Breastfeeding Interruption After Radiopharmaceuticals
Some radiopharmaceuticals appear in breast milk and can deliver an ingestion dose to a nursing infant. Interruption recommendations are chosen to keep the infant's effective dose below about 1 mSv, following NRC Regulatory Guide 8.39 and ICRP Publication 106, with radionuclide-specific periods ranging from none to complete cessation for I-131 sodium iodide.
MRI Safety Program: ACR Zones and Roles
An MRI safety program controls four invisible hazards through zones, trained personnel, and implant screening. Here is how to build one around the 2024 ACR Manual on MR Safety and the Joint Commission's 2026 imaging goal — and where a medical physicist fits as your MR Safety Expert.
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.
Radiation Area Posting and Labeling Rules
Radiation area posting and labeling under 10 CFR Part 20 Subpart J is one of the most frequently cited—and most fixable—areas of radiation safety. This guide explains the dose-rate thresholds that define radiation, high radiation, and very high radiation areas, the exact sign wording required, container labeling rules, and how to classify an area from a survey measurement using inverse-square geometry.
Shipping Radioactive Material: DOT 49 CFR
Shipping and receiving radioactive material is governed by DOT 49 CFR Parts 171–173, NRC 10 CFR Part 71, and the IATA Dangerous Goods Regulations for air. This guide explains package types, White-I/Yellow-II/Yellow-III labeling, the Transport Index, surface dose-rate and contamination limits, hazmat training, and the receiving survey under 10 CFR 20.1906.
Public Dose Limits Under 10 CFR Part 20
The NRC caps radiation dose to individual members of the public at 1 mSv (100 mrem) per year and 0.02 mSv in any one hour in an unrestricted area. Meeting those limits is not enough — a licensee must be able to demonstrate compliance through surveys, calculations, or effluent monitoring, and design shielding and controls to a stricter ALARA goal. This guide explains the limits, the definitions behind them, and how to prove compliance.
Fetal Dose in Medical Imaging: Thresholds
Fetal (conceptus) dose is the radiation dose absorbed by the developing embryo or fetus during a maternal imaging exam. Below roughly 50 mGy there is no measurable increase in malformation or pregnancy-loss risk, and most diagnostic exams fall far below that level—so an informed dose estimate, not reflexive avoidance or termination, should drive patient management.
Radiation Survey Meter Selection Guide
Not all radiation survey meters answer the same question. Learn how GM meters, ion chambers, hybrid meters, x-ray survey sensors, and imaging survey meters work so you can match the right instrument to contamination control, leakage surveys, and shielding verification.
NRC Inspection Prep: An RSO Checklist
NRC and Agreement-State inspectors review the entire 10 CFR Part 35 program — credentials, dosimetry, QC records, sealed-source inventory, surveys, and written directives — not just individual procedures. This guide walks RSOs and program managers through every inspection element, from document binder preparation to corrective-action responses, so the program is ready before the inspector arrives.
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.
The Radiation Safety Committee Explained
The Radiation Safety Committee is the governance body that holds a medical radioactive-material program accountable. Required for licensees with multiple types of medical use, it brings authorized users, the RSO, nursing, and management to one table to oversee ALARA, dose trends, new uses, and program changes — turning radiation safety from one person's job into an institutional commitment.
Written Directives in Nuclear Medicine
A written directive is the dated, signed order an authorized user must complete before certain radiopharmaceutical therapies and I-131 administrations. This guide explains 10 CFR 35.40 and 35.41: when a directive is required, what it must contain, the oral-directive 48-hour rule, the verification procedures, and how directives prevent medical events.
RSO Role: Duties, Authority, and Qualifications
What a Radiation Safety Officer actually does — the authority and responsibilities of 10 CFR 35.24, the 35.50 qualification pathways, ALARA and investigational levels, the Radiation Safety Committee for broad-scope licenses, and the annual program review that keeps a license in good standing.
Authorized User Training & Experience (10 CFR 35)
Before a physician can order radiopharmaceutical therapy or a physicist can calibrate a therapy unit, they must be named on the radioactive material license as an authorized user or authorized medical physicist. 10 CFR Part 35 Subpart J defines two routes to that status — board certification and a training-and-experience pathway — each with specific hour and case requirements and preceptor attestation.
Radioactive Package Receipt and Wipe Testing
Every radioactive material package arriving at a medical facility must be monitored for external radiation and surface contamination on a defined schedule. A wipe test converts a count-rate reading into removable activity per unit area, which is compared against DOT and NRC limits. This guide explains the survey procedure, the wipe-test math, the action levels, and the records that keep package receipt defensible.
