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CAMRT Nuclear Medicine study materials
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CAMRT Nuclear Medicine practice questions

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Question 1Nuclear Medicine

Which radionuclide is most commonly used as the labeling agent in routine skeletal scintigraphy?

  1. Thallium-201
  2. Technetium-99m Correct answer.
  3. Iodine-131
  4. Gallium-67

Explanation

Technetium-99m is the workhorse of nuclear medicine because it has a 6-hour half-life, a 140 keV gamma emission ideal for gamma cameras, and is readily available from a generator. It is bound to diphosphonates for bone imaging. The other listed radionuclides have different emission energies and clinical roles.

Question 2Nuclear Medicine

The 140 keV photon emitted by technetium-99m is advantageous for gamma camera imaging primarily because it:

  1. Balances tissue penetration with efficient collimator and crystal detection Correct answer.
  2. Allows imaging without any collimator
  3. Matches the energy of positron annihilation photons
  4. Is below the energy of most scattered photons

Explanation

Photons around 140 keV penetrate tissue adequately while still being efficiently stopped by thin sodium iodide crystals and lead collimators. Much lower energies are heavily attenuated by tissue, while much higher energies require thicker septa and reduce spatial resolution. This intermediate energy therefore offers a practical compromise for planar and SPECT imaging.

Question 3Nuclear Medicine

During a gastric emptying study, the patient should be positioned:

  1. Supine for the entire acquisition Correct answer.
  2. Alternating between left and right lateral decubitus
  3. Seated upright for the entire acquisition
  4. Anterior with the patient standing and walking between images

Explanation

Gastric emptying is standardized with the patient supine so that gravity does not accelerate emptying and geometry remains constant between frames. Anterior or left anterior oblique projections are typically acquired over 60 to 90 minutes. Consistent posture ensures that changes in counts reflect emptying rather than positional shifts.

Question 4Nuclear Medicine

In a ventilation-perfusion lung scan, the ventilation phase is usually performed first because:

  1. Ventilation activity is low and would be obscured by residual perfusion activity Correct answer.
  2. Ventilation tracer has a long half-life and would mask the perfusion study
  3. Perfusion tracer emits a lower-energy photon than ventilation tracer
  4. Perfusion tracer is cleared from the lungs within seconds

Explanation

Ventilation studies use small activities of a tracer such as Tc-99m DTPA aerosol or xenon gas. If perfusion imaging were done first, the higher retained activity in the lungs would interfere with the low-count ventilation images. Performing ventilation first avoids this crossover contamination.

Question 5Nuclear Medicine

A patient scheduled for a radioiodine thyroid uptake study reports recent ingestion of a large amount of kelp supplement. What is the most appropriate action?

  1. Increase the administered radioiodine dose to compensate
  2. Add a perchlorate discharge test on the same day
  3. Proceed with the study as scheduled
  4. Reschedule the study because stable iodine can block uptake Correct answer.

Explanation

Kelp is rich in stable iodine, which competes with radioiodine for thyroid uptake and can falsely lower measured uptake. Studies should be deferred until the iodine load has cleared, typically several weeks depending on the source. Simply increasing the dose does not correct the underlying blockade.

Question 6Nuclear Medicine

Which collimator type is designed for imaging low-energy photons while maximizing sensitivity?

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

Explanation

Low-energy high-resolution collimators have thin septa and many small holes suited to photons near 140 keV, providing good spatial resolution. High-energy and medium-energy collimators use thicker septa for higher-energy photons. The pinhole collimator magnifies small organs rather than maximizing sensitivity for low-energy photons.

Question 7Nuclear Medicine

The radiopharmaceutical most commonly used for myocardial perfusion imaging at rest and stress is:

  1. In-111 pentetreotide
  2. Tc-99m sulfur colloid
  3. I-123 ioflupane
  4. Tc-99m sestamibi Correct answer.

Explanation

Tc-99m sestamibi is a lipophilic cation taken up by myocardial mitochondria in proportion to blood flow, making it a standard agent for perfusion imaging. It is used for both rest and stress acquisitions. The other agents target the reticuloendothelial system, somatostatin receptors, or dopamine transporters.

