New research is revealing the level at which radiation exposure received during CT scanning damages DNA.

The prospective cohort study looked at 67 patients undergoing cardiac CT angiography (CTA) at two California medical centers, Stanford Hospital and the Veterans Affairs Palo Alto Health Care System.

More than half the participants scanned (36) showed biomarkers indicating DNA damage as calibrated by genome sequencing and other measures.

The research was led by Patricia Nguyen, MD, an assistant professor of cardiovascular medicine at Stanford University School of Medicine, and Joseph Wu, MD, PhD, director of Stanford’s Cardiovascular Institute and a Stanford radiology professor specializing in molecular imaging. 

Their work was published online July 22 in the Journal of the American College of Cardiology: Cardiovascular Imaging.

The researchers did not detect any DNA damage in patients receiving radiation doses lower than or equal to 7.5 milliSieverts—the approximate equivalent of 50 chest x-rays or one cardiac CTA using state-of-the-art technology—and who were of average weight and had regular heart rates.

However, numerous patients exposed to more than 7.5 mSv did show evidence of DNA damage.

In the study report, the authors point out that they did not directly measure DNA damage, as such quantification is not possible with current techniques.

Nor did the work assess the risk of cancer from the cardiac CTA radiation exposure, as most of the damaged cells self-repaired, and “only cells that evade cellular repair and programmed cell death survive and produce cancer long-term.”

“Because identifying these cells is not yet feasible, interpretation of these findings should be limited to the cellular effects of radiation from CTA in the short-term,” the authors write. “Although this study was not designed to assess cancer risk, it does provide valuable insight into the biological response to radiation from medical imaging.”

In comments published by Stanford Medicine’s news center, Nguyen said that, regardless of the lack of a connection with cancer or any other negative effect to the patients studied, the DNA-damage findings should further nudge physicians toward adherence with current dose-reduction strategies.

“We need to learn more because it’s not a benign effect, even at these low dosages,” Nguyen said. “Our research supports the idea that maybe physicians shouldn’t just use the best image quality in all cases.”

The study arrives at an interesting time. Earlier this month a peer-reviewed paper cast a skeptical eye on reams of previous research linking cancer with radiation received in medical imaging.

To read the Stanford study, click here.