ACR Accreditation Physics Requirements

Introduction

ACR accreditation requires modality-specific physics testing and documentation, performed by a qualified medical physicist, to demonstrate that imaging equipment meets defined performance and image-quality standards. The American College of Radiology (ACR) operates accreditation programs that many payers, states, and hospital systems treat as a condition of reimbursement and operation. Understanding what each program tests, what tolerances apply, what documentation it expects, and how submission works is essential for a successful, on-time accreditation.¹²

This guide walks through the ACR physics requirements modality by modality, including a crosswalk table of accrediting program, testing scope and frequency, and representative measured parameters; a worked CT pass-fail example; the documentation package the ACR reviews; the submission workflow; and the practical steps that keep imaging centers from failing on avoidable issues. It is written for technologists, medical physicists, and imaging administrators who need a clear, accurate roadmap. Throughout, the post distinguishes between voluntary ACR criteria and the one program — mammography — where physics testing is mandated by federal law under the Mammography Quality Standards Act (MQSA).³

Topic Explanation: What ACR Accreditation Is

ACR accreditation is a peer-reviewed evaluation in which an imaging facility submits physics testing, equipment data, and clinical images that ACR reviewers compare against published standards for each modality. Accreditation is typically awarded for a three-year cycle, after which the facility must reaccredit.¹

ACR offers accreditation programs for multiple imaging modalities:

• ACR-CTAP: CT Accreditation Program
• ACR-MRAP: MRI Accreditation Program
• ACR-PETAP: PET Accreditation Program
• ACR-NMAP: Nuclear Medicine Accreditation Program
• ACR-MAP: Mammography Accreditation Program
• ACR-UAP: Ultrasound Accreditation Program

A central concept across every program is the qualified medical physicist (QMP) — a physicist who meets ACR's program-specific education, board-certification, and continuing-education criteria. The physics testing, the test report, and the interpretation of results must be performed and signed by a QMP. At DRPS, ACR surveys are performed by board-certified (DABR) medical physicists.²

ACR is dominant, but not the only accrediting body

ACR is the most widely used imaging accrediting organization in the United States, but it is not the only one, and for mammography the accrediting bodies are formally approved by the FDA. For CT, MRI, nuclear medicine, and PET, the Centers for Medicare & Medicaid Services (CMS) recognizes multiple accrediting organizations for advanced diagnostic imaging under the Medicare Improvements for Patients and Providers Act (MIPPA), including ACR, the Intersocietal Accreditation Commission (IAC), and The Joint Commission.⁴ For mammography, MQSA requires accreditation by an FDA-approved accreditation body; ACR is one such body, alongside certain state programs that FDA has approved.³ Facilities should confirm which accrediting organization their payers and state require before assuming ACR is mandatory; in practice ACR is the most common choice and the focus of this guide.

Key Technical Principles: Physics Testing by Modality

Each ACR program defines a specific set of physics tests, acceptance criteria, and a phantom or measurement protocol that the medical physicist must follow exactly. The categories below summarize the core physics measurements per modality, and the crosswalk table that follows ties each program to its accrediting framework, the physicist's testing scope and frequency, and representative measured parameters.

Modality crosswalk: program, scope, frequency, and parameters

Notes: scope and frequency reflect common practice and the ACR program manuals; the precise QC schedule and tolerances are defined in each current ACR program manual and, for mammography, in the MQSA regulations and the manufacturer's QC manual or the ACR mammography QC program adopted by the facility.¹³⁵ The MIPPA advanced-diagnostic-imaging accreditation mandate applies to CT, MRI, nuclear medicine, and PET — not ultrasound, fluoroscopy, or mammography (mammography is governed by MQSA). ACR, the Intersocietal Accreditation Commission (IAC), and The Joint Commission (TJC) are the CMS-designated accreditation organizations for those advanced-imaging modalities; confirm current designations as CMS lists are updated periodically.⁴

CT Accreditation (ACR-CTAP)

Physics testing includes:

• Equipment Performance: Spatial resolution, contrast resolution, noise, uniformity
• Radiation Dose: CTDIvol and DLP measurements
• Image Quality: Clinical image quality assessment
• Safety: Collimation accuracy, table movement, laser alignment

