TUESDAY, June 12, 2012 (HealthDay News) -- The number of advanced diagnostic scans, such as CTs and MRIs, has zoomed upward since 1996, greatly boosting the amount of estimated radiation that patients receive, according to a new analysis of the medical records of millions of Americans in HMO health plans.
It's not clear what extra risk the radiation poses, nor is it known how much difference the scans have made in terms of diagnosing and treating illness. Still, the existing research raises questions about overuse of the scans, said study lead author Dr. Rebecca Smith-Bindman, a professor at the University of California, San Francisco.
"We spend in the ballpark of $100 billion a year on medical imaging, and we need to invest some research dollars to figure out how best to spend these dollars and when to image more and when to image less," she said. "The impact on health outcomes should be the driver of these decisions, rather than the fact that a new test has simply become available and we are enamored with the images."
The researchers studied millions of patients from six large HMO (health maintenance organization) health care systems over the period from 1996 to 2010. They followed 1 million to 2 million patients each year.
According to the findings, published in the June 13 issue of the Journal of the American Medical Association, patients underwent an average of just over one imaging examination -- such as an X-ray -- per year. A little over one-third were advanced diagnostic imaging tests, such as CT (computed tomography), MRI (magnetic resonance imaging), nuclear medicine, a subset of nuclear medicine called PET (positron emission tomography), and ultrasound scans.
The researchers found that CT scans grew by nearly 8 percent a year, MRIs by 10 percent a year, and ultrasounds by nearly 4 percent a year. Nuclear medicine scans, which are fairly uncommon, dipped by 3 percent a year, however PET scans grew rapidly from 2004 to 2010 -- by 57 percent annually.
The researchers calculated that the percentage of patients who received high or very high levels of radiation through scans also rose over the 15 years. Of those who received scans in 2010, nearly 7 percent received high annual radiation exposure and nearly 4 percent received very high annual exposure.
Smith-Bindman said the scan rates in the HMOs in the study were a bit lower than in traditional fee-for-service systems, but the growth rates were the same. "While the financial incentives are very different in the [HMO] setting, the other factors that have led to the dramatic rise in imaging are all the same -- physician and patient demand, improvement in the technologies that allow it to answer a broad range of questions, fear of medical malpractice suits, and uncertainty due to the lack of clinical guidelines on when to use imaging," she said.
CT scans are often unnecessary, Smith-Bindman added, and she believes that there aren't enough good guidelines regarding the use of scans in general.
Scanning technology has become much more accurate and useful over time, said Dr. Hiroto Hatabu, an associate professor of radiology at Brigham and Women's Hospital in Boston, who co-wrote a commentary accompanying the study.
For example, Hatabu said, scans make it much less difficult to diagnose bleeding in the brain.
But he acknowledged that high-tech scans can be overused. "I think we can use information technology and try to control it in the future. And there are ongoing efforts to decrease the radiation doses and get the same information."
The Medical Imaging & Technology Alliance, a trade organization for the medical imaging industry, announced last week that it has launched new projects to protect patients from being exposed to unnecessary levels of radiation.
More information
For more about CT scans, visit the U.S. National Library of Medicine.
