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NMAA practice questions

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Question 1Nuclear Medicine Technology (NMAA content outline not published in source)

Which radionuclide is most commonly used as the labeling isotope in Tc-99m radiopharmaceuticals prepared in a nuclear pharmacy?

  1. I-131
  2. Ga-67
  3. F-18
  4. Tc-99m Correct answer.

Explanation

Technetium-99m is the workhorse of nuclear medicine because its 6-hour half-life and 140 keV gamma emission suit gamma camera imaging, and it is eluted from a Mo-99/Tc-99m generator as pertechnetate for kit labeling. The other nuclides listed are used for specific studies but are not the standard kit-labeling isotope in routine practice.

Question 2Nuclear Medicine Technology (NMAA content outline not published in source)

A patient scheduled for a Tc-99m bone scan has a creatinine of 2.8 mg/dL. Which consideration is most relevant to the technologist's protocol?

  1. The radiopharmaceutical must be switched to I-131
  2. Renal clearance affects soft-tissue background and may warrant delayed imaging Correct answer.
  3. The dose should be doubled to compensate for slow excretion
  4. Renal function is irrelevant because bone uptake is purely mechanical

Explanation

Tc-99m MDP is cleared by the kidneys, so impaired renal function increases soft-tissue retention and background activity, and imaging may need to be delayed or adjusted. Dose is not increased and the tracer is not changed based on creatinine alone.

Question 3Nuclear Medicine Technology (NMAA content outline not published in source)

When preparing a Tc-99m sulfur colloid kit, which quality control test is essential before patient administration?

  1. Determination of the octanol-water partition coefficient
  2. Measurement of particle size distribution and radiochemical purity Correct answer.
  3. Assay of I-131 contamination only
  4. Measurement of positron yield

Explanation

Sulfur colloid depends on particle size for its biodistribution (reticuloendothelial uptake), so particle size and radiochemical purity must be verified. Positron yield and partition coefficient are not relevant to this colloid preparation.

Question 4Nuclear Medicine Technology (NMAA content outline not published in source)

The primary reason a Mo-99/Tc-99m generator is eluted no more frequently than every 6 hours is to:

  1. Allow Tc-99m activity to reaccumulate to a useful yield Correct answer.
  2. Maintain the saline eluent at body temperature
  3. Avoid exceeding the column's total elution volume
  4. Prevent Mo-99 breakthrough into the eluate

Explanation

Tc-99m grows in from Mo-99 with a 6-hour half-life, so eluting too soon after a prior elution yields low activity. Mo-99 breakthrough is controlled by the alumina column and is tested, not by elution interval.

Question 5Nuclear Medicine Technology (NMAA content outline not published in source)

Which gamma camera component converts light photons from the scintillation crystal into an electronic signal?

  1. Xenon photomultiplier grid
  2. Pulse-height analyzer
  3. Collimator
  4. Photomultiplier tube Correct answer.

Explanation

The photomultiplier tube converts scintillation light into an amplified electronic pulse that position logic uses to localize events. The collimator only restricts incident gamma direction and the pulse-height analyzer sorts energy.

Question 6Nuclear Medicine Technology (NMAA content outline not published in source)

A Tc-99m image is acquired with a photopeak window set too low. What is the most likely effect?

  1. Automatic correction of uniformity
  2. Increased scatter acceptance and degraded image contrast Correct answer.
  3. Improved spatial resolution
  4. Complete loss of all counts

Explanation

The photopeak window must be centered on 140 keV; lowering it admits more Compton-scattered photons, which degrades contrast. It does not eliminate counts or improve resolution.

Question 7Nuclear Medicine Technology (NMAA content outline not published in source)

Which collimator is best suited for imaging a high-energy photon emitter such as I-131?

  1. Pinhole collimator
  2. Low-energy high-resolution collimator
  3. High-energy collimator with thick septa Correct answer.
  4. Parallel-hole low-energy general collimator

Explanation

I-131 emits higher-energy photons (364 keV), so septa must be thick enough to prevent penetration; a high-energy collimator is required. Low-energy collimators are designed for 140 keV and allow septal penetration at higher energies.

