BCNP flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Radiochemical purity

The fraction of total radioactivity present in the desired chemical form, determined by chromatography and expressed as a percentage of activity in the product peak relative to total activity.

Radionuclidic purity

The fraction of total radioactivity attributable to the intended radionuclide, assessed by gamma spectroscopy; contaminating radionuclides must remain below specified limits before a product is released.

Mo-99 breakthrough limit

The maximum allowable Mo-99 contamination in Tc-99m eluate is 0.15 kBq per MBq of Tc-99m (0.15 µCi per mCi), tested at each elution using a dose calibrator or dedicated breakthrough detector.

Tc-99m half-life check

Technetium-99m has a 6.01-hour physical half-life; measuring activity over time should show roughly a 50% decrease every 6 hours, confirming radionuclidic identity within acceptable tolerance.

Decay equation

Activity at time t equals initial activity multiplied by e raised to the negative decay constant times t, where the decay constant is 0.693 divided by the physical half-life.

Precalibration correction

When a dose is calibrated for a future time, activity at use equals the calibrated activity multiplied by e raised to the positive decay constant times the elapsed interval, increasing the value.

Effective half-life

The combined removal rate from physical decay and biological clearance, calculated so that one divided by effective half-life equals one divided by physical plus one divided by biological half-life.

Generator elution principle

Mo-99 bound to an alumina column decays to Tc-99m, which is eluted as sodium pertechnetate with 0.9% sodium chloride; eluate is collected in a shielded vial and assayed.

Wet column elution schedule

Wet-column generators should be eluted at least every 24 hours; waiting longer allows Mo-99 and Tc-99m to accumulate, increasing breakthrough risk and radiolytic degradation of the eluate.

Dose calibrator constancy

Daily constancy testing uses a long-lived sealed source such as Cs-137 or Co-57; the measured value must fall within the established tolerance, usually plus or minus 10 percent of the reference.

Dose calibrator accuracy

Accuracy is verified across multiple radionuclides and geometries by comparing measured activity to decay-corrected reference activity, typically requiring agreement within plus or minus 5 to 10 percent.

Occupational dose limits

Annual limits for radiation workers are 50 mSv whole-body effective dose, 150 mSv for the lens, and 500 mSv for extremities and skin; a declared pregnant worker has a 0.5 mSv gestational limit.

Inverse square law

Radiation exposure rate from a point source decreases with the square of distance; doubling the distance from a source reduces the exposure rate to one quarter of its original value.

Laminar flow hood use

Aseptic radiopharmaceutical preparation occurs in an ISO Class 5 vertical laminar flow hood inside a controlled environment, with syringe shields and lead pigs limiting technologist exposure.

Tc-99m MDP

A diphosphonate bone-imaging agent labeled with technetium-99m that localizes to areas of osteoblastic activity and is used for skeletal scintigraphy and metastasis detection.

Tc-99m sulfur colloid

A particulate technetium-99m agent taken up by the reticuloendothelial system, used for liver and spleen imaging and for evaluating marrow distribution after intravenous injection.

Tc-99m MAA

Macroaggregated albumin labeled with technetium-99m, trapped in pulmonary capillaries after injection, permitting lung perfusion imaging and evaluation of pulmonary embolism.

Tc-99m DTPA

A chelating agent labeled with technetium-99m used for renal imaging and glomerular filtration rate measurement; it is cleared primarily by glomerular filtration.

Tc-99m sestamibi

A lipophilic cationic technetium-99m complex taken up by myocardial mitochondria, used for myocardial perfusion imaging and parathyroid localization; hepatobiliary clearance is expected.

Kit preparation records

Documentation for each radiopharmaceutical kit includes eluate activity and volume, generator identification, time of preparation, radiochemical purity results, and the preparing technologist's identity.

Visual inspection requirement

Before administration, each radiopharmaceutical dose is inspected for particulate matter, discoloration, and container integrity; any abnormality requires rejection of the product.

Decay-in-storage waste

Radioactive waste is segregated by half-life and held until activity decays to background, typically about ten half-lives, with documentation of survey results before disposal as nonradioactive waste.

Patient dose assay

The syringe activity is measured in a dose calibrator before administration, the assay time is recorded, and the prescribed activity is confirmed after decay correction to the administration time.

Pregnancy and breastfeeding

Radiopharmaceutical administration during pregnancy or lactation requires justification and counseling; some agents require interruption of breastfeeding for a defined period based on radionuclide excretion.

Thyroid blocking

Potassium iodide or perchlorate may be given before certain iodine-containing radiopharmaceuticals to reduce thyroid uptake and protect the gland from unnecessary radiation exposure.

Radiation safety shielding

Shielding material and thickness depend on photon energy; lead effectively attenuates technetium-99m emissions at 140 keV, while higher-energy emitters require denser or thicker barriers.

Sterility testing

Sterility and bacterial endotoxin testing are required for parenteral radiopharmaceuticals; results may be retrospective for short-lived products while release is based on validated aseptic process controls.

Eluate assay timing

Eluate activity is measured in the dose calibrator immediately after collection, and the time is recorded because technetium-99m decays by half approximately every six hours.

Half-life calculation

Half-life is determined from activity measurements at two times using the relationship half-life equals 0.693 times elapsed time divided by the natural logarithm of the initial-to-final activity ratio.

Radiation survey meter

A calibrated survey meter is used to check work areas, shielding, and waste storage; daily surveys document exposure rates and confirm that areas remain within posted limits.

Contamination control

Absorbent bench pads, gloves, and frequent surveys limit radioactive contamination; spills are contained, marked, surveyed, and decontaminated until removable activity is below established limits.

Dose calibrator geometry

Sample volume, container type, and position within the dose calibrator affect measured activity; consistent geometry and correct radionuclide selection are required for accurate assay.