Pb-212 Targeted Alpha Therapy: Physics & Dosimetry
Lead-212 is an in vivo generator alpha emitter: it delivers one high-LET alpha per decay through its short-lived daughter chain, with a 10.64-hour half-life convenient for radiopharmaceutical shipping and dosing. This guide covers the decay physics, MIRD-style dosimetry, the 203Pb imaging surrogate, and the radiation-safety wrinkle its 2.6 MeV daughter photon creates.
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.
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.
PET/MR Radiation Safety: Hot Lab Meets the Magnet
A PET/MR suite stacks two unrelated hazard domains in one room: positron-emitting tracers and 511 keV photons governed by NRC radiation rules, and an always-on magnet governed by ACR accreditation and the Joint Commission. Neither program covers the other, so a combined suite needs both an RSO-led radiation-safety program and an MRMD/MRSO/MRSE-led MR-safety program, coordinated so the hot-lab workflow does not fight the ACR four-zone model.
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.
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.
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.
Radionuclide Cisternography with In-111 DTPA
Radionuclide cisternography uses intrathecally injected indium-111 DTPA — the only FDA-approved intrathecal radiotracer — to image cerebrospinal fluid flow over 24 to 72 hours. Its 67-hour half-life and dual 171 and 245 keV photopeaks make delayed imaging feasible but demand a medium-energy collimator and correct dual-window setup. The study answers three questions: is there a CSF leak, is this normal-pressure hydrocephalus, and is the shunt patent.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Count Rate and Dead Time in Nuclear Medicine
Every counting detector misses events when they arrive too close together. In nuclear medicine this dead time caps usable count rate and, at high activities, biases images and quantitative dosimetry. This guide covers the paralyzable and non-paralyzable models, the NEMA count-rate tests, the 20% count-loss benchmark, and where it matters clinically.
Y-90 PET/CT After Radioembolization
Y-90 is a near-pure beta emitter, yet a tiny internal-pair-production branch lets PET/CT image the microsphere distribution after radioembolization with better resolution and quantitative accuracy than bremsstrahlung SPECT. This guide covers the decay physics, why the images are count-starved, the local deposition dosimetry method, and the QC that makes post-therapy dose numbers defensible.
FDG PET/CT for Cardiac Sarcoidosis
Cardiac FDG PET/CT lives or dies on dietary preparation. The goal is to starve normal myocardium of glucose so that inflammatory cells light up against a dark background. This guide explains the substrate-suppression physics, compares dietary protocols with published suppression rates, works through SUV quantitation, and covers dose and QC for a defensible cardiac sarcoidosis program.
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.
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.
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.
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.
Intraoperative Gamma Probe QC & Performance Testing
The handheld gamma probe is the instrument a surgeon trusts to find a sentinel node or a parathyroid adenoma, yet it is often the least QC'd device in the department. NEMA NU 3-2004 defines the sensitivity, spatial and angular resolution, energy resolution, and shielding tests that keep a probe dependable in the operating room.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
SPECT/CT Attenuation Correction Explained
SPECT/CT attenuation correction uses the co-acquired CT to build a patient-specific map of photon attenuation, scale it to the emission energy, and recover the counts lost to absorption inside the body. It is essential for quantitative SPECT and for artifact-free cardiac and bone imaging, but it introduces its own failure modes — misregistration, truncation, and metal artifacts — that a medical physicist has to detect and control.
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.
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.
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.
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.
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.
C-11 PET Radiopharmaceuticals: Physics and Use
Carbon-11 is a positron emitter with a ~20.4-minute half-life, which makes it one of the most demanding radionuclides in clinical PET. That single number forces an on-site cyclotron, batch synthesis with decay during production and QC, no shipping, and dose-on-demand scheduling. This guide covers C-11 nuclear and positron physics, production via the 14N(p,α)11C reaction, the main tracers (C-11 choline, acetate, methionine, and PiB), quality control under USP and cGMP, decay-correction math, and the radiation-safety implications of a rapid-decay positron emitter.
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.
Holmium-166 Radioembolization Physics
Holmium-166 microsphere radioembolization pairs a therapeutic beta emitter with an imageable gamma line and paramagnetic behavior, so the same particle that treats the tumor can be quantified by SPECT, CT, and MRI. This guide covers Ho-166 decay physics, the scout-dose work-up, personalized dosimetry targets, imaging quantification, and how it differs from Y-90.
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.
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.
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.
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 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
CZT Cardiac SPECT: Physics and Performance
Dedicated cadmium-zinc-telluride (CZT) cardiac SPECT cameras replaced the rotating Anger head with stationary solid-state detectors purpose-built for the heart. Direct conversion sharpens energy resolution, multiplies system sensitivity several fold, and enables large reductions in acquisition time and patient dose — while opening the door to dynamic SPECT and quantitative myocardial blood flow. This guide connects the detector physics to measurable performance.
