Free ARRT Nuclear Medicine Exam Flashcards

The ordering or performing physician is responsible for explaining the procedure's risks, benefits, and alternatives. The technologist's role is to verify that consent was properly obtained and witness the patient's signature, not to provide the medical explanation.

Staff may access, use, or disclose only the protected health information needed to perform their specific task. Sharing more patient information than required for the job at hand violates the HIPAA Privacy Rule, even without malicious intent.

Six links: infectious agent, reservoir, portal of exit, mode of transmission, portal of entry, and susceptible host. Breaking any single link, such as hand hygiene interrupting the portal of exit or entry, stops disease transmission.

Applied to every patient regardless of diagnosis. Assumes all blood, body fluids, secretions, and nonintact skin are potentially infectious. The core practices are hand hygiene plus PPE selected based on anticipated exposure.

Watch for urticaria, pruritus, and flushing as early cutaneous signs. Progression to bronchospasm, laryngeal edema, or hypotension is anaphylaxis, a medical emergency requiring immediate cessation of administration and emergency response.

Comparing a patient's current medication list against known interactions and contraindications, for example thyroid hormone before an iodine uptake study, or metformin before FDG PET/CT (it causes intense diffuse bowel uptake that can obscure abdominal disease, so many protocols hold it for about 48 hours before the scan), helps prevent invalid results and missed findings.

In the photoelectric effect, a low-energy photon is completely absorbed and ejects an inner-shell electron; the photon does not exit to be detected. In Compton scattering, a higher-energy photon interacts with an outer-shell electron, loses some energy, and changes direction, which is the main source of scatter that degrades image contrast.

Deterministic effects, such as skin erythema or cataracts, have a dose threshold and increase in severity with dose. Stochastic effects, such as cancer and genetic effects, have no threshold; only the probability of occurrence increases with dose, not the severity.

Minimize TIME spent near a source, maximize DISTANCE from it (dose falls off by the inverse square law), and add appropriate SHIELDING for the radiation type. Together these implement ALARA, keeping exposure As Low As Reasonably Achievable.

The occupational whole-body effective dose limit is 5 rem (50 mSv) per year under 10 CFR 20.1201. The limit for members of the public from licensed activities is 100 mrem (1 mSv) per year under 10 CFR 20.1301, one-twentieth of the occupational limit.

Per 10 CFR 20.1003, a Radiation Area could cause a dose over 5 mrem in 1 hour at 30 cm from the source. A High Radiation Area could cause a dose over 100 mrem in 1 hour at 30 cm. Both classifications require specific posting.

Under 10 CFR 35.3045, a reportable medical event requires both conditions: the delivered dose differs from the prescribed dose by 20 percent or more, AND that difference exceeds 5 rem (0.05 Sv) effective dose, 50 rem (0.5 Sv) to an organ or tissue, or 50 rem (0.5 Sv) shallow dose to the skin. The rem figures measure the size of the error, not the size of the total dose given.

A GM counter is highly sensitive and used for low-level contamination and wipe-test surveys, but it saturates and reads falsely low at high dose rates. An ionization chamber (a 'cutie pie') is less sensitive but accurately measures the higher dose rates found during area and spill surveys.

Constancy is checked daily with a long-lived reference source, such as Cs-137. Accuracy is checked at installation and annually against a NIST-traceable source. Linearity is checked at installation and quarterly across the clinical activity range. Geometry is checked at installation for different volumes and containers.

A well counter surrounds a sample for high-sensitivity in vitro counting, such as blood or urine samples and wipe tests. A thyroid uptake probe is a collimated NaI detector positioned externally over the neck to measure percent thyroid uptake in vivo without acquiring an image.

Performed daily to confirm a gamma camera responds uniformly across its entire field of view. A nonuniform flood points to a PMT, crystal, or electronic problem, and the camera should not be used for SPECT acquisitions until the issue is corrected.

A parallel-hole collimator is the general-purpose choice; image size stays equal to object size regardless of distance. A pinhole collimator magnifies small superficial structures, such as a pediatric thyroid, but image size shrinks as the object moves farther from the pinhole aperture.

More angular views over the acquisition arc improve angular sampling and reduce streak artifacts, at the cost of longer scan time. Arc length is a separate choice: a full 360-degree orbit is standard for most SPECT studies, but myocardial perfusion SPECT uses a 180-degree arc (RAO 45 to LPO 45) because it gives better contrast and resolution for the heart, since the posterior projections contribute mostly attenuation and scatter.

