RSO, CHP, Medical Physicist: what each role actually does
A clear breakdown of the three roles often confused in procurement decisions, when each is required by regulation, and how to scope work across them.
Three credentials get conflated in radiation procurement decisions more often than they should: the Radiation Safety Officer (RSO), the Certified Health Physicist (CHP), and the Medical Physicist. They overlap in some functions, but they're not interchangeable — and assuming they are can produce expensive scoping mistakes. Here's how each role is actually defined, when each is required, and how procurement should think about routing work between them.
The Radiation Safety Officer (RSO) is a position, not a credential. Every organization that holds an NRC or Agreement State radioactive materials license is required to name an RSO on the license. The RSO is the person legally accountable for the radiation safety program at that facility. The credential requirements vary by license category — a broad-scope research license imposes much higher RSO qualification standards than a sealed-source-only nuclear gauge license — but in every case, the RSO is responsible for ensuring the program complies with the conditions of the license and the applicable regulations.
What the RSO actually does day-to-day: maintains the radiation safety manual, oversees individual monitoring (dosimetry badges, bioassays), runs the ALARA program, conducts and documents area surveys, manages sealed source inventory and leak tests, handles incident response, signs off on radiation work permits, trains authorized users and workers, interfaces with regulators during inspections, and maintains the records that prove all of the above. In small organizations the RSO is often part-time and wears other hats; in large research universities or hospitals the RSO is full-time and runs a team.
The Certified Health Physicist (CHP) is a credential, not a position. Certification by the American Board of Health Physics (ABHP) requires a degree in a physical science, several years of professional experience, and passing two demanding examinations. The CHP credential signals deep technical competence across the breadth of radiation protection — internal and external dosimetry, instrumentation, regulatory frameworks, shielding calculations, decommissioning, emergency response, and the rest. There are roughly 1,300 CHPs in the United States.
A CHP is not automatically an RSO, and an RSO is not automatically a CHP. Many large organizations require their RSO to be a CHP for the most demanding license categories, particularly broad-scope research licenses and complex therapeutic medical licenses. Many smaller organizations have RSOs without CHP credentials and operate perfectly well. The relevant question is whether the license category requires a CHP-level RSO, not whether the credential is generally better.
The Medical Physicist is a clinically-credentialed specialist for healthcare radiation programs. ABR-certified diagnostic medical physicists and therapy medical physicists hold board certifications specifically tied to imaging and radiation therapy practice in clinical settings. The training pathway is distinct from health physics — typically a graduate degree in medical physics, a CAMPEP-accredited residency, and ABR board examinations.
Medical physicists are required by Joint Commission accreditation standards, state regulations, and (in the therapy world) by Medicare and Medicaid reimbursement requirements for specific clinical functions: annual physics surveys of imaging equipment, machine commissioning, treatment planning validation, IMRT/VMAT QA, brachytherapy source calibration, and a long list of others. The work is clinical and patient-facing in ways that broader RSO/CHP work generally is not.
Where the roles overlap, and where they don't. A medical physicist serving a hospital can also function as the named RSO on the hospital's materials license, provided the license category and state regulations permit it. A CHP can do most of the work an RSO does, plus the high-complexity work that some RSOs can't do alone. But a CHP is generally not the right person to commission a linear accelerator or validate a treatment plan, and a medical physicist focused on therapy is generally not the right person to manage a campus-wide ALARA program with a hundred individual users.
The clearest mental model: medical physicists own the clinical interface between radiation and patients. CHPs own the technical depth across the breadth of radiation protection. RSOs own the legal and operational accountability for compliance at a specific licensed facility. The three frequently work together; they're not substitutes for each other.
When you actually need each one. If you operate a clinical radiation therapy program: you need a medical physicist (typically retained or in-house) for clinical QA, commissioning, and treatment validation. You also need an RSO for the materials license, who may or may not be the same person.
If you operate a diagnostic imaging facility: you need a medical physicist for annual physics surveys (required by Joint Commission, most states, and Medicare) and shielding evaluations. The RSO role may or may not be required depending on whether you have a materials license — most diagnostic-only x-ray facilities don't need one; nuclear medicine practices do.
If you operate a research lab with radioactive materials: you need an RSO. The qualifications depend on the license category. For most broad-scope research licenses, the RSO is expected to be CHP-credentialed or have equivalent experience. For sealed-source-only licenses, a less senior RSO may be acceptable.
If you operate an industrial radiography or nuclear gauge program: you need an RSO. The qualifications are lower than for medical or research uses. Many small operations use a part-time RSO who also has other responsibilities, supplemented by a contracted CHP consultant for periodic technical reviews.
If you're decommissioning a facility: you need a CHP-level consultant to manage the technical work — characterization surveys, derived concentration guideline level calculations, final status surveys — regardless of whether your current RSO is CHP-credentialed. This is one of the highest-stakes areas of radiation protection and benefits from outside expertise.
Scoping work across the three roles. A reasonable operating model for a mid-size organization: an in-house or part-time RSO (CHP-credentialed where the license requires it) handles day-to-day compliance, monitoring, and recordkeeping. A retained outside CHP firm provides quarterly or annual technical review, special projects (shielding evaluations, license amendments, training development), and incident response. A retained medical physics firm handles clinical functions on the schedule required by accreditation and regulation.
This split keeps fixed labor cost low while ensuring deep expertise is available when needed. It also distributes risk — a single in-house person is a single point of failure for a complex compliance program, while the retained CHP and medical physics relationships provide continuity if your in-house RSO leaves.
The procurement implications. When you're scoping work, name the credential you need explicitly. "We need a medical physicist for annual diagnostic surveys" gets a different vendor than "we need an RSO for our nuclear gauge license" or "we need a CHP for a shielding evaluation." Asking generically for radiation safety consulting wastes everyone's time and produces quotes that aren't comparable. A vendor who tries to convince you that any of the three credentials is equivalent to any other should be a candidate for elimination, not engagement.