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.
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