CT heart scans cut X-ray dose to patients

Heart scans that detect blocked arteries can be performed with half the amount of radiation exposure to patients to make them safer, researchers said.

The Michigan study measured the radiation dose from heart CT scans of 4,862 patients in 15 hospitals from July 2007 to April 2008. A quality control program lowered the median radiation dose - expressed in units known as millisieverts - to 10 from 21, according to a study in the Journal of the American Medical Association. The scans produced good quality diagnostic images, the study authors said.

Use of computed tomography, or CT, scans of all organs is growing rapidly and accounts for half of the collective dose of medical radiation U.S. patients received in 2006, the American Heart Association said. The association urged doctors to keep doses of radiation from heart scans "as low as reasonably achievable," and to use them appropriately.

"This is a terrific study," Timothy Gardner, president of the heart association, said. "The approach they've taken, plus refinements in technology, have reduced radiation exposure to address some of the concerns about safety."

CT heart scans are used to detect artery blockages that may lead to heart attacks and other problems. Cardiovascular disease, the top cause of death in the industrialized world, led to 864,480 deaths in the U.S. in 2005, according to the heart association.

The number of CT tests in the U.S. surged to an estimated 62 million a year in 2006 from about 3 million a year in 1980, according to a 2007 review in the New England Journal of Medicine. About 800,000 of the procedures in 2006 were heart scans, according to a 2008 study in Health Physics.

High cumulative doses of medical radiation may raise the risk of cancer, though researchers aren't certain how much radiation may cause malignancy, said Gilbert Raff, the lead author of today's study. Research in the Feb. 4 issue of the Journal of the American Medical Association estimated radiation from a cardiac CT scan equals 600 chest x-rays.

Raff said previous studies estimated a 60-year-old man with one coronary CT scan would face a 1-in-1,241 chance of developing a tumor from the exposure. Repeated scans may magnify such risk, he said.

Cardiac CT imaging is gaining popularity because of its efficiency and economy, Raff said. CT scans are faster, less invasive and cheaper than some older imaging procedures, costing about $750 or one-tenth the cost of a cardiac catheterization, Raff estimated.