- How the Published Blueprint Is Organized
- Exam Format and Registration Mechanics
- Part I: The Physics Domains (1-8)
- Part II: The Imaging Domains (9-18)
- How the Oral Examination Connects to Domains 9-18
- Reading the Question Counts Without Inventing Weights
- Sequencing the Domains in Your Preparation
- After You Pass: OCC and Ongoing Requirements
- Frequently Asked Questions
- The AOBR written exam is 300 multiple-choice questions in three 100-minute sections, with approximately 50 physics and 250 imaging questions.
- Domains 1-8 mirror Part I (Physics); Domains 9-18 mirror Part II (Diagnostic Imaging), including repeated Ultrasound and Nuclear Medicine headings.
- The passing score is scaled 500 on a 200-800 scale; the issuer publishes no percentage weights per domain.
- Written and oral fees are $800 each, so the two standard initial-stage fees total $1,600.
How the Published Blueprint Is Organized
Primary Certification in Diagnostic Radiology is issued by the American Osteopathic Board of Radiology (AOBR), with AOA certification approval. It is a distinct pathway from the ABR Core exam, ARRT credentialing, or radiation oncology certification, and nothing on this page should be read as describing those programs. If you are still orienting yourself to the credential, start with What Is Diagnostic Radiology Certification? and then return here for the content map.
The AOBR publishes its Exam Content Outline as a list of topic entries rather than a formal tree of weighted domains. For this guide, those entries are numbered 1 through 18. Domains 1-8 reproduce the Part I (Physics) topic bullets, and Domains 9-18 reproduce the Part II (Diagnostic Imaging) topic bullets. The number 18 is simply the count of published entries supplied here; the issuer does not declare "18 top-level domains" in so many words. That distinction matters because it tells you how to read the list: as a coverage checklist, not as a weighted pie chart.
Two headings repeat on purpose. Ultrasound appears in Domain 6 (physics of ultrasound) and again in Domain 13 (ultrasound as an imaging discipline). Nuclear Medicine appears in Domain 8 (physics and instrumentation) and again in Domain 18 (clinical imaging). The repetition preserves the different parts the issuer assigns them to, and you should prepare for each appearance with a different lens.
Exam Format and Registration Mechanics
The written exam is a single combined sitting of 300 multiple-choice questions, divided into three sections of 100 minutes each. That totals five hours of testing time. Optional ten-minute breaks between sections sit outside the timed portion. The issuer states approximately 50 physics questions and 250 imaging questions, so imaging dominates by count even though physics supplies the first eight domains.
| Element | Written Examination | Oral Examination |
|---|---|---|
| Format | 300 multiple-choice questions, three 100-minute sections | Case-based stations; 4.5 hours, eight cases, 20 minutes per case, pass all ten stations (as stated on the oral page) |
| Scoring | Scaled 500 on a 200-800 scale | Pass all ten stations |
| Fee | $800, including the listed reexamination fee | $800, including the listed reexamination fee |
| Training prerequisite | Third-year or later residents for the combined written exam | Written success plus fourth-year or later training |
| Delivery | Remote option via MonitorEDU Secure Browser/PARADIGM instructions | See the AOBR oral exam page |
Fee details are covered in Diagnostic Radiology Certification Cost 2026: Complete Pricing Breakdown, and the scoring scale is unpacked in Diagnostic Radiology Passing Score 2026: Exactly What You Need to Pass. Eligibility is summarized in Diagnostic Radiology Requirements 2026: Eligibility, Prerequisites & How to Qualify: a qualifying medical degree or valid ECFMG pathway, a one-year approved internship, a four-year diagnostic-radiology residency that includes 700 nuclear-medicine training hours, active licensure, and ethics and training approval.
Remote delivery follows the MonitorEDU Secure Browser/PARADIGM instructions on the AOBR remote-proctored exams page. Run the technical checks well ahead of your sitting; a five-hour exam is a poor time to debug a browser lockdown. Scheduling windows and deadlines live in Diagnostic Radiology Exam Dates 2026: Testing Windows, Deadlines & Scheduling. Note that the timeline page's oral application dates conflict with the oral page's relative application windows, so verify oral timing directly with the board.
Part I: The Physics Domains (1-8)
Roughly 50 of the 300 questions come from physics. Fewer questions does not mean lower stakes: physics is where many residents feel least fluent, and the topics are interdependent. Radiation safety reasoning, for instance, rests on the interaction physics you learn in Domain 2.
Domain 1: Biological effects and safety
The entry point to the physics section frames radiation as both a diagnostic tool and a hazard.
- Link biological effect to dose and exposure conditions rather than memorizing isolated facts.
- Expect questions that ask you to choose the safer or more justified approach in a clinical scenario.
