Lu-177 Theranostics Dosimetry: MIRD and SPECT/CT
Lu-177 dosimetry turns a therapy isotope into a measurable absorbed dose. This guide explains the MIRD schema, quantitative SPECT/CT, organ-at-risk doses for Lutathera and Pluvicto, and why FDA labels stay fixed-activity while physicists push for personalization.
RPT Shielding for Lu-177, Ra-223, and Ac-225
RPT shielding is a radionuclide- and workflow-specific radiation safety review. Lu-177, Ra-223, and Ac-225 differ in photon emissions, contamination pathways, waste handling, patient workflow, and shielding needs, so each therapy program needs its own source-term, occupancy, and operational-control assessment.
Airborne Radioactivity Areas and Ventilation
An airborne radioactivity area is a regulatory designation with a precise definition tied to the derived air concentration and DAC-hours. Managing it is mostly an engineering-controls problem: ventilation, fume hoods, and negative pressure keep airborne concentrations and internal dose ALARA, with posting, air sampling, and bioassay closing the loop.
F-18 Fluoroestradiol (FES) PET for ER+ Breast Cancer
F-18 fluoroestradiol (FES) PET/CT noninvasively maps estrogen receptor expression across all sites of disease at once. Approved as Cerianna in 2020, it complements FDG PET by imaging receptor status rather than glucose metabolism, guiding endocrine therapy decisions in recurrent or metastatic ER-positive breast cancer, resolving inconclusive lesions, and revealing receptor heterogeneity that a single biopsy can miss.
SPECT Scatter Correction: TEW, DEW, and Beyond
Compton-scattered photons blur SPECT images and inflate apparent activity, so scatter correction is essential wherever SPECT is used quantitatively — from Tc-99m perfusion to Lu-177 dosimetry. Triple-energy-window (TEW) and dual-energy-window (DEW) methods estimate the scatter in the photopeak from adjacent energy windows and subtract it, while model-based and Monte Carlo methods reconstruct the scatter directly.
PET/CT Respiratory Gating & Motion Management
Respiratory motion blurs PET/CT images of the lung bases and upper abdomen, lowering measured SUV and misregistering the attenuation-correction CT. This guide explains phase and amplitude gating, external-device versus data-driven signals, the count-statistics trade-off, and how motion management improves quantification and radiotherapy planning.
Rb-82 Generator Quality Control
A Sr-82/Rb-82 generator delivers a 75-second cardiac PET tracer on demand, but its long-lived parent, Sr-82, can bleed into the patient dose. Rb-82 generator QC is the daily strontium-breakthrough test — plus elution technique, calibration, and recordkeeping — that keeps Sr-82 and Sr-85 below the NRC limits in 10 CFR 35.204 and prevents the kind of overexposure documented in past breakthrough incidents.
Quantitative SPECT/CT: Calibration & SUV
Quantitative SPECT/CT converts reconstructed counts into an absolute activity concentration in becquerels per milliliter, unlocking SUV in SPECT and patient-specific dosimetry for radiopharmaceutical therapy. Getting there requires a traceable system calibration factor, CT-based attenuation and scatter correction, resolution recovery, partial-volume correction, and rigorous QC — because vendor algorithms can otherwise disagree by more than 100%.
Sentinel Events vs Serious Reportable Events
Sentinel events and serious reportable events are converging. Here is what the January 1, 2027 Joint Commission–NQF alignment means for hospital safety reporting, and for radiology, MRI, nuclear medicine, and radiation therapy.
PET/MR Attenuation Correction: The Bone Problem
Attenuation correction is the hardest quantitative problem in PET/MR. Unlike PET/CT, MR signal does not map to 511 keV attenuation, and bone and lung are invisible to standard Dixon sequences. This guide explains MR-based attenuation correction methods, the resulting SUV bias, and how ZTE/UTE and deep-learning pseudo-CT approaches close the gap.
Ra-223 Dichloride Therapy for Prostate Cancer
Radium-223 dichloride (Xofigo) is an alpha-emitting, bone-seeking therapy that prolongs survival in metastatic castration-resistant prostate cancer with symptomatic bone metastases. This guide covers alpha radiobiology, the 55 kBq/kg dosing regimen, the ERA-223 abiraterone restriction, contamination control, and the medical physicist and RSO role.
Gamma Camera Uniformity QC: Floods and Limits
Flood-field uniformity is the daily heartbeat of gamma camera QC. This guide covers what integral and differential uniformity measure, the difference between intrinsic and extrinsic floods, how counting statistics set the required count density, and how to read the NEMA numbers before an artifact reaches a patient study.
SPECT Reconstruction: FBP vs Iterative OSEM
SPECT image reconstruction turns raw projection data into cross-sectional images two ways: analytic filtered back projection (FBP), which is fast but noisy and cannot model physics, and iterative OSEM, which converges on a statistically consistent image while modeling attenuation, scatter, and collimator blur. Understanding both is essential to reading, optimizing, and quantifying modern SPECT and SPECT/CT.
