NNC NSREN Specialist cheat sheet

Photomultiplier tube (PMT) gain rises steeply with applied high voltage; a small HV drift shifts energy-peak position, so daily photopeak checks detect gain instability.

Anger-camera position logic: each PMT signal is weighted by its position and summed; the ratio of weighted sums to total energy gives X and Y coordinates, while total energy gives the Z (pulse-height) signal.

Energy resolution is reported as FWHM divided by photopeak energy, expressed as a percent; for Tc-99m at 140 keV, a gamma camera typically achieves about 9-11% FWHM.

Sensitivity is counts per unit activity (cps/MBq or cpm/uCi) measured with a source in air; it is distinct from spatial resolution, which is measured as FWHM of a line-spread function in mm.

Uniformity is assessed with a flood field: integral uniformity is the maximum-minimum count difference over the whole field; differential uniformity uses a 5-pixel-wide moving window along each row and column.

Collimator choice sets both resolution and sensitivity: a low-energy high-resolution (LEHR) parallel-hole collimator gives finer resolution but lower sensitivity than a low-energy general-purpose (LEGP) collimator.

A parallel-hole collimator's resolution degrades with distance from the collimator face; a pinhole collimator magnifies small organs but its field of view shrinks as the aperture-to-organ distance decreases.

Dead-time losses follow a paralyzable (extending) or nonparalyzable model; the observed rate approaches a maximum and then falls with a paralyzable system, so decay-corrected count rates must be checked for linearity.

Dose equivalent: H = D x w_R (radiation weighting factor); 1 Sv = 100 rem. For gamma and beta radiation w_R = 1, so 1 Gy = 1 Sv for these radiations.

Effective dose E = sum over tissues of w_T x H_T; tissue weighting factors sum to 1.0, and the ICRP 103 values are used in current practice.

Inverse-square law: exposure rate falls as 1/r^2, so doubling distance from a point source cuts the exposure rate to one quarter.

Half-value layer (HVL) = 0.693/mu; shielding thickness for a required attenuation factor follows n = ln(attenuation)/ln(2) half-value layers.

Annual occupational effective dose limit is 50 mSv (5 rem); lens of eye 150 mSv (15 rem); skin and extremities 500 mSv (50 rem); declared pregnant worker 5 mSv (0.5 rem) to the fetus over the declared gestation.

Public dose limit is 1 mSv/y (100 mrem/y); a minor (under 18) occupational limit is 5 mSv/y (0.5 rem/y).

ALARA is implemented with time, distance, and shielding; a lead apron of 0.5 mm Pb attenuates Tc-99m 140 keV photons by roughly 90%.

A dose calibrator must be checked for constancy, accuracy (with a certified source such as Cs-137 or Co-57), linearity, and geometry; linearity is verified with a decay method or a set of calibrated attenuators.

Records of occupational dose are maintained on an NRC Form 5 or equivalent; a licensee must report a dose exceeding 250 mSv (25 rem) to the individual and the agency within the required timeframe.

Tc-99m is eluted from a Mo-99/Tc-99m generator; the Mo-99 breakthrough limit in eluate is 0.15 kBq Mo-99 per MBq Tc-99m (0.15 uCi Mo-99 per mCi Tc-99m).

Alumina column breakthrough (aluminum ion) limit is 10 ug/mL of eluate; measured with a colorimetric assay or a commercial test kit.

Radionuclidic purity of eluate: Mo-99 breakthrough is tested at first elution and at the end of the generator's useful life; the generator's Mo-99 activity must not exceed 0.15 kBq per MBq of Tc-99m at the time of use.

Radiochemical purity is the fraction of total activity in the desired chemical form; it is measured by thin-layer chromatography, paper chromatography, or HPLC, and each radiopharmaceutical has a specified minimum (often 90-95%).

For Tc-99m MDP, radiochemical purity is checked with a chromatographic system that separates free pertechnetate and hydrolyzed-reduced technetium from the labeled complex; the labeled fraction must meet the package-insert limit.

A dose calibrator uses a well ionization chamber; constancy is checked daily, accuracy with a certified source, and geometry with a syringe versus vial of the same activity.

Radiopharmaceuticals must be tested for sterility (membrane filtration or direct inoculation) and bacterial endotoxin (LAL test); the 0.22 um filter is used for terminal filtration of Tc-99m products.

The expiration time of a Tc-99m kit is set by the manufacturer's instructions; beyond it, radiochemical purity may fall below the specification even though Tc-99m activity remains.

Myocardial perfusion: Tc-99m sestamibi or tetrofosmin, about 740-1110 MBq (20-30 mCi) per injection; redistribution is minimal, so rest and stress images are acquired separately.

Bone scan: Tc-99m MDP, about 740-925 MBq (20-25 mCi) adult dose; imaging begins 2-4 h after injection, and hydration plus voiding before imaging reduces bladder and pelvic artifact.

