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CNMT practice questions

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Question 1General Nuclear Medicine (CNMT)

Which radiopharmaceutical is most commonly used for a routine bone scan?

  1. Tc-99m sulfur colloid
  2. Tc-99m DTPA
  3. Tc-99m MDP Correct answer.
  4. Tc-99m pertechnetate

Explanation

Tc-99m MDP (methyl diphosphonate) localizes to bone by chemisorption onto hydroxyapatite crystal surfaces, giving high bone-to-background uptake. It is the standard agent for skeletal scintigraphy.

Question 2General Nuclear Medicine (CNMT)

A patient arrives for a thyroid uptake study after recent iodinated contrast. Which mechanism explains interference with the result?

  1. Increased renal clearance of pertechnetate
  2. Reduction of the technetium generator yield
  3. Direct chemical destruction of thyroid follicular cells
  4. Competitive inhibition of iodine uptake by the thyroid gland Correct answer.

Explanation

Stable iodine from contrast competes with radioiodine (or pertechnetate) for the sodium-iodide symporter, reducing measured uptake. The study should be delayed until the iodine load clears.

Question 3General Nuclear Medicine (CNMT)

Which agent is used for a ventilation study in a V/Q lung scan?

  1. Tc-99m MAA
  2. Tc-99m DTPA aerosol Correct answer.
  3. Tc-99m macroaggregated albumin
  4. Tc-99m MAG3

Explanation

Aerosolized Tc-99m DTPA deposits in the airways and alveoli to map ventilation. Perfusion is assessed separately with Tc-99m MAA particles trapped in pulmonary capillaries.

Question 4General Nuclear Medicine (CNMT)

In a hepatobiliary (HIDA) scan, which finding is most consistent with acute cholecystitis?

  1. Prompt gallbladder visualization within 30 minutes
  2. Uniform hepatic uptake with delayed bowel activity
  3. Nonvisualization of the gallbladder with visualization of the liver and bowel Correct answer.
  4. Increased splenic uptake of the tracer

Explanation

A patent cystic duct is required for gallbladder filling. Failure of the gallbladder to appear despite adequate hepatic uptake and bowel transit indicates cystic duct obstruction, the hallmark of acute cholecystitis.

Question 5General Nuclear Medicine (CNMT)

Which radiopharmaceutical is used to evaluate renal tubular function and effective renal plasma flow?

  1. Tc-99m MDP
  2. Tc-99m MAG3 Correct answer.
  3. Tc-99m DMSA
  4. Tc-99m sulfur colloid

Explanation

MAG3 is secreted by renal tubular cells and provides an estimate of effective renal plasma flow. It is preferred in patients with impaired renal function because of its efficient extraction.

Question 6General Nuclear Medicine (CNMT)

A DMSA scan shows a focal cortical defect in the upper pole of the left kidney. What does this most likely represent?

  1. A bladder diverticulum
  2. A renal artery stenosis
  3. A ureteral obstruction
  4. A cortical scar from prior pyelonephritis Correct answer.

Explanation

DMSA localizes to functioning proximal tubules, so areas of cortical loss appear as photopenic defects. Focal defects correspond to scarring, commonly from prior infection.

Question 7General Nuclear Medicine (CNMT)

Which radiopharmaceutical is used for myocardial perfusion imaging at rest and stress?

  1. Tc-99m sulfur colloid
  2. Tc-99m sestamibi Correct answer.
  3. Tc-99m MAA
  4. Tc-99m pertechnetate

Explanation

Sestamibi is a lipophilic cation retained in myocardial mitochondria in proportion to regional blood flow. It is used with rest and stress protocols to detect ischemia and infarction.

Question 8General Nuclear Medicine (CNMT)

On a myocardial perfusion scan, a defect present at stress but not at rest most likely indicates which condition?

  1. Normal myocardium
  2. Reversible ischemia Correct answer.
  3. Fixed infarction
  4. Artifact from breast attenuation

Explanation

A defect that fills in at rest represents tissue that is viable but underperfused during stress-reversible ischemia. A defect present at both stress and rest suggests scar.

Question 9General Nuclear Medicine (CNMT)

Which agent is used for a gastric emptying study?