Domain 2: Radiological Physics (radiation production and interaction with matter)
The mechanical core of the exam. Everything downstream depends on understanding how x-rays are produced and how they interact with tissue and detectors.
- Know the production process and the interaction mechanisms well enough to predict how changing a technical factor changes the image or the dose.
- Practice reasoning from cause to effect, since stems often describe a change and ask for its consequence.
Domain 3: Radiation Biology (health effects)
Covers what radiation does to living tissue.
- Separate deterministic from stochastic reasoning and be able to apply each to a patient or worker scenario.
- Pair this domain with Domain 1 in your notes; the two overlap heavily.
Domain 4: Radiation Safety and Protection
The practical, policy-adjacent side of the physics section.
- Be ready for scenario questions about protecting patients, staff, and the public.
- Understand the logic of protection principles so you can apply them to unfamiliar setups.
Domain 5: Radiological Imaging (radiography, fluoroscopy, CT, mammography)
Four modalities sharing one domain heading, so breadth matters.
- Compare what each modality optimizes: contrast, resolution, dose, speed.
- Mammography physics is a frequent blind spot for candidates who study only general radiography.
Domain 6: Ultrasound
The physics of sound in tissue and the instrumentation that exploits it.
- Focus on wave behavior, transducer function, and the origins of common artifacts.
- Keep this separate in your notes from Domain 13, which is about clinical interpretation.
Domain 7: MRI
Magnetic resonance physics, often the most conceptually demanding topic for residents.
- Build intuition for how sequence choices change tissue contrast.
- Understand safety considerations alongside signal generation.
Domain 8: Nuclear Medicine
Physics and instrumentation for radionuclide imaging.
- Learn how radiopharmaceuticals, decay behavior, and detectors combine to form an image.
- Your 700 required nuclear-medicine training hours give you clinical exposure; use the study period to shore up the underlying physics.
Part II: The Imaging Domains (9-18)
Approximately 250 questions come from diagnostic imaging, which is why most of your preparation time belongs here. The ten domains below map onto organ systems and subspecialty areas, and they are also the structure of the oral examination, as discussed in the next section. For a broader plan that ties these domains to a calendar, see Diagnostic Radiology Study Guide 2026: How to Pass on Your First Attempt.
| Domain | Name | What to emphasize |
|---|---|---|
| 9 | Neuroradiology | Pattern recognition across modalities; MRI sequence interpretation reinforces Domain 7 |
| 10 | Vascular/Interventional Radiology | Procedural reasoning, indications, and complications |
| 11 | Cardiopulmonary | Chest imaging fundamentals and cardiac findings |
| 12 | Genitourinary Tract | Cross-modality workup of renal, urinary, and reproductive tract findings |
| 13 | Ultrasound | Clinical sonographic interpretation, distinct from Domain 6 physics |
| 14 | Breast Radiology | Screening and diagnostic imaging logic; ties to mammography physics in Domain 5 |
| 15 | Gastrointestinal Tract | Fluoroscopic, CT, and cross-sectional evaluation of the GI system |
| 16 | Musculoskeletal | Radiographic and MRI patterns of bone, joint, and soft-tissue disease |
| 17 | Pediatric Radiology | Age-specific anatomy, disease, and dose awareness |
| 18 | Nuclear Medicine | Clinical studies and interpretation, distinct from Domain 8 physics |
Where candidates commonly lose points
Because the written exam is multiple choice, the main risk is not obscure trivia but second-best-answer errors on common conditions. Pediatric Radiology (Domain 17) trips up residents whose rotations leaned adult, since normal variants and disease patterns differ. Vascular/Interventional Radiology (Domain 10) rewards candidates who think like an operator: why this approach, what could go wrong. Domain 11 (Cardiopulmonary) and Domain 16 (Musculoskeletal) are high-volume areas where steady daily image review pays off.
Key Takeaway
Treat Domains 13 and 18 as capstones for Domains 6 and 8. After you finish the physics of a modality, schedule a clinical pass through its imaging domain within a few weeks so the mechanism and the appearance reinforce each other.
How the Oral Examination Connects to Domains 9-18
The written exam is only the first stage. Oral entry requires written success and fourth-year or later training. The AOBR oral page states a duration of 4.5 hours, eight cases, 20 minutes per case, and a requirement to pass all ten stations. Those statements are reproduced as written; they do not support a reconciled case count or a derived per-station timer, so do not build a minute-by-minute plan from them. Confirm current logistics directly with the board.
What is clear is the content link: all ten oral subject headings are retained within Domains 9-18. In practice that means the imaging domains you master for the written exam are the same territory you will defend aloud. Candidates who study only for recognition on multiple-choice stems sometimes struggle when asked to describe findings, build a differential, and recommend next steps in their own words. Practice narrating cases from the start, not only after the written exam.
