- What This Exam Actually Is (and Is Not)
- Format, Scoring and Fee Mechanics
- Part I: The Physics Block (Domains 1-8)
- Part II: Diagnostic Imaging (Domains 9-18)
- Eligibility and Timing Before You Study
- A Domain-Ordered Study Sequence
- Five Hours of Testing: Pacing and Remote Delivery
- After the Written: Oral Exam and Maintaining Certification
- Frequently Asked Questions
- The written exam is 300 multiple-choice questions in three 100-minute sections: roughly 50 physics and 250 diagnostic imaging.
- The passing score is a scaled 500 on a 200-800 scale, issued by the American Osteopathic Board of Radiology (AOBR).
- Written and oral examination fees are $800 each, so the two standard initial-stage fees total $1,600.
- Imaging dominates by question count, but physics is a distinct block with its own eight published topic entries.
What This Exam Actually Is (and Is Not)
Before you buy a single textbook, confirm you are preparing for the right credential. Primary Certification in Diagnostic Radiology, as discussed on this site, is the pathway administered by the American Osteopathic Board of Radiology (AOBR) with AOA certification approval. It is not the ABR Core examination, not an ARRT technologist credential, and not a radiation oncology exam. Question banks, pass-rate statistics and fee schedules built for those programs will mislead you here.
The pathway has two main gates: a combined written examination and a subsequent oral examination. This guide focuses on the written gate, because that is where most preparation time is spent, and then briefly maps what comes after. If you want broader orientation first, see What Is Diagnostic Radiology Certification? or the overview at Diagnostic Radiology Certification.
Format, Scoring and Fee Mechanics
The structure of testing day
The written exam consists of 300 multiple-choice questions delivered in three sections of 100 minutes each, for five hours of total testing time. Optional ten-minute breaks between sections fall outside that testing clock. The issuer describes the content as approximately 50 physics questions and 250 imaging questions. It does not publish percentage weights, so treat those counts as a rough guide to emphasis rather than a guaranteed per-domain distribution.
Scoring
The passing score is a scaled 500 on a 200-800 scale. A scaled score is not the same as answering 500 questions correctly or a simple percent-correct threshold, so avoid planning around a raw-percentage target you read elsewhere. For a deeper treatment, read Diagnostic Radiology Passing Score 2026. Notably, no AOBR diagnostic radiology pass rate has been verified, and pass-rate figures from other boards or from individual residency programs are not valid substitutes. The page Diagnostic Radiology Pass Rate 2026: What the Data Shows explains how to interpret that gap honestly.
Fees at a glance
| Stage | Fee | Notes |
|---|---|---|
| Written examination | $800 | Includes the listed corresponding reexamination fee |
| Oral examination | $800 | Includes the listed corresponding reexamination fee |
| Two standard initial-stage fees | $1,600 | Simple sum of the two stages above |
Always confirm current amounts on the AOBR applications-and-payment page before submitting, and see Diagnostic Radiology Certification Cost 2026 for a fuller breakdown of what is and is not included.
Part I: The Physics Block (Domains 1-8)
The first eight published topic entries reproduce the Part I physics bullets. Although physics accounts for far fewer questions than imaging, it is often the block candidates under-prepare, because residency rotations rarely drill it daily. Here is how the eight entries cluster in practice.
Domains 1, 3 and 4: Biological Effects, Radiation Biology, and Safety/Protection
These three entries overlap heavily. Expect questions that connect dose to biological consequence and then to protective practice.
- Distinguish deterministic from stochastic effects and know which dose concepts apply to each.
- Understand how shielding, distance, and time translate into practical protection decisions.
- Be ready to reason about health effects of exposure, not just recall definitions.
Domain 2: Radiological Physics (Radiation Production and Interaction with Matter)
This is the conceptual foundation for everything else in the physics block.
- How x-rays are produced and how they interact with tissue.
- Why attenuation differs between materials, and how that drives image contrast.
Domain 5: Radiological Imaging (Radiography, Fluoroscopy, CT, Mammography)
Modality-specific physics questions tend to ask "why does this artifact or technique choice occur," not "what is the definition."
