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NMTCB(RS) study materials
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NMTCB(RS) practice questions

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Question 1General Nuclear Medicine (CNMT)

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

  1. Tc-99m DTPA
  2. Tc-99m MDP Correct answer.
  3. Tc-99m sulfur colloid
  4. Ga-67 citrate

Explanation

Tc-99m labeled diphosphonates such as MDP localize to bone by chemisorption onto hydroxyapatite crystal surfaces. They provide high target-to-background uptake with the favorable imaging characteristics of Tc-99m.

Question 2General Nuclear Medicine (CNMT)

What is the primary mechanism by which Tc-99m pertechnetate is concentrated in the thyroid gland?

  1. Receptor-mediated endocytosis of iodide
  2. Binding to thyroglobulin in the colloid
  3. Passive diffusion across follicular membranes
  4. Active transport via the sodium-iodide symporter Correct answer.

Explanation

The thyroid follicular cell traps pertechnetate through the sodium-iodide symporter, the same active transport mechanism used for iodide. Pertechnetate is trapped but not organified, so it reflects trapping function rather than hormone synthesis.

Question 3General Nuclear Medicine (CNMT)

A patient is injected with Tc-99m MAA for a lung perfusion scan. What is the expected distribution pattern in a normal study?

  1. Activity concentrated in the lung apices
  2. No pulmonary activity because MAA is cleared hepatically
  3. Uniform activity throughout both lung fields with gravity-dependent gradient Correct answer.
  4. Intense uptake in the central hila only

Explanation

MAA particles lodge in the pulmonary capillary bed in proportion to regional blood flow, producing a fairly uniform distribution with a slight gradient toward dependent regions. Any focal deficit suggests a perfusion defect.

Question 4General Nuclear Medicine (CNMT)

Which tracer is preferred for detecting a Meckel diverticulum containing ectopic gastric mucosa?

  1. Tc-99m pertechnetate Correct answer.
  2. Tc-99m MDP
  3. In-111 oxine
  4. Tc-99m sulfur colloid

Explanation

Pertechnetate is taken up by ectopic gastric mucosa, which is present in a bleeding Meckel diverticulum. The study is most sensitive when the diverticulum contains sufficient gastric tissue.

Question 5General Nuclear Medicine (CNMT)

In a gastric emptying study, which finding is most consistent with delayed emptying?

  1. More than 10 percent of the meal retained at 4 hours Correct answer.
  2. Uniform tracer distribution in the stomach at 1 hour
  3. Rapid clearance of tracer within 30 minutes
  4. Early antral activity with prompt small bowel transit

Explanation

Gastric emptying is generally considered delayed when retention exceeds the established reference value at 4 hours, commonly about 10 percent for a solid meal. Retention above that threshold supports gastroparesis.

Question 6General Nuclear Medicine (CNMT)

A hepatobiliary scan shows prompt liver uptake but no gallbladder visualization at 4 hours, with normal small bowel activity. What is the most likely interpretation?

  1. Acute cholecystitis Correct answer.
  2. Common bile duct obstruction
  3. Normal variant with no abnormality
  4. Hepatocellular failure

Explanation

Nonvisualization of the gallbladder with preserved liver uptake and bile reaching the bowel indicates cystic duct obstruction, classically acute cholecystitis. Small bowel activity confirms that the common duct is patent.

Question 7General Nuclear Medicine (CNMT)

What is the purpose of adding stannous ion in the preparation of Tc-99m labeled radiopharmaceuticals?

  1. To reduce pertechnetate so it can bind to the ligand Correct answer.
  2. To increase the pH of the final product
  3. To chelate free pertechnetate for renal excretion
  4. To act as a bacteriostatic preservative

Explanation

Stannous ion reduces pertechnetate from the +7 to a lower oxidation state, allowing it to bind to the ligand in the kit. Without adequate reduction, free pertechnetate remains and degrades image quality.

Question 8General Nuclear Medicine (CNMT)

Which radiopharmaceutical is used for sentinel lymph node localization before surgery?

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

Explanation

Filtered sulfur colloid particles are small enough to migrate through lymphatics and are retained in the sentinel node. This allows preoperative or intraoperative identification of the first draining node.

Question 9General Nuclear Medicine (CNMT)

Which agent is most appropriate for a parathyroid localization study when a dual-phase technique is planned?