Question 8Nuclear Medicine Technology (NMAA content outline not published in source)

A technologist notices a uniform flood image shows a ring artifact after replacing a photomultiplier tube. The most appropriate next step is to:

  1. Increase the photopeak window width
  2. Perform a new uniformity calibration and repeat the flood Correct answer.
  3. Reduce the acquisition matrix size
  4. Administer a higher patient dose

Explanation

Replacing a PMT changes detector response, so uniformity correction must be recalibrated before clinical use. Window width, matrix size, and dose do not correct detector non-uniformity.

Question 9Nuclear Medicine Technology (NMAA content outline not published in source)

In a SPECT acquisition, the primary purpose of acquiring multiple angular projections is to:

  1. Increase the photopeak energy
  2. Reconstruct a three-dimensional distribution from projection data Correct answer.
  3. Eliminate the need for a collimator
  4. Reduce the patient's radiation dose

Explanation

SPECT reconstructs tomographic slices from many planar projections acquired around the patient. It does not reduce dose, remove collimator needs, or change photon energy.

Question 10Nuclear Medicine Technology (NMAA content outline not published in source)

A patient's thyroid uptake measurement is scheduled after a recent contrast-enhanced CT scan. Why might the result be falsely low?

  1. Contrast increases renal clearance of the tracer
  2. Contrast destroys the gamma camera crystal
  3. CT contrast emits gamma rays that cancel the signal
  4. Iodinated contrast blocks thyroid uptake of the radiotracer Correct answer.

Explanation

Stable iodine in contrast competes with radioiodine for thyroid uptake, suppressing the measured uptake. This is a competition effect, not a clearance or detector effect.

Question 11Nuclear Medicine Technology (NMAA content outline not published in source)

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

  1. I-123 MIBG
  2. Tc-99m sestamibi Correct answer.
  3. Tc-99m DTPA aerosol
  4. Tc-99m MDP

Explanation

Tc-99m sestamibi (and tetrofosmin) distributes with myocardial blood flow and is used for rest/stress perfusion SPECT. MDP is for bone, DTPA aerosol for lung ventilation, and MIBG for neuroendocrine imaging.

Question 12Nuclear Medicine Technology (NMAA content outline not published in source)

A ventilation/perfusion lung scan is ordered to evaluate suspected pulmonary embolism. Which combination best represents a standard study?

  1. Tc-99m MDP ventilation and I-131 perfusion
  2. Tc-99m DTPA aerosol ventilation and Tc-99m MAA perfusion Correct answer.
  3. F-18 FDG ventilation and Tc-99m MAA perfusion
  4. Xe-133 perfusion and Ga-67 ventilation

Explanation

Ventilation is typically performed with an aerosol such as Tc-99m DTPA, and perfusion with Tc-99m macroaggregated albumin, which traps in pulmonary capillaries. The other pairings use agents with unrelated biodistributions.

Question 13Nuclear Medicine Technology (NMAA content outline not published in source)

During a Tc-99m MAA perfusion scan, the technologist notes the syringe contains visible clumps. What is the correct action?

  1. Inject slowly to break up the clumps
  2. Add saline to dissolve the aggregates
  3. Proceed because clumping improves lung trapping
  4. Do not inject and obtain a new, properly prepared dose Correct answer.

Explanation

Large aggregates can cause microembolic obstruction in the lung or elsewhere, so a dose with visible clumping must be rejected and replaced. Dilution or slow injection does not resolve the safety issue.

Question 14Nuclear Medicine Technology (NMAA content outline not published in source)

Which finding on a Tc-99m sulfur colloid liver scan suggests a focal hepatic lesion?

  1. Diffuse homogeneous uptake
  2. Increased splenic uptake with a normal liver
  3. Uniform bone marrow uptake
  4. A photopenic defect in an otherwise uniform liver Correct answer.

Explanation

Kupffer cells take up sulfur colloid uniformly; a space-occupying lesion lacking these cells appears as a photon-deficient defect. Homogeneous uptake is normal, and splenic or marrow uptake reflects altered distribution rather than a focal defect.

