- The 500 Scaled Score: What the Number Actually Means
- What Is Being Scored: 300 Questions Across Physics and Imaging
- Why You Cannot Convert 500 Into a Percent Correct
- The Physics Block: Domains 1-8
- The Imaging Block: Domains 9-18
- Test-Day Mechanics That Protect Your Score
- The Oral Exam Standard: Different Rules, Different Pass Logic
- Fees, Reexamination, and the Cost of a Missed Score
- After You Pass: OCC and Keeping the Credential
- A Score-Driven Study Sequence
- Frequently Asked Questions
- The AOBR written passing score is a scaled 500 on a 200-800 scale, not a raw percentage.
- The written exam is 300 multiple-choice questions in three 100-minute sections: roughly 50 physics and 250 imaging.
- No percentage domain weights are published, so do not convert question counts into weights.
- Written and oral fees are $800 each, totaling $1,600 for the two standard initial stages.
The 500 Scaled Score: What the Number Actually Means
If you are preparing for Primary Certification in Diagnostic Radiology from the American Osteopathic Board of Radiology (AOBR), the single most important number to understand is 500. The written passing score is a scaled 500 on a 200-800 scale. That is the standard you are held to, and it is the number every other decision in your preparation should be built around.
A scaled score is not the same as a raw score. Scaling is a statistical process that translates your performance into a common reporting range so that results remain comparable across different forms of an examination. The practical consequence for you is straightforward: the passing line is defined on the 200-800 reporting scale, and the issuer does not publish a "you need to get X questions right" cutoff. Anyone who tells you that you need exactly 60 percent or 70 percent correct is guessing, and you should treat that kind of claim with suspicion.
What Is Being Scored: 300 Questions Across Physics and Imaging
The written examination is a combined exam of 300 multiple-choice questions delivered in three 100-minute sections, for five hours of testing time. Optional ten-minute breaks between sections fall outside that testing time, so you do not lose exam minutes by using them.
The issuer describes the content as approximately 50 physics questions and 250 imaging questions. Those are approximate counts, and the AOBR does not attach percentage weights to them. This matters for your score strategy in two ways:
- Imaging dominates the question count, so your overall scaled score will be driven mostly by clinical imaging knowledge across the organ-system domains.
- Physics is a smaller block but is a distinct body of knowledge. Candidates who treat it as an afterthought can lose ground in a way that is hard to recover elsewhere, because physics questions test principles rather than pattern recognition.
For a full walkthrough of how the content outline is organized, see our complete guide to the Diagnostic Radiology exam domains.
| Written Exam Element | What the Issuer States |
|---|---|
| Format | Multiple choice |
| Total questions | 300 |
| Sections | Three, 100 minutes each |
| Total testing time | Five hours |
| Breaks | Optional ten-minute breaks outside testing time |
| Physics content | Approximately 50 questions |
| Imaging content | Approximately 250 questions |
| Passing score | Scaled 500 on a 200-800 scale |
Why You Cannot Convert 500 Into a Percent Correct
It is tempting to turn "500 out of 800" into a percentage and call it a day. Do not. The 200-800 range is a reporting scale with a floor of 200, so 500 does not equal 62.5 percent of anything meaningful. Likewise, you cannot take the approximate 50/250 split and invent domain percentages, because the AOBR explicitly publishes counts without weights.
A related honesty point: no AOBR diagnostic-radiology pass rate has been verified for this article, and ABR statistics or residency-level rates are not valid substitutes. If you want to understand what is and is not known about outcomes, our page on the Diagnostic Radiology pass rate explains the data limits rather than filling the gap with borrowed numbers.
The Physics Block: Domains 1-8
The published outline reproduces Part I: Physics topic entries as the first eight domains. Because physics is about 50 questions, each topic gets limited coverage, which means shallow familiarity will not be enough. You need clean conceptual command.
Domains 1-4: Biological Effects, Radiological Physics, Radiation Biology, Radiation Safety
These are the foundation domains: Biological effects and safety; Radiological Physics (radiation production and interaction with matter); Radiation Biology (health effects); and Radiation Safety and Protection.
- Know how radiation is produced and how it interacts with matter, since interaction mechanisms underpin image formation and dose.
- Be able to reason about health effects of radiation exposure and the protective principles used in practice.
- Expect questions that require you to apply a principle to a scenario, not recite a definition.