  1. I-123 sodium iodide
  2. Tc-99m sestamibi Correct answer.
  3. Tc-99m MAA
  4. Tc-99m DMSA

Explanation

Sestamibi accumulates in thyroid and parathyroid tissue but washes out of normal thyroid more rapidly, so delayed images can reveal parathyroid adenomas. This differential washout underlies the dual-phase technique.

Question 10General Nuclear Medicine (CNMT)

In a renal scan, what does the term split renal function describe?

  1. The ratio of glomerular filtration to tubular secretion
  2. The difference between peak and baseline activity in the bladder
  3. The division of renal uptake between cortex and medulla
  4. The relative contribution of each kidney to total renal function Correct answer.

Explanation

Split renal function expresses each kidney's percentage share of total function, typically derived from uptake during the cortical or parenchymal phase. It is useful for assessing asymmetric renal impairment.

Question 11General Nuclear Medicine (CNMT)

A patient with suspected pulmonary embolism has a ventilation/perfusion scan. Which pattern is most suggestive of pulmonary embolism?

  1. Diffuse uniform tracer distribution
  2. Mismatched perfusion defects with normal ventilation Correct answer.
  3. Matched defects in both ventilation and perfusion
  4. Increased perfusion in the affected region

Explanation

Pulmonary embolism produces perfusion defects because blood flow is obstructed while ventilation to the same region remains intact, creating a mismatch. Matched defects are more typical of parenchymal lung disease.

Question 12General Nuclear Medicine (CNMT)

Which statement best describes the normal biodistribution of I-123 MIBG?

  1. Uptake in salivary glands, liver, and myocardium Correct answer.
  2. Uptake in thyroid and stomach
  3. Uptake in renal cortex and bladder
  4. Uptake in bone marrow and spleen only

Explanation

MIBG is an analog of norepinephrine and is taken up by sympathetic nerve terminals, producing normal uptake in salivary glands, liver, and myocardium. Recognizing this pattern helps distinguish physiologic from pathologic uptake.

Question 13General Nuclear Medicine (CNMT)

What is the primary purpose of a transmission scan in PET imaging?

  1. To calibrate the patient's blood glucose level
  2. To measure tissue attenuation for correction Correct answer.
  3. To improve spatial resolution of the scanner
  4. To reduce the injected dose required

Explanation

Transmission or CT-based attenuation data allow the reconstruction to correct for photon attenuation within the patient. Without attenuation correction, deep structures appear artificially low in activity.

Question 14General Nuclear Medicine (CNMT)

During a gastric emptying study, the patient should be instructed to do which of the following?

  1. Void immediately before each image
  2. Lie supine for the entire study
  3. Fast for 24 hours before the test
  4. Remain upright and maintain consistent positioning between images Correct answer.

Explanation

Consistent positioning, typically upright, ensures that gastric geometry is reproducible across images so that retention can be compared accurately. Changing posture alters gastric emptying and image geometry.

Question 15General Nuclear Medicine (CNMT)

A bone scan shows intense uptake in the region of a healing fracture. What is the most likely explanation?

  1. Normal physiologic uptake unrelated to the fracture
  2. Decreased bone mineral density at the site
  3. Increased osteoblastic activity and blood flow at the repair site Correct answer.
  4. Artifact from patient motion

Explanation

Bone-seeking tracers accumulate where osteoblastic activity and regional blood flow are increased, as occurs during fracture healing. Uptake can remain elevated for months after the injury.

Question 16General Nuclear Medicine (CNMT)

What is the most common cause of a false-positive finding on a Tc-99m MAA lung perfusion scan?

  1. Incomplete labeling of the MAA kit
  2. Physiologic clearance of particles
  3. Normal gravity-dependent gradient
  4. Particle clumping or injection into an artery Correct answer.

Explanation

Clumped MAA particles or inadvertent arterial injection can produce focal hot spots or abnormal distribution that mimic disease. Careful preparation and intravenous administration reduce this artifact.

Question 17General Nuclear Medicine (CNMT)

Which patient preparation is required before a thyroid uptake study with I-123?

  1. Avoiding iodine-containing medications and contrast for an appropriate interval Correct answer.
  2. Discontinuing all antihypertensive drugs for one week
  3. Fasting for 12 hours
  4. Voiding immediately before injection

Explanation

Iodine-containing medications, supplements, and contrast media can block thyroid uptake and invalidate the study. The required washout interval depends on the specific agent.

Question 18General Nuclear Medicine (CNMT)

In a normal liver-spleen scan with Tc-99m sulfur colloid, which organ typically shows the greatest uptake?