Question 15Nuclear Medicine Technology (NMAA content outline not published in source)

A patient with suspected GI bleeding is injected with Tc-99m labeled red blood cells. The study is most sensitive when imaging is:

  1. Performed serially over an extended period to capture intermittent bleeding Correct answer.
  2. Acquired with a pinhole collimator only
  3. Delayed 24 hours after injection
  4. Completed within 5 minutes only

Explanation

Labeled RBCs remain in the vascular space, allowing serial imaging over hours to detect intermittent extravasation. A brief early acquisition may miss episodic bleeding, and a 24-hour delay is impractical due to decay.

Question 16Nuclear Medicine Technology (NMAA content outline not published in source)

Which renal scintigraphy agent is preferred for assessing effective renal plasma flow?

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

Explanation

MAG3 is secreted by the proximal tubules and provides excellent dynamic imaging of renal perfusion and function. DMSA binds cortical tissue for static imaging, while MDP and sulfur colloid are unrelated to renal function.

Question 17Nuclear Medicine Technology (NMAA content outline not published in source)

A renal scan shows delayed tracer clearance from a dilated renal pelvis that improves after the patient stands. This pattern is most consistent with:

  1. Complete ureteral obstruction
  2. Renal artery stenosis
  3. Physiologic stasis rather than true obstruction Correct answer.
  4. Acute tubular necrosis

Explanation

Dependent pooling in a dilated pelvis can mimic obstruction, and positional change or diuretic challenge helps distinguish stasis from true obstruction. Complete obstruction would not resolve with posture, and vascular or tubular disease produces different patterns.

Question 18Nuclear Medicine Technology (NMAA content outline not published in source)

Which radionuclide is a positron emitter used for FDG PET imaging?

  1. Tc-99m
  2. I-123
  3. F-18 Correct answer.
  4. In-111

Explanation

Fluorine-18 has a 110-minute half-life and decays by positron emission, enabling coincidence detection in PET. Tc-99m, I-123, and In-111 are single-photon emitters used with gamma cameras.

Question 19Nuclear Medicine Technology (NMAA content outline not published in source)

Before an FDG PET scan, a diabetic patient's blood glucose is 240 mg/dL. Why is this a concern?

  1. High glucose increases positron range and blurs the image
  2. High glucose destroys the PET detector
  3. High glucose competes with FDG and reduces tumor uptake Correct answer.
  4. High glucose converts FDG to a gamma emitter

Explanation

FDG competes with circulating glucose for cellular uptake, so hyperglycemia lowers target-to-background and can mask lesions. The issue is biodistribution competition, not detector function or decay mode.

Question 20Nuclear Medicine Technology (NMAA content outline not published in source)

Which agent is used for sentinel lymph node localization in breast cancer surgery?

  1. Tc-99m sulfur colloid filtered for smaller particle size Correct answer.
  2. I-131 sodium iodide
  3. Tc-99m MAA
  4. Ga-67 citrate

Explanation

Filtered Tc-99m sulfur colloid particles are small enough to migrate through lymphatics to the sentinel node for intraoperative detection. The other agents target thyroid, lung capillaries, or inflammation/lymphoma.

Question 21Nuclear Medicine Technology (NMAA content outline not published in source)

A technologist receives a package containing I-131. Which survey and documentation practice is required before use?

  1. Only verify the shipping label
  2. Survey the package and record removable contamination and exposure readings Correct answer.
  3. Discard the package if any reading is above background
  4. Immediately open and administer the material

Explanation

Radioactive packages must be surveyed for external exposure and removable contamination, and results documented before use. Label verification alone is insufficient, and any reading above background does not mandate disposal.

Question 22Nuclear Medicine Technology (NMAA content outline not published in source)

Which principle states that radiation exposure should be kept as low as reasonably achievable while considering economic and social factors?

  1. Decay correction
  2. ALARA Correct answer.
  3. Geometric mean
  4. Photopeak

Explanation

ALARA guides radiation protection by minimizing dose through time, distance, and shielding. Decay correction, photopeak selection, and geometric mean are imaging or calculation concepts, not protection principles.

Question 23Nuclear Medicine Technology (NMAA content outline not published in source)

A technologist must minimize exposure while working near a radioactive source. Which combination is most effective?

  1. Longer time, increased distance, and no shielding
  2. Longer time, closer distance, and no shielding
  3. Short time, closer distance, and thin shielding
  4. Short time, increased distance, and appropriate shielding Correct answer.

