ACR Bulletin

Covering topics relevant to the practice of radiology

Advancing Quality and Safety

Participating in the ACR’s DIR helps radiologists become key contributors to ongoing quality improvement efforts.
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The DIR lets facilities compare their radiation dose indices to regional and national values.

April 28, 2021

The Dose Index Registry (DIR) is a data registry that allows facilities to compare their CT dose indices to regional and national values. Information related to dose indices for all CT exams is collected, anonymized, transmitted to the ACR, and stored in a database. Institutions are then provided with periodic feedback reports comparing their results by body part and exam type to aggregate results. The DIR is the largest registry under the ACR National Radiology Data Registry (NRDR®), and it currently has more than 3,100 institutions participating and has analyzed more than 100 million exams.

The Bulletin spoke with William F. Sensakovic, PhD, chair of the DIR and chair of the division of medical physics and associate professor at Mayo Clinic (Arizona), about the DIR and how facilities can use it to understand how much radiation they are using for various exams, as well as how their numbers compare to those of their peers.

How does the DIR improve quality and safety?

The DIR lets facilities compare their radiation dose indices to regional and national values. We’re gathering that data into a massive collection of dose metrics — larger than any single institution could ever put together. That way, we can analyze it for information about the radiation we’re exposing our patients to so that we can help lower risk while continuing to provide solid image quality to facilitate diagnosis. Participants in DIR receive quarterly feedback reports comparing their results to aggregate results by body part and exam type.

Why is it important to compare dose indices against regional and national benchmarks?

The benchmark reports allow facilities to understand how much radiation they are using and compare their doses for various exams to national averages, to similar institutions, and to other facilities in their geographic area, which is important because there are differences in both patient characteristics and radiology practices based on region. In other words, they can parse the feedback reports down to various comparisons to see how they’re doing and optimize their dose for various exams to bring them in line with standard practices.

How is the DIR expanding to other modalities beyond CT doses?

For many years, the DIR has only benchmarked CT doses. Now, we are adding dose metrics for three other modalities: fluoroscopy, nuclear medicine/PET, and digital radiography. We initially focused on CT for several reasons: In addition to being the single biggest contributor to patient dose, CT was also the most standardized modality in terms of reporting, which made it relatively straight forward to implement compared to other modalities. The success of the DIR created a kind of push-me pull-you effect — seeing impactful analysis accomplished because of standardization encourages more standardization in our field, both for CT and other modalities.

While CT has been the easiest to benchmark due to existing standardization, it is not the only modality that exposes our patients to radiation. We have now turned our attention to other places where we could apply the value of benchmarking to improve quality and safety. The goal is to encourage standardization of the data for fluoroscopy, nuclear medicine/PET, and digital radiography exams to create dose registries that allow comparisons to peers. This effort is an impetus toward standardization in places where it is lacking in the imaging community.

The DIR is not only about dose management; it can also provide us with important insights into things like utilization and patient care.

When and how can facilities participate in the new DIR modules?

The DIR Fluoroscopy Module is now available for enrollment and data submission. Anyone who is currently sending data to the DIR can participate. You can read about the features of the new interactive fluoroscopy standardized DIR reports in the NRDR Knowledge Base user guide. The pilots of the Nuclear Medicine/PET Module and the Digital Radiography Module are now underway.

Are there any other potential uses of the data that’s being collected in the DIR?

I want to stress that quality improvement using DIR data is not only about lowering dose. If a facility’s doses are substantially lower than its peers, then it might indicate an opportunity to increase dose and by doing so increase image quality and hopefully diagnostic confidence. DIR data is also utilized within the ACR to inform other activities (e.g., ACR Appropriateness Criteria®) and outside the ACR by researchers who partner with the ACR for research initiatives. A link to request use of DIR data for research purposes is available on the NRDR Data Access and Publications Policy page.

The DIR is not only about dose management; it can also provide us with important insights into things like utilization and patient care. For example, a recent paper published in the JACR® — “CT Volumes from 2,398 Radiology Practices in the United States: A Real-Time Indicator of the Effect of COVID-19 on Routine Care, January to September 2020”— used DIR data to highlight the impact of COVID-19 on scanning volume.1 Data that facilities contribute to the ACR registries helps us explore a wide range of questions about the practice of radiology and identify new areas for improvement.

How does participating in the DIR help radiologists and physicists demonstrate their value as members of the patient care team?

The DIR is an easy reference tool, especially for radiologists who are not knowledgeable about doses. If you gain a little bit of knowledge about what typical doses are for a given exam, you can speak more intelligently with patients about what the risks are and reassure them that they’re safe. When speaking with referring physicians and patients, this knowledge can give you added confidence that you’re doing things right. That can be important when calming a worried patient or when trying to convince a referring physician or patient that an exam that uses radiation is safe and important for their care.

Beyond that, participation in the DIR is a key part of ongoing quality improvement efforts. Step one is to compare. Pull your benchmark reports for your scans and see if you deviate from your peers. Step two is to investigate. Follow up to determine why your doses are higher or lower than other comparable facilities. Step three is to modify, as needed. Then rinse and repeat. For larger institutions the reports can also be used to ensure that all machines are using similar doses across their fleet.


1. Davenport MS, Fruscello T, Chatfield M, Weinstein S, Sensakovic WF, Larson DB.
CT volumes from 2,398 radiology practices in the United States: a real-time indicator
of the effect of COVID-19 on routine care, January to September 2020. J Am Coll
. 2021;18(3):380–387.