Question 8Nuclear Medicine

The main purpose of quality control on a gamma camera's energy spectrum is to ensure that:

  1. Uniformity correction is disabled
  2. Spatial resolution is maximized
  3. Collimator septa are intact
  4. Photopeak window is correctly centered on the radionuclide's photon energy Correct answer.

Explanation

Energy peaking verifies that the pulse height analyzer window is centered on the photopeak of the radionuclide being used. A miscentered window reduces detected counts and degrades image quality. Uniformity and resolution are assessed by separate tests.

Question 9Nuclear Medicine

A technologist needs to reduce the radiation dose to a technologist's hands while preparing a Tc-99m radiopharmaceutical. Which practice is most effective?

  1. Working quickly without shielding to reduce time near the source
  2. Wearing lead-lined gloves during all handling
  3. Using syringe shields and minimizing handling time Correct answer.
  4. Increasing distance between the source and the body only after drawing the dose

Explanation

Dose reduction follows the principles of time, distance, and shielding. Syringe shields provide substantial shielding for the high-energy photons emitted during dose preparation, and minimizing handling time adds further reduction. Lead-lined gloves offer little benefit for 140 keV photons and can increase handling difficulty.

Question 10Nuclear Medicine

In a SPECT brain perfusion study using Tc-99m exametazime, the tracer is taken up in proportion to:

  1. Blood-brain barrier permeability
  2. Cerebrospinal fluid production rate
  3. Glucose metabolism over the following hour
  4. Regional cerebral blood flow at the time of injection Correct answer.

Explanation

Tc-99m exametazime is a lipophilic complex that crosses the blood-brain barrier and is retained in brain tissue in proportion to regional perfusion at the moment of injection. Once trapped, the distribution remains fixed, so images reflect the injection-time flow pattern. It is not a direct measure of metabolism or barrier permeability.

Question 11Nuclear Medicine

A lymphoscintigraphy study for sentinel node mapping uses Tc-99m sulfur colloid injected intradermally. The rationale for intradermal injection is to:

  1. Permit renal excretion of the tracer
  2. Keep the tracer at the injection site for delayed imaging
  3. Allow rapid lymphatic drainage to the sentinel node Correct answer.
  4. Avoid uptake in the regional lymph nodes

Explanation

Intradermal injection places the colloid in the rich superficial lymphatic plexus, promoting rapid transit to the draining sentinel node. This allows imaging within minutes and helps localize the node before surgery. Intramuscular or deeper injection would drain more slowly and less predictably.

Question 12Nuclear Medicine

On a Meckel diverticulum scan, which finding is considered positive for ectopic gastric mucosa?

  1. Focal activity in the left upper quadrant
  2. Focal activity in the right lower quadrant appearing with gastric mucosa and moving with it Correct answer.
  3. Activity in the urinary bladder
  4. Diffuse activity throughout the small bowel

Explanation

A positive Meckel scan shows a focal area of tracer uptake in the right lower abdomen that appears and intensifies in parallel with the stomach. This reflects ectopic gastric mucosa containing mucin cells that take up pertechnetate. Activity in the bladder or bowel is normal and not diagnostic.

Question 13Nuclear Medicine

The most important reason to obtain a recent creatinine value before administering a gadolinium-based or iodine-based contrast agent is to assess:

  1. Renal clearance Correct answer.
  2. Thyroid status
  3. Hepatic function
  4. Coagulation profile

Explanation

Renal function determines clearance of contrast agents and the risk of contrast-induced nephropathy or nephrogenic systemic fibrosis. A recent creatinine allows estimation of glomerular filtration rate. Hepatic, thyroid, and coagulation status do not primarily govern contrast safety.

Question 14Nuclear Medicine

A patient with suspected pulmonary embolism has a perfusion scan showing multiple segmental mismatched defects. The most likely interpretation is:

  1. Artifact from patient motion
  2. Intermediate to high probability of pulmonary embolism Correct answer.
  3. Low probability of pulmonary embolism
  4. Normal study

Explanation

Multiple segmental perfusion defects with normal ventilation, known as mismatched defects, are characteristic of pulmonary embolism. The probability classification depends on the number and pattern of mismatches. A normal study would show matched perfusion and ventilation.