CT testing is performed using the ACR CT accreditation phantom, which contains modules for CT number accuracy, low-contrast resolution, high-contrast (spatial) resolution, and uniformity. The CT number (Hounsfield unit) accuracy module is anchored to water, which is defined as 0 HU by construction of the Hounsfield scale, with air at −1000 HU. The physicist measures the mean CT number in a region of interest placed in the water-equivalent material and compares it against the program tolerance for water and for the other reference materials (for example, polyethylene, acrylic, bone-equivalent, and air inserts). Dose indices reported to ACR are the volume CT dose index (CTDIvol) and dose-length product (DLP); for a deeper treatment of these metrics, see our guide on CTDIvol and DLP in CT dose optimization and on balancing dose, image quality, and compliance in CT protocols. CT acceptance testing methodology has long been guided by AAPM Report No. 39 and subsequent task-group work.⁶

The CT module-by-module evaluation also includes representative dose pass-fail limits that ACR publishes by anatomic protocol — historically CTDIvol pass (upper) values of about 80 mGy for the adult head, 30 mGy for the adult abdomen, and 20 mGy for the pediatric abdomen (reduced from 25 mGy in 2013), with lower reference (achievable) levels set below each pass value. Always confirm the current pass values and the water CT-number tolerance against the active ACR CT Accreditation Program manual, because ACR periodically revises them.

MRI Accreditation (ACR-MRAP)

Physics testing includes:

• Image Quality: Spatial resolution, contrast, uniformity, artifacts
• Geometric Accuracy: Slice thickness, image distortion
• Signal-to-Noise Ratio: SNR measurements
• Safety: Magnetic field measurements, safety systems

MRI testing uses the standard ACR MRI phantom and evaluates parameters such as geometric accuracy, high-contrast spatial resolution, slice-thickness accuracy, slice-position accuracy, image intensity uniformity, percent signal ghosting, and low-contrast object detectability. The ACR phantom and its seven quantitative tests form the backbone of both the annual physicist survey and the weekly technologist QC, so that drift in geometric accuracy, ghosting, or low-contrast detectability is caught between annual surveys.⁷ The physicist also reviews magnet siting, the 5-gauss line, quench-vent and zone management, and the facility's MRI safety program; for the broader safety framework that complements ACR-MRAP, see our MRI safety program guide.

PET Accreditation (ACR-PETAP)

Physics testing includes:

• PET Performance: Spatial resolution, sensitivity, image quality
• CT Component: CT performance evaluation
• Image Quality: Clinical image quality assessment
• Dose: Patient dose measurements

Because modern PET systems are PET/CT, the CT subsystem must also meet CT performance expectations, and the physicist evaluates it against the CT parameter set above. Quantitative accuracy — the reliability of SUV measurements — depends on scanner calibration, clock synchronization, dose-calibrator accuracy, uptake timing, and reconstruction; related reading includes our overviews of PET uptake time and quantification and time-of-flight (TOF) in PET imaging. ACR-PETAP requires submission of phantom and clinical data, and SUV accuracy is a recurring source of findings because a small calibration or residual-activity error propagates directly into reported uptake values.

Nuclear Medicine (ACR-NMAP)

Physics testing includes:

• System Performance: Uniformity, resolution, sensitivity
• Image Quality: Clinical image quality assessment
• Dose Calibrator: Calibration and linearity testing
• Quality Assurance: Daily, weekly, monthly QA testing

For gamma cameras and SPECT systems, the physicist evaluates intrinsic and extrinsic (system) uniformity, spatial resolution, sensitivity, and energy resolution, and reviews the dose calibrator's accuracy, linearity, constancy, and geometry tests. Dose-calibrator constancy is checked daily by the technologist using a long-lived reference source (commonly Cs-137 or Co-57), while accuracy and linearity are checked at defined intervals — the linearity test must span the range of activities used clinically because activity-dependent error directly affects every administered dose.⁵

Mammography (ACR-MAP) and Ultrasound (ACR-UAP)

Mammography accreditation is unique because the physics testing is required by federal law under the Mammography Quality Standards Act (MQSA), enforced by the FDA, not merely by a voluntary accreditation criterion. Under MQSA (21 CFR 900), every mammography facility must be accredited by an FDA-approved accreditation body and certified, and a qualified medical physicist must perform an annual survey covering image quality, mean glandular dose, phantom scoring, kVp accuracy, half-value layer, AEC performance, artifact evaluation, and equipment performance, in addition to ACR program requirements.³ The mean glandular dose for a single craniocaudal view of a standard phantom (approximating a 4.2 cm compressed breast of 50% glandular tissue) must not exceed 3.0 mGy (0.3 rad) per exposure — a hard regulatory limit, not a soft target.³ The phantom image must also achieve a minimum score for visible fibers, speck groups, and masses, demonstrating that the system resolves clinically relevant low-contrast and high-contrast detail — historically a minimum of the four largest fibers, the three largest speck groups, and the three largest masses on the ACR accreditation phantom (the ACR Digital Mammography phantom uses its own scoring key).³

Ultrasound accreditation (ACR-UAP) emphasizes transducer and system performance and clinical image quality across the practice's scanners. The physicist or qualified engineer evaluates each transducer for element dropout, image uniformity, depth of penetration, and geometric accuracy, because a small number of dead elements can degrade clinical images while passing a casual visual check.