Domain 5: Radiological Imaging (Radiography, Fluoroscopy, CT, Mammography)
This domain groups the projection and cross-sectional modalities that produce most of your daily images.
- Understand the physics of image formation, contrast, noise and artifacts for radiography, fluoroscopy, CT and mammography.
- Connect technique choices to dose and image quality tradeoffs.
Domains 6-8: Ultrasound, MRI, Nuclear Medicine
The physics block also includes Ultrasound, MRI and Nuclear Medicine as their own entries.
- Ultrasound: sound propagation, transducers, resolution and artifacts.
- MRI: signal generation, contrast mechanisms, sequences and artifacts.
- Nuclear Medicine: radionuclide properties, instrumentation and radiopharmaceutical principles.
Notice that Ultrasound and Nuclear Medicine appear twice in the outline, once in the physics part and again in the imaging part. This repetition is intentional: the physics versions test underlying principles, while the imaging versions test clinical application. Study them as two layers of the same subject.
The Imaging Block: Domains 9-18
Domains 9-18 reproduce Part II: Diagnostic Imaging, which carries roughly 250 questions. Since the AOBR does not publish weights, do not assume equal distribution across these ten entries. Instead, build uniform competence and let practice questions reveal where you are weakest.
- Domain 9: Neuroradiology covers brain, spine, head and neck imaging patterns.
- Domain 10: Vascular/Interventional Radiology covers vascular anatomy, pathology and procedure-related knowledge.
- Domain 11: Cardiopulmonary covers chest and cardiac imaging.
- Domain 12: Genitourinary Tract covers renal, urinary tract and reproductive imaging.
- Domain 13: Ultrasound is the clinical imaging counterpart to the physics ultrasound entry.
- Domain 14: Breast Radiology covers breast imaging interpretation and assessment concepts.
- Domain 15: Gastrointestinal Tract covers GI imaging across modalities.
- Domain 16: Musculoskeletal covers bone, joint and soft-tissue imaging.
- Domain 17: Pediatric Radiology covers imaging of children and congenital or age-specific conditions.
- Domain 18: Nuclear Medicine is the clinical imaging counterpart to the physics nuclear medicine entry.
Key Takeaway
Eighteen is the count of published topic entries, not an issuer-declared number of top-level domains. Use the list as a coverage checklist, and remember that the heavy question volume sits in domains 9-18.
Because the imaging block is so large, steady coverage beats late cramming. Our Diagnostic Radiology study guide lays out how to sequence the organ-system domains, and the one-page Diagnostic Radiology cheat sheet is useful for last-pass review of high-yield facts.
Test-Day Mechanics That Protect Your Score
Your scaled score reflects what you can demonstrate under timed conditions, so the logistics of delivery are part of score protection.
Pacing across three sections
Three 100-minute sections of about 100 questions each works out to roughly a minute per question as a planning figure, but treat that as arithmetic, not an official guideline. Imaging questions that rely on recognizing a pattern tend to go faster than physics calculations or multi-step reasoning, so give yourself permission to bank time on quick recognitions.
Remote delivery
The written exam follows MonitorEDU Secure Browser and PARADIGM instructions for remote proctored delivery. Confirm your technical setup using the issuer's remote-proctoring instructions well before exam day. A technical problem you could have prevented is a self-inflicted threat to your score.
Use the optional breaks
The ten-minute breaks sit outside the 100-minute section clocks, so using them costs you nothing in testing time. Fatigue across five hours is real, and a short reset can protect your accuracy in the final section.
For scheduling specifics, deadlines and windows, check our page on Diagnostic Radiology exam dates, and keep in mind that the issuer's timeline and its oral page do not fully agree on oral application dates, so confirm directly with the AOBR.
The Oral Exam Standard: Different Rules, Different Pass Logic
The scaled 500 applies to the written examination only. The oral stage works differently, and it is worth understanding so you do not confuse the two standards.
- Oral entry requires success on the written exam and fourth-year or later training.
- The oral page states 4.5 hours, eight cases, 20 minutes per case, and passing all ten stations.
- All ten oral subject headings are retained within domains 9-18.
The practical implication is that the oral exam is a separate hurdle with its own pass condition, and your written score does not carry over as a measure of oral readiness. The ten oral subject areas map onto the same organ-system content you studied for the imaging block, so strong written preparation in domains 9-18 pays forward.