Cyclotron Production of Fluorine-18 for PET
Fluorine-18 is the workhorse of clinical PET, and almost all of it is made on a medical cyclotron via the 18O(p,n)18F reaction on enriched water targets. This guide explains the production physics, saturation yield, targetry, automated radiochemistry, and the FDA, USP, and NRC framework that governs PET radiopharmaceutical production and release.
Tc-99m Generator QC: Mo-99 Breakthrough Testing
A PhysicsPulse reference on the Mo-99/Tc-99m generator—how transient equilibrium drives elution timing, what every eluate QC test checks, and the molybdenum and aluminum breakthrough limits the NRC and USP require before a dose reaches a patient.
Amyloid and Tau Brain PET: SUVR and Centiloid
Amyloid and tau PET have moved from research tools to clinically actionable tests, especially with anti-amyloid therapies. Reliable interpretation depends on harmonized quantification: the Centiloid scale anchors amyloid burden on a common 0–100 axis, but it only works when scanner calibration, reconstruction, and analysis pipelines are controlled. This is squarely a medical physics problem.
MUGA and LVEF: Count-Based Ejection Fraction
The gated blood pool scan (MUGA/ERNA) measures left ventricular ejection fraction from counts, not geometry, which is why it remains the most reproducible LVEF tool for detecting small serial changes in cancer patients on cardiotoxic therapy. This guide explains the count-based physics, the acquisition, and where MUGA still beats echo.
Pediatric Nuclear Medicine Dosing Explained
Pediatric nuclear medicine dosing balances diagnostic image quality against the heightened radiosensitivity of children. This guide explains weight-based administered-activity scaling, minimum activities, and the North American consensus guidelines—including the 2024 update—and walks through worked dose calculations and the regulatory framework that governs administered activity in children.
Lu-177 PSMA Therapy: Dosimetry & Safety
Lu-177 PSMA-617 (Pluvicto) is a beta-emitting radioligand therapy for PSMA-positive metastatic castration-resistant prostate cancer. Because Lu-177 pairs a therapeutic beta particle with imageable low-energy gammas, treatment planning couples MIRD-based organ dosimetry — where the kidneys and salivary glands are the dose-limiting organs — with an outpatient radiation-safety workflow built on patient-release calculations, contamination control, and NRC medical-use requirements.
Ga-68 PSMA PET/CT: Physics, SUV, and QC
Ga-68 PSMA PET/CT images prostate cancer by targeting prostate-specific membrane antigen. Its physics — a 68-minute half-life, high-energy positrons, and on-site generator production — drives the imaging workflow, the SUV quantification chain, and the radiopharmaceutical and scanner quality control a defensible program must document.
Total-Body PET and Long Axial FOV Scanners
Total-body and long axial field-of-view PET scanners cover 106 cm to 194 cm of the patient in a single position instead of the roughly 15-26 cm of a conventional system. That geometry raises coincidence sensitivity by about an order of magnitude, which a facility can spend on faster scans, lower injected activity, delayed low-count imaging, or whole-body dynamic kinetics — but only with the right acceptance testing and quantitative calibration.
Gamma Camera Collimator Selection Guide
The collimator is the resolution-limiting component of every gamma camera, and it forces an unavoidable trade-off: any change that sharpens images costs sensitivity, and vice versa. Choosing correctly means matching hole geometry and septal thickness to the photon energy of the radionuclide while balancing count rate against spatial resolution for the clinical task. This guide covers the physics, the math, and the QC that keep the choice defensible.
Dose Calibrator QC: The Four Required Tests
Dose calibrator quality control is the program of four tests—constancy, accuracy, linearity, and geometry—that proves a nuclear medicine clinic measures patient dosages correctly. Each test checks a different failure mode, runs on a different schedule, and is tied to NRC and license expectations.
Cardiac SPECT MPI: Physics, OSEM, and QC
Cardiac SPECT myocardial perfusion imaging combines radiopharmaceutical selection, gamma-camera acquisition, iterative reconstruction, attenuation and scatter correction, and ECG-gated LVEF analysis into a complex imaging chain where each step has its own quality-control requirements. A well-run cardiac SPECT MPI program aligns radiopharmaceutical protocols, daily and weekly QC, reconstruction parameters, and artifact awareness with ASNC, SNMMI, NEMA, and AAPM guidance.
Y-90 Radioembolization Radiation Safety
Yttrium-90 radioembolization is a pure beta-emitting therapy, and its radiation safety program looks nothing like a gamma-emitter's. This guide explains Y-90's decay physics, why low-Z shielding and contamination control matter more than lead walls, the dose-assay and post-procedure survey workflow, patient release, and the NRC and Agreement State framework for a defensible program.