Question 15Nuclear Medicine

In a hepatobiliary iminodiacetic acid scan, nonvisualization of the gallbladder at 4 hours with normal hepatic uptake and bowel activity most suggests:

  1. Normal gallbladder function
  2. Hepatic failure
  3. Acute cholecystitis Correct answer.
  4. Common bile duct obstruction

Explanation

Failure of the gallbladder to fill despite normal hepatic uptake and intestinal activity indicates cystic duct obstruction, most often acute cholecystitis. Normal hepatic uptake excludes hepatocellular failure as the cause. Bowel activity confirms that the common bile duct is patent.

Question 16Nuclear Medicine

Which factor most directly degrades spatial resolution in planar gamma camera imaging?

  1. Higher administered activity
  2. Longer acquisition time
  3. Increased collimator hole size Correct answer.
  4. Use of a larger display matrix

Explanation

Spatial resolution is limited primarily by collimator geometry, and larger holes or thicker septa allow more oblique photons to reach the detector, blurring the image. Increasing activity or acquisition time improves count statistics but not intrinsic resolution. Display matrix size affects sampling, not the underlying resolution.

Question 17Nuclear Medicine

A pregnant technologist is assigned to work with I-131 therapy patients. The most appropriate radiation safety consideration is that:

  1. I-131 emits high-energy gamma rays requiring increased distance and shielding Correct answer.
  2. I-131 emits only alpha particles
  3. I-131 has a very short half-life, so no precautions are needed
  4. I-131 is excreted only through the skin

Explanation

I-131 emits beta particles plus gamma photons at 364 keV, so therapy patients require distance, shielding, and time controls. A pregnant worker should minimize exposure and follow institutional dose limits. Alpha emission and skin-only excretion do not describe I-131.

Question 18Nuclear Medicine

In a Tc-99m DTPA renal scan, the glomerular filtration rate is estimated from:

  1. The rate of tracer clearance from the blood pool and renal uptake Correct answer.
  2. The patient's urine specific gravity
  3. The size of the kidneys on ultrasound
  4. The rate of tracer accumulation in the bladder only

Explanation

GFR estimation relies on the rate at which the tracer is cleared from the blood pool and taken up by the kidneys. DTPA is filtered by the glomerulus without tubular secretion or reabsorption, so its clearance reflects GFR. Bladder accumulation alone or ultrasound size does not quantify filtration.

Question 19Nuclear Medicine

A patient with a suspected parathyroid adenoma undergoes a dual-phase Tc-99m sestamibi scan. The characteristic finding is:

  1. Early uptake that washes out on delayed images
  2. No uptake at any phase
  3. Early uptake that persists on delayed images Correct answer.
  4. Diffuse uptake in the thyroid only

Explanation

Sestamibi accumulates in both thyroid and parathyroid tissue early, but it washes out of normal thyroid tissue faster than from a parathyroid adenoma. Persistent focal uptake on delayed images is characteristic of an adenoma. Washout of all activity would suggest normal thyroid tissue.

Question 20Nuclear Medicine

Which of the following is the most appropriate way to reduce the radiation dose to the bladder in a bone scan patient?

  1. Encouraging hydration and frequent voiding after injection Correct answer.
  2. Administering a diuretic routinely
  3. Restricting fluids before the study
  4. Delaying imaging for 24 hours

Explanation

Tc-99m diphosphonates are excreted by the kidneys, so hydration and frequent voiding reduce bladder residence time and dose. Patients are typically encouraged to drink fluids and void before imaging. Fluid restriction or routine diuretics are not standard.

Question 21Nuclear Medicine

In a myocardial perfusion study, a reversible perfusion defect on stress images that normalizes at rest indicates:

  1. Myocardial infarction
  2. Normal myocardium
  3. Attenuation artifact
  4. Stress-induced ischemia Correct answer.

Explanation

A defect present on stress images but normal on rest images is termed reversible and reflects stress-induced ischemia. Fixed defects that persist at rest suggest infarction or scar. Attenuation artifact tends to be fixed and related to body habitus.

