The risk of getting cancer in their lifetime increases for people exposed to radiation during cardiac screening with a 64-slice CT scanner, an increasingly popular diagnostic tool, doctors said Tuesday.
Known technically as computed tomography coronary angiography, or CTCA, the test has become widely used because it is noninvasive and generates sharp cross-sectional computerized images of the heart and coronary arteries. Doctors can see inside a beating heart and are able to determine from the test whether arteries are obstructed. When ordered for patients rushed into an emergency room, doctors can visualize a heart attack. The U.S. Food and Drug Administration approved 64-slice CT scanning in 2004.
Dr. Andrew Einstein, a cardiologist at Columbia University Medical Center in New York, has found in a study that some patients, particularly women and young people, increase their cancer risk when they undergo the 64-slice scan. The device, he said, delivers an especially high dose of radiation compared with other forms of X-ray technology.
``Before this study, no one had really quantified the cancer risk,'' Einstein said.
Although men and women receive the same dose of radiation from the scan, the cancer risk is higher in women, Einstein said, basing his estimate on data that dates to studies involving radiation absorption in the atomic bombings of Hiroshima and Nagasaki at the end of World War II.
He and his collaborators found, based on standard amounts of radiation emitted from the scanning device, that the lifetime cancer risk for a 20-year-old woman diagnosed with the device is 1 in 143 compared with 1 in 3,261 for an 80-year-old man. A 60-year-old woman would have a 1 in 715 chance of developing cancer, but a 60-year-old man would have a 1 in 1,911 chance of developing cancer.
Einstein reports his research in Wednesday's Journal of the American Medical Association.
Dr. David Brown, chief of cardiovascular medicine at Stony Brook University Medical Center, described the radiation dose from the scanners as significant. He estimates it to be four times as much as the dosage delivered during routine cardiac catheterization.
Brown said the scanner is used most effectively in emergency situations and in instances when patients have a history of heart disease or familial cardiac disorders.
In the United States, the scanners are manufactured by several companies, including Siemens USA.
``The question here is, how many people are getting large doses,'' Brown said, adding that the scanners are being promoted in stand-alone imaging centers as tools for people to determine their heart disease risk. No one, he said, should use the machine for preventive purposes.