NEMA NU 2 PET/CT Performance Testing
NEMA NU 2 is the common language of PET/CT performance. It defines reproducible measurements of spatial resolution, sensitivity, scatter fraction and count-rate performance (including NECR), accuracy of corrections, image quality, and time-of-flight resolution, so that scanners can be compared, accepted, and monitored against vendor specifications on an apples-to-apples basis.
Skin Dose from Radioactive Contamination
Skin contamination is a dose problem a personnel badge never sees. When a radionuclide lands on skin, the dose that matters is the shallow-dose equivalent to the sensitive basal layer at 7 mg/cm², averaged over 10 cm², and it is dominated by beta and low-energy photon emissions that never reach a deep-dose dosimeter. This guide explains how skin dose is defined, how it is assessed with VARSKIN-class tools, the regulatory limit and averaging rules, and the practical response that keeps a spill from becoming a recordable dose.
SPECT/CT Quality Control Program
SPECT/CT quality control is the scheduled program of gamma camera and tomographic tests—uniformity, center of rotation, spatial and energy resolution, sensitivity, and CT co-registration—that keeps a hybrid system performing to specification and ready for accreditation.
PET Spatial Resolution and Positron Range
PET spatial resolution is not set by the reconstruction algorithm alone — it is bounded by physics: the finite size of the detector element, the ~0.5° non-collinearity of annihilation photons, and the distance a positron travels before it annihilates. Positron range is the term that changes most between radionuclides, which is why an F-18 image is sharper than a Ga-68 or Rb-82 image on the very same scanner.
Ga-68 DOTATATE PET/CT for Neuroendocrine Tumors
Ga-68 DOTATATE PET/CT maps somatostatin-receptor expression to detect and stage neuroendocrine tumors and select patients for Lu-177 DOTATATE therapy, and its Ga-68 physics, SUV calibration, and Krenning-score reporting decide whether the result can be trusted.
I-131 Therapy for Hyperthyroidism: Dosimetry
Radioiodine (I-131) is a definitive therapy for hyperthyroidism, but choosing the administered activity is a physics decision as much as a clinical one. This article compares fixed and calculated (uptake-corrected) dosing, works through the concentration and absorbed-dose formulas, and connects the calculation to NRC written-directive and patient-release requirements.
Radiochemical Purity and TLC/ITLC QC
Radiochemical purity is the fraction of a radiopharmaceutical's activity that is in the desired labeled chemical form. Thin-layer chromatography (TLC/ITLC) separates the labeled product from free pertechnetate and hydrolyzed-reduced technetium so a clinic can prove a kit is fit for the patient before it is injected.
Radiopharmaceutical Extravasation: Dose & Reporting
Radiopharmaceutical extravasation deposits part of an injected dose into soft tissue instead of the bloodstream, and in significant events the local absorbed dose can reach several gray. This is a radiation-safety and dosimetry problem: knowing when to identify, quantify, document, and report an extravasation protects patients and keeps a nuclear medicine program defensible.
V/Q Lung Scintigraphy: Physics & Dosimetry
Ventilation–perfusion (V/Q) lung scintigraphy is built on a deliberate physics trade-off: Tc-99m macroaggregated albumin transiently occludes a tiny fraction of the pulmonary microvasculature to map perfusion, while Xe-133 gas, Tc-99m DTPA aerosol, or Technegas maps ventilation. This guide covers the particle-number safety margin, radiopharmaceutical physics and dosimetry, Xe-133 room-ventilation controls, and why V/P SPECT outperforms planar imaging.
I-131 MIBG Therapy: Physics and Safety
I-131 metaiodobenzylguanidine (MIBG) delivers targeted beta radiation to norepinephrine-transporter-expressing tumors — pheochromocytoma, paraganglioma, and neuroblastoma. This guide explains the nuclear-medicine physics: I-131 decay, why thyroid blockade is mandatory, bone marrow as the dose-limiting organ, MIRD-based dosimetry, the FDA-approved high-specific-activity product Azedra, and the NRC patient-release framework under 10 CFR 35.75 and Regulatory Guide 8.39.
Ac-225 Targeted Alpha Therapy: Physics & Safety
Actinium-225 targeted alpha therapy exploits the short range and high linear energy transfer of alpha particles to kill tumor cells while sparing nearby tissue. Its four-alpha decay chain, recoiling radioactive daughters, and low-but-nonzero photon output make Ac-225 a distinctive physics, dosimetry, and radiation-safety problem that differs from Lu-177 and Ra-223 therapy.
Tc-99m MDP Bone Scintigraphy: Technique and QC
The Tc-99m MDP bone scan remains the workhorse of skeletal nuclear medicine. Its diagnostic power rests on physics: chemisorption of diphosphonate onto bone mineral, a 140 keV photon well matched to the gamma camera, delayed imaging that lets soft tissue clear, and SPECT/CT that turns a hot spot into an anatomic diagnosis. This guide connects each step to the acquisition parameters and QC that keep the study reliable.
PET Uptake Time: Why It Affects SUV and Quality
A PhysicsPulse guide to PET uptake time, why the injection-to-scan interval governs SUV accuracy, lesion contrast, and reproducible follow-up imaging.
