ARRT Nuclear Medicine cheat sheet

Tc-99m MDP bone scintigraphy uses flow, blood-pool, and delayed phases; focal increased uptake reflects osteoblastic activity, while photopenic foci can indicate aggressive lysis, infarction, or prosthesis.

Myocardial perfusion uses stress and rest Tc-99m sestamibi or tetrofosmin; a defect that improves at rest is reversible ischemia, whereas a fixed defect suggests scar or attenuation artifact.

V/Q lung scan uses Tc-99m MAA perfusion and aerosol or technegas ventilation; a perfusion defect with normal ventilation (mismatch) raises PE probability, especially with high clinical pretest probability.

Hepatobiliary scan uses Tc-99m mebrofenin or disofenin; gallbladder nonvisualization at 4 hours with intestinal activity suggests acute cholecystitis, and morphine augmentation can shorten the study.

Renal scintigraphy uses Tc-99m DTPA for GFR, Tc-99m MAG3 for tubular secretion and ERPF, and Tc-99m DMSA for cortical imaging; captopril renography assesses renovascular hypertension.

Thyroid imaging uses Tc-99m pertechnetate or I-123; a cold nodule requires correlation, and I-131 whole-body scanning follows thyroidectomy for differentiated thyroid cancer.

GI bleeding imaging with Tc-99m RBC can detect bleeding at approximately 0.1 mL/min; Meckel diverticulum imaging uses Tc-99m pertechnetate uptake by ectopic gastric mucosa.

Sentinel node lymphoscintigraphy uses Tc-99m sulfur colloid or tilmanocept injected near the tumor; the first draining node is identified with a gamma probe for biopsy.

Brain death imaging uses Tc-99m DTPA or HMPAO to demonstrate absent cerebral perfusion; the study must follow institutional criteria and may be confounded by scalp or venous activity.

Mo-99/Tc-99m generator: Mo-99 (66 h) decays to Tc-99m (6.01 h); eluate must be assayed for Mo-99 breakthrough, with a limit of 0.15 kBq per MBq (0.15 µCi/mCi) Tc-99m.

Aluminum breakthrough limit is 10 µg/mL of eluate; excess Al3+ can aggregate particulate radiopharmaceuticals and alter biodistribution.

Purity types include radionuclidic purity (unwanted radionuclides), radiochemical purity (desired chemical form), chemical purity (nonradioactive impurities), plus sterility and apyrogenicity.

Common Tc-99m agents: MDP for bone, MAA for lung perfusion, MAG3 for renal tubular function, DTPA for GFR, sulfur colloid for liver/spleen/marrow, sestamibi for myocardial and parathyroid imaging, and pertechnetate for thyroid, Meckel, and gastric imaging.

PET isotopes: F-18 110 min, Ga-68 68 min, C-11 20 min, N-13 10 min, O-15 2 min, and Rb-82 76 sec; short half-lives dictate on-site production and rapid imaging.

Half-lives used for decay correction: I-131 8.02 days, I-123 13.2 h, Tc-99m 6.01 h, In-111 2.8 days, and Tl-201 73 h.

Kit preparation follows the package insert, verifies expiration and labeling efficiency, inspects for particles or discoloration, and uses aseptic technique with appropriate shielding.

Particle size: MAA 10-90 µm lodges in pulmonary capillaries; sulfur colloid 0.1-1 µm is phagocytosed by reticuloendothelial cells; filtered colloid is used for sentinel node mapping.

Dose calibration measures activity in a dose calibrator before administration and records time, activity, and volume, with decay correction to the calibration time on the label.

NaI(Tl) detector: a gamma ray produces light, photomultiplier tubes convert it to an electrical pulse, and a pulse-height analyzer selects the photopeak; energy resolution at Tc-99m 140 keV is about 10%.

Tc-99m photopeak window is commonly 140 keV ±10% (126-154 keV); I-131 is 364 keV and F-18 is 511 keV; incorrect windows increase scatter or lose true counts.

Collimator choice: parallel-hole preserves size, pinhole magnifies small organs, converging magnifies, and diverging minifies; resolution improves with longer holes and smaller hole diameter but sensitivity falls.

Daily gamma camera QC includes a uniformity flood; extrinsic uniformity includes the collimator; center of rotation and resolution/sensitivity checks follow defined schedules.

SPECT uses a 360-degree orbit with 60-120 projections; filtered backprojection or iterative reconstruction is used, with attenuation, scatter, and resolution recovery corrections improving quantitation.

PET detects 511-keV annihilation photons in coincidence; time-of-flight improves localization, and CT attenuation correction plus scatter correction are required for quantitative SUV.

CT numbers: water is 0 HU, air is about -1000 HU, and bone is high positive; window width and level control display, while pitch and mAs affect dose and image noise.

Image matrix: pixel size equals field of view divided by matrix width; a larger matrix yields smaller pixels but fewer counts per pixel, increasing noise unless counts are adequate.

High count rate causes dead time and pulse pileup; paralyzable systems show decreasing observed count rate at very high activity, so activity must be reduced or split.