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

Explanation

Sulfur colloid is phagocytosed by the reticuloendothelial system, and the liver contains the largest mass of these cells. The spleen shows lesser uptake, and marrow appears only when hepatic clearance is impaired.

Question 19General Nuclear Medicine (CNMT)

A myocardial perfusion study uses Tc-99m sestamibi. What property allows delayed imaging after injection?

  1. Diffusion into extracellular fluid
  2. Retention in myocardial mitochondria with slow redistribution Correct answer.
  3. Rapid renal clearance
  4. Binding to red blood cells

Explanation

Sestamibi accumulates in myocardial mitochondria and remains trapped with minimal redistribution, allowing imaging to occur after the stress or rest injection. This property supports separate stress and rest acquisitions.

Question 20General Nuclear Medicine (CNMT)

Which finding on a radioiodine whole-body scan suggests functioning thyroid tissue in the neck?

  1. Uptake in the urinary bladder
  2. Uniform uptake in the salivary glands
  3. Diffuse uptake in the liver
  4. Focal uptake in the thyroid bed Correct answer.

Explanation

Radioiodine is trapped and organified by thyroid tissue, so focal uptake in the thyroid bed represents functioning thyroid tissue. Extrathyroidal uptake should be evaluated for metastatic disease or physiologic excretion.

Question 21General Nuclear Medicine (CNMT)

What is the primary purpose of a diuretic challenge during a renal scan?

  1. To increase renal blood flow for better visualization
  2. To improve glomerular filtration rate measurement
  3. To distinguish obstructive uropathy from nonobstructive stasis Correct answer.
  4. To reduce radiation dose to the bladder

Explanation

A diuretic such as furosemide promotes urine flow, helping differentiate a dilated but unobstructed collecting system from true obstruction. Washout after the diuretic suggests stasis rather than obstruction.

Question 22General Nuclear Medicine (CNMT)

Which radiopharmaceutical is used for a lymphoscintigram of the lower extremity?

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

Explanation

Filtered sulfur colloid particles are small enough to enter lymphatic channels and are retained in lymph nodes, allowing mapping of lymphatic drainage. It is commonly used for sentinel node and lymphedema evaluation.

Question 23General Nuclear Medicine (CNMT)

A patient scheduled for a bone scan has a recent nuclear medicine study using a long-lived isotope. What is the main concern regarding the timing of the bone scan?

  1. Residual activity from the prior study may interfere with image interpretation Correct answer.
  2. The prior study may alter renal clearance of MDP
  3. The prior isotope may reduce the half-life of Tc-99m
  4. The bone scan tracer may displace the prior isotope

Explanation

Residual activity from a prior study can obscure or mimic findings on the new scan, so the timing should account for the physical half-life of the earlier isotope. This is especially important with agents that have long half-lives.

Question 24General Nuclear Medicine (CNMT)

What is the purpose of acquiring anterior and posterior views in a whole-body bone scan?

  1. To increase the injected dose
  2. To account for attenuation and improve lesion detection Correct answer.
  3. To reduce imaging time
  4. To measure renal function

Explanation

Anterior and posterior views provide complementary information because lesions closer to the detector appear more intense, and attenuation differs by view. Together they improve detection and localization of lesions.

Question 25General Nuclear Medicine (CNMT)

Which statement about the use of Tc-99m DMSA is correct?

  1. It binds to renal cortical tubules and is used for cortical imaging Correct answer.
  2. It is filtered and excreted rapidly by glomeruli
  3. It is taken up by the reticuloendothelial system
  4. It localizes to bone mineral

Explanation

DMSA binds to proximal tubular cells, providing images of functioning renal cortex. Cortical defects appear as areas of reduced uptake, which is useful for detecting scarring or pyelonephritis.

Question 26General Nuclear Medicine (CNMT)

Which radiopharmaceutical is most commonly used for a first-pass radionuclide ventriculography (MUGA) study to assess left ventricular function?

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

Explanation

First-pass studies require a bolus of activity that remains in the vascular pool during the initial transit through the heart, and Tc-99m pertechnetate given as a tight bolus is standard. The other agents either bind bone, deposit in lung, or are cleared by the reticuloendothelial system.

Question 27General Nuclear Medicine (CNMT)

A patient arrives for a Tc-99m MDP bone scan and reports voiding two hours ago. What instruction should be given before imaging?