Zr-89 ImmunoPET: Physics and Dosimetry
Zirconium-89 immunoPET matches a 78.4-hour physical half-life to the multi-day pharmacokinetics of antibodies, enabling whole-body PET days after injection. But the same nuclide carries a low positron branching ratio and an intense 909 keV prompt gamma that shape image quality, quantification, patient dose, and staff radiation safety in ways F-18 imaging never demands.
Radioactive Waste in Nuclear Medicine
A practical, answer-first guide to managing radioactive waste in nuclear medicine — decay-in-storage, sanitary-sewer release, licensed disposal and transfer, and return-to-supplier — with the worked decay math, a pathway comparison table, and the NRC and Agreement State rules that govern each route.
F-18 Fluciclovine PET/CT for Prostate Cancer
F-18 fluciclovine (Axumin) is a synthetic amino-acid PET tracer for suspected prostate cancer recurrence after treatment. Its physics — a low-energy positron, a 109.77-minute half-life, and rapid amino-acid kinetics — shapes a pelvis-first acquisition that must beat bladder activity, and its detection rate climbs steeply with PSA.
Lymphoscintigraphy & Sentinel Node Mapping
Sentinel lymph node mapping succeeds or fails on the physics of the injected tracer: particle size governs nodal migration, administered activity and decay govern how much signal survives to the operating room, and a well-tuned gamma camera plus a calibrated probe turn that signal into an accurate map. This guide connects the radiopharmaceutical choice, imaging protocol, dosimetry, and QC that make lymphoscintigraphy defensible.
Renal Scintigraphy: Split Function & GFR
Renal scintigraphy turns a dynamic renogram into two numbers a clinician acts on: split (relative) renal function and glomerular filtration rate. Both depend on getting the physics right — region-of-interest counts corrected for background and for kidney depth. This guide walks through the quantification, the camera-based Gates GFR method, and where the accuracy is won or lost.
I-123 MIBG Imaging: Collimators & H/M Ratio
I-123 MIBG imaging looks simple until the numbers move: the same patient can read a heart-to-mediastinum ratio of 1.4 on a low-energy collimator and 1.8 on a medium-energy one. High-energy I-123 photons penetrating collimator septa are why collimator choice, energy windows, and cross-calibration decide whether an H/M ratio is comparable across cameras and studies.
Tc-99m MAA Lung Shunt Fraction for Y-90
Before Y-90 radioembolization, a Tc-99m MAA scan estimates how much of the injected dose would shunt to the lungs. That lung shunt fraction sets the lung dose, drives activity reduction or a treatment hold, and — done on planar instead of SPECT/CT — is often overestimated enough to deny a treatable patient.
Ge-68/Ga-68 Generator Quality Control
The Ge-68/Ga-68 generator supplies gallium-68 for PET radiopharmaceuticals such as Ga-68 DOTATATE and Ga-68 PSMA. Its quality control centers on germanium-68 breakthrough testing, radionuclidic and radiochemical purity, metal-ion impurities, and elution performance, judged against compendial and labeled specifications so the eluate is safe to radiolabel and inject.
PET Bayesian Penalized-Likelihood Reconstruction
Bayesian penalized-likelihood (BPL) reconstruction — GE's Q.Clear — lets PET images fully converge while a penalty term controls noise, improving contrast recovery, small-lesion detectability, and SUV accuracy over early-stopped OSEM. This guide explains the relative difference prior, the beta and gamma parameters, how to choose beta, and why EARL harmonization and consistent settings matter for quantitative reads.
Radium-223 (Xofigo) Therapy: Physics & Safety
Radium-223 dichloride (Xofigo) is a calcium-mimetic, bone-seeking alpha emitter used to treat symptomatic bone metastases in castration-resistant prostate cancer. Its physics — a short-range, high-LET alpha cascade with very low photon yield — makes contamination control, accurate activity measurement, and correct written-directive and patient-release handling the central radiation-safety tasks, not structural shielding.
F-18 Flurpiridaz Cardiac PET Perfusion Imaging
Flurpiridaz F-18 is the first fluorine-18 PET myocardial perfusion tracer approved in the United States. Its 110-minute half-life allows unit-dose delivery from a regional PET pharmacy and true exercise stress, while its low positron energy sharpens image quality and supports absolute myocardial blood flow quantification. This guide explains the physics, the phase 3 evidence, dosimetry, and the QC and regulatory context for adopting it.
Lu-177 DOTATATE PRRT for Neuroendocrine Tumors
Lu-177 DOTATATE (Lutathera) is the somatostatin-receptor peptide receptor radionuclide therapy for gastroenteropancreatic neuroendocrine tumors, delivered as four 7.4 GBq cycles. Behind each administration is a specific physics and radiation-safety workflow: amino-acid renal protection, dose-limiting kidney and marrow dosimetry, Lu-177 decay characteristics, and patient release under 10 CFR 35.75. This guide walks through the physics that makes PRRT safe and effective.
