Coronary Calcium Scans and Radiation Exposure in the Multi-Ethnic Study of Atherosclerosis

This study from the Multi-Ethnic Study of Atherosclerosis used 3,442 participants and contemporary CT scanners to measure the actual radiation dose from coronary artery calcium scoring — addressing the concern that radiation risk might offset the screening benefit of CAC testing.

The mean effective dose was 1.05 mSv — approximately half or less of earlier estimates based on older scanner technology. This dose is equivalent to about three to four months of natural background radiation, comparable to a mammogram. The estimated lifetime fatal malignancy risk from a single CAC scan was 1 in 20,000. No significant dose differences were found by sex or BMI below 40.

The clinical and policy significance is direct. Radiation concern has been a barrier to CAC scanning in younger patients and those undergoing repeat testing. With contemporary prospective ECG-gated protocols and modern detector technology, the actual dose is low enough that it should not be a decisive factor against scanning in guideline-appropriate patients — particularly those in whom the CAC result would materially change treatment decisions.

We rate the evidence strong. A well-designed study from a major cohort providing contemporary radiation dose data that substantially revises earlier estimates downward — reducing a meaningful practical barrier to CAC testing.