Explanation

Dose is reduced by decreasing time, increasing distance (inverse-square relationship), and using shielding. Any approach that increases time or decreases distance raises exposure.

Question 24Nuclear Medicine Technology (NMAA content outline not published in source)

A pregnant technologist is assigned to a PET area. Which statement best reflects appropriate radiation protection practice?

  1. Continue all duties without modification because fetal dose is negligible
  2. Declare pregnancy and review duties to limit fetal dose within regulatory limits Correct answer.
  3. Avoid wearing a dosimeter to reduce recorded dose
  4. Work only with I-131 therapy patients

Explanation

A declared pregnancy triggers dose monitoring and duty review to keep fetal exposure within regulatory limits. Assuming negligible fetal dose or avoiding dosimetry is inappropriate.

Question 25Nuclear Medicine Technology (NMAA content outline not published in source)

In a gamma camera, the purpose of the pulse-height analyzer is to:

  1. Accept events within a selected energy window Correct answer.
  2. Amplify light from the crystal
  3. Collimate the incident photons
  4. Position the patient for acquisition

Explanation

The pulse-height analyzer discriminates events by energy, accepting those within the photopeak window and rejecting scatter. Amplification occurs in the PMT, and collimation occurs before the crystal.

Question 26Nuclear Medicine Technology (NMAA content outline not published in source)

Which property of technetium-99m makes it especially favorable as the workhorse radionuclide for gamma camera imaging?

  1. It emits a 511 keV annihilation photon suitable for SPECT
  2. It emits a 140 keV gamma ray with no significant particulate emission Correct answer.
  3. It emits a 364 keV gamma ray with abundant beta particles
  4. It emits a 159 keV gamma ray together with alpha particles

Explanation

Tc-99m decays by isomeric transition to a 140 keV gamma emission that matches the energy resolution of a sodium iodide crystal well, and the absence of significant particulate radiation keeps patient absorbed dose low. Its six-hour half-life also allows kit labeling and same-day imaging.

Question 27Nuclear Medicine Technology (NMAA content outline not published in source)

A generator eluate is tested and found to contain an unacceptable level of molybdenum-99 breakthrough. What is the correct action?

  1. Use the eluate only for in vitro studies
  2. Allow the eluate to decay for one hour before use
  3. Dilute the eluate and proceed with imaging
  4. Discard the eluate and notify the authorized user Correct answer.

Explanation

Mo-99 breakthrough limits are regulatory, and an eluate exceeding the limit must not be administered to patients. The eluate is set aside to decay and the responsible authorized user or radiation safety officer is informed so the generator can be evaluated.

Question 28Nuclear Medicine Technology (NMAA content outline not published in source)

In a gamma camera, which component converts the light flash from the scintillation crystal into an electrical signal?

  1. The collimator
  2. The pulse-height analyzer
  3. The photomultiplier tube Correct answer.
  4. The sodium iodide crystal

Explanation

The photomultiplier tube detects the scintillation light and multiplies it into a measurable electrical pulse. Position logic then uses the relative signals from multiple tubes to localize the event.

Question 29Nuclear Medicine Technology (NMAA content outline not published in source)

A patient scheduled for a Tc-99m bone scan has a serum creatinine of 2.8 mg/dL with markedly reduced estimated glomerular filtration rate. How should the technologist proceed?

  1. Administer the full standard dose without modification
  2. Substitute a radiopharmaceutical that requires no renal handling
  3. Consult the authorized user about possible dose adjustment before injection Correct answer.
  4. Cancel the study permanently because the agent is contraindicated

Explanation

Tc-99m MDP is cleared mainly by the kidneys, so impaired renal function prolongs retention and increases marrow and soft-tissue background. The authorized user should decide whether to adjust activity, extend imaging times, or modify the protocol.

Question 30Nuclear Medicine Technology (NMAA content outline not published in source)

Which radiopharmaceutical is most commonly used for a gastric emptying study?

  1. Tc-99m pertechnetate given intravenously
  2. Tc-99m sestamibi injected at rest
  3. Tc-99m sulfur colloid in a solid or liquid meal Correct answer.
  4. Tc-99m DTPA aerosol by inhalation

Explanation

For gastric emptying, Tc-99m sulfur colloid is mixed into a standardized meal so that the tracer moves with the food through the stomach. Serial images quantify the retained fraction over time.