Y-90 Radioembolization Dosimetry Methods
Y-90 radioembolization (SIRT) treats liver tumors with millions of beta-emitting microspheres. This guide explains the decay physics, the three dosimetry methods (BSA, MIRD mono-compartment, and partition model), Tc-99m-MAA mapping and lung shunt limits, and the radiation-safety and regulatory framework under 10 CFR 35.1000.
F-18 FDG PET/CT Dose Optimization
FDG PET/CT image quality is set by the product of injected activity and acquisition time, not activity alone. Because randoms grow with the square of activity while trues grow linearly, more dose eventually stops helping — the fix is often time, not activity.
The MIRD Schema for Internal Dosimetry
The MIRD schema is the standardized framework nuclear medicine uses to estimate the radiation absorbed dose delivered to organs and tissues by internally administered radiopharmaceuticals. At its core, absorbed dose equals time-integrated activity multiplied by a radionuclide- and geometry-specific S value. This guide explains the equations, the biokinetic and physical inputs, the software, and how the schema supports modern theranostics dosimetry.
Lead Shielding Design for CT and PET/CT
How medical physicists design lead shielding for CT, fluoroscopy, interventional radiology, PET/CT, and radionuclide therapy—covering workload, use factor, occupancy, distance, the NCRP 147 transmission equation, tenth-value-layer barrier thickness, and a worked numeric example under 10 CFR 20.
Parathyroid Scintigraphy: Sestamibi & SPECT/CT
Parathyroid scintigraphy localizes hyperfunctioning glands before minimally invasive parathyroidectomy. Tc-99m sestamibi can be imaged with a dual-phase washout technique or a dual-tracer subtraction technique, and adding SPECT/CT raises sensitivity and pins the gland to an anatomic location. The physics — tracer kinetics, collimator choice, tomographic timing, and dosimetry — decides whether the surgeon gets a usable map.
F-18 PSMA PET/CT: Piflufolastat Imaging
Fluorine-18–labeled PSMA agents such as piflufolastat F-18 and flotufolastat F-18 pair the well-behaved physics of fluorine-18 — a 110-minute half-life and a short positron range — with prostate-specific membrane antigen targeting. The longer half-life enables unit-dose distribution without an on-site generator, and the low positron energy supports near scanner-limited spatial resolution, which together shape logistics, image quality, and quantitative QC differently from gallium-68 PSMA-11.
Sentinel Node Surgery: Staff Radiation Safety
Sentinel lymph node biopsy injects only tens of megabecquerels of Tc-99m, so measured doses to surgeons, scrub staff, and pathologists sit far below regulatory limits. But 'very low' is not 'zero': a defensible program still needs dose data, specimen-handling rules, and a documented ALARA basis for why the operating-room team is not classified as radiation workers.
Gamma Camera Testing with NEMA NU-1
NEMA NU 1 defines how gamma camera performance is measured and reported, from intrinsic spatial resolution and energy resolution to flood-field uniformity, sensitivity, count-rate behavior, and SPECT center of rotation. Understanding these parameters lets a medical physicist separate acceptance testing from routine QC and catch detector drift before it reaches patients.
Well Counter QC for Bioassay and Wipe Tests
The scintillation well counter is the low-activity workhorse of a nuclear medicine department—it counts wipe tests, I-131 thyroid bioassays, and blood samples. Its quality control is a small set of interlocking tests: energy peaking, chi-square constancy, efficiency (sensitivity) calibration, background, and minimum detectable activity. Each rests on counting statistics, and each protects a different regulatory or clinical decision.
Nuclear Medicine Hot Lab Design and Safety
The hot lab is where nuclear medicine radiation safety is won or lost. A defensible design sizes shielding, workflow zoning, contamination control, and instrumentation to the actual radionuclides handled — Tc-99m, F-18, I-131, and Lu-177 each pose different external-dose and contamination problems — and verifies the built room with a post-construction survey.
PET/CT ACR Accreditation Phantom QC
The ACR PET phantom is the accreditation test that proves a PET/CT scanner recovers accurate SUV and resolves small structures. It measures background SUV near 1.0, hot-cylinder contrast recovery, and cold-rod visibility so a laboratory can defend that its quantitative reads mean what they claim across scanners and over time.
PET Detectors: Crystals, SiPMs, and TOF
Every PET image begins as a flash of light in a scintillator crystal. This guide explains how crystal properties—light yield, decay time, density, and effective Z—and the transition from photomultiplier tubes to silicon photomultipliers determine energy resolution, coincidence timing, and the time-of-flight capability that sharpens modern PET, and how those detector fundamentals connect to NEMA acceptance testing.
Gamma Camera Energy Resolution & Photopeak QC
A gamma camera's energy resolution and photopeak calibration decide how well it separates true photopeak events from scatter. Energy resolution is the full width at half maximum of the photopeak expressed as a percentage of the photon energy — typically 9–10% for Tc-99m — and it drives the energy window that controls contrast, count rate, and uniformity.
