CNMT cheat sheet

Effective half-life: 1/Te = 1/Tp + 1/Tb; Te is always shorter than either physical or biologic half-life.

Tc-99m decays by isomeric transition with a 6.02-hour physical half-life and 140 keV gamma emission.

Mo-99/Tc-99m generator: elute with 0.9% saline; Mo-99 breakthrough limit is 0.15 kBq Mo-99 per MBq Tc-99m (0.15 µCi/mCi).

Alumina column breakthrough limit for Al+3 in eluate is 10 µg/mL.

Radiopharmaceutical dose is adjusted by body weight for children per North American consensus guidelines; adult reference activities scale by weight fraction.

Tc-99m MDP localizes to bone via chemisorption to hydroxyapatite; kidney and bladder activity is normal.

MAA particles are trapped in pulmonary capillaries by precapillary blockade; typical adult dose 2-4 mCi with 200,000-700,000 particles.

Free pertechnetate is identified on scan by thyroid, salivary gland, and stomach uptake; reducing agent failure is a common cause.

Tc-99m sulfur colloid is cleared by the reticuloendothelial system; used for liver/spleen and marrow imaging.

CT number (Hounsfield unit) = 1000 × (µtissue − µwater) / µwater; water = 0 HU, air ≈ −1000 HU.

Window width controls contrast (displayed gray range); window level controls brightness (center HU).

Pitch = table travel per gantry rotation / beam collimation width; pitch >1 reduces dose and increases noise.

CTDIvol estimates dose per slice; DLP = CTDIvol × scan length; effective dose ≈ DLP × k-factor.

ALARA dose reduction tools: automatic exposure control (mA modulation), iterative reconstruction, tube voltage lowering.

Beam hardening appears as cupping or dark streaks between dense structures; corrected by filtration and beam-hardening algorithms.

Spatial resolution is improved by small focal spot, thin slices, and small field of view (matrix size / FOV = pixel size).

Contrast-induced nephropathy risk is reduced by hydration and minimizing volume; metformin may require holding per protocol.

CTDI100 is measured in a 100-mm pencil ionization chamber in standard 16-cm (head) or 32-cm (body) phantoms.

Tc-99m sestamibi and tetrofosmin are lipophilic cations taken up by mitochondria; myocardial uptake proportional to perfusion.

Rest/stress protocol: stress dose typically 8-12 mCi Tc-99m; rest dose 8-12 mCi, or same-day rest-then-stress with lower rest activity.

Adenosine, regadenoson, and dipyridamole cause coronary vasodilation via A2A receptors; contraindicated with severe asthma or high-grade AV block.

Caffeine and methylxanthines must be withheld before regadenoson/dipyridamole stress (typically ≥12 hours for caffeine).

Dipyridamole/regadenoson effects are reversed with aminophylline; adenosine infusion is stopped for severe symptoms.

Treadmill Bruce protocol endpoint: ≥85% of age-predicted maximum heart rate (220 − age) or symptom-limited.

Gated SPECT: 8 or 16 frames per R-R interval; arrhythmia causes beat rejection and requires rhythm monitoring.

Tc-99m sestamibi hepatobiliary clearance can cause subdiaphragmatic activity; a fatty meal or delay reduces artifact.

Thallium-201 has 73 keV mercury X-rays and redistributes; Tc-99m agents do not redistribute significantly.

F-18 has a 109.8-minute half-life and emits a positron; annihilation produces two 511 keV photons at ~180°.

FDG patient preparation: fast ≥4-6 hours, glucose ideally <200 mg/dL (or per protocol), and no vigorous exercise 24 hours prior.

FDG uptake time is typically 60 minutes; uptake is high in brain, myocardium (variable), kidneys, bladder, and tumor.

Standardized uptake value (SUV) = activity concentration / (injected dose / body weight); SUVmax is the common metric.

Coincidence detection uses a timing window (typically ~4-6 ns); random coincidences increase with count rate.

Time-of-flight PET improves signal-to-noise by localizing annihilation along the line of response.

Attenuation correction uses CT (or transmission) data; misregistration between PET and CT causes artifacts.

F-18 NaF bone PET localizes to osteoblastic activity; normal uptake in skeleton and kidneys/bladder.

Rb-82 has a 76-second half-life and is generator-produced; requires a strontium-82/rubidium-82 generator.

Scope of NMAA practice is defined by state law and institutional policy; tasks are performed under direct supervision of a licensed technologist or physician.

Standard precautions apply to all patients; hand hygiene is the primary infection-control measure.

