NNC NSREN Specialist flashcards

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

Photopeak position check

Daily gamma-camera test confirming that the photopeak for a given radionuclide, such as Tc-99m at 140 keV, falls within the accepted window; drift indicates PMT gain or high-voltage instability.

Energy resolution definition

The FWHM of a photopeak divided by its centroid energy, expressed as a percent. Lower values mean better separation of scattered from primary photons; a Tc-99m camera typically gives 9-11%.

Integral uniformity

The maximum minus minimum count difference across the entire useful field of view of a flood image, divided by the maximum plus minimum and expressed as a percent.

Paralyzable dead time

A detection model in which each event, including one occurring during dead time, extends the dead period. The observed count rate peaks and then decreases as the true rate rises.

Collimator resolution versus distance

For a parallel-hole collimator, spatial resolution worsens linearly as the source-to-collimator distance increases; sensitivity stays roughly constant with distance.

Effective dose formula

E equals the sum of tissue weighting factors multiplied by the equivalent dose in each tissue. Tissue weights sum to 1.0, and the result is expressed in sieverts.

Occupational dose limits

Annual limits: 50 mSv effective dose, 150 mSv lens of eye, 500 mSv skin and extremities, and 5 mSv to the fetus of a declared pregnant worker.

Half-value layer relation

HVL equals 0.693 divided by the linear attenuation coefficient. The number of half-value layers needed equals the natural log of the required attenuation factor divided by ln 2.

Inverse-square law

Exposure rate from a point source is inversely proportional to the square of the distance. Tripling distance reduces the exposure rate to one ninth.

Mo-99 breakthrough limit

The allowable Mo-99 activity in Tc-99m eluate is 0.15 kBq per MBq of Tc-99m (0.15 uCi per mCi) at the time of use.

Aluminum breakthrough limit

Alumina column eluate must contain no more than 10 micrograms of aluminum per milliliter, measured by colorimetric assay; excess aluminum affects labeling efficiency.

Radiochemical purity

The fraction of total radioactivity present in the desired chemical form, determined by chromatography and required to meet the package-insert specification before patient administration.

Dose calibrator constancy test

A daily measurement of a long-lived check source, such as Cs-137, to confirm that the ionization-chamber response has not drifted from its established baseline value.

MAA particle count limit

A Tc-99m MAA perfusion dose typically contains 100,000 to 500,000 particles; fewer are used in pulmonary hypertension or right-to-left shunt to limit capillary blockade.

Bone scan timing

After Tc-99m MDP injection, imaging begins 2 to 4 hours later to allow skeletal uptake and renal clearance, with hydration and voiding to reduce bladder artifact.

Tc-99m pertechnetate trapping

Pertechnetate is trapped by thyroid follicular cells but is not organified, so it cannot evaluate organification defects; iodine-123 is used when organification must be assessed.

Hepatobiliary scan endpoint

Visualization of the gallbladder within about 60 minutes after Tc-99m mebrofenin injection makes acute cholecystitis unlikely; nonvisualization suggests cystic duct obstruction.

FDG uptake preparation

Patients fast, control blood glucose, avoid strenuous exercise, and rest in a warm quiet room before F-18 FDG injection to reduce muscle and brown adipose uptake.

Radioiodine release instructions

Written instructions are required when another person could receive more than 5 mSv from the released patient; they cover distance, contact time, and separate sleeping arrangements.

Lung shunt fraction

The fraction of Tc-99m MAA activity reaching the lungs, estimated before Y-90 microsphere therapy; a shunt above 20% contraindicates hepatic arterial treatment.

Strontium-89 chloride use

A beta-emitting bone-seeking agent for palliation of painful osteoblastic metastases. It suppresses bone marrow, so blood counts must be checked before administration.

Pregnancy exclusion before therapy

A negative pregnancy test is required before radioiodine therapy in patients of childbearing age, because I-131 crosses the placenta and can ablate fetal thyroid tissue.

Bar phantom QC

A weekly or monthly test using a bar phantom to check spatial resolution and linearity of a gamma camera; the bars of each size must be visually resolved.

Dose calibrator linearity test

Verification of activity measurement across a range of activities, using decay or attenuating sleeves, with results required to fall within about 5% of expected values.

Survey meter calibration

Annual calibration traceable to a national standard plus a daily check-source response and battery check; recalibration is required after repair or a dropped instrument.

PET daily detector check

A daily scan of detector blocks, such as a blank or normalization acquisition, to confirm that all detectors respond and that timing offsets remain within specification.

Two-identifier verification

Before radiopharmaceutical administration, staff confirm the patient's name and date of birth or medical record number against the request and the labeled dose.

Extravasation response

Stop the injection, remove the needle, elevate the limb, apply the compress specified for that radiopharmaceutical, and document the event and estimated retained activity.

Informed consent elements

Disclosure of the procedure's purpose, risks, benefits, alternatives, and the right to refuse, documented before the study or therapy proceeds.

Breastfeeding after I-131

Breastfeeding must be discontinued permanently after radioiodine therapy because iodine is concentrated in breast tissue and secreted in milk, delivering a dose to the infant.

Absolute risk communication

Explaining radiation risk with concrete absolute numbers and comparisons rather than vague reassurance, so the patient can weigh benefit against risk.

Scope of practice

Technologists perform imaging and therapy procedures under authorized-user supervision and refer diagnostic interpretation and clinical decisions to the physician.