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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 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.
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 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.
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.
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 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.
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.
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.
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.
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.