  1. Have the patient void again immediately before imaging Correct answer.
  2. Have the patient drink two liters of water and return in one hour
  3. Ask the patient to hold urine until the scan is finished
  4. Delay imaging until the patient has fasted for six hours

Explanation

A full bladder can obscure pelvic bones and adds unnecessary radiation dose to the patient, so voiding just before imaging is standard practice. Hydration and frequent voiding after injection also improve image quality by reducing soft-tissue background.

Question 28General Nuclear Medicine (CNMT)

Which collimator is generally preferred for imaging I-131 in the thyroid bed?

  1. Low-energy high-resolution
  2. High-energy parallel-hole Correct answer.
  3. Medium-energy parallel-hole
  4. Pinhole with low-energy insert

Explanation

I-131 emits high-energy photons (364 keV), so a high-energy collimator is needed to limit septal penetration and scatter. Lower-energy collimators are designed for photons below about 200 keV and would produce poor resolution with I-131.

Question 29General Nuclear Medicine (CNMT)

What is the physical half-life of Tc-99m?

  1. 6 hours Correct answer.
  2. 2.8 days
  3. 13 hours
  4. 8 days

Explanation

Tc-99m has a physical half-life of approximately 6 hours, which is convenient for same-day imaging while limiting patient dose. The 2.8-day value corresponds to the Mo-99 parent, and 13 hours corresponds to I-123.

Question 30General Nuclear Medicine (CNMT)

In a Tc-99m MAA perfusion lung scan, what does a wedge-shaped defect with pleural-based concavity most directly indicate?

  1. Diffuse alveolar inflammation
  2. Reduced regional pulmonary blood flow Correct answer.
  3. Pleural effusion compressing the lung
  4. Airway obstruction with air trapping

Explanation

MAA particles are trapped in pulmonary capillaries in proportion to regional blood flow, so a defect reflects decreased perfusion to that segment. Ventilation imaging is needed to distinguish matched from mismatched defects.

Question 31General Nuclear Medicine (CNMT)

Which patient instruction is appropriate before a Tc-99m sulfur colloid liver-spleen scan?

  1. Avoid all caffeine for 24 hours
  2. Discontinue thyroid medication for one week
  3. No specific dietary restriction is required Correct answer.
  4. Fast for at least eight hours

Explanation

A sulfur colloid liver-spleen scan does not depend on fasting, thyroid status, or caffeine intake, so no special dietary preparation is needed. Routine identification and pregnancy screening still apply.

Question 32General Nuclear Medicine (CNMT)

Which radionuclide is used as the parent in a generator to produce Tc-99m?

  1. Ga-68
  2. I-123
  3. Mo-99 Correct answer.
  4. Sr-82

Explanation

A Mo-99/Tc-99m generator produces Tc-99m by decay of its molybdenum parent, which is adsorbed on an alumina column. The other nuclides are either reactor- or cyclotron-produced or come from different generators.

Question 33General Nuclear Medicine (CNMT)

What is the purpose of a pinhole collimator when imaging a small structure such as the thyroid?

  1. To magnify the image and improve spatial resolution Correct answer.
  2. To reduce the injected dose required
  3. To allow simultaneous dual-isotope imaging
  4. To shorten the acquisition time

Explanation

A pinhole collimator uses a small aperture to project a magnified image of a small organ onto the detector, improving resolution of fine detail. It does not change the administered activity, acquisition duration, or allow dual-isotope separation.

Question 34General Nuclear Medicine (CNMT)

A patient has a suspected bone infection near a joint prosthesis. Which combined study is most useful for distinguishing infection from normal postoperative change?

  1. Tc-99m MAA perfusion scan with a ventilation scan
  2. Tc-99m sulfur colloid scan alone
  3. Tc-99m MDP bone scan with an In-111 labeled leukocyte scan Correct answer.
  4. I-123 MIBG scan with a whole-body sweep

Explanation

Bone-seeking tracer uptake alone can remain elevated for months after surgery, so pairing a bone scan with labeled leukocytes improves specificity for infection. Concordant increased uptake on both studies favors osteomyelitis.

Question 35General Nuclear Medicine (CNMT)

During a Tc-99m DTPA aerosol ventilation study, the patient suddenly develops a cough and the camera shows intense central airway activity. What is the most appropriate interpretation?

