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Medical imaging test use rises over last 15 years

The use of CTs, MRIs and other advanced medical imaging tests has soared over the last 15 years, according to new research that raises questions about whether the benefits of all these scans outweigh the potential risks from radiation exposure and costs to the health care system.

An examination of data from patients enrolled in six large health maintenance organizations found that doctors ordered CT scans at a rate of 149 tests per 1,000 patients in 2010, nearly triple the rate of 52 scans per 1,000 patients in 1996. MRI use nearly quadrupled during the period, jumping from 17 to 65 tests per 1,000 patients, according to results published in today’s edition of the Journal of the American Medical Association.

These and other tests have meant that more patients have absorbed more ionizing radiation as part of their medical care. The proportion of patients in the study who had any amount of radiation exposure – driven by the use of CTs – rose from 28.5 percent in 1996 to 36.2 percent in 2010; among them, their average exposure jumped from 4.8 millisieverts to 7.8 millisieverts.

Advances in imaging technology have allowed doctors to peer inside the body with striking resolution. Computed tomography, or CT, scans combine a series of X-rays into a detailed three-dimensional image. Magnetic resonance imaging machines detect energy emitted by hydrogen atoms in the body and convert that into pictures. Both tests can reveal blockages in arteries, bleeding in the brain, tumors and other life-threatening conditions.

Although MRIs do not use ionizing radiation, CTs do, and that can damage the DNA in cells and lead to mutations that cause cancer. A number of recent studies have linked increases in medical imaging to higher rates of radiation-induced cancers, including a report last week in Lancet that showed a correlation between CT scans in children and their subsequent risk of developing brain tumors or leukemia.

The JAMA report is the first large study to focus on imaging use in health maintenance organizations. The findings suggest that profit-seeking on the part of doctors is not the primary cause of the increase in testing.

Study leader Rebecca Smith-Bindman, a radiologist and epidemiologist at the University of California, San Francisco, offered other explanations for the increase in testing, including unrealistic expectations about the ability of CTs and MRIs to show what is wrong with a patient and doctors’ fear that if they don’t order the tests, they will miss something that could lead to a lawsuit.