CT Scan Use Triples in 15 Years; Radiation Risk Justified?

Test helps diagnose diseases but also raises the risk of cancer.

BySHEILA REDDY, M.D., ABC News Medical Unit
June 12, 2012, 4:33 PM

June 12, 2012— -- The use of CT scans has tripled in the last 15 years, a new study found, which means the average American is exposed to twice as much radiation from medical imaging as in the mid-1990s.

The study, published today in the Journal of the American Medical Association, found the rate of CT scans per 1,000 American adults rose from 52 in 1996 to 149 in 2010 -- an annual growth of 7.8 percent. And experts say the added imaging may not be improving the quality of care.

"There has been the sense that the use of imaging is a panacea to answer questions and as a result, patients and physicians are really drawn to all kinds of imaging," said study author Dr. Rebecca Smith-Bindman, a professor of radiology at the University of California, San Francisco. "While imaging is outstanding in many clinical settings and truly improves patient outcomes, in other settings it is used without improving care at all."

The use of magnetic resonance imaging (MRI) and ultrasound also increased, according to the study. But those tests are not associated with radiation exposure.

Smith-Bindman spoke on June 8 about the safety of medical imaging before Congress.

"Some people have worried about the X-rays at our airports to screen passengers," she said in her testimony. "One CT scan is equal to approximately 200,000 airport screens."

Previous research has found that radiation from CT scans, which provides detailed images of internal organs using much higher doses of radiation than conventional X-rays, can lead to the development of cancer. And many patients receive multiple CT scans over time, compounding the risk.

Dr. Eric Larson, the executive director of the Group Health Research Institute in Seattle, said, "Hardly a person gets out of an [emergency room] visit without a CT."

"For patients, doctors and others to realize that this may be increasing the rate of cancer is really important," Larson said.

In children, the cumulative dose of two brain CT scans triples the risk of brain cancer and leukemia, according to a study published June 7 in The Lancet. But experts agree that if a scan is clinically justified, the benefits far outweigh the risks.

"The increased health risk associated with increased use of radiation procedures is not of concern as long as it is accompanied by an equal or greater health benefit for the patients," said Dr. Tim Jorgensen of the department of radiation medicine at Georgetown University Medical Center.

Smith-Bindman said patients should ask their doctors if a CT scan is really necessary and find out how it will help their care. They should also make sure the doctor is using the lowest possible radiation dose.

The message for doctors ordering these tests is also clear, Smith-Bindman said.

"We need to treat our patients as partners, who need to understand both the benefits as well as the harms from imaging so that they can make informed choices," she said. "In general, patients make good decisions when they are given accurate information."

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