Question 22Nuclear Medicine

A generator eluate is tested for molybdenum-99 breakthrough. If the limit is exceeded, the appropriate action is:

  1. Store the eluate for 24 hours before use
  2. Discard the eluate and notify the authorized user Correct answer.
  3. Dilute the eluate with saline and proceed
  4. Use the eluate only for pediatric patients

Explanation

Mo-99 breakthrough increases patient dose and degrades image quality because Mo-99 emits higher-energy photons and decays to Tc-99m in vivo. Exceeding the regulatory limit requires discarding the eluate and notifying the authorized user. Dilution or storage does not reliably correct the problem.

Question 23Nuclear Medicine

A SPECT acquisition is planned with a 128 by 128 matrix and 120 projections over 360 degrees. Which change would most improve count statistics per projection?

  1. Increasing the radius of rotation
  2. Reducing the matrix to 64 by 64 Correct answer.
  3. Decreasing the acquisition time per projection
  4. Increasing the number of projections to 180

Explanation

A smaller matrix increases the number of counts per pixel for a given acquisition, improving count statistics at the cost of spatial resolution. Increasing projections or decreasing time per projection reduces counts per view. Increasing the radius of rotation degrades resolution without improving counts.

Question 24Nuclear Medicine

A patient with a suspected infected joint undergoes an In-111 labeled leukocyte scan combined with a Tc-99m sulfur colloid marrow scan. The purpose of the marrow scan is to:

  1. Increase the sensitivity of leukocyte labeling
  2. Measure renal function
  3. Assess hepatic clearance of leukocytes
  4. Distinguish marrow uptake from infection Correct answer.

Explanation

In-111 leukocytes can accumulate in normal bone marrow, which may mimic infection. A Tc-99m sulfur colloid marrow scan defines the distribution of functioning marrow so that discordant leukocyte uptake can be identified as infection. The two studies are interpreted together.

Question 25Nuclear Medicine

A patient undergoing radioiodine therapy for thyroid cancer is advised about radiation safety. Which instruction is most consistent with current practice?

  1. Return to work in a crowded office the next day
  2. Share eating utensils with family members
  3. Sleep in the same bed as a partner immediately after therapy
  4. Maintain distance from others and use separate bathroom facilities for a period Correct answer.

Explanation

After radioiodine therapy, patients excrete radioactivity in urine and saliva and emit gamma radiation, so close contact should be limited for a period determined by administered activity and local regulations. Separate sleeping arrangements and bathroom facilities reduce household exposure. Crowded settings and shared utensils increase exposure risk.

Question 26Nuclear Medicine

Which radionuclide is the standard parent in the generator system used to supply most nuclear medicine departments with technetium-99m?

  1. Thallium-201
  2. Gallium-67
  3. Iodine-131
  4. Molybdenum-99 Correct answer.

Explanation

Technetium-99m is produced in a generator from the decay of its parent molybdenum-99, which has a 66-hour half-life. The parent is bound to an alumina column and Tc-99m is eluted with saline as the daughter grows in. This parent-daughter relationship is the basis of daily generator use in most departments.

Question 27Nuclear Medicine

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

  1. 8 days
  2. 2.7 days
  3. 6 hours Correct answer.
  4. 13 hours

Explanation

Tc-99m decays with a physical half-life of approximately 6 hours, which is short enough to limit patient dose while long enough to complete most imaging procedures. Its 140 keV gamma emission is also well suited to the sodium iodide detector. These properties explain why Tc-99m dominates routine nuclear medicine.

Question 28Nuclear Medicine

A technologist is preparing to elute a technetium-99m generator that was last eluted 30 hours ago. How does the available activity compare with the activity obtained at the previous elution?

  1. It is zero because transient equilibrium has been exceeded
  2. It has substantially increased because the daughter has regrown Correct answer.
  3. It has decreased because the parent has decayed completely
  4. It is unchanged because elution does not affect daughter activity

Explanation

After elution removes the daughter, Tc-99m regrows in the generator as molybdenum-99 continues to decay. After about 23 hours the daughter activity is near its maximum, so a 30-hour interval yields substantially more Tc-99m than the previous elution. This transient equilibrium governs how much activity each elution provides.

