Increasing Efforts to Regulate Computed Tomography Scans

Abstract

I n 2009, Cedars – Sinai Medical Center in Los Angeles disclosed that 206 patients had been severely overdosed with radiation while receiving perfusion computed tomography (CT) scans of the brain. That debacle catalyzed a California law that now represents the fi rst effort to regulate U.S. CT scans. Dubbed SB-1237, with an effective date of July 1, 2012, the law directs hospitals in California to record the dose of every CT scan they give in an electronic archive for annual review by a health physicist. And as of July 1, 2013, any facility that offers CT scans will need accreditation from the Centers for Medicare and Medicaid Services (CMS), a CMSapproved body, or the state department of public health. Also, repeat CT scans that exceed certain specifi ed dose levels will have to be reported to California health offi cials. Texas, Florida, and New York are also considering similar legislation, because apart from mammography, which falls under the 1992 Mammography Quality Standards Act, radiation doses from medical imaging in the U.S. aren ’ t subject to evidence-based guidelines or standard protocols. But CT scans raise the most concern because they deliver 10 – 500 times more radiation than most other types of radiography. Although the Cedars – Sinai situation was anomalous, overdosing episodes elsewhere have since been disclosed, and experts worry that even typical CT doses can be unpredictably high. “You could get a CT scan at one facility, and the radiation dose could be a 10 – 100 times higher than it would be somewhere else,” said Rebecca Smith-Bindman, M.D., a radiologist and professor at the University of California ’ s Helen Diller Family Comprehensive Cancer Center in San Francisco. What ’ s the Risk? CT scans improve medical care in many clinical situations, so any discussion of their risks must also consider their benefi ts. Still, the number of U.S. CT scans went from 3 million in 1980 to 80 million in 2010, costing hundreds to several thousand dollars each. Up to 30% of these scans probably aren ’ t medically necessary, according to David J. Brenner, Ph.D., director of the Center for Radiological Research at Columbia University Medical Center in New York. Meanwhile, CT scans account for more than one-third of the U.S. population ’ s total exposure to ionizing radiation, which can break chemical bonds in DNA and produce mutations leading to cancer. That CT scans cause a substantial number of cancers isn ’ t clear; prospective studies of that risk are still under way. Scientists rely on statistical modeling and estimate the risk by using dose – response models derived from other exposed groups, such as atomic bomb survivors or nuclear power plant workers. Using that approach, Amy Berrington de Gonzalez, D.Phil., a senior investigator in the National Cancer Institute ’ s Radiation Epidemiology Branch, predicted that up to 29,000 additional cancers could result from CT scans given over a single year in the U.S. The Archives of Internal Medicine published her results in 2009. In that same issue, Smith-Bindman published a study of modeled risks to individuals. Women in particular — who tend to be more sensitive to radiation than men — could develop cancers at rates ranging from one for every 270 coronary angiography CT scans to one for every 8,100 routine CT scans of the head (the brain is not especially radiosensitive). Developed for 40-year-old women, those estimates double for 20-year-old women.