The number of Americans undergoing advanced imaging tests has skyrocketed, increasing their exposure to radiation that may result in cancer later in life, a study found.
The use of computed tomography, or CT, scans tripled between 1996 and 2010, research today in the Journal of the American Medical Association showed. The number of people receiving high to very high doses of radiation from imaging during a given year doubled over the 15-year study.
Improvements in technology, demand by doctors and patients for the tests, defensive medical practices and medical uncertainty are most likely behind the increased use of advanced imaging, the authors wrote. About 2 percent of future cancers will result from current imaging use if the present rate continues, they said.
“Imaging is clearly overused and we need to begin to make more informed choices regarding when and how to image, understanding that there are clear and definite benefits but also harms from imaging,” said lead study author Rebecca Smith-Bindman, a professor of radiology and biomedical imaging at the University of California, San Francisco, in a June 11 e-mail.
In the study, the first major investigation into how radiation exposure has increased within private health systems, researchers analyzed electronic medical records of six large integrated health-plan systems in the U.S. The health groups included Kaiser Permanente in Colorado, Georgia, Hawaii and Oregon/Washington, Group Health Cooperative in Washington and Marsfield Clinic and Security Health Plan in Wisconsin.
Between 933,897 and 2 million patients were included each year from 1996 to 2010. Over the course of the study, 30.9 million imaging tests were conducted, reflecting an average of 1.18 tests a person per year.
Researchers found that the use of CT scans rose to 149 per 1,000 patients in 2010 from 52 per 1,000 in 1996, reflecting a 7.8 percent annual growth. The use of magnetic resonance imaging, or MRI, which doesn’t use radiation, quadrupled over the same period to 65 per 1,000 patients from 17 per 1,000, reflecting 10 percent annual growth.
The study also found that the percentage of patients who received high exposure to radiation of greater than 20 millisieverts to 50 millisieverts, or very high, which is greater than 50 millisieverts, during a given year doubled. The general population is exposed to about 6.2 millisieverts of radiation each year, half from natural sources such as the sun and the rest from encounters such as medical imaging, according to the U.S. Nuclear Regulatory Commission. The commission limits adults working with radioactive material to exposure of 50 millisieverts a year.
By 2010, 6.8 percent of patients who had an imaging test received a high dose of radiation and 3.9 percent received a very high dose during a single year, twice as much as 15 years earlier, Smith-Bindman said.
“Patients are getting imaged more and imaged with higher dose studies,” she said.
That trend may be changing, according to Brian Connell, director of government relations for the Medical Imaging and Technology Alliance in Washington. For Medicare beneficiaries the use of advanced imaging declined 3 percent between 2009 and 2010, the first years to show a drop in utilization, he said.
“We’ve seen the same trend in the private market,” Connell said in a telephone interview today. “It’s important for every patient to discuss the benefits and risks with their doctor so folks get the imaging that they need.”
Paul Ellenbogen, chairman of the American College of Radiology Board of Chancellors, said in a statement that the group advises clinicians to prescribe advanced imaging only to those with a clear medical need. Those receiving the highest doses of radiation are most likely cancer patients or those with chronic conditions who required multiple scans, he said.
“We need to continue to educate providers to more appropriately use these lifesaving tools, not look backward and set arbitrary limits for care,” he said. “Imaging is the future of medicine. We need to embrace, refine and promote these advances for the good of all of those needing care.”
A new law in California, which goes into effect in July, requires the radiation dose patients receive from tests be put into their medical records so their exposure is tracked, Smith-Bindman said. The law may help reduce and standardize the dose used in advanced imaging so people are exposed to the lowest amount of radiation, she said.
George O’Connor, a professor of medicine at the Boston University School of Medicine and a contributing editor for the Journal of the American Medical Association, and Hiroto Hatabu, an associate professor of radiology at Brigham and Women’s Hospital in Boston, wrote in an accompanying editorial that doctors need to consider the radiation risks when ordering tests for their patients. When doing so, they should take into account how much radiation exposure the patient has had in recent months or years.
“The radiation risks and financial costs of advanced diagnostic imaging clearly warrant more research,” they wrote.
The National Cancer Institute funded the study.