Radiopharmaceutical identification requires checking the label: radionuclide, activity, calibration time, and patient name.

Dose assay uses a dose calibrator; constancy, geometry, and linearity checks are performed per protocol.

Patient identification uses two identifiers (name and date of birth) before any dose administration or imaging.

Pregnancy and breastfeeding screening must be documented before radiopharmaceutical administration.

Sharps and radioactive waste are segregated; contaminated items are held for decay per institutional policy.

Vital signs and IV access are monitored and documented; extravasation is reported to the supervising technologist.

Geiger-Mueller counters detect radiation but cannot measure energy; used for contamination surveys.

Well counter and dose calibrator use ionization chambers; daily constancy check with a long-lived source (e.g., Cs-137).

Octreotide (In-111 pentetreotide) binds somatostatin receptors; normal uptake in liver, spleen, kidneys, and pituitary.

I-131 therapy for hyperthyroidism uses beta emission for tissue destruction; patient release criteria depend on dose rate.

Sentinel node imaging uses filtered Tc-99m sulfur colloid or tilmanocept; injection site and node are imaged.

Renal scan with Tc-99m MAG3 or DTPA: MAG3 is secreted by tubules; DTPA is filtered by glomeruli.

Gastric emptying study uses a standardized solid meal labeled with Tc-99m sulfur colloid; images at intervals over 90-120 minutes.

Meckel diverticulum scan uses Tc-99m pertechnetate; ectopic gastric mucosa concentrates pertechnetate.

Reconstruction kernel choice trades resolution for noise: sharp/bone kernels for bone, soft kernels for soft tissue.

Helical scanning with pitch >1 increases table speed and reduces dose but may increase partial-volume artifact.

kVp affects both dose and contrast; low kVp increases iodine contrast for a given mAs.

CT number depends on effective beam energy; the same tissue may differ between scanners or kVp settings.

Reformatting to coronal/sagittal planes requires thin axial slices and isotropic voxels.

Metal artifact reduction uses iterative algorithms and tube voltage adjustment; severe metal causes streak artifacts.

Radiation dose units: 1 Gy = 1 J/kg; 1 Sv = 1 Gy × radiation weighting factor (1 for X-rays).

Patient shielding and collimation reduce dose to radiosensitive organs such as thyroid and breast.

Patient positioning: left arm raised over head to reduce breast and arm attenuation artifact.

Breast attenuation causes fixed anterior defect; prone imaging or attenuation correction reduces false positives.

Diaphragmatic attenuation causes fixed inferior wall defect; prone imaging or attenuation correction is used.

ECG gating requires a regular rhythm; R-wave triggering rejects ectopic beats.

Left ventricular ejection fraction from gated SPECT is calculated from end-diastolic and end-systolic volumes.

Stress-only protocols reduce dose; normal stress images may avoid rest imaging.

Nitroglycerin may be given before stress per protocol to improve coronary vasodilation.

Tc-99m sestamibi injection during peak stress captures perfusion at the moment of injection; imaging occurs later.

FDG is a glucose analog trapped after phosphorylation by hexokinase; it does not undergo further glycolysis.

Brown adipose tissue uptake is symmetric, supraclavicular, and cold-related; warming and beta-blockade reduce it.

Muscular uptake from recent exercise or insulin can mimic disease; rest and fasting reduce this.

PET/CT acquisition: CT for attenuation correction and localization, then PET emission over multiple bed positions.

Randoms and scatter are corrected; dead-time losses increase with high activity.

SUV is affected by body composition, uptake time, and plasma glucose; serial comparisons require consistent technique.

F-18 FDG is excreted renally; hydration and voiding reduce bladder dose.

PET spatial resolution is limited by positron range and detector size; typical resolution ~4-5 mm.

Dose administration records include radiopharmaceutical, activity, route, time, and lot number.

Patient education includes hydration, voiding, and radiation safety instructions after administration.

Emergency equipment and supplies are checked per institutional schedule.

Radiopharmaceutical storage requires lead shielding and locked, labeled areas.

Spills are contained, reported, and surveyed; decontamination follows institutional radiation safety policy.

IV catheter patency is confirmed before injection; infiltration is documented and reported.

Patient transport and positioning are performed with attention to lines, drains, and radiation exposure.

Quality control records are maintained for dose calibrators and imaging equipment per protocol.

Radioactive decay follows N = N0 e^(−λt); λ = 0.693 / T½.

Activity remaining after n half-lives = A0 × (1/2)^n.

The 10 half-life rule: after 10 half-lives, activity is <0.1% of original.

