CT Radiation Dosing: Where Things Stand, Part 1

While some studies in recent years have suggested overuse of computed tomography (CT) scans and estimates of radiation-induced cancer, new research reveals significant decreases in CT radiation dosing for adults across common CT exams over the last 10 years.

For the retrospective study, published in Radiology, researchers found a 9.3 percent decline in national volume CT dose index (CTDIvol) achievable doses (ADs) across 10 common CT exams for adults in comparison to similar research performed in 2014.^1,2 The current study, which involved a total of 5,234,285 CT exams from 2,802,416 adults, also revealed a 21.8 percent decrease in diagnostic reference levels (DRLs) for CT exams between 2014 and 2025.¹

In a recent interview with Diagnostic Imaging, lead study author Kalpana Kanal, PhD, noted the cohort size and emphasized that a judicious approach to CT radiation dosing appears to be increasingly more common.

“The one message I want to give here is we are not necessarily saying the lower the dose, the better. You have to balance the dose with the image quality, so we don't want to go too low in dose either. We want to have an optimized image quality, but the fact that we are seeing 21.8 percent decrease in dose in the top 10 protocols, when comparing to the 2017 DRL paper, I think is great because we are doing something right across the country. We are moving in the right direction for sure, and there are many reasons for that. … But I think it's a good thing that this dose has gone down,” noted Dr. Kanal, a professor of radiology at the University of Washington in Seattle.

Mahadevappa Mahesh, MS, PhD, FAAPM, FACR, a co-author of the study, also pointed out that while there may be a perception that radiation dose optimization with CT primarily occurs at large academic centers, 67 percent of the study’s data was derived from community practices.

Dr. Mahesh also pointed out that CT scanner technology improvements, such as automatic tube current modulation (ATCM), have had a positive impact as well.

“In the past 10 to 15 years, the dose modulation tube current modulation … across vendors has matured so much. Even a community hospital just turning on the dose modulation immediately drops the dose by 20 to 30 percent easily on average,” posited Dr. Mahesh, a professor of radiology and cardiology at the Johns Hopkins School of University School of Medicine.

(Editor’s note: For related content, see “New Study Shows Substantial Decline in CT Radiation Dosing for Adults Over the Past Decade,” “Study: More than Half of CT Requests in Pediatric Emergency Department are ‘Usually Not Appropriate’” and “Study: PCCT Facilitates Superior SNR and CNR in Lung Cancer Imaging with 55 Percent Reduction in Radiation Dosing.”)

References

1. Kanal KM, Frush DP, Gingold E, et al. A decade of change in adult CT radiation doses: 2025 U.S. diagnostic reference levels. Radiology. 2026;320(1). https://doi.org/10.1148/radiol.260322.

2. Kanal KM, Butler PF, Sengupta D, Bhargavan-Chatfield M, Coombs LP, Morin RL. Radiology. 2017;284(1):120-133.