Worked Example: CT Number and Dose Pass-Fail Logic

A pass-fail decision in CT accreditation is a direct comparison of a measured value to a published tolerance — the logic is simple, but it must be applied to the right region of interest with a correctly calibrated dosimeter. Two of the most common CT checks illustrate the workflow: water CT-number accuracy and CTDIvol.

CT number accuracy. The Hounsfield scale is defined so that water is 0 HU and air is −1000 HU. If the physicist places a region of interest in the water-equivalent module and measures a mean of ${\overline{\text{HU}}}_{\text{water}}$, the deviation from the expected value is:

$$\Delta \text{HU}={\overline{\text{HU}}}_{\text{water}}-0$$

Suppose the ACR program tolerance for water is $0\pm \tau$ HU. The module passes when:

$$|\Delta \text{HU}|\le \tau$$

For example, with a water tolerance window of $\pm 5$ HU (the value commonly applied to the water module — always confirm against the current ACR program manual), a measured mean of $+4.2$ HU passes because $|4.2|\le 5$, whereas a measured $+9.1$ HU would fail and trigger a calibration.

CTDIvol. The volume CT dose index normalizes the measured dose by the pitch. From the weighted CTDI measured in the dosimetry phantom:

$${\text{CTDI}}_{\text{vol}}=\frac{{\text{CTDI}}_w}{\text{pitch}},\text{pitch}=\frac{\text{table travel per rotation}}{N\cdot T}$$

where $N\cdot T$ is the total nominal beam width. A protocol passes the dose check when the measured CTDIvol is at or below the ACR reference (pass) value for that protocol:

$${\text{CTDI}}_{\text{vol, measured}}\le {\text{CTDI}}_{\text{vol, ACR pass}}$$

For instance, if an adult abdomen protocol measures a CTDIvol of $11.8\text{mGy}$ against the ACR adult-abdomen pass value of $30\text{mGy}$, the physicist confirms $11.8\le 30$ and that image noise and low-contrast resolution still meet their own criteria — because a site cannot simply lower dose until the images fail. The same dose-quality balance is the subject of our CT protocol optimization guide.

Clinical Impact

Failing or delaying ACR accreditation can interrupt reimbursement, stall clinical operations, and undermine confidence in diagnostic image quality. Many payers — including Medicare for advanced diagnostic imaging under MIPPA — and several states require ACR (or equivalent) accreditation as a condition of payment.⁴ The practical consequences of a lapse include:

• Revenue interruption if accreditation expires or is denied and payers stop reimbursing.
• Operational disruption when a modality must pause advanced imaging while issues are corrected.
• Regulatory exposure for mammography, where an MQSA lapse can stop a facility from legally performing mammography, because MQSA certification — not just ACR accreditation — is a federal requirement.³
• Diagnostic risk when image-quality deficiencies that accreditation is designed to catch go unaddressed, including monitor performance for interpretation (see evaluating the SMPTE pattern for monitor QC). Display performance for primary interpretation is itself governed by AAPM TG-18, which underpins the diagnostic-monitor QC that accreditation reviewers expect to see.⁸

Robust physics testing therefore protects both compliance standing and patient care.

Practical Tips: Achieving Accreditation Efficiently

Most accreditation failures are preventable, and the single most effective step is to engage a qualified medical physicist early and follow the modality-specific protocol precisely. Recommended best practices:

1. Plan Ahead: Begin the accreditation process well in advance of any deadline or expiration date.
2. Complete Testing: Ensure all required physics tests are performed using the correct phantom and protocol.
3. Document Thoroughly: Maintain complete, clear, and current documentation.
4. Review Images: Carefully review clinical images against ACR standards before submission.
5. Work with Experts: Engage qualified, board-certified medical physicists experienced in ACR accreditation.

Common Issues to Avoid

Common issues leading to accreditation delays or failures:

• Incomplete Testing: Missing required physics tests
• Inadequate Documentation: Insufficient or unclear documentation
• Image Quality Issues: Clinical images not meeting standards
• Equipment Problems: Equipment not meeting performance criteria
• Timing Issues: Expired test results or documentation
• Phantom or scanning errors: Mispositioned phantom, wrong protocol, or incorrect ROI placement that invalidates an otherwise passing system

Documentation Requirements

The ACR review package centers on the physics test report, supporting equipment data, ongoing QA records, and submitted clinical images. Each element must be complete and internally consistent.