Gamma camera energy resolution is typically 10-12% FWHM at 140 keV for Tc-99m.

Photopeak window for Tc-99m is centered at 140 keV with a ±10-20% window.

Collimator choice: low-energy high-resolution for Tc-99m; medium-energy for In-111 and I-131; high-energy for I-131 therapy imaging.

Uniformity and linearity floods are performed daily; resolution and sensitivity are tested per protocol.

Dead time and pulse pileup increase with high activity; count-rate performance is tested.

Matrix size and FOV determine pixel size: pixel = FOV / matrix.

Slice thickness affects partial-volume averaging; thin slices improve z-axis resolution.

Detector row count determines maximum simultaneous slices; cone-beam geometry affects coverage.

Tube current (mA) and exposure time (mAs) are primary dose drivers; mA modulation varies with patient attenuation.

CT fluoroscopy and interventional modes use low-dose settings; operator dose is reduced by distance and shielding.

Quality control includes daily air calibration, water phantom CT number, noise, and uniformity checks.

Artifacts: motion (streaks), ring (detector calibration), and out-of-field (patient truncation) artifacts.

Contrast timing uses bolus tracking or test bolus; scan delay is chosen based on circulation time.

Tc-99m tetrofosmin has rapid clearance from blood and liver; imaging can begin ~15-30 minutes after injection.

Tc-99m sestamibi has slower hepatobiliary clearance; imaging typically begins 45-60 minutes after injection.

Rest-stress same-day order affects residual activity; the higher-dose study is usually performed second.

Treadmill stress uses Bruce protocol with 3-minute stages; heart rate, blood pressure, and ECG are monitored.

Exercise stress is preferred when the patient can achieve adequate workload; pharmacologic stress is used otherwise.

Attenuation correction with CT or line sources improves specificity; misregistration can create artifacts.

Gated SPECT functional parameters include EDV, ESV, and EF; normal EF is generally ≥50%.

Patient motion during acquisition causes blurring and artifacts; motion correction or repeat acquisition is used.

F-18 FDG dose is typically 5-15 mCi for adults; pediatric dosing is weight-based.

Injected dose measurement requires a dose calibrator; residual activity in syringe and tubing is accounted for.

PET/CT patient positioning: arms up for body imaging to reduce attenuation and truncation artifacts.

Respiratory motion degrades PET/CT registration; respiratory gating or coaching reduces motion.

SUV normalization uses lean body mass or body surface area in some protocols; report the method used.

Standard uptake time is 60 minutes; deviations affect SUV and should be documented.

PET detector crystals (e.g., LSO, LYSO, BGO) differ in light output, decay time, and stopping power.

Block detectors and photomultiplier tubes convert scintillation light into electronic signals.

Radiation safety: time, distance, and shielding reduce occupational dose.

Personal dosimeters are worn at collar level and exchanged per institutional schedule.

Pregnant workers should declare pregnancy to allow dose monitoring per policy.

Patient confidentiality and HIPAA apply to all imaging records and communications.

Informed consent and patient rights are documented before procedures when required.

Infection control includes standard precautions and transmission-based precautions as indicated.

Emergency response includes knowing the location of spill kits, eyewash stations, and emergency contacts.

Continuing education and competency documentation are required to maintain role qualifications.

Bone scan: 2-4 hour delay after Tc-99m MDP allows skeletal uptake and renal clearance; hydration and voiding are encouraged.

Three-phase bone scan: flow, blood pool, and delayed phases; used to distinguish cellulitis from osteomyelitis.

Thyroid uptake and scan use I-123 or Tc-99m pertechnetate; normal 24-hour I-123 uptake is roughly 10-30%.

Parathyroid imaging uses Tc-99m sestamibi with delayed imaging; abnormal parathyroid retains tracer.

Lymphoscintigraphy uses Tc-99m filtered sulfur colloid; images are obtained immediately and delayed.

V/Q scan uses Tc-99m DTPA aerosol or Technegas for ventilation and Tc-99m MAA for perfusion.

HIDA scan uses Tc-99m mebrofenin or disofenin; gallbladder visualization within 60 minutes is normal.

GI bleed scan uses Tc-99m labeled red blood cells; positive study shows intraluminal activity that moves.

CT dose index (CTDI) is measured in phantoms; CTDIvol accounts for pitch.

Size-specific dose estimate (SSDE) adjusts CTDIvol for patient size.

Effective dose for a typical chest CT is roughly 5-10 mSv; abdomen/pelvis is higher.

