Skyrocketing numbers of expensive medical imaging procedures - from CT scans to nuclear stress tests - are not just straining the nation's health care system, but are exposing patients to significant amounts of potentially cancer-causing radiation even though little research has been done into whether those tests actually make people healthier, a new study suggests.

The tests, say the study's authors, may be doing more harm than good.


"One reason why these tests are being used more is they're getting better and better and they're an extremely helpful part of diagnosis and treatment," said Dr. Reza Fazel, a cardiologist at Emory University School of Medicine in Atlanta and the lead author of a study in today's New England Journal of Medicine. "But just because we have them doesn't mean we should use them. ... There's a cost with these tests, and it's not just dollars but radiation risk."

No one disputes that advanced medical imaging has transformed medicine by enabling physicians to detect diseases and other medical problems at early stages - and even cure them. But with a rapid rise in expenditures on these tests, one of the fastest-growing costs in health care, there have been calls to rein in the use of unnecessary imaging. CT scans alone, which expose patients to moderate amounts of radiation for each test and are many times repeated, have quadrupled since 1992, according to a 2007 study.


Dr. Michael S. Lauer, director of the NIH's National Heart, Lung, and Blood Institute in Bethesda, said one of the biggest obstacles to restricting the number of radiologic tests is that not enough is known about whether most of them make patients feel better or live longer. X-rays for broken bones are obvious, but high-tech CT scans of the heart haven't been medically proved to improve health and they expose patients to much higher levels of radiation. "The problem that we have here is we don't know if there are too many [tests given], too few or just right," said Lauer, who was not part of the study.

He says only a few imaging tests - mammograms for discovering breast tumors, ultrasound of the abdomen for diagnosing aortic aneurysms - have been scientifically proved to save lives. Many have never been studied in large-scale clinical trials. In addition to leading to high doses of radiation, some tests can find cancers so small they might never have caused problems, leading to unnecessary surgeries and psychological distress.

The New England Journal of Medicine study shows that some of the most popular tests performed - nuclear stress tests, CT scans of the abdomen, pelvis and chest - also provide some of the largest doses of ionizing radiation. MRI, also popular, does not use radiation. As many as 4 million adults under age 65 per year, Fazel estimates, are getting high doses of radiation that could put them in danger in the long term.

Although elderly patients are likely to get more tests, Fazel's study includes some striking data on how many tests even young people get. His research focused on three years' worth of United Healthcare claims data from five major cities, a population of nearly 1 million nonelderly adults. Seven in 10 of people ages 18 to 64 got at least one test over three years and nearly half of those between 18 and 34 got a test. Sometimes, patients get repeated tests by different doctors who don't know the patient has already been scanned. Newer scans - some that use reduced levels of radiation - tend not to replace older tests, just supplement them.

Though the annual average radiation exposure from the tests was low, researchers found about 20 percent of patients were exposed to moderate radiation doses and 2 percent were exposed to high levels. Nearly a quarter of the radiation people received came from CT scans to the heart, so-called "super X-rays" that provide 3-D pictures. And cumulative imaging-related radiation over time, researchers said, can account for 2 percent of cancers.

Congress enacted limits in 2006 to curtail Medicare spending on medical tests and scans, and private insurers have started requiring pre-authorization before some of the more advanced CT scans. A Government Accountability Office report last year showed a 12 percent decline in imaging spending from $13.8 billion in 2006 to $12.1 billion in 2007. But over the same period, the use of CT scans and MRIs continued to rise.

Jean Marshall, a health economist at Georgetown University who has studied spending patterns, said the health care system's fee-for-service model, in which doctors are paid for each service they perform, encourages unnecessary tests. Some doctors who order imaging tests own the equipment and can be reimbursed at both ends. Marshall said she wasn't surprised that the number of tests continued to rise as the reimbursements went down.

"The reimbursement system needs to be changed," Mitchell said, "because it's given them all the wrong incentives." Reforming the way tests are reimbursed, she said, is a touchy subject.


"Every dollar of health care expenditure represents income to a provider - that's why cutting costs is so hard. Do you blame them? I don't."

Many doctors say they order the tests because they think that's what is best for an individual patient. Also, fears of malpractice lawsuits may lead physicians to order extra tests in some circumstances.

"It's not that we should stop imaging," said Dr. Rebecca Smith-Bindman, a professor of radiology and epidemiology at the University of California-San Francisco and co-author of a report on medical imaging in the journal Health Affairs last year. "But the sense is that all imaging is good. Some is good. Some is harmful. We need to get appropriate imaging."

Many medical experts said they worried about whether imaging is used too much for managing chronic illness. Once the disease is diagnosed, in most cases, new imaging isn't needed, Smith-Bindman said. Guidelines for when tests should be used need to be developed and followed and kept current with evolving science.

Meanwhile, she said, Medicare continues to pay for nearly all scans. Only recently did it refuse to pay for screening colonscopies using CT, she said. "They've just been willing to pay for anything," she said.