The CT scan measures tissue density and is used to correct the PET emission data for photon attenuation as photons pass through the body. This correction produces quantitatively accurate images and enables calculation of the standardized uptake value (SUV).

DICOM (Digital Imaging and Communications in Medicine) is the standard for transmitting and storing medical images, such as sending studies to PACS. HL7 (Health Level 7) is the standard for exchanging non-image clinical and administrative data, such as orders and reports, between systems like the RIS and EHR.

Mo-99 (parent, physical half-life about 66 hours) decays to Tc-99m (daughter, physical half-life about 6 hours) bound to an alumina column. Eluting the generator with saline extracts Tc-99m as sodium pertechnetate while Mo-99 stays bound, and activity regenerates as the parent continues to decay.

Molybdenum-99 breakthrough must not exceed 0.15 microcurie of Mo-99 per millicurie of Tc-99m at the time of administration. Aluminum ion breakthrough must not exceed 10 micrograms per milliliter of eluate. Both are tested on every elution before patient use.

1 divided by T-effective equals 1 divided by T-physical plus 1 divided by T-biological. Effective half-life is always shorter than either the physical or biological half-life alone, since it reflects the combined loss of radioactivity from decay and biological clearance.

Physical half-life is about 6 hours; the primary photopeak is 140 keV. This combination of a short half-life and a mid-range gamma energy gives good image quality with low patient dose and efficient collimation, making Tc-99m the workhorse of nuclear medicine.

I-131 has an 8-day half-life, emits a high-energy 364 keV gamma plus beta particles, and is used for thyroid ablation and therapy. I-123 has a 13-hour half-life, emits a cleaner 159 keV gamma with no beta component, and is preferred for diagnostic thyroid uptake and imaging.

Physical half-life is about 110 minutes. F-18 is a positron emitter; when the emitted positron annihilates with a nearby electron, it produces two 511 keV photons traveling in opposite directions, which the PET scanner detects in coincidence.

Labeling efficiency depends on pH, reaction (labeling) time, and temperature. The reducing agent, typically stannous ion, must reduce Tc-99m from its eluted +7 oxidation state so it can bind to the kit's ligand; inadequate reduction leaves free unbound pertechnetate and degrades image quality.

A reversible defect, present on stress imaging but resolved on rest or redistribution imaging, indicates ischemia in viable myocardium supplied by a stenotic vessel. A fixed defect, present on both stress and rest images, indicates infarcted or scarred, nonviable tissue.

Physical half-life is about 73 hours (roughly 3 days). Imaging primarily uses the 69-83 keV mercury x-rays produced during electron capture decay, with a secondary energy window centered on the 167 keV gamma photopeak also acquired to improve counting statistics.

Vasodilators (regadenoson, adenosine, dipyridamole) create coronary flow heterogeneity by dilating normal vessels more than stenotic ones. Dobutamine, an inotrope and chronotrope, is used instead when a patient has a contraindication to vasodilator stress.

Uses Tc-99m-labeled red blood cells with acquisition synchronized to the ECG R-wave to precisely calculate left ventricular ejection fraction. Commonly used to monitor for cardiotoxicity before and during chemotherapy regimens such as doxorubicin or trastuzumab.

Both are lipophilic cationic complexes taken up into myocardial cells and sequestered in mitochondria in proportion to blood flow. Unlike Tl-201, neither shows significant redistribution over time, so separate stress and rest doses are required for a complete study.

Second- or third-degree AV block or sinus node dysfunction without a functional pacemaker contraindicates all three agents. Significant bronchospastic disease, such as unstable asthma, is a labeled contraindication for adenosine and dipyridamole, but only a warning for regadenoson; regadenoson's A2A receptor selectivity is why it is often preferred for patients with reactive airway disease. Caffeine and theophylline are held before any of these agents because they antagonize the adenosine receptors the drugs rely on.

Measures the percentage of an orally administered I-123 (or low-dose I-131) dose trapped by the thyroid at set intervals, commonly around 4-6 hours and 24 hours, using an uptake probe. Elevated uptake suggests hyperthyroidism such as Graves disease; suppressed uptake suggests thyroiditis or recent iodine or thyroid hormone exposure.

Tc-99m sestamibi washes out of normal thyroid tissue faster than it washes out of a hyperfunctioning parathyroid adenoma. A focus of activity that persists on delayed images relative to early images localizes the adenoma.