Question 31Nuclear Medicine Technology (NMAA content outline not published in source)

During a Tc-99m pertechnetate thyroid scan, the technologist notices intense uptake in the salivary glands and stomach in addition to the thyroid. What does this pattern indicate?

  1. There is metastatic thyroid tissue in the abdomen
  2. Free pertechnetate is present and is being taken up by tissues that concentrate it Correct answer.
  3. The camera window is set incorrectly
  4. The radiopharmaceutical has degraded into colloidal particles

Explanation

Pertechnetate is trapped by the thyroid, salivary glands, gastric mucosa, and choroid plexus because these tissues express the sodium-iodide symporter. Visible stomach and salivary activity therefore reflects normal free pertechnetate biodistribution.

Question 32Nuclear Medicine Technology (NMAA content outline not published in source)

In a planar image, what does the spatial resolution of a parallel-hole collimator depend on most directly?

  1. The septal thickness and length and the hole diameter Correct answer.
  2. The thickness of the sodium iodide crystal
  3. The photomultiplier tube gain setting
  4. The pulse-height analyzer window width

Explanation

Resolution of a parallel-hole collimator is governed by hole geometry: smaller diameter holes and longer septa improve resolution but reduce sensitivity. Septal thickness must be sufficient to prevent septal penetration.

Question 33Nuclear Medicine Technology (NMAA content outline not published in source)

A technologist must prepare a radiopharmaceutical kit. Which practice is essential to ensure product quality?

  1. Vigorously shaking the vial to guarantee complete mixing
  2. Adding eluate before the buffer to speed labeling
  3. Following the manufacturer's prescribed order, volumes, and incubation time Correct answer.
  4. Using eluate that has been allowed to stand for 24 hours

Explanation

Kit labeling depends on the exact sequence of reagent addition, activity and volume, and incubation time specified by the manufacturer. Any deviation can reduce labeling efficiency and produce free pertechnetate or colloidal impurities.

Question 34Nuclear Medicine Technology (NMAA content outline not published in source)

A patient receiving I-131 therapy for hyperthyroidism asks how the treatment destroys thyroid tissue. Which mechanism best explains the therapeutic effect?

  1. The iodine atom decays into a stable isotope without emitting radiation
  2. Gamma photons cause ionization throughout the whole body
  3. Alpha particles are emitted and destroy surrounding tissue
  4. Beta particles deposit energy over a short range within the thyroid Correct answer.

Explanation

I-131 emits beta particles with a range of roughly a millimeter, so most of the energy is deposited in the tissue that concentrates the iodine, namely the thyroid. The gamma emission contributes to external exposure but not substantially to treatment.

Question 35Nuclear Medicine Technology (NMAA content outline not published in source)

A patient is referred for a Tc-99m MAA lung perfusion scan. Which condition would most alter the expected distribution of tracer?

  1. A prior appendectomy
  2. A history of seasonal allergies
  3. A right-to-left cardiac shunt Correct answer.
  4. Mild dehydration

Explanation

MAA particles are trapped in the pulmonary capillary bed, so lung uptake reflects pulmonary blood flow. A right-to-left shunt allows particles to bypass the lungs and lodge in systemic organs such as the brain or kidneys.

Question 36Nuclear Medicine Technology (NMAA content outline not published in source)

A hospital receives a shipment of Tc-99m eluate that will be used for patient injections. Which documentation is required before use?

  1. Only the total activity recorded by the supplier
  2. Results of the molybdenum-99 breakthrough and aluminum breakthrough tests Correct answer.
  3. A record of the technologist's continuing education hours
  4. A copy of the patient's prior imaging reports

Explanation

Each eluate must be tested for Mo-99 breakthrough and aluminum ion concentration before patient administration, and the results must be recorded. These tests protect patients from excess dose and from poor labeling caused by aluminum.

Question 37Nuclear Medicine Technology (NMAA content outline not published in source)

During a SPECT acquisition, the camera's uniformity calibration is found to be outside tolerance. What is the most appropriate action?

