Cardiac CT Can Cause Cellular Damage

July 29, 2015

Doses over 7.5 mSv of radiation from cardiac CTA cause cellular damage.

Patients who have undergone cardiac CT scanning show evidence of cellular damage, according to a study published in the Journal of the American College of Cardiology: Cardiovascular Imaging.

Researchers from Stanford University School of Medicine in California sought to evaluate if an association existed between cardiac CT angiography (CTA) and DNA damage, and whether the damage leads to programmed cell death and activation of genes involved in apoptosis and DNA repair.

They conducted a prospective cohort study involving 67 patients who underwent cardiac CTA between January 2012 and December 2013.

"The use of medical imaging for heart disease has exploded in the past decade," senior author Joseph Wu, MD, professor of medicine and radiology and the director of the Stanford Cardiovascular Institute, said in a release. "These tests expose patients to a nontrivial amount of low-dose radiation. 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."[[{"type":"media","view_mode":"media_crop","fid":"39967","attributes":{"alt":"","class":"media-image media-image-right","id":"media_crop_7862440144349","media_crop_h":"0","media_crop_image_style":"-1","media_crop_instance":"4041","media_crop_rotate":"0","media_crop_scale_h":"0","media_crop_scale_w":"0","media_crop_w":"0","media_crop_x":"0","media_crop_y":"0","style":"height: 160px; width: 160px; border-width: 0px; border-style: solid; margin: 1px; float: right;","title":"Joseph Wu, MD","typeof":"foaf:Image"}}]]

The median blood radiation exposure was estimated using phantom dosimetry and biomarkers of DNA damage, and apoptosis were measured by flow cytometry, whole genome sequencing, and single cell polymerase chain reaction.

Findings:

MeasurementAmount
Median dose length product1,535.3 mGy•cm (969.7 to 2,674.0 mGy•cm)
Median radiation dose to the blood29.8 mSv (18.8 to 48.8 mSv)
Median DNA damage3.39% (1.29% to 8.04%)
Median apoptosis3.1-fold (1.4- to 5.1-fold)

 

 

 

 

 

 

 

“Whole genome sequencing revealed changes in the expression of 39 transcription factors involved in the regulation of apoptosis, cell cycle, and DNA repair,” the authors wrote. Genes involved in mediating apoptosis and DNA repair were significantly changed post-radiation, including:

GenesAmount
DDB21.9-fold (1.5- to 3.0-fold)
XRCC43.0-fold (1.1- to 5.4-fold)
BAX1.6-fold (0.9- to2.6-fold)

 

 

 

 

 

Exposure to radiation was associated with DNA damage and DNA damage was associated with apoptosis and gene activation.

The researchers concluded that patients who were exposed to more than 7.5 mSv of radiation from cardiac CTA had evidence of DNA damage. This damage was associated with programmed cell death and activation of genes involved in apoptosis and DNA repair.

"We now know that even exposure to small amounts of radiation from computed tomography scanning is associated with cellular damage," one of the lead authors, Patricia Nguyen, MD, assistant professor of cardiovascular medicine at Stanford, said in the release. "Whether or not this causes cancer or any negative effect to the patient is still not clear, but these results should encourage physicians toward adhering to dose reduction strategies."

"It is important to note that we did not detect any DNA damage in patients receiving the lowest doses of radiation and who were of average weight and had regular heart rates," Nguyen added.