Patients follow a low-iodine diet and stop iodinated contrast and amiodarone for a defined period before therapy, depleting competing stable iodine to maximize thyroid and tumor uptake of the therapeutic dose. TSH must also be elevated to stimulate uptake, either by withdrawing thyroid hormone or by giving recombinant human TSH (Thyrogen), which achieves stimulation without the symptoms of induced hypothyroidism.

MIBG is a norepinephrine analog taken up by adrenergic tissue through active transport, localizing neuroendocrine tumors such as pheochromocytoma and neuroblastoma. Certain medications, including some antihypertensives and tricyclic antidepressants, must be held before the study because they block MIBG uptake, and patients are pretreated with a thyroid-blocking agent such as SSKI or Lugol's solution to prevent the thyroid from taking up any free radioiodine released from the labeled compound.

Both target somatostatin receptors overexpressed on neuroendocrine tumors. In-111 pentetreotide (OctreoScan) is the older SPECT agent, while Ga-68 DOTATATE PET/CT offers higher resolution and has largely replaced it for neuroendocrine tumor localization.

Patients fast for 4-6 hours before injection, and blood glucose is checked because hyperglycemia competes with tumor FDG uptake and degrades image quality. Patients also rest quietly in a warm, dim room after injection to minimize unwanted skeletal muscle and brown fat uptake.

The patient eats a standardized Tc-99m sulfur colloid-labeled solid meal (egg substitute is standard), with images acquired at set intervals over 4 hours. Consensus normal values are less than about 60 percent retention at 2 hours and less than about 10 percent retention at 4 hours.

Uses Tc-99m sodium pertechnetate, which is taken up by ectopic gastric mucosa, the same mucin-secreting cells that concentrate pertechnetate in the normal stomach and are often present within a Meckel diverticulum. Pretreatment with an H2 blocker such as cimetidine can enhance detection.

Uses a Tc-99m iminodiacetic acid analog, such as mebrofenin, that is taken up by hepatocytes and excreted into bile. Nonvisualization of the gallbladder by 60 minutes, or after morphine augmentation, supports a diagnosis of acute cholecystitis from cystic duct obstruction.

In vivo or in vitro labeled Tc-99m red blood cells are imaged dynamically for up to 90 minutes and can detect active bleeding at rates as low as about 0.1 mL per minute, roughly ten times more sensitive than angiography. The long intravascular half-life of labeled RBCs also allows delayed or intermittent imaging to catch slow or intermittent bleeds.

MAG3 is cleared primarily by tubular secretion and has high extraction efficiency, making it preferred for patients with reduced renal function. DTPA is cleared by glomerular filtration and is used to calculate the glomerular filtration rate (GFR).

Phase 1 (flow), acquired in the first minute after injection, shows blood flow. Phase 2 (blood pool), acquired around 5 minutes, shows soft tissue hyperemia. Phase 3 (delayed), acquired 2-4 hours later, shows osteoblastic bone uptake. Osteomyelitis is typically positive on all three phases; cellulitis is positive on phases 1-2 but negative on phase 3.

A Tc-99m radiopharmaceutical, such as HMPAO or DTPA, is injected as a bolus and dynamically imaged. Absence of any intracranial blood flow, sometimes called the 'hollow skull' sign, with no radiotracer uptake in the brain, supports a diagnosis of brain death.

Tc-99m macroaggregated albumin (MAA) particles temporarily microembolize a small fraction of pulmonary capillaries in proportion to regional blood flow. The particle number administered is reduced in patients with pulmonary hypertension or a right-to-left cardiac shunt to avoid excessive capillary occlusion or systemic embolization.

Xe-133 is a true gas (half-life about 5.24 days, 81 keV photopeak) requiring a closed delivery system with negative-pressure exhaust trapping. Tc-99m DTPA aerosol is nebulized into fine droplets and uses the same isotope and energy window as a same-day Tc-99m perfusion scan, but it deposits unevenly in obstructed airways.

A small, often filtered volume of Tc-99m sulfur colloid is injected around a tumor site, such as breast cancer or melanoma. It drains through the lymphatics to the first-draining, or sentinel, node, which is then imaged and marked for targeted biopsy instead of full lymph node dissection.

A radiotracer, such as In-111 DTPA for cisternography or Tc-99m DTPA for a shunt patency study, is introduced into the CSF space by lumbar puncture or shunt reservoir and imaged over time to confirm flow direction and patency and to rule out a CSF leak or shunt malfunction.