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Study finds cardiac CT scans damage cells

by Lisa Chamoff, Contributing Reporter | July 27, 2015
CT Risk Management X-Ray
Exposure to even low levels of radiation from CT scans produces cellular damage, according to new research from scientists at the Stanford University School of Medicine.

For the study, published online in the Journal of the American College of Cardiology: Cardiovascular Imaging, researchers examined the blood of 67 patients at two U.S. medical centers both before and after they underwent cardiac CT angiograms. Using flow cytometry, whole-genome sequencing, and single cell polymerase chain reaction, the researchers measured biomarkers of DNA damage and saw an increase in DNA damage and cell death, as well as increased expression of genes involved in cell repair and death. While most of the damaged cells were repaired, a small percentage died, according to the study.

The median radiation dose to the blood was 29.8 milliSieverts. There was no DNA damage detected in patients who received doses lower than or equal to 7.5 milliSieverts, or the equivalent of 50 chest X-rays or one cardiac CT angiography using state-of-the-art technology, according to the study.
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Dr. Patricia Nguyen, an assistant professor of cardiovascular medicine at Stanford and one of the study’s lead authors, said that while a few earlier studies had shown changes in one of the cell markers, this research was more complex and examined multiple markers.

“X-rays or radiation exposure is known to result in DNA double strand breaks,” Nguyen told HCB News. “What is not known is to what extent that could be detected with lower doses.”

While it’s still not clear whether exposure to low levels of radiation causes cancer or any other negative effects, the study shows that health care providers need to be mindful of radiation dose and use the lowest dose possible for an adequate diagnostic image, Nguyen said. Despite the technology that has allowed scans to be performed with lower doses, it’s often difficult to use a lower dose on larger patients and patients who have irregular heart rates.

“Studies like this reinforce that message and also encourage companies and providers to advance imaging technology so you can lower the dose even further,” Nguyen said. “A lot of hospitals still have the old technology. That might be a consideration if they have new purchases to make.”

The researchers tested a population of cells that are mature lymphocytes, and that are not going to reproduce. The next step, according to Nguyen, is to look at other cell types that might be affected by radiation exposure, which could be more dangerous because they replicate. The scientists are also looking at some of the patients who had more sensitivity to radiation than others, for reasons that are unclear.

Researchers can also look into whether it’s possible to give patients something to protect against cell damage, Nguyen said.

Dr. Joseph Wu, a professor of medicine and of radiology, director of the Stanford Cardiovascular Institute, and a senior author of the study, said the findings show the need for more research.

“These tests expose patients to a nontrivial amount of low-dose radiation,” Wu said in a statement. “But nobody really knows exactly what this low-dose radiation does to the patient. We now have the technology that allows us to look at very subtle, cell-level changes.”

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