- Link technique parameters to image quality and patient dose across radiography, fluoroscopy, CT and mammography.
- Know the characteristic limitations and artifacts of each modality.
Domains 6, 7 and 8: Ultrasound, MRI and Nuclear Medicine (Physics Versions)
Ultrasound and Nuclear Medicine each appear twice in the outline, once in the physics part and once in the imaging part. Study the physics version as a principles topic: transducers, Doppler behavior and acoustic artifacts for ultrasound; signal generation, relaxation and sequence logic for MRI; radiopharmaceutical behavior and detection principles for nuclear medicine.
Part II: Diagnostic Imaging (Domains 9-18)
Roughly 250 of the 300 questions fall in the diagnostic imaging part, which is where most of your points are won or lost. The ten entries below map directly to the ten subject headings that also frame the oral examination, which means material you master for the written exam keeps paying off later.
| Domain | What to emphasize |
|---|---|
| 9: Neuroradiology | Pattern recognition across brain, spine and head-and-neck imaging; modality choice by clinical question |
| 10: Vascular/Interventional Radiology | Vascular anatomy, procedural indications, complications and imaging findings |
| 11: Cardiopulmonary | Chest radiography and CT patterns, cardiac and thoracic differentials |
| 12: Genitourinary Tract | Renal, adrenal, bladder and reproductive tract imaging across modalities |
| 13: Ultrasound | Clinical ultrasound interpretation, distinct from the physics version in Domain 6 |
| 14: Breast Radiology | Mammographic and supplemental imaging findings and assessment logic |
| 15: Gastrointestinal Tract | Fluoroscopic, CT and cross-sectional evaluation of the GI tract |
| 16: Musculoskeletal | Trauma, tumor, arthropathy and marrow patterns on radiographs, CT and MRI |
| 17: Pediatric Radiology | Age-specific anatomy, congenital and acquired conditions, and pediatric-specific pitfalls |
| 18: Nuclear Medicine | Clinical scan interpretation, distinct from the physics version in Domain 8 |
How the imaging questions tend to behave
Because the exam is multiple-choice and image-heavy in subject matter, you should expect to be asked to interpret findings, narrow a differential, or choose the next appropriate study. Practice making a commitment from a single best-answer set rather than reading passively. For a content-area-by-content-area walkthrough, see Diagnostic Radiology Exam Domains 2026: Complete Guide to All 18 Content Areas.
Key Takeaway
Do not treat the repeated Ultrasound and Nuclear Medicine headings as duplicates. Domains 6 and 8 test physics principles; Domains 13 and 18 test clinical imaging interpretation. Build separate notes for each.
Eligibility and Timing Before You Study
Candidates are expected to hold a qualifying medical degree (or a valid ECFMG pathway), complete a one-year approved internship, and complete a four-year diagnostic radiology residency that includes 700 hours of nuclear medicine training. Active licensure, ethics standing and training approval are also required.
One wrinkle deserves honesty. The written-exam page contains a second-year eligibility bullet, yet it also explicitly restricts the combined written examination to residents in their third year or later. Those statements conflict, and this guide does not try to smooth them over. Resolve the question directly with the AOBR before you build a timeline around a specific sitting. Oral entry, by contrast, requires written success and fourth-year or later training.
For the complete checklist, see Diagnostic Radiology Requirements 2026: Eligibility, Prerequisites & How to Qualify, and for scheduling, Diagnostic Radiology Exam Dates 2026. Note that the AOBR timeline page's oral application dates conflict with the oral page's relative application windows, so verify deadlines at the source rather than relying on any single summary.
A Domain-Ordered Study Sequence
Generic study advice is easy to find; what matters here is the order in which you attack this particular outline. The sequence below front-loads the physics concepts that support later imaging reasoning, then moves through imaging domains from highest cognitive load to lowest, and reserves the final weeks for mixed review. Adjust the length to your own calendar and training schedule.
Radiation fundamentals
- Domains 1-4: biological effects, radiation production and interaction, radiation biology, safety and protection.
- Why first: these concepts underpin every modality question that follows.
