Authorized User (AU)

An Authorized User (AU) is a physician, dentist or podiatrist who meets US Nuclear Regulatory Commission training-and-experience requirements under 10 CFR Part 35 and is named as such on a specific medical-use license (or an equivalent permit). Only AUs, and authorized nuclear pharmacists preparing material under their direction, may prescribe or administer byproduct material to patients in the practice of medicine; every administration must follow either an individually written prescription from an AU or a licensee-approved written protocol.

The requirements differ by category of use. For imaging and localisation studies not requiring a written directive (10 CFR 35.290, covering diagnostic PET and SPECT tracers), a physician needs 700 hours of training and experience including a minimum of 80 hours of classroom and laboratory instruction in radiation physics, protection, mathematics of radioactivity, chemistry of byproduct material and radiation biology, plus supervised work experience covering ordering and receiving radioactive material, dose-calibrator quality control, dosage calculation, and eluting generators. For uses requiring a written directive (10 CFR 35.390, covering therapeutic radiopharmaceuticals such as lutetium-177 or iodine-131 therapy), the bar is higher: 700 hours of training including a minimum of 200 hours of classroom and laboratory work, plus supervised experience administering at least three cases in each dosage category for which authorisation is sought (for example, specific activity thresholds of oral sodium iodide-131). Board certification by a recognised specialty board (such as the American Board of Nuclear Medicine or American Board of Radiology) can substitute for the itemised hour requirements if the certifying board's own process covers the same content and includes an examination.

An AU already qualified under 35.390 for therapeutic use can add 35.290 diagnostic authorisation with a smaller increment of generator-elution experience, recognising the overlapping physics and safety curriculum. All training and experience must have been obtained within the seven years preceding the license application, or be supported by continuing education and experience since. Individual attestation is provided by a preceptor AU or a residency programme director, and the NRC or Agreement State reviews the credentials before amending the license; the NRC does not issue any credential directly to the individual.