  1. Tc-99m DTPA aerosol
  2. Tc-99m sulfur colloid in a solid meal Correct answer.
  3. Tc-99m pertechnetate orally
  4. Tc-99m MAA intravenously

Explanation

A standardized solid meal labeled with Tc-99m sulfur colloid is imaged over time to measure the rate of gastric emptying. The tracer must be bound to the meal to reflect solid-phase transit.

Question 10General Nuclear Medicine (CNMT)

A Meckel diverticulum scan uses which radiopharmaceutical?

  1. Tc-99m pertechnetate Correct answer.
  2. Tc-99m sulfur colloid
  3. Tc-99m MDP
  4. Tc-99m MAG3

Explanation

Pertechnetate is taken up by ectopic gastric mucosa, which is present in many symptomatic Meckel diverticula. Uptake in the right lower quadrant that appears and clears with the stomach suggests the diagnosis.

Question 11General Nuclear Medicine (CNMT)

Which radiopharmaceutical is used for sentinel lymph node mapping in breast cancer?

  1. Tc-99m sulfur colloid Correct answer.
  2. Tc-99m pertechnetate
  3. Tc-99m DTPA
  4. Tc-99m MDP

Explanation

Filtered Tc-99m sulfur colloid is injected near the tumor and migrates through lymphatics to the first draining node. The sentinel node is identified by focal uptake on imaging and by intraoperative gamma probe.

Question 12General Nuclear Medicine (CNMT)

Which radioisotope is most commonly used for thyroid imaging and uptake studies?

  1. I-131
  2. I-123 Correct answer.
  3. F-18
  4. Ga-67

Explanation

I-123 has a short half-life and low-energy gamma emission with minimal beta dose, making it well suited for diagnostic thyroid imaging and uptake. I-131 is used more for therapy.

Question 13General Nuclear Medicine (CNMT)

Which radiopharmaceutical is used for a parathyroid scan in a two-phase or subtraction technique?

  1. Tc-99m MAG3
  2. Tc-99m sestamibi Correct answer.
  3. Tc-99m MDP
  4. Tc-99m DMSA

Explanation

Sestamibi accumulates in both thyroid and parathyroid tissue but washes out of the thyroid more rapidly, allowing a delayed image to reveal parathyroid adenomas. Subtraction with pertechnetate or iodine can further isolate parathyroid uptake.

Question 14General Nuclear Medicine (CNMT)

In a V/Q scan, multiple segmental perfusion defects with normal ventilation most likely indicate which condition?

  1. Normal lung
  2. Chronic obstructive pulmonary disease
  3. Pulmonary embolism Correct answer.
  4. Pneumonia

Explanation

Pulmonary embolism obstructs pulmonary arteries, producing wedge-shaped perfusion defects while ventilation remains intact. This mismatch pattern is the classic finding.

Question 15General Nuclear Medicine (CNMT)

Which quality control test is performed on a Tc-99m generator to determine the amount of Mo-99 breakthrough?

  1. Measurement of the eluate pH
  2. Measurement of Mo-99 activity in the eluate Correct answer.
  3. Measurement of Tc-99m activity in the eluate
  4. Measurement of the eluate color

Explanation

Molybdenum breakthrough is evaluated by measuring Mo-99 activity in the eluate and comparing it with the Tc-99m activity. The limit is typically 0.15 kBq of Mo-99 per MBq of Tc-99m.

Question 16General Nuclear Medicine (CNMT)

What is the primary purpose of performing a radionuclide cystogram (RNC)?

  1. To evaluate renal cortical scarring
  2. To detect vesicoureteral reflux Correct answer.
  3. To assess renal artery stenosis
  4. To measure glomerular filtration rate

Explanation

A radionuclide cystogram instills radiotracer into the bladder and images during filling and voiding to detect reflux into the ureters. It is more sensitive than a plain fluoroscopic cystogram for reflux.

Question 17General Nuclear Medicine (CNMT)

Which radiopharmaceutical is used to evaluate liver and spleen function via the reticuloendothelial system?

