AOBNM Nuclear Medicine key terms

A radioactive drug that combines a radionuclide with a carrier molecule so it localizes in specific tissue, allowing imaging or therapy of that tissue.

A radiopharmaceutical given in trace amounts purely to map physiologic or pathologic processes, producing negligible pharmacologic effect while emitting detectable radiation.

An unstable form of an element that decays by emitting radiation; its physical half-life and emission type determine how and when it can be imaged.

The time required for half of a radioactive sample to decay, a fixed property of the nuclide independent of biology or patient factors.

The time for half of a substance to be cleared from the body by physiologic processes such as excretion or metabolism, independent of radioactive decay.

The combined result of radioactive decay and biologic clearance, calculated as the product of physical and biologic half-lives divided by their sum.

The pattern and timing of uptake, retention, and clearance of a radiopharmaceutical across organs and tissues after administration.

An imaging device that detects gamma photons emitted from a patient and converts them into planar images of radiotracer distribution.

A lead or tungsten plate with holes placed over the detector to restrict incoming photons to a defined direction, allowing spatial localization at the cost of sensitivity.

The full-energy peak in a gamma spectrum produced when a photon deposits all its energy in the detector; imaging windows are set around it.

A selected range of pulse heights accepted by the camera, centered on the photopeak, that limits detection to photons of the intended energy.

Detection of photons that have changed direction and lost energy through Compton interactions in the patient or detector, degrading image contrast if not excluded.

Single-photon emission computed tomography; acquisition of planar projections from multiple angles that are reconstructed into three-dimensional maps of radiotracer distribution.

Positron emission tomography; detection of paired annihilation photons to localize positron-emitting tracers with high sensitivity and spatial resolution.

The PET principle of recording two nearly simultaneous 511 keV photons arriving from opposite directions, which defines a line along which the annihilation occurred.

The pair of 511 keV photons emitted in opposite directions when a positron combines with an electron, forming the signal detected in PET imaging.

Correction of image data for photon loss as radiation travels through tissue, typically using a transmission or CT-derived map, to improve quantification and uniformity.

Fluorine-18 fluorodeoxyglucose, a glucose analog trapped in cells after phosphorylation; its uptake reflects regional glucose metabolism and is increased in many tumors and inflamed tissues.

Meta-iodobenzylguanidine, a norepinephrine analog labeled with iodine-123 or iodine-131 that accumulates in sympathetic nerve terminals and neural crest tumors.

A technetium-99m-labeled lipophilic cation taken up by mitochondria, used for myocardial perfusion and parathyroid imaging.

Stress and rest radiotracer studies that show regional myocardial blood flow, used to detect ischemia, scar, and viability.

Paired ventilation and perfusion lung imaging used to identify mismatched perfusion defects suggesting pulmonary embolism.

The first lymph node draining a tumor bed, identified by radiotracer and often blue dye, which is sampled to stage regional nodal spread.

Imaging of radiotracer flow through lymphatic channels after interstitial injection, used to map drainage and locate sentinel nodes.

Administration of iodine-131 to ablate or treat thyroid tissue, exploiting selective iodine uptake by thyroid cells and differentiated thyroid cancer.

Calculation of absorbed radiation dose to organs and tissues from administered activity, based on biodistribution, clearance, and decay data.

The principle of keeping radiation exposure as low as reasonably achievable, applied through time, distance, and shielding during imaging and therapy.

Standardized uptake value; a semiquantitative PET metric that normalizes tissue activity to injected dose and body size, used to characterize lesion intensity.

A test result that fails to identify a condition that is actually present, lowering sensitivity and potentially delaying diagnosis.

A test result that suggests a condition is present when it is not, lowering specificity and prompting unnecessary follow-up.

The proportion of people who truly have a condition that the test correctly identifies as positive.

The proportion of people who truly lack a condition that the test correctly identifies as negative.

Impaired or altered function of related components of the somatic system, identified by tenderness, asymmetry, restricted motion, and tissue texture change.

The four diagnostic findings of somatic dysfunction: tissue texture abnormality, asymmetry, restriction of motion, and tenderness.

A set of hands-on techniques used by osteopathic physicians to diagnose and treat somatic dysfunction and support the body's self-regulatory capacity.

A reflex in which visceral dysfunction produces localized somatic changes such as muscle tension, tenderness, and altered tissue texture at related spinal levels.

A small, tender, edematous nodule in fascia or muscle linked by osteopathic tradition to drainage of a specific viscus.

The osteopathic concept that breathing and circulation of body fluids are linked, and that impaired motion of the diaphragm or thoracic cage affects fluid exchange.