  1. Diffuse pulmonary embolism affecting both lungs
  2. Normal uniform alveolar distribution
  3. Central deposition from turbulent airflow, reducing peripheral lung information Correct answer.
  4. Complete tracheal obstruction

Explanation

Coughing and turbulent airflow cause the aerosol to deposit in the large airways rather than reaching the alveoli, which degrades the peripheral ventilation image. Peripheral, uniform deposition is the goal of an adequate ventilation study.

Question 36General Nuclear Medicine (CNMT)

Why is a Tc-99m labeled red blood cell study preferred over Tc-99m pertechnetate for detecting gastrointestinal bleeding?

  1. Labeled red cells are taken up by the liver and spleen
  2. Pertechnetate cannot be imaged in the abdomen
  3. Pertechnetate is cleared too slowly to show bleeding
  4. Labeled red cells remain in the vascular space longer, allowing delayed imaging Correct answer.

Explanation

In vitro or modified in vivo labeling keeps the activity within the blood pool for hours, allowing repeated imaging to detect intermittent bleeding. Pertechnetate leaks from vessels and is also taken up by the thyroid, stomach, and salivary glands.

Question 37General Nuclear Medicine (CNMT)

A patient is scheduled for a Tc-99m DMSA renal cortical scan. Which statement best describes the expected normal distribution?

  1. Cortical binding with the highest concentration in the kidneys Correct answer.
  2. Rapid glomerular filtration with early bladder filling
  3. Bone marrow uptake with splenic clearance
  4. Hepatobiliary excretion with gallbladder visualization

Explanation

DMSA binds to proximal tubular cells, giving a cortical image of functioning renal tissue with high kidney-to-background ratio. It is not primarily filtered like MAG3 or DTPA, so it does not provide a dynamic clearance curve.

Question 38General Nuclear Medicine (CNMT)

A parathyroid sestamibi scan shows persistent focal uptake in the neck on delayed images. What does this finding most likely represent?

  1. Normal thyroid tissue with rapid washout
  2. A hot thyroid nodule that has cleared
  3. Salivary gland uptake that has faded
  4. A parathyroid adenoma retaining the tracer Correct answer.

Explanation

Parathyroid adenomas typically retain sestamibi longer than normal thyroid tissue, so focal activity that persists on delayed imaging suggests adenoma. Normal thyroid tissue generally washes out faster than abnormal parathyroid tissue.

Question 39General Nuclear Medicine (CNMT)

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

  1. The energy window width only
  2. The radiopharmaceutical half-life
  3. Intrinsic detector resolution and collimator geometry Correct answer.
  4. Patient body weight alone

Explanation

Overall spatial resolution depends on the intrinsic resolution of the detector crystal and, in most clinical systems, the collimator's hole size and length. The collimator is often the dominant limiting factor in planar imaging.

Question 40General Nuclear Medicine (CNMT)

A thyroid uptake study is planned with I-123. Which medication history would most likely cause falsely low uptake?

  1. Recent use of acetaminophen
  2. Recent intake of thyroid hormone replacement Correct answer.
  3. Recent use of inhaled bronchodilators
  4. Recent use of oral antihistamines

Explanation

Exogenous thyroid hormone suppresses TSH and reduces thyroidal iodine uptake, producing a falsely low result. Antithyroid drugs, iodinated contrast, and iodine-rich foods can also interfere and should be documented.

Question 41General Nuclear Medicine (CNMT)

Why is a transmission scan acquired during a PET/CT or dedicated PET study?

  1. To measure the radiopharmaceutical half-life
  2. To confirm the injected dose in the syringe
  3. To measure tissue attenuation for correction of emission data Correct answer.
  4. To assess renal clearance of the tracer

Explanation

A transmission scan uses an external source to map tissue density so that attenuation of annihilation photons can be corrected. Modern PET/CT systems derive this correction from the CT images.

Question 42General Nuclear Medicine (CNMT)

A patient with a suspected pheochromocytoma is scheduled for I-123 MIBG imaging. Which medication should be reviewed because it can interfere with MIBG uptake?

  1. Acetaminophen
  2. Tricyclic antidepressants Correct answer.
  3. Inhaled corticosteroids
  4. Oral contraceptives

Explanation

Many sympathomimetic and antidepressant drugs block the norepinephrine transporter and reduce MIBG uptake, so a medication review is essential. Acetaminophen, oral contraceptives, and inhaled steroids are not classic MIBG blockers.

Question 43General Nuclear Medicine (CNMT)

During a gastric emptying study, a region of interest is drawn over the stomach. Which parameter is typically reported?