  1. Tc-99m MDP
  2. Tc-99m DTPA
  3. Tc-99m sulfur colloid Correct answer.
  4. Tc-99m MAA

Explanation

Sulfur colloid particles are phagocytosed by Kupffer cells in the liver and macrophages in the spleen and marrow. Distribution reflects reticuloendothelial function and can reveal focal lesions.

Question 18General Nuclear Medicine (CNMT)

Which finding on a hepatobiliary scan suggests biliary atresia in a neonate?

  1. No bowel activity after adequate hepatic uptake Correct answer.
  2. Increased renal uptake of tracer
  3. Prompt gallbladder filling
  4. Uniform hepatic uptake with rapid bowel transit

Explanation

In biliary atresia, bile cannot reach the intestine, so no bowel activity appears even after adequate hepatic uptake. Neonatal hepatitis may show delayed but eventual bowel activity.

Question 19General Nuclear Medicine (CNMT)

Which radiopharmaceutical is used for a captopril renogram to detect renovascular hypertension?

  1. Tc-99m MAA
  2. Tc-99m sulfur colloid
  3. Tc-99m MDP
  4. Tc-99m MAG3 Correct answer.

Explanation

Captopril renography uses a tubular agent such as MAG3 to detect a decline in renal function after ACE inhibition in a kidney with renal artery stenosis. A positive study shows delayed uptake or retention on the affected side.

Question 20General Nuclear Medicine (CNMT)

What does a normal Tc-99m pertechnetate thyroid image show in a patient with Graves disease?

  1. Absent uptake in the gland
  2. Multiple cold nodules
  3. Diffusely increased uptake throughout an enlarged gland Correct answer.
  4. A single focal area of increased uptake

Explanation

Graves disease is caused by thyroid-stimulating immunoglobulins that drive diffuse glandular overactivity. The scan shows uniform, increased uptake in an enlarged gland.

Question 21General Nuclear Medicine (CNMT)

Which radiopharmaceutical is used for brain death confirmation with SPECT imaging?

  1. Tc-99m MDP
  2. Tc-99m MAA
  3. Tc-99m DTPA Correct answer.
  4. Tc-99m sulfur colloid

Explanation

A flow study with Tc-99m DTPA (or pertechnetate) is used to demonstrate absence of cerebral perfusion. Lack of intracranial activity is consistent with brain death.

Question 22General Nuclear Medicine (CNMT)

Which factor most affects the spatial resolution of a gamma camera image?

  1. The room temperature
  2. The type of computer monitor used
  3. The patient's skin color
  4. The collimator hole size and septal thickness Correct answer.

Explanation

Collimator geometry determines the acceptance angle of emitted photons and is the dominant factor in spatial resolution for a gamma camera. Smaller holes and appropriate septa improve resolution at the cost of sensitivity.

Question 23General Nuclear Medicine (CNMT)

Which collimator is best suited for imaging I-131?

  1. High-energy collimator Correct answer.
  2. Pinhole collimator
  3. Medium-energy collimator
  4. Low-energy collimator

Explanation

I-131 emits high-energy gamma photons (364 keV), so a high-energy collimator with thick septa is required to prevent septal penetration. Low- and medium-energy collimators would not adequately shield these photons.

Question 24General Nuclear Medicine (CNMT)

A patient is scheduled for a bone scan and reports recent use of a gadolinium-based contrast agent. What is the primary concern?

  1. Immediate anaphylaxis to the radiopharmaceutical
  2. Reduced generator yield
  3. Possible interference with tracer uptake interpretation Correct answer.
  4. Increased radiation dose to the bone marrow

Explanation

Gadolinium can alter tissue signal and has been associated with altered biodistribution or artifacts on some nuclear studies. The study may need to be delayed or interpreted with caution.

Question 25General Nuclear Medicine (CNMT)

Which radiopharmaceutical is used for lymphoscintigraphy of the sentinel node in melanoma?

  1. Tc-99m sulfur colloid Correct answer.
  2. Tc-99m MDP
  3. Tc-99m DTPA
  4. Tc-99m MAG3

Explanation

Filtered sulfur colloid is injected intradermally around the melanoma and imaged to identify the first draining node. It is the standard agent for lymphatic mapping.