  1. Reduce the acquisition time to hide the artifact
  2. Perform the calibration correction and verify uniformity before acquiring patient data Correct answer.
  3. Proceed with imaging and correct the images later
  4. Increase the photopeak window width to compensate

Explanation

Uniformity defects propagate into tomographic reconstruction as ring artifacts that cannot be reliably removed after the fact. The correction must be completed and verified with a flood image before clinical acquisition.

Question 38Nuclear Medicine Technology (NMAA content outline not published in source)

A technologist performs a daily dose calibrator check and finds that the reading for a Cs-137 reference source differs from the expected value by 15 percent. What is the correct response?

  1. Record the value and continue because the difference is small
  2. Increase the sample volume to improve accuracy
  3. Use the calibrator only for high-activity doses
  4. Repeat the measurement and then take the instrument out of service if the discrepancy persists Correct answer.

Explanation

Daily constancy testing must agree with the established reference value within the facility's tolerance, typically about 10 percent. A persistent 15 percent discrepancy indicates the instrument needs recalibration or repair and must not be used for patient doses.

Question 39Nuclear Medicine Technology (NMAA content outline not published in source)

Which factor most strongly degrades image contrast in a planar Tc-99m image?

  1. Use of a low-energy high-resolution collimator
  2. Adequate patient hydration
  3. A short imaging distance from the detector
  4. Scattered photons accepted within the photopeak window Correct answer.

Explanation

Compton-scattered photons that lose little energy still fall within the photopeak window and are recorded at incorrect positions, raising background and reducing contrast. Correct window setting and scatter correction help limit this effect.

Question 40Nuclear Medicine Technology (NMAA content outline not published in source)

In FDG PET imaging, why is it important that the patient rest quietly in a warm room before tracer injection and during the uptake period?

  1. To accelerate hepatic metabolism of the tracer
  2. To prevent radiolysis of the FDG molecule
  3. To increase renal clearance of the tracer
  4. To reduce physiologic uptake in skeletal muscle and brown adipose tissue Correct answer.

Explanation

Muscle contraction and cold-induced brown fat activation both consume glucose and can produce misleading FDG uptake. Rest and warmth reduce this physiologic background so that pathologic uptake is easier to identify.

Question 41Nuclear Medicine Technology (NMAA content outline not published in source)

A sentinel lymph node procedure uses a Tc-99m filtered sulfur colloid. Why is the product filtered before injection?

  1. To control particle size so the tracer migrates to the sentinel node Correct answer.
  2. To shorten the half-life of the radionuclide
  3. To increase the gamma energy of the emission
  4. To remove free pertechnetate that would concentrate in the thyroid

Explanation

Particle size determines how quickly and how far colloid travels through lymphatics. Filtering removes larger aggregates so that the remaining particles reach the sentinel node promptly and produce a discrete focus for the surgeon's probe.

Question 42Nuclear Medicine Technology (NMAA content outline not published in source)

A patient scheduled for a parathyroid sestamibi scan is taking a medication that is known to interfere with tracer retention. What is the most appropriate technologist action?

  1. Double the injected activity to overcome the interference
  2. Notify the authorized user so the study can be rescheduled or the medication reviewed Correct answer.
  3. Substitute a bone scan agent without consulting anyone
  4. Proceed with the scan and ignore the medication history

Explanation

Certain medications and concurrent thyroid disease can alter sestamibi retention in parathyroid and thyroid tissue, so the clinical team must decide whether to adjust the medication or reschedule. The technologist should communicate the history rather than change the protocol independently.

Question 43Nuclear Medicine Technology (NMAA content outline not published in source)

Which statement best describes the ALARA principle as applied to nuclear medicine practice?

  1. All radiation exposure should be eliminated regardless of clinical benefit
  2. Exposure limits apply only to members of the public
  3. Exposures should be kept as low as reasonably achievable while allowing the required diagnostic information Correct answer.
  4. Doses should be reduced only when required by regulation

Explanation

ALARA balances dose reduction against the need for a medically useful study, using time, distance, and shielding. It applies to occupational and patient exposures and is a continuous optimization process rather than a fixed threshold.