Physics Test Reports

Detailed reports documenting:

• Test procedures performed
• Results obtained
• Comparison to acceptance criteria
• Equipment specifications
• Test dates and personnel

Equipment Information

Complete equipment documentation including:

• Manufacturer and model
• Serial numbers
• Installation dates
• Software versions
• Calibration records

Quality Assurance Records

Ongoing QA documentation including:

• Daily QA test results
• Weekly QA procedures
• Monthly comprehensive evaluations
• Annual physics surveys

Clinical Images

Submission of clinical images demonstrating:

• Image quality standards
• Protocol compliance
• Diagnostic adequacy
• Technical factors

Submission Process

ACR submission is a defined sequence: apply, complete physics testing, submit clinical images and documentation, and await ACR review and decision. The standard workflow is:

1. Application: Complete accreditation application
2. Physics Testing: Comprehensive physics evaluation by a qualified medical physicist
3. Image Submission: Clinical images meeting quality standards
4. Documentation: All required physics and equipment documentation
5. Review: ACR review and decision

Regulatory Considerations

ACR accreditation intersects with federal and state regulation, most directly through MQSA for mammography and through payer and state mandates that recognize ACR accreditation. Key points for facilities in DRPS service areas:

• Mammography (MQSA, 21 CFR 900) requires an annual medical physicist survey and is enforced federally regardless of state. ACR is an FDA-approved accreditation body for mammography, and the facility must also hold MQSA certification to legally operate.³
• Advanced diagnostic imaging (CT, MRI, nuclear medicine, PET) falls under MIPPA, which requires accreditation by a CMS-recognized organization (ACR, IAC, or The Joint Commission) for Medicare Part B reimbursement of the technical component.⁴
• Jurisdiction for diagnostic X-ray machines is distinct from byproduct material. Diagnostic X-ray units (CT, mammography, rad/fluoro) are regulated by the FDA and by state radiation-control programs; the byproduct material used in nuclear medicine and PET (such as Tc-99m, F-18, and dose-calibrator reference sources) is regulated by the NRC or an Agreement State under 10 CFR Parts 20 and 35. Among DRPS service areas, Florida, Maryland, Virginia, California, and Nevada are Agreement States, while Washington DC is regulated directly by the NRC.
• State requirements can layer additional radiation-machine registration, inspection, and QA obligations on top of ACR. For Florida facilities, ACR physics testing complements — but does not replace — state radiation rules; see our overview of Florida radiation safety requirements for imaging centers and common radiation safety violations and how to avoid them.
• DRPS provides ACR accreditation physics services across Florida, Maryland, Virginia, Washington DC, California, and Nevada, coordinating ACR requirements with each jurisdiction's radiation-control regulations.

Frequently Asked Questions (FAQs)

What physics testing is required for ACR accreditation?

ACR requires modality-specific physics testing of equipment performance and image quality, performed and documented by a qualified medical physicist. Each program (CT, MRI, PET, nuclear medicine, mammography, ultrasound) has its own phantom, test set, and acceptance criteria submitted with clinical images.

Who is qualified to perform ACR accreditation physics testing?

ACR requires a qualified medical physicist who meets program-specific education, board-certification, and continuing-education criteria. DRPS uses board-certified (DABR) medical physicists for ACR surveys across Florida, Maryland, Virginia, Washington DC, California, and Nevada.

How often must ACR accreditation physics testing be repeated?

ACR accreditation is generally granted for a three-year cycle, with an annual physics survey required for most modalities and routine daily, weekly, and monthly QA performed between surveys. Mammography requires an annual MQSA physicist survey, enforced under federal law independent of the ACR cycle.

Is ACR the only accrediting body for these modalities?

No. ACR is the dominant imaging accrediting body, but CMS also recognizes the Intersocietal Accreditation Commission (IAC) and The Joint Commission for advanced diagnostic imaging under MIPPA. For mammography, the accrediting bodies are FDA-approved under MQSA, and ACR is one of them.

What is the MQSA mean glandular dose limit for mammography?

Under MQSA (21 CFR 900), the mean glandular dose for a single craniocaudal view of a standard phantom approximating a 4.2 cm compressed breast must not exceed 3.0 mGy (0.3 rad) per exposure. Exceeding this limit is a regulatory failure, not just an ACR finding.