GI Bleeding Scintigraphy: Tc-99m RBC Imaging
Technetium-99m labeled red blood cell scintigraphy detects and localizes active gastrointestinal bleeding at rates far lower than catheter angiography can, and its ability to image intermittently over hours is a real physical advantage. Getting it right depends on red blood cell labeling efficiency, continuous dynamic (cine) acquisition, and disciplined interpretation — supported by SPECT/CT when localization is uncertain.
Siemens PET Flow (FlowMotion) Explained
A PhysicsPulse guide to Siemens PET Flow (FlowMotion) continuous bed motion: how it improves image uniformity, quantitative SUV accuracy, and workflow compared with step-and-shoot PET, and how technologists optimize protocols.
Patient Radiation Alarms After Nuclear Medicine
Patients who have had a nuclear medicine study or radionuclide therapy can set off sensitive radiation detectors at airports, borders, and secure buildings for days to months afterward. NRC Regulatory Guide 8.39 expects licensees to warn them and, when appropriate, issue a wallet card documenting the treatment.
FAPI PET Imaging: Ga-68 and F-18 Physics
FAPI PET targets fibroblast activation protein on cancer-associated fibroblasts rather than glucose metabolism, so it images tumors with high contrast, no fasting, and low background in brain, liver, and the GI tract. The physics differs by radionuclide: Ga-68 is generator-based, F-18 gives sharper resolution and batch distribution, and a shared DOTA chelator opens a theranostic path.
Cu-64 DOTATATE PET/CT for Neuroendocrine Tumors
Copper-64 DOTATATE (Detectnet) is an FDA-approved somatostatin-receptor PET agent for neuroendocrine tumors. Its 12.7-hour half-life allows centralized production and unit-dose distribution, while its low positron energy gives F-18-like spatial resolution — a different physics profile from generator-produced Ga-68 DOTATATE that changes logistics, image quality, and QC.
Quantitative Myocardial Blood Flow with Cardiac PET
Quantitative myocardial blood flow adds absolute, per-gram perfusion numbers to the relative pictures of cardiac PET. By acquiring a dynamic scan, sampling the arterial input, and fitting a kinetic model, the physicist and physician recover rest and stress flow in mL/min/g and their ratio, myocardial flow reserve. Done rigorously, it uncovers balanced multivessel disease and microvascular dysfunction that relative perfusion alone can miss, but only if tracer physics, dynamic acquisition, and model fitting are controlled.
PET Partial Volume Effect & Recovery Coefficients
The partial volume effect is the systematic blurring-driven bias that makes small lesions on PET look less intense than they truly are. Because of finite scanner resolution, activity spills out of small objects and background spills in, so SUV is underestimated for structures smaller than roughly two to three times the system resolution. Recovery coefficients quantify and correct that bias — and understanding them is essential to defensible quantitative PET.
Time-of-Flight PET: How TOF Improves SNR
Time-of-Flight (TOF) PET uses photon timing differences to localize annihilation events more precisely, improving image quality, quantitative SUV accuracy, and scan efficiency.
PET/CT Shielding Calculations: TG-108 and NCRP 147
PET/CT shielding is a mixed-modality problem: the injected patient, hot lab, uptake rooms, scanner room, and CT subsystem can all contribute to adjacent-area dose. A defensible design combines PET-specific TG-108 methods, CT shielding principles from NCRP 147, realistic workload and occupancy assumptions, and post-construction verification.
PET and Radiopharmaceutical Therapy Isotopes Reference
A Physics Pulse reference guide to the most common PET and radiopharmaceutical therapy isotopes—their decay physics, photon and particle emissions, clinical applications, and the radiation safety practices that keep technologists and patients protected.
Gallium-67 Citrate Imaging: Physics and QC
Gallium-67 citrate is a classic multi-photopeak SPECT agent whose physics still teaches the fundamentals: a four-line electron-capture emitter that demands a medium-energy collimator, a triple energy-window acquisition, and 48-to-72-hour imaging. This guide covers Ga-67 decay data, collimator and window selection, dosimetry, protocol design, and where Ga-67 still fits now that FDG PET/CT has taken most of its indications.
WBC Infection Imaging: In-111 & Tc-99m HMPAO
Radiolabeled autologous white blood cell (WBC) scintigraphy remains a reference standard for imaging occult infection and inflammation. The choice between Tc-99m HMPAO and In-111 oxine is a physics and workflow decision — photon energy, half-life, labeling efficiency, image quality, and radiation burden all differ — and the labeling quality-control steps are what make the study diagnostic.
Brain FDG-PET for Dementia and Epilepsy
Brain FDG-PET maps regional glucose metabolism to support the differential diagnosis of dementia and the presurgical localization of epilepsy. Patient preparation, a resting uptake environment, consistent reconstruction, and semiquantitative analysis against a normal database all shape whether the metabolic pattern is read correctly.