Question 44Nuclear Medicine Technology (NMAA content outline not published in source)

A technologist must handle a vial containing a high-energy positron emitter. Which combination of measures best reduces occupational dose?

  1. Minimizing time, maximizing distance, and using appropriate shielding Correct answer.
  2. Maximizing time near the source and minimizing distance
  3. Using lead shielding for all positron emitters without considering bremsstrahlung
  4. Relying solely on a film badge reading

Explanation

Occupational dose is reduced by shortening time near the source, increasing distance, and using shielding matched to the radiation type. For positron emitters, high-density shielding such as tungsten or lead is used, and the added bremsstrahlung from nearby beta interactions is considered.

Question 45Nuclear Medicine Technology (NMAA content outline not published in source)

A radiopharmaceutical is prepared with an activity that must be injected within a specified time after kit formulation. What is the main reason for this time limit?

  1. The collimator must be recalibrated
  2. The kit vial will become radioactive to staff after the limit
  3. The patient's consent expires at that time
  4. The radionuclide half-life causes the activity to decay below the useful range Correct answer.

Explanation

Because Tc-99m decays with a six-hour half-life, the activity available for injection falls continuously, and labeling impurities can also increase over time. The manufacturer's expiration time ensures adequate activity and acceptable radiochemical purity.

Question 46Nuclear Medicine Technology (NMAA content outline not published in source)

A patient with a suspected pulmonary embolism has a perfusion scan showing multiple wedge-shaped defects but a normal ventilation scan. How should this pattern be interpreted?

  1. Artifact from patient motion
  2. High probability of pulmonary embolism Correct answer.
  3. Normal variant requiring no further action
  4. Findings consistent with pneumonia

Explanation

Mismatched defects, meaning normal ventilation with absent perfusion in the same region, indicate that airways are patent while blood flow is obstructed. Multiple segmental mismatched defects are interpreted as high probability for pulmonary embolism.

Question 47Nuclear Medicine Technology (NMAA content outline not published in source)

Which instruction is most important to give a patient before a Tc-99m MDP bone scan?

  1. Discontinue thyroid medication for one week
  2. Avoid all fluids for six hours
  3. Fast for at least twelve hours
  4. Empty the bladder immediately before imaging Correct answer.

Explanation

An empty bladder reduces pelvic activity that can obscure the pelvis and interfere with interpretation. Hydration and frequent voiding are also encouraged after injection to reduce soft-tissue and bladder background.

Question 48Nuclear Medicine Technology (NMAA content outline not published in source)

A technologist evaluates a renogram and observes that the time to peak activity in the transplanted kidney is prolonged, with slow subsequent decline. Which interpretation is most appropriate?

  1. The patient should be rescanned after a week
  2. The findings suggest impaired perfusion or obstruction and should be reported for clinical correlation Correct answer.
  3. The study should be repeated with a different collimator only
  4. The curve is normal and requires no comment

Explanation

A delayed peak and slow washout can reflect impaired perfusion, acute tubular injury, or obstruction, and the curve must be interpreted with clinical information. The findings should be documented and communicated so further evaluation can be arranged.

Question 49Nuclear Medicine Technology (NMAA content outline not published in source)

What is the main purpose of performing a daily flood image on a gamma camera?

  1. To calculate the radiochemical purity of a kit
  2. To measure the patient's absorbed dose
  3. To determine the collimator's septal thickness
  4. To verify detector uniformity and detect changes in camera performance Correct answer.

Explanation

A flood image assesses the uniformity of the detector's response across the field of view. Nonuniformities that appear as hot or cold spots or rings can degrade clinical images and should be corrected before patient studies.

Question 50Nuclear Medicine Technology (NMAA content outline not published in source)

A patient is injected with a radiopharmaceutical and then imaged with a parallel-hole collimator. If the collimator is changed to one with longer septa and smaller holes, what trade-off is expected?

  1. No change in either resolution or sensitivity
  2. Improved resolution with decreased sensitivity Correct answer.
  3. Improved sensitivity with decreased resolution
  4. Improved resolution and improved sensitivity simultaneously

Explanation

Longer septa and smaller holes restrict the acceptance angle, improving spatial resolution but reducing the number of photons reaching the crystal. This sensitivity loss may require longer acquisition times or higher activity.