- What the Credential Actually Is
- Who Issues It and How It Is Approved
- The Written Exam: Format and Scoring
- What the Exam Covers: Physics Then Imaging
- The Oral Examination Stage
- Eligibility Pathway
- Fees and Registration Mechanics
- Remote Proctored Delivery
- Keeping the Certification Current
- Sequencing Your Preparation
- Credentials It Is Not
- Frequently Asked Questions
- This credential is issued by the American Osteopathic Board of Radiology (AOBR), not by ABR, ARRT or a radiation oncology board.
- The written exam is 300 multiple-choice questions in three 100-minute sections: roughly 50 physics and 250 imaging items.
- The written passing score is a scaled 500 on a 200-800 scale.
- Written and oral fees are $800 each, so the standard initial stages total $1,600.
What the Credential Actually Is
Primary Certification in Diagnostic Radiology is the board certification pathway a radiology resident follows to demonstrate readiness to practice independent diagnostic imaging. It is a two-stage process: a combined written examination covering radiologic physics and diagnostic imaging, followed by an oral examination that tests case-based interpretation across ten subject areas. Passing both stages is what earns the certificate.
If you are searching for a plain-language definition of the specialty itself, our explainers on what diagnostic radiology is and the meaning of diagnostic radiology cover that ground. This article focuses on the certification: who grants it, how the exam is built, what it costs, and how you keep it. For a broader overview, see the hub page on diagnostic radiology certification.
Who Issues It and How It Is Approved
The certifying body is the American Osteopathic Board of Radiology (AOBR), with certification approval through the American Osteopathic Association (AOA). That matters for two reasons. First, the exam content outline, eligibility rules, fees and maintenance requirements all come from AOBR's published materials, so those pages are the authority when anything here seems to differ. Second, the credential sits within the osteopathic board certification system, which has its own continuing certification framework, called OCC, rather than the maintenance model used by other boards.
The official exam-objective source is AOBR's Diagnostic Radiology written exam content outline page. It is an undated, current page, so check it directly before you finalize a study plan.
The Written Exam: Format and Scoring
The written examination is a single combined test of 300 multiple-choice questions, delivered in three sections of 100 minutes each. That is five hours of testing time. Optional ten-minute breaks between sections fall outside the testing clock, so they do not eat into your time on questions.
| Feature | Written Exam Detail |
|---|---|
| Question format | Multiple choice |
| Total questions | 300 |
| Sections | Three, 100 minutes each |
| Total testing time | Five hours |
| Breaks | Optional ten-minute breaks between sections, outside testing time |
| Question split | Approximately 50 physics and 250 imaging |
| Passing score | Scaled 500 on a 200-800 scale |
AOBR gives the approximate question counts but publishes no percentage weights, and this article does not convert those counts into percentages. What the counts do tell you plainly is that imaging dominates the test. Physics is a smaller block but a distinct one with its own vocabulary, so candidates who treat it as an afterthought often lose points they could have banked. For a deeper look at how the scaled score works, read our guide to the diagnostic radiology passing score.
What the Exam Covers: Physics Then Imaging
The published content outline is organized into two parts. Part I covers physics topics; Part II covers diagnostic imaging by body system. Reading the outline as eighteen topic entries is a practical way to plan, though eighteen is the count of published entries, not a number AOBR itself declares as its top-level domain count. Ultrasound and Nuclear Medicine each appear twice because they appear in both parts, once as physics and once as clinical imaging, and the two treatments test different things. The full breakdown lives in our diagnostic radiology exam domains guide.
Part I: Physics Topics (Domains 1-8)
Domains 1-4: Biological Effects, Radiological Physics, Radiation Biology, Radiation Safety
This cluster is the foundation: biological effects and safety, radiation production and its interaction with matter, the health effects of radiation, and protection practices.
- How radiation is produced and how it interacts with matter
- Health effects of radiation exposure, as framed by radiation biology
- Radiation safety and protection principles applied to everyday imaging practice
Domain 5: Radiological Imaging (Radiography, Fluoroscopy, CT, Mammography)
The physics of the modalities that use ionizing radiation. Expect questions on how image formation works and what controls image quality and dose.