DaTscan (I-123 Ioflupane) SPECT Imaging
DaTscan (I-123 ioflupane) SPECT visualizes striatal dopamine transporter density to separate neurodegenerative parkinsonism from essential tremor and other non-degenerative causes. Getting it right depends on correct thyroid blocking, careful acquisition, gamma-camera QC, and a sound understanding of semiquantitative striatal binding ratios. This guide covers the physics, protocol, and clinical interpretation.
PET Randoms, Dead Time, and NECR
PET count-rate performance is a balance of physics working against each other: true coincidences build the image, random coincidences grow with the square of activity, and dead time throws away counts when the detectors are busiest. The Noise-Equivalent Count Rate (NECR) folds all three into one figure of merit. This guide explains randoms, dead time, and NECR, and why more injected activity is not always more signal.
Y-90 Bremsstrahlung SPECT/CT Imaging & Dosimetry
Yttrium-90 is a nearly pure beta emitter, so post-radioembolization imaging relies on the faint bremsstrahlung X-rays produced as those betas slow down. This guide explains why bremsstrahlung SPECT/CT is hard, how to choose the energy window and collimator, how quantitative correction enables post-therapy dosimetry, and how it compares to Y-90 PET.
FDG PET/CT for Infection and Inflammation
FDG is not just an oncology tracer. Activated leukocytes and macrophages are avid glucose consumers, so FDG PET/CT has become the method of choice for a wide range of infectious and inflammatory disorders — from prosthetic valve endocarditis to cardiac sarcoidosis to fever of unknown origin. But the study only works when patient preparation, uptake time, quantification, and interpretation pitfalls are handled with the same rigor a physicist brings to any quantitative PET exam.
HIDA Scan and Gallbladder Ejection Fraction
Hepatobiliary scintigraphy (the HIDA scan) images bile flow with a Tc-99m iminodiacetic-acid tracer and quantifies gallbladder contraction as the gallbladder ejection fraction. Standardized sincalide infusion, morphine augmentation, and correct counting technique are what make the study reproducible and clinically decisive.
PET SUV Quantification and QC
The standardized uptake value (SUV) turns a PET image into a quantitative measurement, but an SUV is only as trustworthy as the calibration and protocol behind it. SUV depends on accurate activity assay, body weight, uptake time, blood glucose, decay correction, and a valid cross-calibration between the dose calibrator and the scanner. This guide explains the SUV equations, the dominant error sources, and the QC that keeps serial and multicenter SUVs comparable.
Securing Licensed Material: 10 CFR 20.1801/20.1802
Securing and controlling licensed material is one of the most frequently cited requirements in NRC and Agreement State inspections. 10 CFR 20.1801 governs stored material and 20.1802 governs material in use. Both apply to every quantity of licensed material a facility possesses, not just the large sources covered by Part 37, and both come down to a simple test: is the material either secured or under someone's constant watch?
CT-Based Attenuation Correction in PET/CT
CT-based attenuation correction converts the CT image into a 511 keV attenuation map so PET activity can be quantified. This guide explains the bilinear HU-to-mu conversion, the artifacts it can introduce — metal, contrast, respiratory mismatch, truncation — and the QC that keeps SUV quantification trustworthy.
Thyroid Uptake Measurement: RAIU & Probe QC
The radioactive iodine uptake test quantifies the fraction of administered iodine trapped by the thyroid at a fixed time. A defensible RAIU result depends on a calibrated uptake probe, a decay-corrected standard, correct neck-to-standard geometry, background and tissue-attenuation correction, and an understanding of the radionuclide used, so the percent uptake supports a correct diagnosis and therapy dose.
F-18 Sodium Fluoride Bone PET/CT: Physics & QC
F-18 sodium fluoride (NaF) is a bone-seeking PET tracer that images osteoblastic activity with far higher resolution and target-to-background than Tc-99m bone scintigraphy. This guide covers the tracer physics and kinetics, SUV quantification and attenuation-correction pitfalls, patient dosimetry using ICRP coefficients, and the QC and cross-calibration a defensible NaF PET/CT program needs.
PET/CT Daily QC and Scanner Calibration
PET/CT is a quantitative imaging modality, so its quality control program has to protect both image quality and the numerical accuracy of the SUV. This means layering daily detector and CT checks, periodic normalization and uniformity tests, and a scanner-to-dose-calibrator cross-calibration that ties measured activity concentration back to a traceable standard — all documented to meet ACR, NEMA, and accreditation expectations.
Tc-99m PYP Cardiac Amyloidosis Imaging
Technetium-99m pyrophosphate (PYP) scintigraphy noninvasively diagnoses transthyretin cardiac amyloidosis (ATTR-CM). A reliable study depends on standardized acquisition, mandatory SPECT to separate myocardial retention from blood pool, the heart-to-contralateral (H/CL) ratio and Perugini grade for interpretation, and exclusion of light-chain amyloidosis — each a place where physics and protocol discipline decide whether the result can be trusted.