Question 26General Nuclear Medicine (CNMT)

Which organ is the primary site of radiopharmaceutical uptake in a normal sulfur colloid liver-spleen scan?

  1. Bone marrow
  2. Spleen
  3. Lungs
  4. Liver Correct answer.

Explanation

Sulfur colloid is taken up by the reticuloendothelial system, with the majority of uptake in the liver (approximately 80-90%), followed by the spleen and bone marrow. This distribution reflects the density of Kupffer cells.

Question 27General Nuclear Medicine (CNMT)

What is the typical appearance of a normal gallbladder on a hepatobiliary scan?

  1. Nonvisualization at any time
  2. Visualization within 30 minutes of injection Correct answer.
  3. Visualization that appears simultaneously with the liver
  4. Visualization only after 4 hours

Explanation

In a normal hepatobiliary scan, the gallbladder should be visualized within 30 minutes (often by 15-20 minutes) after tracer administration. Nonvisualization beyond 60 minutes suggests cystic duct obstruction or chronic cholecystitis.

Question 28General Nuclear Medicine (CNMT)

Which radiopharmaceutical is most commonly used for a renal perfusion and function study (renogram)?

  1. Tc-99m pertechnetate
  2. Tc-99m DTPA Correct answer.
  3. Tc-99m sulfur colloid
  4. Tc-99m MDP

Explanation

Tc-99m DTPA is filtered by the glomeruli and is used to assess renal perfusion and glomerular filtration rate. It provides both vascular and functional information in a renogram.

Question 29General Nuclear Medicine (CNMT)

Which finding on a thyroid uptake scan is most characteristic of subacute thyroiditis?

  1. Diffusely increased uptake
  2. Focally increased uptake
  3. Markedly decreased uptake Correct answer.
  4. Normal uptake

Explanation

Subacute thyroiditis typically presents with a painful goiter and markedly reduced or absent thyroid uptake due to follicular destruction and release of preformed hormone. This distinguishes it from Graves' disease, which shows diffusely increased uptake.

Question 30General Nuclear Medicine (CNMT)

A bone scan performed 24 hours after a radionuclide cystogram using Tc-99m DTPA shows intense uptake in the kidneys and bladder. What is the most likely cause?

  1. Recent administration of a nephrotoxic drug
  2. Residual activity from the prior study Correct answer.
  3. Urinary tract infection
  4. Renal failure

Explanation

Tc-99m DTPA is cleared by the kidneys, and residual activity from a recent cystogram can persist in the kidneys and bladder for up to 24 hours, causing intense uptake on a subsequent bone scan. This is a recognized pitfall that can mimic renal pathology.

Question 31General Nuclear Medicine (CNMT)

Which parameter is most important to monitor to ensure proper performance of a dose calibrator?

  1. Temperature
  2. Humidity
  3. Constancy Correct answer.
  4. Light level

Explanation

Constancy is a daily quality control test that verifies the dose calibrator's response over time using a long-lived source. It ensures that the instrument's measurements remain stable and accurate.

Question 32General Nuclear Medicine (CNMT)

What is the primary reason for using a pinhole collimator in thyroid imaging?

  1. To magnify the image and improve spatial resolution Correct answer.
  2. To increase sensitivity for low-count studies
  3. To allow simultaneous imaging of both thyroid lobes
  4. To reduce scatter from surrounding tissues

Explanation

A pinhole collimator provides magnification of small organs such as the thyroid, which improves spatial resolution and allows detection of small nodules. The trade-off is reduced sensitivity and a limited field of view.

Question 33General Nuclear Medicine (CNMT)

A patient with suspected pulmonary embolism undergoes a V/Q scan. The perfusion images show a single subsegmental defect, while the ventilation images are normal. How should this finding be interpreted?

  1. Low probability of pulmonary embolism Correct answer.
  2. Normal study
  3. High probability of pulmonary embolism
  4. Indeterminate for pulmonary embolism

Explanation

A single subsegmental mismatched defect is considered low probability for pulmonary embolism according to the PIOPED criteria. High probability requires multiple segmental or larger mismatched defects.