Modality physics
- Domains 5-8: radiography/fluoroscopy/CT/mammography, ultrasound, MRI, nuclear medicine physics.
- Write one-page principle sheets per modality to reuse later.
High-density organ systems
- Domains 9, 11 and 16: neuroradiology, cardiopulmonary, musculoskeletal.
- These carry broad pattern libraries and benefit from the longest runway.
Abdominopelvic and procedural
- Domains 12, 15, 10 and 13: genitourinary, gastrointestinal, vascular/interventional, ultrasound interpretation.
Specialty and nuclear clinical
- Domains 14, 17 and 18: breast, pediatric, nuclear medicine interpretation.
- Pediatric rewards deliberate attention to age-specific differences.
Mixed timed practice
- Full-length, three-section simulations at 100 minutes each; review every miss by domain.
If you are weighing how much runway you need, How Hard Is the Diagnostic Radiology Exam? discusses where candidates typically feel the most pressure. A condensed refresher is available in the Diagnostic Radiology Cheat Sheet, and you can pressure-test your recall with the full question bank on the main practice test site.
Five Hours of Testing: Pacing and Remote Delivery
Three 100-minute sections means each section carries about 100 questions, so you are working at roughly one minute per item. Image-based interpretation can eat time quickly, so practice flagging a question, committing to a best guess, and moving on. Use the optional ten-minute breaks, which do not count against your testing time, to reset rather than to keep studying.
The written exam can be delivered remotely. Remote delivery follows the AOBR's MonitorEDU Secure Browser and PARADIGM instructions, so complete any system checks and read the procedural requirements well in advance. Treat technical readiness as part of your preparation: a flawed setup costs focus you cannot recover mid-section. Practice a full three-section simulation in conditions that resemble your intended testing environment.
Key Takeaway
Rehearse the physical endurance of five hours of testing at least once before exam day. Cognitive fatigue in the third section is a common, avoidable source of lost points.
After the Written: Oral Exam and Maintaining Certification
The oral examination
Success on the written exam opens the door to the oral, which requires fourth-year or later training. The oral page describes a 4.5-hour examination involving eight cases, 20 minutes per case, and passing all ten stations. Those statements do not neatly reconcile into a single case count or timer, so rely on the AOBR's own oral-exam page for the current format rather than deriving numbers yourself. All ten oral subject headings are retained within Domains 9-18, which is a strong argument for studying the imaging domains thoroughly rather than just enough to pass the written.
Staying certified
Current Osteopathic Continuous Certification (OCC) 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 must also complete 15 SAMs/SA-CME per three-year cycle (which also 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. Older policy documents describe legacy ten-year certificates, but a new-certificate validity term is not independently asserted here, so confirm your own certificate's terms with the AOBR.
If you are thinking about the career side, see Is the Diagnostic Radiology Certification Worth It?, Diagnostic Radiology Salary Guide 2026, and Diagnostic Radiology Jobs. For background on the specialty and its training, start with What Is Diagnostic Radiology? and Diagnostic Radiology Training. The canonical version of this guide is also at Diagnostic Radiology Study Guide 2026, and you can keep drilling at the practice test hub.
Frequently Asked Questions
The written exam has 300 multiple-choice questions in three 100-minute sections, totaling five hours of testing. Optional ten-minute breaks between sections fall outside the testing time. The issuer describes the mix as approximately 50 physics and 250 diagnostic imaging questions.
The written passing score is a scaled 500 on a 200-800 scale. Because it is scaled, it does not translate directly into a fixed percentage of questions answered correctly.
Written and oral fees are $800 each, so the two standard initial-stage fees add up to $1,600. The listed fees include the corresponding reexamination fees. Verify current amounts on the AOBR applications-and-payment page before paying.
No AOBR diagnostic radiology pass rate has been verified. Statistics from other boards or from individual residency programs are not valid substitutes, so plan around the content outline and your own practice results instead.
The AOBR written-exam page lists a second-year eligibility bullet but also explicitly restricts the combined written examination to third-year or later residents. Because those statements conflict, contact the AOBR to confirm your eligibility before scheduling.