ALARA: reduce time, increase distance, and use shielding; exposure rate obeys the inverse square law I1/I2 = (d2/d1)^2 for a point source.

NCRP occupational limits: 50 mSv/year effective dose, 150 mSv/year lens, and 500 mSv/year skin and extremities; the public limit is 1 mSv/year.

A declared pregnant worker has an embryo-fetus limit of 0.5 mSv/month and 5 mSv over gestation; duties are reviewed to maintain ALARA.

Half-value layer: lead HVL for Tc-99m is about 0.3 mm; a 0.5-mm lead apron attenuates a large fraction but not all gamma rays, and 511-keV PET photons require more shielding.

Waste decay: hold short-lived radionuclides for about 10 half-lives; Tc-99m requires about 60 hours and I-131 about 80 days; survey and document before disposal.

Contamination monitoring: a thin-window GM detector detects beta, a NaI scintillation detector detects gamma, and wipe tests identify removable contamination counted in a well counter.

Spill response: contain, mark, shield, survey personnel and area, remove contamination without spreading it, and report according to institutional and regulatory requirements.

Dose quantities: absorbed dose is in Gy, equivalent dose is in Sv with radiation weighting, and effective dose is in Sv with tissue weighting; these allow risk and limit comparisons.

Package receipt: survey the transport package, check removable contamination, verify the label and dosimeter, and document findings before radiopharmaceutical use.

Patient identification uses at least two identifiers and matches the dose label, order, and patient before administration; documentation includes radiopharmaceutical, activity, route, and time.

Pregnancy and lactation screening is performed before radiopharmaceutical administration; the authorized user provides fetal dose estimates and breastfeeding interruption guidance.

Dose calibrator QC includes daily constancy, quarterly linearity, quarterly accuracy, and geometry checks; results are recorded and the calibrator is removed from service if outside tolerance.

Gamma camera QC includes daily uniformity flood and periodic resolution, sensitivity, and center-of-rotation checks; collimator and detector artifacts are corrected before imaging.

Radiopharmaceutical QC includes visual inspection for particles or discoloration, pH where required, radiochemical purity by chromatography, and sterility or pyrogen testing per kit instructions.

Adverse reactions include anaphylaxis, vasovagal response, and extravasation; the study is stopped, basic life support is provided, the authorized user is notified, and the event is documented.

Pediatric dosing adjusts activity by weight or body surface area per institutional protocol; the smallest volume consistent with accurate counting is used and repeat imaging is minimized.

Patient instructions include hydration and frequent voiding to reduce bladder dose, plus breast-feeding and contact precautions specific to the radiopharmaceutical.

Tc-99m MDP bone scintigraphy uses flow, blood-pool, and delayed phases; focal increased uptake reflects osteoblastic activity, while photopenic foci can indicate aggressive lysis, infarction, or prosthesis.

Myocardial perfusion uses stress and rest Tc-99m sestamibi or tetrofosmin; a defect that improves at rest is reversible ischemia, whereas a fixed defect suggests scar or attenuation artifact.

V/Q lung scan uses Tc-99m MAA perfusion and aerosol or technegas ventilation; a perfusion defect with normal ventilation (mismatch) raises PE probability, especially with high clinical pretest probability.

Hepatobiliary scan uses Tc-99m mebrofenin or disofenin; gallbladder nonvisualization at 4 hours with intestinal activity suggests acute cholecystitis, and morphine augmentation can shorten the study.

Renal scintigraphy uses Tc-99m DTPA for GFR, Tc-99m MAG3 for tubular secretion and ERPF, and Tc-99m DMSA for cortical imaging; captopril renography assesses renovascular hypertension.

Thyroid imaging uses Tc-99m pertechnetate or I-123; a cold nodule requires correlation, and I-131 whole-body scanning follows thyroidectomy for differentiated thyroid cancer.

GI bleeding imaging with Tc-99m RBC can detect bleeding at approximately 0.1 mL/min; Meckel diverticulum imaging uses Tc-99m pertechnetate uptake by ectopic gastric mucosa.

Sentinel node lymphoscintigraphy uses Tc-99m sulfur colloid or tilmanocept injected near the tumor; the first draining node is identified with a gamma probe for biopsy.

Brain death imaging uses Tc-99m DTPA or HMPAO to demonstrate absent cerebral perfusion; the study must follow institutional criteria and may be confounded by scalp or venous activity.

Mo-99/Tc-99m generator: Mo-99 (66 h) decays to Tc-99m (6.01 h); eluate must be assayed for Mo-99 breakthrough, with a limit of 0.15 kBq per MBq (0.15 µCi/mCi) Tc-99m.

Aluminum breakthrough limit is 10 µg/mL of eluate; excess Al3+ can aggregate particulate radiopharmaceuticals and alter biodistribution.

Purity types include radionuclidic purity (unwanted radionuclides), radiochemical purity (desired chemical form), chemical purity (nonradioactive impurities), plus sterility and apyrogenicity.

Common Tc-99m agents: MDP for bone, MAA for lung perfusion, MAG3 for renal tubular function, DTPA for GFR, sulfur colloid for liver/spleen/marrow, sestamibi for myocardial and parathyroid imaging, and pertechnetate for thyroid, Meckel, and gastric imaging.