Dynamic PET and Tracer Kinetic Modeling
A standardized uptake value is one number from one time point; dynamic PET follows the tracer through blood and tissue and separates delivery from trapping. Tracer kinetic modeling turns that time course into physiological parameters such as the net influx rate Ki and the total distribution volume, using compartment models, an input function, and graphical methods like Patlak and Logan analysis. Long-axial-field-of-view scanners now make whole-body dynamic imaging and non-invasive input functions practical.
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.
F-18 FDOPA PET: A Multi-Target Tracer
F-18 FDOPA is one of the most versatile PET tracers in clinical use — a fluorinated amino-acid analog of L-DOPA that images dopaminergic nerve terminals in parkinsonism and amino-acid transport in neuroendocrine tumors, congenital hyperinsulinism, and gliomas. Its physics, the carbidopa premedication decision, quantification methods, and dosimetry all differ by indication, so a defensible FDOPA program is really several protocols under one tracer name.
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.
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.
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.
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.
PET Normalization and Detector Efficiency
PET normalization corrects for the fact that every line of response has a slightly different intrinsic detection efficiency. Without it, a uniform source produces non-uniform images, ring and diagonal artifacts appear, and SUV is systematically wrong. This article explains direct and component-based normalization, the normalization scan, worked coefficient math, and how normalization QC protects quantitative accuracy.
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.
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.
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.
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%.
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.
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.
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.
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.
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.
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.
N-13 Ammonia Cardiac PET Perfusion Imaging
N-13 ammonia is a cyclotron-produced PET myocardial perfusion tracer with a 9.97-minute half-life, high first-pass extraction, and a short positron range that yields excellent image quality and quantitative myocardial blood flow. Its physics, on-site production logistics, and QC set it apart from Rb-82 and F-18 flurpiridaz.
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.
Radiopharmaceutical Dosimetry with ICRP 128
Every diagnostic nuclear medicine study delivers a patient radiation dose that scales with the administered activity through a radiopharmaceutical-specific dose coefficient. ICRP Publication 128 is the current compendium of those coefficients. This guide explains how effective dose is estimated, how to use the coefficients, where they are heading, and what it means for justification and optimization.
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.
Contamination Monitoring in Nuclear Medicine
Contamination monitoring — routine surveys, personnel frisking, hand-foot monitors, and wipe tests — is the daily backbone of a nuclear medicine radiation safety program. Doing it defensibly means choosing the right instrument for each radionuclide, setting action levels that make sense, and proving your survey can actually detect the contamination limit through a minimum detectable activity calculation, not just waving a probe and hoping.
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.
I-124 PET Imaging and Thyroid Dosimetry
I-124 is a long-lived positron emitter that lets PET/CT measure radioiodine uptake and project lesion absorbed dose before I-131 therapy. Its complex decay scheme — a low positron branch, high positron energy, and abundant prompt gamma rays — makes accurate quantification a physics problem, not a push-button one.
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.
Y-90 Ibritumomab (Zevalin) Radioimmunotherapy
Y-90 ibritumomab tiuxetan (Zevalin) is an anti-CD20 radioimmunotherapy for B-cell non-Hodgkin lymphoma. Because Y-90 is a high-energy, pure beta emitter with no primary gamma, its physics — weight-based dosing, a platelet-driven activity cap, bremsstrahlung-only external field, and straightforward outpatient release — differs sharply from gamma-emitting therapies, and the medical physicist and RSO have to plan the program around those emissions.
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.
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.
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 Sensitivity QC
System sensitivity — the count rate a gamma camera records per unit of source activity — is a fundamental performance measure that ties directly to image quality, acquisition time, and quantitative accuracy. Measuring it correctly means decay-correcting the source activity, subtracting background, and comparing the result against the NEMA baseline and manufacturer specification. Trending sensitivity over time is one of the clearest early warnings of a degrading collimator, crystal, or detector.
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.
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.
FDG PET/CT in Lymphoma: Deauville Response
Response assessment in FDG-avid lymphoma runs on a deceptively simple physics foundation: the Deauville five-point scale compares residual tumor uptake to two internal references — the mediastinal blood pool and the liver. Making that visual score reproducible across scanners and time points depends on standardized acquisition, SUV quantification, and the harmonization that lets a scan today be compared to a scan three months ago.
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.
PET PSF Reconstruction: Resolution Recovery
Point spread function (PSF) reconstruction, or resolution modeling, sharpens PET images by putting the scanner's measured blur into the system model. It improves contrast recovery and lesion detectability, but it also introduces edge overshoot (Gibbs) artifacts and can make small-lesion SUVs less reproducible. Understanding when PSF helps and when it distorts quantification is essential for defensible PET reporting and harmonization.