Question 34General Nuclear Medicine (CNMT)

Which radiopharmaceutical is used for a direct radionuclide cystogram (DRNC) to evaluate vesicoureteral reflux?

  1. Tc-99m MAA
  2. Tc-99m pertechnetate Correct answer.
  3. Tc-99m DTPA
  4. Tc-99m sulfur colloid

Explanation

Tc-99m pertechnetate is commonly used for direct radionuclide cystography because it is inexpensive, readily available, and provides good counting statistics. It is instilled into the bladder along with saline.

Question 35General Nuclear Medicine (CNMT)

A patient with a suspected pheochromocytoma undergoes I-123 MIBG imaging. Which medication must be discontinued before the study to avoid false-negative results?

  1. Labetalol Correct answer.
  2. Levothyroxine
  3. Omeprazole
  4. Metformin

Explanation

Labetalol and other sympathomimetic amines can interfere with MIBG uptake and lead to false-negative results. It should be discontinued for at least 5-7 days before the study.

Question 36General Nuclear Medicine (CNMT)

Which statement best describes the purpose of a transmission scan (e.g., with a Co-57 sheet source) in PET/CT imaging?

  1. To assess renal function
  2. To correct for photon attenuation Correct answer.
  3. To measure patient blood glucose level
  4. To determine the injected dose

Explanation

A transmission scan uses an external source to measure photon attenuation through the patient's body, which is then used to correct the emission data. This improves image quality and quantitative accuracy.

Question 37General Nuclear Medicine (CNMT)

A 65-year-old man with known coronary artery disease undergoes a stress myocardial perfusion scan. The images show a reversible defect in the inferior wall. What is the most likely cause?

  1. Artifact from diaphragmatic attenuation
  2. Myocardial infarction
  3. Normal variant
  4. Ischemia Correct answer.

Explanation

A reversible defect (present on stress, absent on rest) indicates ischemia. Fixed defects are more consistent with infarction or artifact.

Question 38General Nuclear Medicine (CNMT)

Which radiopharmaceutical is used for a gastric emptying study?

  1. Tc-99m pertechnetate in milk
  2. Tc-99m sulfur colloid in scrambled eggs Correct answer.
  3. Tc-99m MAA in water
  4. Tc-99m DTPA in orange juice

Explanation

For a gastric emptying study, the radiopharmaceutical is typically mixed with a solid meal such as scrambled eggs. Tc-99m sulfur colloid is commonly used because it binds well to the egg and is not absorbed.

Question 39General Nuclear Medicine (CNMT)

A patient is scheduled for a Tc-99m bone scan. Which medication should be discontinued for at least 24 hours before the study to avoid potential interference with bone uptake?

  1. Lisinopril
  2. Atorvastatin
  3. Acetaminophen
  4. Iron supplements Correct answer.

Explanation

Iron supplements can interfere with Tc-99m MDP bone scan by causing increased uptake in the liver and spleen or by competing with the tracer. They should be withheld for 24 hours before the study if clinically feasible.

Question 40General Nuclear Medicine (CNMT)

In a Tc-99m DTPA aerosol ventilation study, what is the primary purpose of adding a small amount of oxygen to the aerosol?

  1. To enhance alveolar deposition
  2. To reduce clumping of particles
  3. To prevent hypoxia during the study Correct answer.
  4. To improve aerosol particle size

Explanation

Adding oxygen to the aerosol helps prevent hypoxia in patients during the ventilation study, especially those with compromised pulmonary function. It does not significantly alter particle size or deposition.

Question 41Computed Tomography (NMTCB(CT), post-primary)

On a CT image, the gray scale is calibrated so that water is assigned a Hounsfield unit value of approximately what number?

  1. 1000
  2. 0 Correct answer.
  3. -1000
  4. 100

Explanation

The Hounsfield scale is defined with water at 0 HU, air near -1000 HU, and dense bone well above 0 HU. This calibration allows tissue attenuation to be compared consistently across scanners.

Question 42Computed Tomography (NMTCB(CT), post-primary)

Which CT reconstruction filter kernel would best preserve fine bony detail in a head CT?

  1. A low-pass noise-reduction kernel
  2. A smooth soft-tissue kernel
  3. A standard soft-tissue kernel
  4. A sharp high-frequency kernel Correct answer.