Decay-in-Storage of Radioactive Waste (35.92)
Decay-in-storage (DIS) is the most practical disposal pathway for short-lived medical radioactive waste. Under 10 CFR 35.92 a licensee may hold byproduct material with a half-life of 120 days or less until a surface survey with a suitable meter on its most sensitive scale, no interposed shielding, cannot distinguish it from background — then dispose of it as ordinary trash after removing all radiation labels.
Radioactive Material Spill Response Procedures
A radioactive material spill is a time-sensitive contamination event, and the response depends on whether it is classified as minor or major. This guide explains the major-versus-minor spill criteria, the NRC spill-kit and step-by-step response, decontamination and survey verification, removable-contamination action levels, and the reporting and program requirements an RSO must build in advance.
Medical Event Reporting: 10 CFR 35.3045
A medical event is not the same as patient harm — it is a regulatory definition. Under 10 CFR 35.3045, specific dose and percentage thresholds, wrong-patient or wrong-radiopharmaceutical administrations, and leaking sources trigger mandatory notification of the NRC, the referring physician, and the patient on a strict timeline. Knowing the thresholds and building a written-directive workflow that prevents them is core RSO work.
Patient Release After Radiopharmaceutical Therapy
Patient release after radiopharmaceutical therapy is governed by a dose-based limit, not an activity cutoff. This guide explains the 10 CFR 35.75 5 mSv (0.5 rem) release criterion, the three NUREG-1556 / Reg Guide 8.39 methods of demonstrating compliance, the patient-specific dose calculation with effective half-life and an occupancy factor, the 1 mSv written-instruction trigger, and the records you must keep — with a worked I-131 example.
Thyroid Bioassay for Radioiodine Workers
Radioiodine concentrates in the thyroid, so a worker who inhales or ingests I-131 can accumulate a meaningful committed dose to a single organ from a small intake. A thyroid bioassay — a direct measurement of radioiodine in the neck — is the primary tool for detecting and quantifying that intake. This article explains when a bioassay program is required, how measurements are timed and interpreted, and how the committed dose is derived under NRC rules.
Building an ALARA Program for a Medical Facility
ALARA — keeping radiation dose as low as reasonably achievable — is a regulatory expectation, not a slogan. A defensible ALARA program defines management commitment, dose constraints, investigational levels, time-distance-shielding controls, monitoring, training, and periodic review. This guide explains how to build one that satisfies NRC or Agreement State requirements and actually reduces dose.
Pregnant Radiation Worker: Dose Limits
A pregnant radiation worker can continue working safely in most medical radiation environments, but only under a deliberate program: voluntary written declaration, the 5 mSv embryo/fetus dose limit, fetal dosimetry, and ALARA controls. The decision to declare is the worker's alone, and the radiation safety program's job is to make the safe path the easy path.
Survey Meter Calibration Programs
A survey instrument is only as trustworthy as its calibration. A defensible program covers full calibration before first use, annually, and after repair; routine constancy and operational checks between calibrations; NIST-traceable standards; and documentation that survives an inspection. This guide explains the regulatory basis, the math, and how to build the program.
Extremity Dosimetry in Nuclear Medicine
Nuclear medicine staff receive their highest radiation doses to the fingertips while drawing, dispensing, and injecting radiopharmaceuticals. This guide covers the extremity dose limit, ring-badge monitoring and placement, why ring dosimeters underestimate fingertip dose, and the practical controls that keep hands ALARA.
Effective Dose & ICRP Tissue Weighting Factors
Effective dose is the most used and most misused quantity in radiation protection. It weights organ-level equivalent doses by ICRP 103 tissue weighting factors to produce a single whole-body index of stochastic risk. This guide explains how equivalent dose and effective dose are computed, the current tissue and radiation weighting factors, how they changed from ICRP 60, and the crucial limits on using E to estimate an individual patient's risk.
Radiation Safety Training Programs
A radiation safety training program is the documented system that instructs workers before they begin radiation work and refreshes them annually, as required by 10 CFR 19.12. This guide explains who must be trained, the regulatory basis, effective content, recordkeeping, competency assessment, and how training is examined during NRC and Agreement State inspections.
NRC Occupational Dose Limits: 10 CFR Part 20
10 CFR Part 20 sets the federal radiation dose limits every NRC and Agreement State licensee must meet: the 5 rem annual TEDE limit for workers, separate lens and skin limits, the embryo/fetus limit for a declared pregnant worker, and the public dose limits. This guide explains each limit, the monitoring thresholds that trigger dosimetry, and how ALARA goes beyond the numbers.
Sealed Source Leak Testing & Inventory
Sealed source leak testing and physical inventory are two of the most routine, and most commonly cited, obligations in a materials license. Leak testing confirms a source is intact by wiping it and checking for removable contamination above the 185 Bq (0.005 microcurie) limit; the semiannual inventory confirms every source is accounted for. This guide explains the 10 CFR 35.67 requirements, the exemptions, the recordkeeping rules, and how an RSO builds a defensible program.