Diagnostic reference levels guide dose optimization; institutions compare against national benchmarks.

Iterative reconstruction reduces noise at lower dose compared with filtered back projection.

Organ-based tube current modulation reduces dose to anterior structures such as breast and thyroid.

Automatic tube potential selection chooses kVp based on patient size and contrast needs.

Pediatric CT requires size-adjusted protocols to reduce dose.

Myocardial perfusion imaging detects ischemia as a reversible defect and infarction as a fixed defect.

Reversible defect = decreased uptake on stress with normal rest uptake.

Fixed defect = decreased uptake on both stress and rest; may represent scar or attenuation.

Reverse redistribution can occur with some agents and is interpreted cautiously.

Tracer uptake is proportional to regional blood flow at the time of injection.

Stress ECG changes and symptoms are documented and correlated with perfusion findings.

Beta-blockers and calcium channel blockers may be withheld before exercise stress per protocol.

Patient preparation includes fasting and avoiding caffeine before pharmacologic stress.

FDG PET is used in oncology for staging, restaging, and treatment response assessment.

Brain FDG PET shows high cortical uptake; decreased uptake patterns help evaluate dementia.

Myocardial FDG uptake is variable; viability protocols use glucose loading and insulin.

Infection and inflammation show FDG uptake; this can mimic malignancy.

PET/CT reporting includes SUVmax, lesion location, size, and comparison with prior studies.

Artifacts: misregistration, truncation, and metallic implants can affect interpretation.

Radiotracer half-life determines delivery logistics; F-18 allows transport within a few hours.

Generator-produced Rb-82 requires a generator with a defined shelf life and elution schedule.

Dose calibrator geometric and linearity checks ensure accurate activity measurement across ranges.

Radiopharmaceutical labels include calibration time and expiration; expired doses are not administered.

Patient monitoring includes observation for adverse reactions and extravasation.

Documentation of patient history, allergies, and medications supports safe care.

Radiation warning signs and labels are posted in restricted areas.

Waste decay-in-storage records are maintained until background levels are reached.

Communication with the supervising technologist is required for any deviation from protocol.

Equipment cleaning and disinfection follow institutional policies.

Tc-99m DTPA is used for renal imaging and glomerular filtration measurement; it is filtered by glomeruli.

Tc-99m DMSA binds renal cortex; used for cortical scarring evaluation.

Tc-99m MAA lung perfusion is contraindicated in right-to-left shunt and pulmonary hypertension per labeling.

I-123 is preferred over I-131 for thyroid imaging due to lower dose and better image quality.

Tc-99m pertechnetate is used for thyroid, salivary, and Meckel imaging.

Radiation safety: lead shielding reduces exposure; inverse square law applies to distance.

Decay correction adjusts activity to a reference time using the half-life formula.

Dose calibrator accuracy is verified with a certified source.

MPR and 3D reconstructions require thin-slice acquisition and adequate overlap.

Windowing presets: bone (wide width, high level), soft tissue (narrower width, lower level), lung (wide width, low level).

CT number calibration uses water and air phantoms; drift indicates need for service.

Noise is reduced by higher mAs, thicker slices, and iterative reconstruction.

Spatial resolution is limited by focal spot size, detector size, and reconstruction kernel.

Pitch <1 increases dose and overlap; pitch >1 reduces dose and may increase noise.

Patient centering affects dose and image quality; isocenter positioning is important.

Contrast media osmolality and viscosity affect injection rate and patient comfort.

Radiotracer injection during stress should be followed by a flush to ensure full dose delivery.

Imaging delays depend on tracer kinetics; sestamibi and tetrofosmin have different clearance profiles.

Attenuation correction maps must be registered with emission data; misregistration causes artifacts.

Gated SPECT acquisition uses multiple projections over 180° or 360° depending on protocol.

Reconstruction uses filtered back projection or iterative methods; iterative reduces noise.

Normal databases are used for quantitative perfusion scoring.

Patient coaching reduces motion and improves image quality.

Stress test monitoring includes ECG, vital signs, and symptom assessment.

PET/CT acquisition includes a CT scout, CT acquisition, and PET emission scan.

CT is used for attenuation correction and anatomic localization.

PET image reconstruction includes attenuation, scatter, randoms, and dead-time corrections.

SUVmax is sensitive to noise and small lesions; SUVmean and peak SUV are alternatives.

Dual-time-point imaging can help distinguish malignant from inflammatory uptake.

Patient preparation instructions must be clear and documented.

Radiation exposure to staff is reduced by distance, shielding, and efficient workflow.