Question 29Nuclear Medicine

Which property of technetium-99m makes it especially attractive for gamma camera imaging?

  1. A 140 keV gamma emission with high abundance Correct answer.
  2. A long half-life allowing delayed imaging
  3. Alpha particle emission that improves contrast
  4. A 364 keV gamma emission with low abundance

Explanation

Tc-99m emits a 140 keV gamma ray in high abundance, which is close to optimal for sodium iodide detectors and low-energy collimators. This yields good sensitivity and resolution while keeping patient dose modest. Its short half-life also reduces the total radiation burden.

Question 30Nuclear Medicine

A radiopharmaceutical is described as having high target-to-background uptake. What does this primarily determine?

  1. The energy of the emitted gamma photons
  2. The rate of elution from the generator
  3. The physical half-life of the radionuclide
  4. The image contrast between the organ of interest and surrounding tissue Correct answer.

Explanation

Target-to-background ratio describes how much more activity accumulates in the organ of interest than in adjacent tissue. A high ratio produces high image contrast, making the target easier to distinguish. Physical half-life, photon energy, and elution rate affect other aspects of imaging rather than contrast directly.

Question 31Nuclear Medicine

Which radiopharmaceutical is most commonly used for bone scintigraphy?

  1. Tc-99m sulfur colloid
  2. Tc-99m diethylenetriamine pentaacetate
  3. Tc-99m methylene diphosphonate Correct answer.
  4. Tc-99m pertechnetate

Explanation

Tc-99m methylene diphosphonate is a diphosphonate that adsorbs to bone mineral, giving high skeletal uptake and rapid renal clearance. It is the standard bone scan agent because of its favorable bone-to-background ratio. Other Tc-99m agents target different tissues.

Question 32Nuclear Medicine

A patient is scheduled for a thyroid uptake study with iodine-123. Which instruction should the technologist give before the study?

  1. Increase dietary iodine to improve thyroid uptake
  2. Avoid iodine-rich foods and iodinated contrast for several days before the test Correct answer.
  3. Fast from all food and fluids for 24 hours before the test
  4. Stop all medications permanently before the test

Explanation

Iodine-123 uptake depends on the thyroid's ability to trap iodine, so recent iodine load can suppress uptake and invalidate results. Patients should avoid iodinated contrast and iodine-rich foods for an appropriate period beforehand. Fasting and permanent medication changes are not required for this study.

Question 33Nuclear Medicine

In a gastric emptying study using a radiolabeled solid meal, which finding indicates delayed gastric emptying?

  1. Retention of more than 10 percent of the meal at 4 hours Correct answer.
  2. Emptying of half the meal within 60 minutes
  3. Complete emptying within 2 hours
  4. Immediate transit of the meal into the small bowel

Explanation

Delayed gastric emptying is defined by retention of an abnormally high fraction of the solid meal at a defined time, commonly more than 10 percent at 4 hours. Normal emptying proceeds faster, with roughly half the meal leaving by about 90 minutes. The retained fraction at 4 hours is the standard quantitative endpoint.

Question 34Nuclear Medicine

A ventilation-perfusion lung scan is performed with Tc-99m macroaggregated albumin. What is the mechanism by which the particles localize in the lungs?

  1. Binding to pulmonary surfactant
  2. Capillary blockade after intravenous injection Correct answer.
  3. Diffusion across the alveolar membrane
  4. Active transport into alveolar cells

Explanation

Macroaggregated albumin particles are large enough to lodge temporarily in the pulmonary capillary bed after intravenous injection. Their distribution reflects regional pulmonary blood flow, which is the basis of the perfusion image. The particles are subsequently metabolized and cleared.

Question 35Nuclear Medicine

Which agent is used as an aerosol for the ventilation phase of a lung scan?

  1. Tc-99m diethylenetriamine pentaacetate aerosol Correct answer.
  2. Tc-99m sulfur colloid
  3. Tc-99m macroaggregated albumin
  4. Tc-99m sestamibi

Explanation

Tc-99m DTPA aerosol is inhaled and deposited in the airways and alveoli, allowing imaging of ventilation distribution. Macroaggregated albumin is injected for perfusion imaging, not inhaled. The ventilation images are compared with perfusion images to detect mismatched defects.