Occupational Eye-Lens Dose in Fluoroscopy
The lens of the eye is one of the most radiosensitive tissues in the body, and interventional fluoroscopy operators can accumulate enough scatter dose to risk cataract. After ICRP lowered the recommended occupational eye-lens limit to 20 mSv per year, monitoring with the Hp(3) quantity, leaded eyewear, ceiling-suspended shields, and good technique became central to staff radiation protection — even though the U.S. NRC limit remains 150 mSv per year.
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.
Lead Apron QC: Testing and Rejection Criteria
Protective aprons only work if they are intact. This guide covers lead apron integrity testing: inspection methods, dose-based rejection criteria for holes and tears over critical organs, lead-equivalence standards under IEC 61331, inspection frequency, and how to build a defensible protective-garment QC program.
Sewer Disposal of Radioactive Material
Releasing licensed radioactive material into the sanitary sewer is permitted under 10 CFR 20.2003, but only within tight limits. The material must be readily soluble or dispersible, the monthly average concentration must stay below Appendix B Table 3 values, mixtures must satisfy a sum-of-fractions test, and total annual releases are capped. This guide explains the rule, the math, the records, and the common RSO mistakes.
Reporting Radiation Incidents to the NRC
NRC regulations set specific, tiered timeframes — immediate, 24-hour, and 30-day — for reporting radiation overexposures, lost or stolen licensed material, and doses that exceed regulatory limits. Knowing which threshold triggers which report, and having the phone numbers and written-report content ready before an event, is a core radiation safety officer responsibility.
ALI, DAC & Internal Dose Limits (10 CFR 20)
Internal radiation dose limits are hard to apply directly, so 10 CFR 20 converts them into two practical quantities: the annual limit on intake (ALI) and the derived air concentration (DAC). This guide explains how ALI and DAC are defined in Appendix B, how DAC-hours track intake against the occupational dose limit, when individual monitoring is required, and how the SUM of internal and external dose forms the total effective dose equivalent.
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.
Stochastic vs Deterministic Radiation Effects
Stochastic effects such as cancer are modeled as having no dose threshold, so their probability rises with dose while severity does not. Deterministic tissue reactions such as cataract and skin injury have practical thresholds, and their severity climbs with dose once the threshold is crossed. The distinction is the physics behind every dose limit, ALARA decision, and patient risk conversation.
Occupational Radiation Exposure Monitoring
A practical guide to designing and maintaining an effective occupational radiation monitoring program in healthcare—from dosimeter selection and badge placement to ALARA investigation levels and NRC recordkeeping.
Radioactive Spill Response in Nuclear Medicine
A practical, answer-first guide to radioactive spill response and decontamination in nuclear medicine, covering containment, survey-to-contamination math, wipe-test action levels, waste handling, and NRC and state regulatory compliance.
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.
Decommissioning a Radioactive Materials License
Closing a radioactive-materials program and terminating an NRC or Agreement State license is a defined, dose-based process. The licensee must decommission the use area, demonstrate that residual radioactivity meets the radiological criteria for license termination through a final status survey, and document compliance using derived concentration guideline levels and detection-capable instrumentation.
Minimum Detectable Activity for Contamination Surveys
Minimum detectable activity (MDA) is the smallest amount of radioactivity a counting setup can reliably distinguish from background — the statistical floor that decides whether a contamination survey can actually see the limit it must enforce.
Common Radiation Safety Violations to Avoid
A practical guide to the radiation safety violations most often cited during imaging and nuclear medicine inspections, mapped to the exact 10 CFR Part 20 and Part 35 sections, with the root causes and corrective actions that keep facilities off the enforcement list.
NRC Radioactive Material License: Medical Use
A practical guide to obtaining and maintaining an NRC or Agreement State radioactive material license for medical use, covering 10 CFR Part 35 use categories, the NRC Form 313 / NUREG-1556 application, RSO and Authorized User requirements, ALARA, source security, amendments, and ongoing compliance.
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.
Florida Radiation Safety Rules for Imaging Centers
What imaging centers in Florida must do to comply with radiation safety regulations, from 64E-5 equipment registration and personnel licensure to annual physics evaluations and inspections.
Radioactive Source Security: 10 CFR Part 37
10 CFR Part 37 sets security requirements for category 1 and category 2 quantities of radioactive material. Compliance turns on aggregating your sources against the Appendix A thresholds, granting unescorted access only to trustworthy and reliable individuals, maintaining security zones with monitoring and immediate detection, coordinating with local law enforcement, and protecting material in use and transit.