured in a lead pot to suppress Tc-99m 140 keV photons and count the 740/780 keV Mo-99 gammas), (2) Al3+ chemical purity ≤10 μg/mL (tested with color-spot indicator paper), and (3) pH. For Tc-99m radiochemical purity of kits, use thin-layer chromatography (>90-95% tagged depending on product). Teff < Tp always — effective half-life is shorter than physical due to biological clearance.

2FDG-PET preparation pearls — fast 4-6 h (reduces serum glucose and insulin to drive FDG into tumor rather than muscle/liver), blood glucose <200 mg/dL (hyperglycemia competes with FDG at GLUT/hexokinase), avoid strenuous exercise 24 h (reduces muscle uptake), and warm the patient with a blanket and warm room to suppress brown adipose tissue activation (a beta-blocker can also be used). Delay PET-CT at least 6 weeks after surgery, 4-6 weeks after chemotherapy, and 10-12 weeks after radiation therapy to avoid inflammatory false-positive uptake. Diabetics: hold short-acting insulin; metformin can increase bowel FDG uptake (not an absolute contraindication).

3V/Q vs CTPA in pregnancy — in a pregnant patient with suspected PE and a normal chest X-ray, V/Q scan is typically preferred because fetal dose from perfusion-only or low-dose V/Q is lower than from standard CTPA, and maternal breast dose (and breast cancer risk) is considerably lower. If CXR is abnormal, CTPA is often preferred. A normal perfusion scan effectively excludes PE. PIOPED high-probability criteria = ≥2 large (>75% of segment) or the equivalent of 2 segmental mismatched defects. Reduce Tc-99m MAA particle number to ~100,000-200,000 in pregnancy and in known right-to-left shunt/pulmonary hypertension.

4NRC I-131 patient release criteria — patients can be released after I-131 therapy when either: (a) measured dose rate at 1 m is ≤7 mrem/hr, OR (b) the calculated total effective dose equivalent (TEDE) to the maximally exposed individual is <5 mSv (500 mrem). Written instructions are required if the released dose could exceed 1 mSv. Occupational dose limits — 5 rem/yr whole-body TEDE, 50 rem/yr extremities, 15 rem/yr lens (recently reduced debate), and 0.5 rem gestational to a declared pregnant worker over the entire pregnancy. Declared pregnant worker declaration must be in writing.

5Cardiac theranostics and amyloid — Tc-99m PYP (or HMDP/DPD) planar + SPECT at 1 hour is the workhorse for ATTR cardiac amyloidosis screening. A heart-to-contralateral lung (H/CL) ratio ≥1.5 at 1 h, or visual grade 2-3 (uptake equal to or greater than rib), in the absence of a monoclonal protein (negative SPEP/UPEP + serum free light chains) essentially establishes ATTR cardiac amyloidosis WITHOUT endomyocardial biopsy (Gillmore criteria). If a monoclonal protein is present, AL amyloid must be excluded with biopsy. This non-invasive diagnostic pathway is a very high-yield topic for the CAQ exam.

Frequently Asked Questions

What is the ABR Nuclear Radiology Subspecialty CAQ?

The ABR Nuclear Radiology Subspecialty Certificate of Added Qualification (CAQ) is a 1-day computer-based examination administered by the American Board of Radiology (ABR) at Pearson VUE test centers. It certifies expertise in diagnostic and therapeutic applications of radiopharmaceuticals — including FDG-PET oncology, cardiac MPI, bone and renal imaging, thyroid diagnosis and therapy, V/Q scanning for PE, and modern theranostics (Lu-177 DOTATATE/PSMA-617, Y-90 TARE, Ra-223). The CAQ is taken after ABR Diagnostic Radiology primary certification plus ACGME nuclear radiology training, or via the ABNM pathway.

Who is eligible to sit for the Nuclear Radiology CAQ?

Candidates must hold ABR Diagnostic Radiology primary certification and have satisfactorily completed ACGME-accredited Nuclear Radiology training — either a minimum of 4 months integrated during diagnostic radiology residency or a 1-year Nuclear Radiology fellowship. Physicians holding ABNM certification may also qualify for the CAQ through an alternative pathway. Candidates must hold a valid unrestricted medical license and submit application through the ABR during the designated eligibility window.

What is the format of the exam?

The exam is a 1-day computer-based test delivered at Pearson VUE test centers. It consists of approximately 200 single-best-answer multiple-choice items covering the full 2026 ABR Nuclear Radiology content outline. Questions frequently include clinical vignettes paired with representative imaging (planar scintigraphy, SPECT/CT, PET/CT), radiation safety calculations, radiopharmacy QC scenarios, and therapeutic dose planning for I-131 and theranostic agents.

How much does the 2026 ABR Nuclear Radiology CAQ cost?

The 2026 exam fee is approximately $1,950. Cancellation and refund policies follow the ABR schedule with decreasing refunds as the exam date approaches. Retakes within the eligibility window require full re-registration and fee payment. Enrollment in the ABR Online Longitudinal Assessment (OLA) Continuing Certification program includes annual activities and associated fees.

What are the highest-yield topics?

Highest-yield topics include: Mo-99/Tc-99m generator QC limits (Mo-99 breakthrough ≤0.15 μCi/mCi Tc-99m); FDG-PET oncology staging with Deauville scoring for lymphoma and delay of 12 weeks after radiation for H&N; MPI SPECT vs PET (Rb-82, N-13 ammonia) and pharmacologic stress pharmacology; amyloid PYP H/CL >1.5 for ATTR cardiac amyloidosis; V/Q PIOPED criteria and preference in pregnancy; I-131 thyroid therapy (Graves 10-15 mCi, DTC 30-150 mCi) and NRC release criteria (≤7 mrem/hr at 1 m or <5 mSv); DaT scan interpretation for Parkinson disease; Lu-177 DOTATATE (NETTER-1), Lu-177 PSMA-617 (VISION), Y-90 TARE MAA shunt <15%, and Ra-223 ALSYMPCA indications.

How should I study for the Nuclear Radiology CAQ?

Plan 150-300 hours during and after nuclear radiology training. Core resources include Mettler and Guiberteau's Essentials of Nuclear Medicine and Molecular Imaging, SNMMI procedure standards and appropriate-use criteria, the ACR/SPR nuclear medicine practice parameters, RSNA/AAPM physics review (Huda/Bushberg), and the ABR Nuclear Radiology study guide. Drill high-volume MCQs with timed sets, memorize common isotope properties (T1/2, energy, decay mode), master radiation safety limits and release criteria, and complete 2-3 full-length timed mock exams.

When is the 2026 exam administered?

ABR subspecialty exams are typically offered annually. Applications open months before the exam with a submission deadline prior to the testing window, after which candidates schedule specific Pearson VUE appointments. Exact 2026 dates should be confirmed on the ABR Nuclear Radiology subspecialty page.

How is the exam scored?

ABR uses a criterion-referenced scaled scoring system with a passing standard set by subject-matter experts. A candidate's pass/fail result depends on performance relative to the fixed cut-score rather than on other test-takers. Score reports include subdomain performance to guide future learning. Results are typically released several weeks after the testing window closes.