- Radiography and fluoroscopy image formation
- CT acquisition and reconstruction concepts
- Mammography technique from the physics side
Domains 6-8: Ultrasound, MRI, Nuclear Medicine (Physics)
The non-ionizing and radiopharmaceutical modalities, treated as physics. Ultrasound and MRI tend to reward conceptual fluency over memorization, while nuclear medicine physics ties into radiation safety.
- Ultrasound principles and instrumentation
- MRI principles and image contrast
- Nuclear medicine physics and instrumentation
Part II: Diagnostic Imaging (Domains 9-18)
The clinical half runs from Neuroradiology (Domain 9) through Nuclear Medicine (Domain 18), and it is where most of your 250 imaging questions live. The ten subject headings are:
- Neuroradiology
- Vascular/Interventional Radiology
- Cardiopulmonary
- Genitourinary Tract
- Ultrasound (clinical applications)
- Breast Radiology
- Gastrointestinal Tract
- Musculoskeletal
- Pediatric Radiology
- Nuclear Medicine (clinical applications)
These same ten subject headings also structure the oral examination, which is why clinical imaging study pays off twice. Because the outline shows no per-domain weights, a sensible assumption is that breadth matters: a candidate who is strong in neuroradiology and musculoskeletal but weak in pediatrics and breast imaging is exposed on both stages. Our difficulty guide discusses where candidates commonly feel pressure.
The Oral Examination Stage
Passing the written exam does not complete the pathway. The oral examination is the second stage, and entry requires written success plus fourth-year or later training status.
AOBR's oral page states a 4.5-hour examination, eight cases, 20 minutes per case, and a requirement to pass all ten stations. Those statements do not reconcile into a single clean case count or timer when put side by side, so this article does not derive one. Treat the oral page itself as the authority and read it carefully before your session. What is clear is that the oral stage is organized around the same ten clinical subject areas listed above, and that passing every station is the standard, not an average across them.
Key Takeaway
Plan for the oral stage while studying for the written stage. Because the oral exam draws on the same ten clinical subject headings, case-based review in each of Domains 9-18 serves both exams, and the "all ten stations" standard rewards breadth over a single standout strength.
One more caution on dates: the oral application dates on the overall timeline page conflict with the relative application windows described on the oral page. If you are planning a submission, confirm directly with AOBR rather than relying on either figure. Our exam dates guide tracks how to approach scheduling.
Eligibility Pathway
Eligibility builds on a standard training sequence. The listed requirements include:
- A qualifying medical degree, or a valid ECFMG pathway for international graduates
- One year of approved internship
- A four-year diagnostic radiology residency that includes 700 hours of nuclear medicine training
- Active licensure
- Ethics and training approval
There is a genuine inconsistency worth knowing about. The written exam page contains a bullet about second-year eligibility, yet it also explicitly restricts the combined written examination to third-year or later residents. That conflict is retained here rather than papered over. If you are a second-year resident wondering whether you can sit, ask AOBR for written confirmation instead of assuming. The full prerequisite list is covered in our requirements guide, and the training side is discussed in diagnostic radiology training.
Fees and Registration Mechanics
The fee structure is simple compared with many certification programs:
| Stage | Fee |
|---|---|
| Written examination | $800 |
| Oral examination | $800 |
| Standard initial-stage total | $1,600 (by addition) |
The listed fees include the corresponding reexamination fees, so the $800 figure for each stage is not a base price that grows on a retake. The $1,600 total is simply the two standard initial-stage fees added together; it is not a separately published package price. Applications and payment run through AOBR's applications and payment page. For a fuller cost picture, including how to think about total spend, see the certification cost breakdown.
