Improving Health Through Medical Physics

ACR Accreditation: Frequently Asked Questions for Medical Physicists

Dustin A. Gress, MS | Reston, VA

AAPM Newsletter — Volume 44 No. 3 — May | June 2019
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In each issue of this newsletter, I'll present frequently asked questions (FAQs) or other information of particular importance for medical physicists. You may also check out the ACR's accreditation web site portal for more FAQs, accreditation application information, and QC forms.

Before I present FAQs, I am proud to share that the ACR's inaugural awardee of the Richard L, Morin, PhD, Fellowship in Medical Physics is Ashley E. Rubinstein, PhD. Dr. Rubinstein is a medical physics resident at UTHealth McGovern Medical School in Houston, TX, and was featured in the April 11 entry of the Voice of Radiology Blog. The Morin Fellowship is ACR's eighth fellowship and the only one exclusively for medical physics residents and fellows, recognizing the importance of our incoming generations of medical physicists and the value of mentoring them in the work of the ACR. Congratulations, Dr. Rubinstein! Now, some FAQs.

Last November, the ACR released its 2018 Digital Mammography QC Manual with 2D and Digital Breast Tomosynthesis. The following are select FAQs pertaining to the manual. Current, FDA-approved FAQs can be found on the ACR Digital Mammography QC Manual Resources web page, where you can also find updated Microsoft Excel forms for technologist and medical physicist QC (free to download), and recordings and slides from recent webinars pertaining to the manual. Please contact us if you have questions.

Q: Can ACR Members in Physics access the manual for free?
A: Yes. When members login at acr.org they can now access our Medical Physics Resources page, which includes all of our current QC manuals available for download.

Q. May I use our old ACR phantom to perform the tests in the ACR Digital Mammography QC Manual instead of obtaining the new ACR Digital Mammography Phantom?
A. No. The ACR Digital Mammography QC Manual procedures were designed around the new ACR Digital Mammography Phantom. The old ACR phantom cannot be used to conduct the tests in the manual.

Q. If our facility does not want to purchase the new ACR Digital Mammography Phantom, can we continue to use the old phantom and follow the manufacturer's QC manual?
A. Yes.

Q. Where do I obtain the ACR Digital Mammography Phantoms?
A. The ACR posts the name and contact information for approved vendors of the ACR Digital Mammography Phantom on the ACR Digital Mammography QC Manual Resources web page. For a manufacturer to sell the new phantom, they must have it reviewed and approved by the ACR.

Q. How much is the new ACR Digital Mammography Phantom?
A. Please contact the phantom manufacturers for their pricing.

Q. How does the new ACR Digital Mammography Phantom differ from the old one?
A. The main differences are as follows:
  • The new phantom is large enough to cover most of the detector. This enables artifact evaluation to be done at the same time that the phantom image quality is evaluated.
  • The largest test objects have been removed and smaller ones have been added. The gradations between test objects are also smaller so that the phantom is more sensitive to changes.
  • The tolerances for test object size and location are much tighter ensuring minimal phantom-to-phantom variation.
  • A filter has been included under the wax insert so that the signal throughout the phantom is much more uniform.

Q. What is the biggest change in evaluating the new ACR Digital Mammography Phantom image relative to the old phantom?
A. The biggest change is failing the phantom image for artifacts. QC technologists, medical physicists and ACR phantom reviewers should fail the phantom image if there is a clinically significant artifact in a location that could impact clinical interpretation, even if all fibers, speck groups and masses pass. This change was made since phantom reviewers noted that phantom images submitted for accreditation would occasionally contain clinically-significant artifacts that would not prompt failure since they did not obscure test objects in the old phantom.

Q. Can my unit fail accreditation if the ACR phantom reviewers fail my ACR Digital Mammography Phantom image submitted for accreditation due to clinically-significant artifacts?
A. Yes.

Q. I am still using the old, small ACR Mammography Phantom for routine QC using the manufacturer's QC manual and am submitting that phantom's image for accreditation. Will the ACR phantom reviewers fail my phantom image if clinically-significant artifacts are present but all fibers, speck groups and masses pass?
A. No. At this time, ACR phantom reviewers will continue to use the scoring protocol outlined in the 1999 ACR Mammography Quality Control Manual. This means they will not fail the old phantom images for artifacts if all fibers, speck groups and masses pass. However, they will note that the artifacts are “unacceptable” and provide possible causes. If this occurs, the facility should work with their medical physicist to further diagnose and eliminate the artifact.

Q. What are clinically-significant artifacts?
A. Clinically-significant artifacts may be broad-area artifacts (e.g., non-uniformities, blotches, and streaks) or detailed artifacts (e.g., black or white pixels, clusters of pixels, lines, or dust particles). This aspect of the test fails if any artifacts are in a location that could impact clinical interpretation and the artifacts:
  • Are as prominent as (or more prominent than) the visible test objects in the phantom image, or
  • Obscure test objects in the phantom, or
  • Could affect clinical interpretation.
For more information, see the Artifact Evaluation Guide in the ACR Digital Mammography QC Manual.
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