CAMRT Nuclear Medicine flashcards
CAMRT Nuclear Medicine · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Decay constant
- The probability per unit time that a radionuclide atom decays; λ = ln2 divided by physical half-life, used in activity equations.
- Tc-99m half-life
- Technetium-99m has a physical half-life of 6.02 hours, giving a 140 keV gamma emission suitable for gamma camera imaging.
- F-18 half-life
- Fluorine-18 has a physical half-life of 109.8 minutes and emits positrons; annihilation produces two 511 keV photons detected in coincidence.
- Mo-99 breakthrough test
- A measurement of molybdenum-99 contamination in eluted technetium-99m; the limit must be verified before the eluate is administered to patients.
- Effective half-life
- Combined physical and biological clearance: one over effective half-life equals one over physical plus one over biological half-life.
- Radiochemical purity
- The fraction of total radioactivity present as the desired chemical form, measured by chromatography before patient administration.
- MDP bone agent
- Technetium-99m methylene diphosphonate adsorbs to bone hydroxyapatite; uptake reflects osteoblastic activity and regional blood flow.
- MAG3 renal agent
- Technetium-99m mercaptoacetyltriglycine is secreted by renal tubules and is used for renal function and transplant evaluation.
- MIBI perfusion agent
- Technetium-99m sestamibi accumulates in myocardium proportional to perfusion and mitochondrial membrane potential; used for stress and rest imaging.
- Pertechnetate use
- Technetium-99m pertechnetate is trapped by thyroid, salivary glands, and gastric mucosa, useful for thyroid and Meckel diverticulum imaging.
- I-131 therapy
- Iodine-131 emits beta particles and gamma photons, used to ablate thyroid tissue; it is contraindicated in pregnancy and breastfeeding.
- Collimator function
- A lead or tungsten grid that limits photon acceptance angle, determining trade-off between spatial resolution and sensitivity for the gamma camera.
- Photopeak window
- An energy acceptance range centered on the isotope photopeak, typically plus or minus 10 percent, to reduce scatter detection.
- NaI crystal
- Thallium-doped sodium iodide crystal converts gamma photons to light flashes, which photomultiplier tubes amplify into measurable electrical pulses.
- Pulse-height analyzer
- An electronic circuit that sorts detector pulses by amplitude, allowing selection of the photopeak energy window and rejection of scatter.
- Flood field uniformity
- A quality control image of uniform activity used to verify detector uniformity and identify photomultiplier tube drift or crystal defects.
- Spatial resolution
- The smallest distance between two points that can be distinguished, expressed as full width at half maximum of the line spread function.
- PET coincidence detection
- Simultaneous detection of two 511 keV annihilation photons by opposing detectors within a timing window, localizing the positron emission.
- Attenuation correction
- Correction for photon absorption and scatter within the patient, using CT or transmission data, required for quantitative PET and SPECT.
- OSEM reconstruction
- Ordered subset expectation maximization, an iterative SPECT or PET reconstruction method that reduces noise and streak artifacts compared with filtered back-projection.
- Dead time
- The interval after a detected event during which the system cannot record another pulse, causing count loss at high activity.
- Absorbed dose
- Energy deposited per unit mass of tissue, measured in gray, where one gray equals one joule per kilogram.
- Effective dose
- A tissue-weighted sum of equivalent doses used to express overall stochastic radiation risk in sieverts.
- Occupational dose limit
- ICRP recommends an average of 20 mSv per year over five years and no more than 50 mSv in any single year for radiation workers.
- Inverse square law
- Photon fluence rate decreases with the square of distance from a point source, so doubling distance reduces dose rate to one quarter.
- Decay-in-storage
- Holding radioactive waste until activity has decayed to background levels, after which it may be disposed of as nonradioactive waste.
- Pregnancy screening
- Verification of pregnancy status before radiopharmaceutical administration, especially before iodine-131 therapy or high-dose diagnostic studies.
- V/Q mismatch
- A perfusion defect with preserved ventilation on lung scanning, suggesting pulmonary embolism when multiple segments are involved.
- Reversible perfusion defect
- A myocardial stress defect that fills in at rest, indicating ischemia rather than infarction; a fixed defect suggests scar.
- Three-phase bone scan
- Flow, blood pool, and delayed imaging after technetium-99m MDP, used to separate cellulitis from osteomyelitis.
- FDG PET preparation
- Fasting and glucose control before fluorine-18 FDG administration, because elevated glucose competes with tracer uptake in tumors.
- Meckel diverticulum scan
- Technetium-99m pertechnetate imaging showing focal uptake in ectopic gastric mucosa, typically in the right lower abdomen.