PET/CT Scatter Correction Explained
Scattered coincidences make up a third or more of the events in a modern 3D PET scan, and left uncorrected they flood the image with a low, diffuse background that destroys quantitative accuracy. Scatter correction — usually single-scatter simulation — estimates and removes that background so SUVs mean what they claim to mean.
PET SUV Harmonization and EARL Accreditation
A standardized uptake value is only meaningful if it means the same thing on every scanner. Because point-spread-function and time-of-flight reconstruction can inflate SUVs by tens of percent, the same patient can produce different numbers on different systems. SUV harmonization programs such as EANM Research Ltd (EARL) constrain scanner performance with phantom-based recovery-coefficient and calibration specifications so that quantitative PET is comparable across sites and over time.
Tc-99m DMSA Renal Cortical Scintigraphy
Tc-99m DMSA renal cortical scintigraphy binds to proximal tubular cells and images functioning cortex, making it the reference test for renal scarring and differential renal function. A defensible study depends on correct geometric-mean quantification with background subtraction, SPECT or pinhole imaging in children, weight-based pediatric activity, and documented dose-calibrator and radiochemical-purity QC.
Molecular Breast Imaging: CZT Cameras & Dose
Molecular breast imaging (MBI) uses a dedicated cadmium-zinc-telluride gamma camera and Tc-99m sestamibi to detect functional tumor uptake, giving it real supplemental value in mammographically dense breasts. Its clinical case depends on physics: direct-conversion detectors, optimized collimation, and dose reduction that brought the effective dose down to a screening-acceptable range.
Rubidium-82 Cardiac PET Myocardial Perfusion
Rubidium-82 cardiac PET is a generator-based myocardial perfusion technique with a 76-second tracer, pharmacologic stress, and the ability to quantify absolute myocardial blood flow and flow reserve. Its short half-life drives fast, low-dose imaging but demands strict generator QC, daily strontium-breakthrough testing, and careful attention to timing, motion, and quantification.
Radiopharmacy Aseptic Technique and QC
A radiopharmacy must do two hard things at once: keep doses sterile and keep staff dose low. Aseptic technique, engineering controls, and quality control under USP <825>, <797>, and <823> hold that balance — protecting patients from microbial and endotoxin contamination while respecting the ALARA constraints unique to radioactive drugs.
USP 825: Radiopharmaceutical Compounding Safety
USP General Chapter 825 is the compounding standard written specifically for radioactive drugs. It defines how nuclear pharmacies and nuclear medicine departments prepare, compound, dispense, and repackage radiopharmaceuticals safely—reconciling the sterile-compounding engineering controls of USP 797 with the radiation-safety realities of short half-lives, contamination control, and NRC and FDA oversight. This guide explains the chapter's scope, its place among the USP compounding chapters, and how a facility builds a compliant program.
Gastric Emptying Scintigraphy: Standard Method
Gastric emptying scintigraphy is only reliable when it is standardized. The SNMMI 3.0 solid-meal protocol fixes the meal, the imaging times of 0, 1, 2, and 4 hours, and the quantification: geometric mean of anterior and posterior counts, decay-corrected, expressed as percent gastric retention. Gastric retention above 10% at 4 hours indicates delayed emptying.
PERCIST: Quantitative PET Tumor Response
PERCIST 1.0 turns FDG PET into a reproducible measure of tumor treatment response using SULpeak in a fixed 1.2-cm region, a liver reference threshold, and a 30 percent change rule. This guide explains the SUL math, the response categories, the scanner calibration and protocol consistency it demands, and why it outperforms size-based criteria.
SPECT Center of Rotation: Calibration and QC
SPECT center-of-rotation (COR) calibration aligns the camera's electronic matrix with the true mechanical axis of rotation. An uncorrected COR error blurs reconstructions, creates ring or tuning-fork artifacts, and can mimic perfusion defects on cardiac SPECT. This guide covers the physics, the point-source test, NEMA NU 1-2023 and AAPM guidance, tolerances, and QC frequency.
Brain Perfusion SPECT: HMPAO and ECD Imaging
Brain perfusion SPECT with Tc-99m HMPAO or Tc-99m ECD maps regional cerebral blood flow by trapping a lipophilic tracer in proportion to perfusion at the moment of injection. Diagnostic image quality depends on radiopharmaceutical stability, correct energy windowing and collimation, reliable center-of-rotation and uniformity QC, and attenuation and scatter correction — plus, increasingly, semiquantitative comparison to a normal database.
I-131 Therapy for Thyroid Cancer
I-131 therapy for differentiated thyroid cancer spans three distinct intents — remnant ablation, adjuvant treatment, and treatment of known disease — each with different administered activities. This guide explains the nuclear-medicine physics: fixed-activity versus dosimetry-guided dosing, patient preparation, post-therapy SPECT/CT, effective half-life, and MIRD blood dosimetry.