CT Scan Radiation Doses Vary Widely by Facility
A study of 783,634 adult scans found 30.7% exceeded radiation thresholds for their exam type.
Updated on Nov. 3, 2026 in Cancer
Live Poll
Do you trust that your CT scans use only the radiation they need?
A study published November 2 in the Journal of the American College of Radiology assessed how CT facilities perform on the CMS ExRad measure, which flags scans that used more radiation than needed or produced images too noisy to read. Among 783,634 adult CT exams from 254 voluntarily reporting U.S. facilities, 30.7% exceeded the radiation threshold for their exam type.
Why it matters
Studies have linked CT exams above recommended radiation thresholds to lifetime cancer risk, so variation in how much dose patients receive matters for prevention. The study arrives as CMS has built ExRad into three quality reporting programs, putting radiation practices under federal measurement for the first time at this scale.
This cross-sectional analysis of voluntarily reported data covered 783,634 adult CT examinations from 254 facilities across 16 CT categories, with exams recorded from May 2025 through August 2026. Because participation was voluntary, the findings describe reporting facilities rather than a random national sample.
The players
Rebecca Smith-Bindman, MD
Radiologist and epidemiologist at the University of California San Francisco who has published widely on medical radiation exposure and imaging safety.
Centers for Medicare & Medicaid Services (CMS)
The federal agency that administers Medicare and sets quality reporting programs, including the programs that adopted the ExRad measure.
Journal of the American College of Radiology
A peer-reviewed journal of the American College of Radiology covering imaging practice, quality, and policy.
The details
The ExRad measure checks each CT scan against a dose threshold set for its exam type and flags scans that used more radiation than the clinical indication required, as well as scans whose images were too noisy to interpret. Researchers found that facility scores ranged widely, and the gap between a facility's best and worst CT categories had a median of 74 percentage points. Most out-of-range exams came from routine-dose categories, with abdomen and pelvis, chest, and head scans accounting for 71.9% of them.
Timeline
January 2025: Voluntary ExRad reporting began as an automated CT quality measure in CMS payment programs.
May 2025 through August 2026: Period covered by the CT examinations analyzed.
November 2, 2026: Study published in the Journal of the American College of Radiology.
Health Landscape
The ExRad measure places CT dose and image quality under the same kind of federal quality reporting that has long applied to other clinical services, marking a shift toward measuring imaging radiation as a standard performance metric. This analysis gives early benchmark data on how U.S. facilities currently compare under that approach.
If you have a CT scan planned, it is reasonable to ask your care team how the radiation dose is set for your exam and whether it is tailored to your clinical need. Repeat or unnecessary scans are worth discussing with your doctor, since the study ties above-threshold doses to cancer risk at the population level.
The takeaway
Radiation dose varies substantially from one CT facility to another, and this study shows that gap is measurable. When a CT scan is recommended, asking your doctor whether it is needed and how its dose will be managed is a reasonable, low-risk step.
Further reading
For related context, explore our Cancer coverage on how medical imaging exposure fits into long-term cancer prevention.
Live Poll
Do you trust that your CT scans use only the radiation they need?