Question 36Nuclear Medicine

A patient with a suspected infection undergoes an In-111 labeled leukocyte scan. What is the most important precaution when labeling the leukocytes?

  1. Maintain strict aseptic technique during blood handling and labeling Correct answer.
  2. Use a high-energy collimator during the labeling procedure
  3. Add iodinated contrast to the labeling vial
  4. Store the labeled cells at room temperature for 24 hours

Explanation

Leukocyte labeling involves withdrawing blood, separating white cells, and reinjecting them, so aseptic technique is essential to prevent contamination and sepsis. The labeled cells must also be handled promptly and per validated protocol. Collimator choice and contrast are unrelated to the labeling step.

Question 37Nuclear Medicine

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

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

Explanation

Filtered Tc-99m sulfur colloid particles are small enough to migrate through lymphatics after intradermal or peritumoral injection and lodge in the sentinel node. The node is then identified with a gamma probe or lymphoscintigraphy. Particle size is critical to lymphatic transit.

Question 38Nuclear Medicine

In a renal scan using Tc-99m mercaptoacetyltriglycine, what does the renogram curve primarily reflect?

  1. Hepatic metabolism of the tracer
  2. Glomerular filtration alone
  3. Renal perfusion and tubular extraction with subsequent excretion Correct answer.
  4. Bladder storage capacity alone

Explanation

MAG3 is extracted by the renal tubules and excreted, so the renogram curve reflects both perfusion and tubular function. The curve rises with uptake and falls as the tracer is excreted. This makes it useful for assessing relative renal function and obstruction.

Question 39Nuclear Medicine

A patient with suspected osteomyelitis has a three-phase bone scan. What does focal hyperemia on the blood flow and blood pool phases suggest?

  1. Reduced blood supply to the region
  2. Normal bone remodeling only
  3. A healed old fracture with no activity
  4. An active inflammatory or infectious process Correct answer.

Explanation

The flow and blood pool phases reflect regional perfusion and tissue hyperemia. Focal increased activity in these phases suggests an active inflammatory or infectious process. The delayed phase then shows whether there is associated bone involvement.

Question 40Nuclear Medicine

Which collimator is most appropriate for imaging iodine-131, which emits a 364 keV gamma ray?

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

Explanation

Septal penetration increases when photon energy greatly exceeds the collimator's design range. Iodine-131 photons at 364 keV require a high-energy collimator with thick septa to limit penetration. Low- and medium-energy collimators would allow excessive septal penetration and poor image quality.

Question 41Nuclear Medicine

Which statement best describes the purpose of a uniformity flood image in gamma camera quality control?

  1. It calibrates the dose calibrator for syringe geometry
  2. It determines the patient's renal clearance rate
  3. It measures the physical half-life of the radionuclide
  4. It detects regional variations in detector sensitivity across the field of view Correct answer.

Explanation

A uniformity flood exposes the detector to a uniform source and reveals regional differences in sensitivity. Nonuniformities can produce artifacts that mimic disease. Regular flood imaging is therefore a core quality control test for the gamma camera.

Question 42Nuclear Medicine

A technologist notices that a gamma camera's photopeak has drifted away from 140 keV. What is the most appropriate first action?

  1. Shorten the acquisition time
  2. Change to a high-energy collimator
  3. Increase the administered dose to compensate
  4. Perform energy calibration and peaking according to the quality control protocol Correct answer.

Explanation

Photopeak drift reduces sensitivity and degrades image quality, so the camera must be peaked and energy-calibrated per protocol. Adjusting dose, collimator, or acquisition time does not correct an energy calibration error. Proper peaking restores the correct window around the photopeak.

Question 43Nuclear Medicine

A patient arrives for a bone scan and reports voiding two hours ago. Why is hydration and frequent voiding encouraged after tracer injection?

  1. To reduce radiation dose to the bladder and improve pelvic image quality Correct answer.
  2. To speed up the physical decay of technetium-99m
  3. To increase tracer uptake in the skeleton
  4. To prevent allergic reactions to the tracer

Explanation

Tc-99m MDP is excreted by the kidneys, so activity accumulates in the bladder. Frequent voiding reduces bladder wall dose and removes activity that could obscure pelvic bone detail. Hydration supports this clearance.