Fees, Reexamination, and the Cost of a Missed Score
Missing the 500 threshold has a financial dimension. The written fee is $800 and the oral fee is $800, and the listed fees include the corresponding reexamination fees. The two standard initial-stage fees total $1,600 by simple addition. The details are on the issuer's applications and payment page, and our Diagnostic Radiology certification cost breakdown walks through the pricing in context.
| Stage | Fee | Notes |
|---|---|---|
| Written | $800 | Includes the listed corresponding reexamination fee |
| Oral | $800 | Includes the listed corresponding reexamination fee |
| Standard initial stages combined | $1,600 | By addition of the two stage fees |
Eligibility also shapes when you can sit for the score that matters. Requirements include a qualifying medical degree or valid ECFMG pathway, a one-year approved internship, a four-year diagnostic-radiology residency with 700 nuclear-medicine training hours, active licensure, and ethics and training approval. The written page contains a second-year eligibility bullet but explicitly restricts the combined written examination to third-year or later residents. That conflict exists in the issuer's own material, so confirm your eligibility year with the AOBR before registering. Our Diagnostic Radiology requirements guide covers the prerequisites in detail.
After You Pass: OCC and Keeping the Credential
Clearing the 500 scaled score is the entry point, not the end of the obligation. Current Osteopathic Continuous Certification (OCC) includes automatic enrollment for time-limited diplomates and a $300 annual fee. Under current component guidance for 2025-2027, expect the following per three-year cycle:
- CME: 60 credits per three-year cycle with no category or specialty quota. This current component guidance takes precedence over the overview's older specialty-credit wording.
- Self-assessment: 15 SAMs/SA-CME per cycle, which also count toward CME.
- Practice and licensure: 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 new-certificate validity term is not independently asserted here, and the AOBR Policies and Procedures document (revised September 2013) describes a historical separate-exam structure and legacy ten-year certificates, so it should not be read as the current combined-exam blueprint. For the bigger picture on whether the credential pays off, see whether the Diagnostic Radiology certification is worth it and the Diagnostic Radiology salary guide.
A Score-Driven Study Sequence
Here is one way to schedule preparation around the structure of the 500 threshold. Adjust the timing to your own residency calendar; the logic is what matters, not the week count.
Physics foundation (Domains 1-8)
- Start with radiation production, interaction and safety, because the later modality physics builds on it.
- Then move through imaging physics, ultrasound, MRI and nuclear medicine principles.
High-volume imaging (Domains 9-12, 15-16)
- Neuroradiology, vascular/interventional, cardiopulmonary, genitourinary, GI and musculoskeletal carry broad case variety.
- Pair each with timed question blocks to practice pattern recognition.
Remaining imaging and clinical ultrasound/nuclear (Domains 13, 14, 17, 18)
- Cover ultrasound and nuclear medicine as clinical applications of the physics you already learned.
- Add breast and pediatric radiology, which have distinct vocabulary and presentation patterns.
Full-length simulation
- Practice three consecutive 100-minute blocks to build five-hour stamina.
- Review weak domains and rehearse remote-proctoring setup.
The reasoning behind the order is simple: physics first because it is conceptually foundational and easy to neglect, then the organ systems where question volume is greatest, and finally full-length simulation so the five-hour format is not a surprise. When you are ready to measure yourself against exam-style questions, use the Diagnostic Radiology practice tests to find your weak domains before the real exam does.
Frequently Asked Questions
The written passing score is a scaled 500 on a 200-800 scale. It is a scaled value, not a raw percentage, and the issuer does not publish a number-of-questions-correct cutoff.
The written exam has 300 multiple-choice questions in three 100-minute sections, for five hours of testing. Optional ten-minute section breaks fall outside that testing time. The issuer describes approximately 50 physics and 250 imaging questions.
No. Because the score is scaled and the issuer publishes no raw-score conversion or domain percentage weights, any specific "you need X correct" figure would be invented. Aim for strong performance across all domains instead.
No. The scaled 500 applies to the written exam. The oral exam is a separate stage that requires written success and fourth-year or later training, and the oral page states passing all ten stations.
The written and oral fees are $800 each, including the listed corresponding reexamination fees, so the two standard initial-stage fees total $1,600 by addition. Confirm current details on the issuer's applications and payment page, and see our passing score overview for related context.