PET isotopes: F-18 110 min, Ga-68 68 min, C-11 20 min, N-13 10 min, O-15 2 min, and Rb-82 76 sec; short half-lives dictate on-site production and rapid imaging.

Half-lives used for decay correction: I-131 8.02 days, I-123 13.2 h, Tc-99m 6.01 h, In-111 2.8 days, and Tl-201 73 h.

Kit preparation follows the package insert, verifies expiration and labeling efficiency, inspects for particles or discoloration, and uses aseptic technique with appropriate shielding.

Particle size: MAA 10-90 µm lodges in pulmonary capillaries; sulfur colloid 0.1-1 µm is phagocytosed by reticuloendothelial cells; filtered colloid is used for sentinel node mapping.

Dose calibration measures activity in a dose calibrator before administration and records time, activity, and volume, with decay correction to the calibration time on the label.

NaI(Tl) detector: a gamma ray produces light, photomultiplier tubes convert it to an electrical pulse, and a pulse-height analyzer selects the photopeak; energy resolution at Tc-99m 140 keV is about 10%.

Tc-99m photopeak window is commonly 140 keV ±10% (126-154 keV); I-131 is 364 keV and F-18 is 511 keV; incorrect windows increase scatter or lose true counts.

Collimator choice: parallel-hole preserves size, pinhole magnifies small organs, converging magnifies, and diverging minifies; resolution improves with longer holes and smaller hole diameter but sensitivity falls.

Daily gamma camera QC includes a uniformity flood; extrinsic uniformity includes the collimator; center of rotation and resolution/sensitivity checks follow defined schedules.

SPECT uses a 360-degree orbit with 60-120 projections; filtered backprojection or iterative reconstruction is used, with attenuation, scatter, and resolution recovery corrections improving quantitation.

PET detects 511-keV annihilation photons in coincidence; time-of-flight improves localization, and CT attenuation correction plus scatter correction are required for quantitative SUV.

CT numbers: water is 0 HU, air is about -1000 HU, and bone is high positive; window width and level control display, while pitch and mAs affect dose and image noise.

Image matrix: pixel size equals field of view divided by matrix width; a larger matrix yields smaller pixels but fewer counts per pixel, increasing noise unless counts are adequate.

High count rate causes dead time and pulse pileup; paralyzable systems show decreasing observed count rate at very high activity, so activity must be reduced or split.

ALARA: reduce time, increase distance, and use shielding; exposure rate obeys the inverse square law I1/I2 = (d2/d1)^2 for a point source.

NCRP occupational limits: 50 mSv/year effective dose, 150 mSv/year lens, and 500 mSv/year skin and extremities; the public limit is 1 mSv/year.

A declared pregnant worker has an embryo-fetus limit of 0.5 mSv/month and 5 mSv over gestation; duties are reviewed to maintain ALARA.

Half-value layer: lead HVL for Tc-99m is about 0.3 mm; a 0.5-mm lead apron attenuates a large fraction but not all gamma rays, and 511-keV PET photons require more shielding.

Waste decay: hold short-lived radionuclides for about 10 half-lives; Tc-99m requires about 60 hours and I-131 about 80 days; survey and document before disposal.

Contamination monitoring: a thin-window GM detector detects beta, a NaI scintillation detector detects gamma, and wipe tests identify removable contamination counted in a well counter.

Spill response: contain, mark, shield, survey personnel and area, remove contamination without spreading it, and report according to institutional and regulatory requirements.

Dose quantities: absorbed dose is in Gy, equivalent dose is in Sv with radiation weighting, and effective dose is in Sv with tissue weighting; these allow risk and limit comparisons.

Package receipt: survey the transport package, check removable contamination, verify the label and dosimeter, and document findings before radiopharmaceutical use.

Patient identification uses at least two identifiers and matches the dose label, order, and patient before administration; documentation includes radiopharmaceutical, activity, route, and time.

Pregnancy and lactation screening is performed before radiopharmaceutical administration; the authorized user provides fetal dose estimates and breastfeeding interruption guidance.

Dose calibrator QC includes daily constancy, quarterly linearity, quarterly accuracy, and geometry checks; results are recorded and the calibrator is removed from service if outside tolerance.

Gamma camera QC includes daily uniformity flood and periodic resolution, sensitivity, and center-of-rotation checks; collimator and detector artifacts are corrected before imaging.

Radiopharmaceutical QC includes visual inspection for particles or discoloration, pH where required, radiochemical purity by chromatography, and sterility or pyrogen testing per kit instructions.

Adverse reactions include anaphylaxis, vasovagal response, and extravasation; the study is stopped, basic life support is provided, the authorized user is notified, and the event is documented.

Pediatric dosing adjusts activity by weight or body surface area per institutional protocol; the smallest volume consistent with accurate counting is used and repeat imaging is minimized.

Patient instructions include hydration and frequent voiding to reduce bladder dose, plus breast-feeding and contact precautions specific to the radiopharmaceutical.