Question 44Nuclear Medicine

A myocardial perfusion scan shows a defect on stress images that is present but smaller on rest images. How is this pattern best described?

  1. Normal variant artifact
  2. Rest-only ischemia
  3. Fixed scar with no viability
  4. Partially reversible ischemia Correct answer.

Explanation

A defect that improves but does not normalize at rest represents partially reversible ischemia. Fully reversible defects normalize at rest, while fixed defects persist and suggest scar. The degree of reversibility reflects the balance of ischemia and scar.

Question 45Nuclear Medicine

What is the main advantage of using a semiconductor detector camera compared with a conventional Anger gamma camera?

  1. Elimination of the need for collimation
  2. Improved energy resolution and compact detector design Correct answer.
  3. Use of alpha-emitting radiopharmaceuticals
  4. Ability to image without any radiotracer

Explanation

Semiconductor detectors such as cadmium zinc telluride convert gamma photons directly into electrical signals, giving better energy resolution and allowing compact camera designs. Collimation is still required to define direction. These cameras can improve contrast and workflow but do not remove basic imaging requirements.

Question 46Nuclear Medicine

A patient receiving iodine-131 therapy for hyperthyroidism asks how to reduce radiation exposure to family members. Which advice is most appropriate?

  1. Return to work immediately in close contact with coworkers
  2. Discontinue all fluids to reduce urinary excretion
  3. Sleep in a separate room and maintain distance from others for the recommended period Correct answer.
  4. Share eating utensils with family members to build tolerance

Explanation

Iodine-131 emits beta particles and gamma rays, and patients excrete activity in urine and saliva. Maintaining distance, sleeping separately, and following the recommended duration of precautions reduce household exposure. These instructions are individualized based on administered activity and local regulations.

Question 47Nuclear Medicine

Which factor most strongly increases the radiation dose to staff during a PET study with fluorine-18 fluorodeoxyglucose?

  1. The low administered activity used in PET
  2. The 511 keV annihilation photons requiring greater shielding Correct answer.
  3. The short 110-minute half-life of fluorine-18
  4. The use of a low-energy collimator

Explanation

Fluorine-18 emits positrons whose annihilation produces 511 keV photons. These high-energy photons penetrate conventional lead shielding more readily, so staff dose per unit activity is higher than with low-energy Tc-99m. Shielding and distance are therefore especially important in PET.

Question 48Nuclear Medicine

A patient with a suspected pulmonary embolism has a normal perfusion scan. What is the most appropriate interpretation?

  1. Pulmonary embolism is effectively excluded Correct answer.
  2. A repeat scan is required within one hour
  3. Anticoagulation should be started immediately
  4. A large embolus is confirmed

Explanation

A normal perfusion scan makes pulmonary embolism highly unlikely, because emboli produce perfusion defects. This high negative predictive value allows the diagnosis to be excluded in most cases. Abnormal scans require comparison with ventilation images or further testing.

Question 49Nuclear Medicine

Which radiopharmaceutical is used to image the liver and spleen by localizing in the reticuloendothelial system?

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

Explanation

Tc-99m sulfur colloid particles are phagocytosed by Kupffer cells in the liver and by macrophages in the spleen and bone marrow. This distribution allows imaging of the reticuloendothelial system. Focal lesions that lack Kupffer cells appear as cold defects.

Question 50Nuclear Medicine

A technologist must choose between a low-energy high-resolution collimator and a low-energy general-purpose collimator for detailed thyroid imaging with Tc-99m. Which choice and rationale are correct?

  1. General-purpose collimator, because it improves resolution by increasing sensitivity
  2. General-purpose collimator, because it eliminates septal penetration
  3. High-resolution collimator, because it increases sensitivity without affecting resolution
  4. High-resolution collimator, because it improves spatial resolution at the cost of sensitivity Correct answer.

Explanation

High-resolution collimators use longer septa and smaller holes, which improves spatial resolution but reduces sensitivity. For a small structure such as the thyroid, the resolution gain is usually worth the longer acquisition. General-purpose collimators trade resolution for sensitivity.