Because the oral requires passing every station, weak subjects cannot hide behind strong ones. That favors broad, even preparation across Domains 9-18 over specializing in your favorite organ system. For a sense of overall difficulty across both stages, read How Hard Is the Diagnostic Radiology Exam? Complete Difficulty Guide 2026.
Reading the Question Counts Without Inventing Weights
The issuer gives approximately 50 physics and 250 imaging questions and publishes no percentage weights for individual domains. It would be tempting to divide 250 by ten and claim each imaging domain gets 25 questions, or to compute a physics percentage and quote it. Don't. Neither is stated by the AOBR, and a study plan built on invented weights can misallocate weeks of effort.
The defensible interpretation is coarse: imaging outweighs physics by a wide margin, so most of your hours belong in Part II, but every domain on the list is fair game. Physics deserves disciplined, front-loaded attention precisely because it is the smaller block that is easiest to neglect and hardest to cram.
Sequencing the Domains in Your Preparation
One domain-driven ordering works well because it follows dependencies rather than convenience. The sample outline below is an illustration, not an official AOBR schedule; stretch or compress it to match your own timeline.
Physics foundations: Domains 1-4
- Production and interaction first (Domain 2), then biology and safety (Domains 1, 3, 4), because protection logic depends on interaction physics.
Modality physics: Domains 5-8
- Radiography through mammography, then ultrasound, MRI, and nuclear medicine physics.
- Do MRI before neuroradiology so sequence logic is fresh.
High-volume imaging: Domains 11, 15, 16
- Cardiopulmonary, GI, and musculoskeletal produce frequent, image-heavy practice material.
Subspecialty imaging: Domains 9, 10, 12, 14, 17
- Neuroradiology, vascular/interventional, GU, breast, and pediatrics, with breast tied back to Domain 5 mammography physics.
Capstones: Domains 13 and 18
- Clinical ultrasound and nuclear medicine imaging, once the physics in Domains 6 and 8 has settled.
Keep a compact running summary as you go. The one-page approach in Diagnostic Radiology Cheat Sheet 2026: One-Page Review of Must-Know Facts can help you consolidate high-yield points across all eighteen entries. To rehearse the 300-question format itself, use the question banks on the main practice test site and build up to full-length, timed sections that mirror the three 100-minute blocks.
After You Pass: OCC and Ongoing Requirements
Certification is not a one-time event. Current OCC (Osteopathic Continuous Certification) includes automatic enrollment for time-limited diplomates and a $300 annual fee. For 2025-2027, the component guidance calls for 60 CME credits per three-year cycle with no category or specialty quota; this current guidance takes precedence over the overview's older specialty-credit wording. You also complete 15 SAMs/SA-CME per cycle, which count toward CME, maintain active licensure, and complete one practice-performance assessment per cycle. A current cognitive assessment replaces the former ten-year OCC examination.
A caution on legacy documents: the AOBR Policies and Procedures document, revised September 2013, describes a historical separate-exam structure, additional physics headings, and legacy ten-year certificates. It is not a verified current combined-exam blueprint, and no new-certificate validity term is independently asserted here. Rely on the current exam content outline and OCC pages instead.
If you are weighing the long-term value of the credential, Is the Diagnostic Radiology Certification Worth It? Complete ROI Analysis 2026 and Diagnostic Radiology Salary Guide 2026: Complete Earnings Analysis discuss career considerations, and Diagnostic Radiology Jobs covers the employer side. For a quick brush-up on the central concept, see What Is Diagnostic Radiology?. You can also revisit this overview later at Diagnostic Radiology Exam Domains 2026: Complete Guide to All 18 Content Areas and test yourself against it on the practice exam platform.
Frequently Asked Questions
This guide lists 18 published topic entries: eight from Part I (Physics) and ten from Part II (Diagnostic Imaging). Eighteen is a count of entries supplied from the Exam Content Outline, not an issuer-declared top-level domain total.
The written exam has 300 multiple-choice questions in three 100-minute sections, for five hours of testing time. Optional ten-minute breaks between sections fall outside that time. Approximately 50 questions cover physics and 250 cover imaging.
The written passing score is scaled 500 on a 200-800 scale. The issuer does not publish per-domain percentage weights, so a scaled score should not be converted into a simple percent-correct target.
The repeated headings preserve the two parts of the exam. Domains 6 and 8 belong to Part I (Physics), while Domains 13 and 18 belong to Part II (Diagnostic Imaging), so each modality is tested once as physics and once as clinical imaging.
The written and oral fees are $800 each, including the listed corresponding reexamination fees, so the two standard initial-stage fees total $1,600. Oral entry requires written success and fourth-year or later training; check the AOBR pages for current application windows.