The use of costly advanced imaging techniques in U.S. emergency rooms tripled in a decade, according to a study in the Journal of the American Medical Assn., meaning many more patients were exposed to higher levels of radiation.

Researchers from Johns Hopkins University in Baltimore studied data on emergency room visits from 1998 to 2007, looking for evidence that “excessive use of medical imaging increases healthcare costs and exposure to ionizing radiation (a potential carcinogen) without yielding significant benefits to all patients,” according to the JAMA report. They found that, while the use of the scans went from 6 percent of ER visits in 1998 to 17 percent in 2008, there was no corresponding increase in the diagnosis of life-threatening conditions or hospital admissions.

“We didn’t notice just a small increase in the utilization of advanced imaging. It was a really significant increase without a corresponding increase in the diagnosis of life-threatening illness,” lead researcher Dr. Frederick Korley told the Bloomberg news service.

“Emergency departments in the United States are excellent at rapidly diagnosing and treating life-threatening illnesses. However, we need to better understand how to provide the same level of care in a cost-effective way,” Korley said, according to BusinessWeek.

Dr. Raul Uppot, an assistant professor at Harvard Medical School, told the magazine that the study neglected to address a key aspect: The importance of negative results from the scans.

“The technological ability to do this in 2010 assures the ER physician that he or she has made a correct diagnosis, reduces the wait time and uncertainty anxiety for the patient, and reduces health-care costs,” Uppot said. “What that the authors completely ignored, and surprisingly do not even address in their conclusion, is the impact of a negative medical imaging study.”

And according to Dr. Levon Nazarian, doctors fear a malpractice suit if they fail to order the tests, which can cost between $270 and $4,800.

“Doctors will say, ‘I need this test for my own peace of mind. If I don’t do this test I may get sued,'” Nazarian, a professor of radiology and vice chairman for education at Thomas Jefferson University Hospital in Philadelphia, told BusinessWeek.

Another factor is the pressure to quickly move patients through the ER. Docs believe they can arrive at a diagnosis in less time, Nazarian added.

Korley’s team found that, of the 324,569 ER visits during the decade studied, 20 percent were injury-related. While the rate of imaging scans rose by a factor of three, there were no statistically significant increases in hospital or intensive care admissions for life-threatening conditions such as cervical spine fracture, skull fracture, intracranial bleeding, or liver and spleen laceration. The prevalence of life-threatening conditions rose from 1.7 percent in 1998 to 2.0 percent in 2007, according to the study.

Admissions to hospitals or ICUs also showed no significant change. Hospital admissions among the sample were 5.9 percent in 1998 and 5.5 percent in 2007; ICU admissions were 0.6 percent in 1998 and 0.8 percent in 2007.

Visits involving the imaging scans took 126 more minutes than visits which didn’t involve CT or MRI.