What are the most common reasons sites fail ACR accreditation?

The most common causes are incomplete physics testing, inadequate or unclear documentation, clinical images that fail quality standards, equipment that does not meet performance criteria, and expired test results. Most failures are preventable with early planning and an experienced physicist.

Does DRPS guarantee ACR accreditation results?

Yes. If a testing package DRPS prepares does not achieve accreditation, DRPS covers the fees associated with resubmission, reflecting confidence in the quality of the testing and documentation.

Key Takeaways

• ACR accreditation requires modality-specific physics testing performed and signed by a qualified medical physicist, plus equipment data, QA records, and clinical images.
• ACR is the dominant accrediting body but not the only one — IAC and The Joint Commission are also CMS-recognized for advanced imaging, and FDA approves the mammography accreditation bodies under MQSA.
• Accreditation runs on a three-year cycle, with annual physics surveys and routine daily/weekly/monthly QA in between for most modalities.
• CT dose is reported as CTDIvol and DLP, water reads as 0 HU on the Hounsfield scale, and CT, MRI, and PET each use a dedicated ACR phantom with defined acceptance criteria.
• Mammography accreditation is governed by MQSA (21 CFR 900), requires an annual medical physicist survey, and caps mean glandular dose at 3.0 mGy per standard-phantom view — a federal limit.
• Most accreditation failures are preventable — they stem from incomplete testing, weak documentation, or images that miss quality standards.
• DRPS performs ACR accreditation physics with board-certified medical physicists across Florida, Maryland, Virginia, Washington DC, California, and Nevada.

How DRPS Can Help

DRPS provides comprehensive ACR accreditation support across all programs, including:

• Complete physics testing for CT, MRI, PET, nuclear medicine, mammography, and ultrasound
• Clinical image reviews
• Documentation preparation
• Submission coordination
• Ongoing QA support and maintenance

Accreditation Success Guarantee: If a testing package DRPS prepares does not achieve accreditation, DRPS will cover the fees associated with resubmission — a reflection of our confidence in the quality of our work.

Contact DRPS to discuss your ACR accreditation needs or learn more about our accreditation support services.

Conclusion

ACR accreditation is achievable and predictable when physics testing is performed to protocol, documented completely, and submitted on time. The facilities that succeed plan early, use a qualified medical physicist, and treat documentation and image quality as seriously as the measurements themselves. They also keep the regulatory hierarchy straight: ACR is the dominant but not the only accrediting body, mammography physics is mandated by MQSA under federal law, and diagnostic X-ray and byproduct-material programs answer to different regulators. With the right physics partner, accreditation becomes a routine, well-managed part of operating a high-quality imaging program.

Related Resources

• CTDIvol and DLP dose metrics
• CT protocol optimization
• Building an MRI safety program
• PET uptake time and quantification
• Time-of-flight (TOF) PET imaging
• ACR accreditation support

References

1. American College of Radiology. ACR Accreditation Programs (CT, MRI, Nuclear Medicine, PET, Ultrasound). accreditationsupport.acr.org
2. American College of Radiology and American Association of Physicists in Medicine. ACR–AAPM Technical Standards for Medical Physics Performance Monitoring of Imaging Equipment. Reston, VA: ACR. acr.org
3. U.S. Food and Drug Administration. Mammography Quality Standards Act and Program; 21 CFR Part 900. ecfr.gov
4. Centers for Medicare & Medicaid Services. Advanced Diagnostic Imaging (ADI) Accreditation under the Medicare Improvements for Patients and Providers Act (MIPPA). cms.gov
5. American College of Radiology. ACR Nuclear Medicine and PET Accreditation Program Requirements. acraccreditation.org
6. American Association of Physicists in Medicine. AAPM Report No. 39: Specification and Acceptance Testing of Computed Tomography Scanners. College Park, MD: AAPM; 1993. aapm.org
7. American College of Radiology. ACR MRI Accreditation Program — Phantom Test Guidance. acraccreditation.org
8. Samei E, Badano A, Chakraborty D, et al. Assessment of display performance for medical imaging systems: executive summary of AAPM TG-18 report. Medical Physics. 2005;32(4):1205-1225. PMID: 15895604. doi:10.1118/1.1861159. aapm.onlinelibrary.wiley.com
9. U.S. Food and Drug Administration. Mammography Quality Standards Act (MQSA) — Policy Guidance Help System. fda.gov
10. American College of Radiology. ACR CT Accreditation Program — Testing Instructions and Phantom Guidance. acraccreditation.org