Explanation

Sharp (high-frequency, bone) kernels enhance edge detail and are used when spatial resolution of dense structures matters most. Smooth kernels suppress high frequencies and blur fine bony trabeculae.

Question 43Computed Tomography (NMTCB(CT), post-primary)

CTDIvol is best described as which of the following?

  1. A standardized index of absorbed dose to a phantom Correct answer.
  2. The dose to a single point in the scan volume
  3. The effective dose in millisieverts
  4. The total energy absorbed by the entire patient

Explanation

CTDIvol is a phantom-based dose index that reflects scanner output normalized to a standard phantom and pitch. It is not a patient-specific absorbed dose or an effective dose.

Question 44Computed Tomography (NMTCB(CT), post-primary)

In CT, increasing the tube current (mAs) while all other parameters are held constant primarily affects which of the following?

  1. Spatial resolution
  2. Slice thickness
  3. Beam hardening
  4. Quantum noise Correct answer.

Explanation

Tube current determines the number of photons reaching the detectors, so higher mAs reduces quantum noise. Spatial resolution and slice thickness are governed by other parameters such as detector size and collimation.

Question 45Computed Tomography (NMTCB(CT), post-primary)

Which of the following best describes the purpose of a bowtie filter in CT?

  1. To shape the beam intensity to the patient's cross-section Correct answer.
  2. To improve high-contrast spatial resolution
  3. To increase the effective energy of the beam
  4. To reduce scatter reaching the detectors

Explanation

The bowtie filter attenuates the beam at the periphery and passes more centrally, matching the roughly cylindrical patient shape. This reduces peripheral dose and detector dynamic-range demands.

Question 46Computed Tomography (NMTCB(CT), post-primary)

Which of the following is a common clinical indication for performing a CT attenuation correction study in nuclear medicine?

  1. To measure bone mineral density
  2. To assess renal perfusion
  3. To calculate the patient's glomerular filtration rate
  4. To provide attenuation maps for PET or SPECT emission data Correct answer.

Explanation

CT-based attenuation correction uses a low-dose CT acquisition to generate attenuation maps that correct emission data in PET/CT and SPECT/CT. This improves quantitative accuracy and image quality.

Question 47Computed Tomography (NMTCB(CT), post-primary)

A CT reconstruction algorithm that models the geometry of the acquisition and iteratively updates the image estimate is known as which of the following?

  1. Filtered back projection
  2. Iterative reconstruction Correct answer.
  3. Fourier reconstruction
  4. Simple back projection

Explanation

Iterative reconstruction repeatedly compares forward projections of an image estimate to measured data and updates the image. This reduces noise and artifacts compared with analytic methods such as filtered back projection.

Question 48Computed Tomography (NMTCB(CT), post-primary)

Which of the following is the primary reason CT images are acquired with narrow detector collimation rather than wide collimation?

  1. To reduce scatter and improve slice profile Correct answer.
  2. To eliminate the need for reconstruction filters
  3. To increase the field of view
  4. To lower the tube voltage

Explanation

Narrow collimation limits the illuminated volume, reducing scatter and improving the slice sensitivity profile. Field of view and kVp are independent of collimation width.

Question 49Computed Tomography (NMTCB(CT), post-primary)

A region of a CT image appears as bright streaks radiating from a dense metallic implant. This is most characteristic of which artifact?

  1. Metal artifact Correct answer.
  2. Motion artifact
  3. Beam-hardening artifact
  4. Photon starvation artifact

Explanation

Dense metal causes severe attenuation and photon starvation along some ray paths, producing characteristic bright and dark streaks. Dedicated metal artifact reduction algorithms can reduce these streaks.

Question 50Computed Tomography (NMTCB(CT), post-primary)

During a PET/CT study, the CT transmission data are used to generate which of the following?

  1. A randoms correction factor
  2. An attenuation correction map Correct answer.
  3. A normalization table
  4. A scatter correction matrix

Explanation

CT data are converted from Hounsfield units to attenuation coefficients at the emission energy to produce an attenuation map. This map is applied to correct PET or SPECT emission data.