Quality control includes daily detector checks and normalization.

Assistive tasks are performed within the scope defined by state law and institutional policy.

Direct supervision means the supervising technologist or physician is available and overseeing the task.

Patient identification uses two identifiers before any procedure.

Allergies and prior reactions are documented before contrast or radiopharmaceutical administration.

Vital signs are recorded before, during, and after procedures as indicated.

IV access care includes site assessment and documentation.

Radiation safety instructions are provided to patients and caregivers.

Incident reports are completed for spills, extravasation, and adverse events.

Radionuclide purity is the fraction of activity from the desired radionuclide; tested with gamma spectroscopy or decay.

Radiochemical purity is the fraction of activity in the desired chemical form; tested with chromatography.

Mo-99 breakthrough is tested after each elution and at generator receipt.

Aluminum breakthrough is tested with a colorimetric method.

Dose calibrator constancy is checked daily with a long-lived source.

Dose calibrator linearity is checked across the activity range used clinically.

Dose calibrator geometry is checked with sources in different volumes and positions.

Records of QC are retained per regulatory requirements.

CTDIvol and DLP are displayed on the scanner console and recorded in dose reports.

Dose-length product (DLP) = CTDIvol × scan length.

Effective dose = DLP × conversion factor (k-factor) for the body region.

Patient size affects dose; SSDE adjusts for diameter.

Automatic exposure control modulates mA based on attenuation.

Iterative reconstruction reduces noise and allows lower dose.

Organ-based modulation reduces dose to anterior organs.

Pediatric protocols use lower kVp and mAs.

Myocardial perfusion imaging uses stress and rest images to assess ischemia and scar.

Reversible defects suggest ischemia; fixed defects suggest scar or attenuation.

Attenuation artifacts are common in the inferior wall and anterior wall.

Prone imaging and attenuation correction reduce artifacts.

Gated SPECT provides functional data including EF and wall motion.

Stress testing requires monitoring and documentation.

Pharmacologic stress agents have specific contraindications and reversal agents.

Patient preparation and instructions are essential for accurate imaging.

FDG is a glucose analog that is trapped in cells after phosphorylation.

FDG uptake is high in brain, kidneys, bladder, and some tumors.

Patient preparation includes fasting and avoiding exercise.

SUV is a semiquantitative measure of uptake.

PET/CT combines functional and anatomic imaging.

Attenuation correction is required for quantitative PET.

Artifacts can arise from motion, misregistration, and metal.

Radiation safety and dose optimization are important in PET.

The NMAA performs tasks under supervision within scope of practice.

Patient identification and safety checks are required before procedures.

Radiation safety principles include time, distance, and shielding.

Infection control and standard precautions apply to all patients.

Documentation of procedures and patient information is required.

Emergency procedures and contacts should be known.

Continuing education and competency are required.

Communication with the supervising technologist is essential.

The gamma camera uses a collimator, scintillation crystal, photomultiplier tubes, and electronics.

The photopeak window is centered on the gamma energy of interest.

Energy resolution is the ability to distinguish energies; it is measured as FWHM.

Uniformity and linearity are tested with flood images.

Sensitivity is the count rate per unit activity.

Resolution is the ability to distinguish small structures.

Dead time and count-rate performance are tested.

Quality control records are maintained.

CT numbers are expressed in Hounsfield units.

Water is 0 HU and air is approximately −1000 HU.

Window width and level control display contrast and brightness.

Pitch affects dose and image noise.

CTDIvol and DLP are dose metrics.

Iterative reconstruction reduces noise.

Patient centering affects dose.

Pediatric protocols reduce dose.

Tc-99m sestamibi and tetrofosmin are perfusion tracers.

Uptake is proportional to blood flow at injection.

Stress and rest images are compared.

Reversible defects indicate ischemia.

Fixed defects indicate scar or attenuation.

Gated SPECT provides EF and wall motion.

Attenuation correction improves specificity.

Patient preparation affects image quality.

F-18 has a 110-minute half-life.

Annihilation produces two 511 keV photons.

Coincidence detection identifies annihilation events.

Attenuation correction is required for quantification.

SUV is a semiquantitative measure.

Patient preparation affects FDG uptake.

Artifacts include motion and misregistration.

Radiation safety is important.

Scope of practice is defined by state law and institutional policy.

Supervision is required for tasks performed by the NMAA.

Patient identification uses two identifiers.

Radiation safety principles apply.

Infection control applies.

Documentation is required.

Emergency procedures should be known.

Continuing education is required.