Meckel Diverticulum Scintigraphy with Tc-99m
A bleeding Meckel diverticulum is the most common congenital anomaly of the gastrointestinal tract, and Tc-99m pertechnetate scintigraphy remains the noninvasive test of choice for locating the ectopic gastric mucosa that causes it. This guide explains the radiopharmaceutical mechanism, the imaging protocol, the premedication that improves sensitivity, and the physics and dosimetry a nuclear medicine team should understand.
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.
SPECT Jaszczak Phantom QC: Resolution & Contrast
A gamma camera can pass every planar quality-control test and still produce poor tomographic images if reconstruction, center-of-rotation, and uniformity are not right. The Jaszczak-style SPECT phantom — cold rods, cold spheres, and a uniform region in one water-filled cylinder — is the single acquisition that reveals reconstructed spatial resolution, contrast detectability, and tomographic uniformity together, which is why it anchors both routine SPECT QC and ACR accreditation.
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.
F-18 FLT PET: Imaging Tumor Proliferation
3'-deoxy-3'-[18F]fluorothymidine (FLT) is a PET tracer that reports cellular proliferation rather than glucose metabolism. Trapped by thymidine kinase 1 in the salvage pathway, FLT uptake correlates with Ki-67 and offers higher tumor specificity than FDG in some settings — but lower absolute uptake and complex kinetics demand careful quantification.
Bone-Pain Palliation: Sr-89, Sm-153, and Ra-223
Bone-seeking radiopharmaceuticals deliver targeted radiation to osteoblastic skeletal metastases. The beta emitters strontium-89 and samarium-153 palliate pain, while the alpha emitter radium-223 both palliates and extends survival in metastatic castration-resistant prostate cancer. Their physics — emission type, energy, half-life, tissue range, and marrow dose — drives the differences in efficacy, myelotoxicity, and radiation safety, and each requires a written directive and a defensible dosimetry and release plan.
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.
Conjugate-View Planar Quantification in Dosimetry
The conjugate-view method uses paired anterior and posterior gamma-camera images to convert counts into absolute activity, correcting for the attenuation that makes a raw planar count depth-dependent. Its geometric-mean core is elegant: the geometric mean of two opposed views is, to first order, independent of source depth, which is why the technique remains a workhorse for time-activity curves and internal dosimetry.
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.
Radionuclide Cystography for Reflux
Direct radionuclide cystography detects vesicoureteral reflux by instilling a small activity of a technetium-99m radiopharmaceutical into the bladder and imaging the tract continuously during filling and voiding. Its two defining advantages are physical: continuous acquisition captures the transient reflux that intermittent fluoroscopy can miss, and instilling a non-absorbed tracer keeps the effective dose very low. Understanding the counting physics, the dosimetry, and the trade-off against fluoroscopic cystography is what lets a nuclear medicine team choose and defend the right study for a child.
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.
In-111 Pentetreotide SRS: Physics and QC
In-111 pentetreotide (OctreoScan) somatostatin receptor scintigraphy localizes somatostatin-receptor-positive neuroendocrine tumors using a gamma emitter that decays by electron capture with 171 and 245 keV photopeaks. A defensible study depends on medium-energy collimation, dual-photopeak energy windows, correct administered activity, standardized 4- and 24-hour imaging, and camera QC anchored to nuclear-medicine physics standards and NRC materials rules.
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 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.
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?
Effective Half-Life in Nuclear Medicine Dosimetry
Effective half-life is where physics meets physiology: it merges a radionuclide's fixed physical decay with the patient-specific biological clearance that removes activity from an organ. Because absorbed dose scales with the time-integrated activity, and that integral is governed by the effective half-life, this single quantity often controls how much dose an organ receives in both diagnostic imaging and radiopharmaceutical therapy.
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.
Counting Statistics in Nuclear Medicine
Radioactive decay is random, so counts from a stable source are, to a good approximation, Poisson distributed: the standard deviation of N counts is √N, and the fractional uncertainty is 1/√N. That single relationship governs image noise, how long to acquire, whether a QC device is behaving, and the smallest activity a counter can detect. Understanding it is the difference between trusting a number and being misled by one.
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.
Gamma Camera Bar Phantom Resolution QC
A four-quadrant bar phantom is the routine weekly check of a gamma camera's spatial resolution and linearity: AAPM Report 177 recommends the extrinsic image with a Co-57 sheet source, and lists the intrinsic image (uncollimated detector, point source) as an alternative. This guide explains what the test measures, how bar visibility maps to FWHM, how uniformity and linearity interact, the tolerances that matter, and how routine bar-phantom QC fits into a defensible acceptance and annual-survey program.
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.