  1. Peak hepatic uptake time
  2. Bone-to-soft-tissue ratio
  3. Percentage of activity remaining at specified time points Correct answer.
  4. Renal split function

Explanation

Gastric emptying is quantified by measuring the fraction of the meal remaining in the stomach at set intervals, commonly 1, 2, and 4 hours. The result is expressed as a percentage of the initial activity.

Question 44General Nuclear Medicine (CNMT)

A patient with a suspected cerebrospinal fluid leak undergoes a radionuclide cisternogram. Which finding confirms a leak?

  1. Delayed appearance of activity in the basal cisterns
  2. Uniform activity along the spinal canal
  3. Activity in the bladder within two hours
  4. Activity appearing outside the subarachnoid space in the nasal or ear region Correct answer.

Explanation

A cisternogram places tracer into the subarachnoid space, so activity detected outside that space, such as on pledgets in the nasal cavity, indicates a leak. Normal studies show activity confined to the CSF pathways.

Question 45General Nuclear Medicine (CNMT)

A brain death study is performed with Tc-99m pertechnetate. What finding supports the diagnosis of brain death?

  1. Absence of intracranial perfusion with activity in the scalp and superior sagittal sinus Correct answer.
  2. Increased cerebellar uptake relative to the cerebrum
  3. Delayed but present cerebral perfusion
  4. Intense uniform cortical perfusion

Explanation

In brain death, cerebral perfusion ceases while scalp and venous sinus activity may persist from external carotid flow, producing the characteristic hollow-skull appearance. Normal studies show cortical perfusion.

Question 46General Nuclear Medicine (CNMT)

A technologist notices that a Tc-99m eluate contains an unusually high concentration of Mo-99. What is the primary concern?

  1. Immediate precipitation of the radiopharmaceutical
  2. Loss of the generator column
  3. A shortened Tc-99m half-life
  4. Increased patient dose from Mo-99 photons and reduced image quality Correct answer.

Explanation

Mo-99 breakthrough delivers unwanted high-energy photons and extra dose to the patient, and the extra activity can degrade image quality. Generator eluate must be tested for Mo-99 breakthrough before use.

Question 47General Nuclear Medicine (CNMT)

In a pediatric patient, the administered activity for a Tc-99m DMSA scan should be determined primarily by which factor?

  1. The patient's age in months only
  2. The size of the imaging table
  3. The room background count rate
  4. Body weight or body surface area using a pediatric dose schedule Correct answer.

Explanation

Pediatric dosing uses a weight- or surface-area-based schedule with a minimum activity to ensure adequate counts. Age alone is less accurate because body size varies widely among children of the same age.

Question 48General Nuclear Medicine (CNMT)

A liver-spleen scan with Tc-99m sulfur colloid shows multiple focal areas of decreased uptake. Which interpretation is most appropriate?

  1. Diffuse hepatocellular dysfunction
  2. Splenic infarction
  3. Space-occupying lesions such as metastases or cysts Correct answer.
  4. Normal variant uptake in the porta hepatis

Explanation

Sulfur colloid is taken up by functioning reticuloendothelial cells, so lesions that displace these cells appear as photopenic defects. Multiple defects raise concern for metastatic disease or other space-occupying processes.

Question 49General Nuclear Medicine (CNMT)

A Tc-99m MAG3 renogram shows a renogram curve that rises continuously without a clear excretory phase in one kidney. What is the most likely explanation?

  1. Complete absence of renal blood flow
  2. Radiopharmaceutical labeling failure
  3. Obstruction at the ureteropelvic junction Correct answer.
  4. Normal function with rapid washout

Explanation

A continuously rising curve indicates retained tracer, consistent with obstruction, especially when a diuretic challenge fails to produce washout. A normal curve rises to a peak and then declines as tracer is excreted.

Question 50General Nuclear Medicine (CNMT)

A patient with a suspected Meckel diverticulum undergoes a Tc-99m pertechnetate scan. Which finding is most specific for a positive study?

  1. Uniform hepatic uptake
  2. Diffuse activity throughout the small bowel
  3. Focal activity in the right lower quadrant that appears with gastric mucosa and moves with peristalsis Correct answer.
  4. Activity in the bladder that increases over time

Explanation

Ectopic gastric mucosa in a Meckel diverticulum concentrates pertechnetate, producing focal activity that appears concurrently with the stomach and may move with bowel peristalsis. Activity confined to the stomach or bladder is expected and not diagnostic.