V/Q lung scan: Tc-99m DTPA aerosol or Technegas for ventilation and Tc-99m MAA (about 100-200 ug MAA, 100,000-500,000 particles) for perfusion; MAA particle count is limited in pulmonary hypertension.

Renal scan: Tc-99m MAG3 or DTPA for dynamic imaging; MAG3 is preferred when renal function is reduced, and furosemide challenge is used for suspected obstruction.

Thyroid uptake and scan: I-123 (about 7.5-14.8 MBq, 200-400 uCi) or Tc-99m pertechnetate (about 74-185 MBq); Tc-99m pertechnetate is trapped but not organified, so it cannot assess organification.

Hepatobiliary scan: Tc-99m mebrofenin or disofenin; gallbladder visualization within 60 min excludes acute cholecystitis, while a morphine-augmented study can shorten the wait.

Sentinel lymph node: Tc-99m sulfur colloid or filtered Tc-99m sulfur colloid injected around the tumor; imaging and gamma-probe counting localize the first draining node.

PET with F-18 FDG: about 185-370 MBq (5-10 mCi) adult dose; blood glucose should be controlled and the patient rested in a quiet, warm room before uptake to reduce muscle and brown-fat uptake.

I-131 therapy for hyperthyroidism uses fixed activities (often 185-555 MBq, 5-15 mCi) or calculated activity from thyroid uptake and mass; ablation after thyroidectomy typically uses 1.1-3.7 GBq (30-100 mCi).

I-131 is concentrated by thyroid tissue; blocking agents (iodine, thyroid hormone, amiodarone) must be stopped before therapy, and pregnancy must be excluded with a negative hCG.

Radioiodine patient release criteria: the measured dose rate at 1 m is used with the NRC release rule; written instructions are required when the total effective dose equivalent to another individual could exceed 5 mSv (0.5 rem).

I-131 bodily fluids are radioactive for days; patients are instructed to flush twice, use separate towels, and avoid sharing utensils, and to sleep in a separate bed for the recommended period.

Y-90 microspheres for hepatic tumors are delivered by interventional radiology; a pre-treatment Tc-99m MAA scan estimates lung shunt fraction, and a shunt fraction above 20% contraindicates therapy.

Sr-89 chloride and Sm-153 lexidronam palliate painful bone metastases; both suppress marrow, so platelet and white-cell counts must be checked before each dose.

Lu-177 DOTATATE for somatostatin-receptor-positive tumors is given with amino-acid infusion to protect the kidneys; the dose is fractionated over multiple cycles.

After therapeutic administration, patient room surveys and dose-rate measurements document exposure; the therapy room is surveyed and decontaminated before reuse.

Daily gamma-camera QC: photopeak position and energy resolution for each radionuclide used, plus a flood-field uniformity image, are performed before patient imaging.

Weekly or monthly QC: spatial resolution and linearity with a bar phantom, and sensitivity with a calibrated source, are performed on a defined schedule.

Dose calibrator daily constancy test uses a long-lived check source (Cs-137 or Co-57); accuracy is tested annually with a certified source traceable to a national standard.

Dose calibrator linearity is tested at installation and after repair by the decay method or with attenuating sleeves; the result must be within +/-5% of expected activity.

Gamma-camera uniformity: integral uniformity should typically be within about 5% and differential uniformity within about 5% for a useful field of view, per the manufacturer's specification.

PET scanner QC includes daily detector checks (e.g., a blank or normalization scan), periodic well-counter calibration, and image quality phantoms; time-of-flight systems require timing-offset calibration.

A survey meter is calibrated annually and after repair; it is checked daily with a check source for response and battery status, and the calibration must be traceable.

Equipment records must document the date, procedure, results, and corrective action; a QC result outside the action level triggers repeat testing and, if persistent, service before clinical use.

Informed consent requires disclosure of purpose, risks, benefits, alternatives, and the right to refuse; for research or novel therapy, written consent is obtained.

Pregnancy screening: ask about pregnancy and last menstrual period for patients of childbearing age before any ionizing radiation procedure; document the response in the record.

Breastfeeding: after Tc-99m MAA or pertechnetate, interruption periods are specified by the radiopharmaceutical; for I-131 therapy, breastfeeding must be stopped permanently.

Patient identification uses two identifiers (name and date of birth or medical record number) checked against the request and the radiopharmaceutical label before administration.

Extravasation management: stop the injection, remove the needle, elevate the limb, apply a cold or warm compress per the radiopharmaceutical, and document the event and estimated activity.

Radiation risk communication should use absolute risk and comparison terms rather than vague reassurance; the ALARA principle and benefit-risk balance are explained in plain language.

Patient confidentiality is protected under HIPAA; images and reports are shared only with authorized persons for treatment, payment, or operations, and de-identification is required for other uses.

Professional scope of practice: technologists perform procedures under physician supervision and refer clinical questions to the authorized user or radiologist rather than interpreting results independently.