Remote Proctored Delivery
The written exam can be taken with remote proctoring. Delivery follows the MonitorEDU Secure Browser and PARADIGM instructions published on AOBR's remote-proctored exams page. Practically, that means you should test your hardware, internet connection and workspace well ahead of exam day, and read the technical instructions closely. For a five-hour exam made of three 100-minute sections, a setup problem in the middle of a section is an avoidable risk.
Keeping the Certification Current
Certification is not a one-time event. Current maintenance runs through OCC (osteopathic continuous certification), which includes automatic enrollment for time-limited diplomates and a $300 annual fee. The components that matter day to day:
OCC Components
The current requirements, as published on AOBR's OCC component pages:
- CME: For 2025-2027, 60 CME credits per three-year cycle, with no category or specialty quota. This current component guidance takes precedence over the overview page's older specialty-credit wording.
- Self-assessment: 15 SAMs/SA-CME per three-year cycle, which also count toward the CME total.
- Licensure and practice performance: Maintain active licensure and complete one practice-performance assessment per cycle.
- Cognitive assessment: The current cognitive assessment replaces the former ten-year OCC examination.
A word of caution on historical documents. AOBR's Policies and Procedures document, revised September 2013, describes a separate-exam structure, additional physics headings and legacy ten-year certificates. It is not a verified current blueprint for the combined exam, and it should not be read as a blanket rule about how long a newly issued certificate is valid. This article does not assert a validity term for new certificates; confirm that with AOBR.
Sequencing Your Preparation
Rather than a generic schedule, sequence your study around the structure of the exam itself. Physics is a smaller block, but it has its own logic, so front-load it. A reasonable order:
Physics foundation (Domains 1-5)
- Radiation production, interaction, biology and safety
- Radiography, fluoroscopy, CT and mammography physics
Non-ionizing and nuclear physics (Domains 6-8)
- Ultrasound and MRI principles
- Nuclear medicine physics, tied back to radiation safety
Clinical imaging by system (Domains 9-18)
- Neuroradiology, cardiopulmonary, GI and GU
- Musculoskeletal, pediatric, breast, vascular/interventional, ultrasound and nuclear medicine
Because roughly 250 of 300 questions are imaging, the clinical phase deserves the larger share of your calendar. Finish with timed practice in 100-minute blocks to mirror the three-section format. Our study guide expands on this approach, and the cheat sheet is useful for last-week review. When you are ready to test yourself under realistic conditions, take a timed set on our practice test platform.
Credentials It Is Not
Several well-known credentials share overlapping vocabulary, which causes real confusion for people searching online. To be clear about what this one is not:
- It is not the ABR Core exam; its issuer, format and fees are different.
- It is not an ARRT technologist credential; this pathway is for physician radiology residents.
- It is not a radiation oncology certification.
If you landed here searching for the acronym's expansion or general meaning, see what diagnostic radiology stands for and what diagnostic radiology certification is. For career context, including who hires radiologists, see diagnostic radiology jobs, the salary guide, and the analysis of whether the certification is worth it. You can also start practicing now at our main exam prep site.
Frequently Asked Questions
The American Osteopathic Board of Radiology (AOBR) issues it, with certification approval through the American Osteopathic Association. It is separate from ABR, ARRT and radiation oncology credentials.
There are 300 multiple-choice questions in three 100-minute sections, for five hours of testing. AOBR describes approximately 50 physics and 250 imaging questions and does not publish percentage weights.
The passing score is a scaled 500 on a 200-800 scale. That is a scaled score, not a percentage of questions answered correctly.
The written and oral examination fees are $800 each, including the listed corresponding reexamination fees, so the two standard initial-stage fees total $1,600 by addition. Maintenance through OCC carries a $300 annual fee.
Entry requires passing the written exam and being in fourth-year or later training. AOBR's oral page describes a 4.5-hour exam organized around ten subject areas and requires passing all ten stations; confirm case counts and timing on that page directly.
Through OCC: 60 CME credits per three-year cycle for 2025-2027, 15 SAMs/SA-CME per cycle that also count toward CME, active licensure, one practice-performance assessment per cycle, and the current cognitive assessment.