The use of CT scans, MRIs and other imaging tests has skyrocketed over the last 15 years, leading some experts to raise alarms over the potential risks of patients’ increased exposure to radiation.
Dr. Rebecca Smith-Bindman, a professor of radiology and biomedical imaging at the University of California San Francisco, and her colleagues report that between 1996 and 2010, the use of computed tomography (CT) scans nearly tripled, from 52 scans per 1,000 patients to 149 scans per 1,000 patients, and rates of magnetic resonance imaging (MRI) increased fourfold, from 17 scans per 1,000 patients to 65 scans per 1,000 p. Nuclear medicine and ultrasound rates also soared.
The rise in CT scans is particularly concerning, says Smith-Bindman, since the technique involves exposure to ionizing radiation, which is associated with increased cancer risk. Typically, the doses of radiation required for a CT scan are about 10 times those required for conventional X-rays. Between 1996 and 2010, the use of CT scans climbed nearly 8% annually. That translated into a doubling of radiation exposure per capita among the study participants, from 1.2 mSv to 2.3 mSv, as well as a doubling of the portion of patients who ended up receiving high (>20-50 mSv) or very high (>50 mSv) doses of radiation from the scans.
“These results confirm that we have to use CT scanning judiciously,” says Smith-Bindman. “While the test can have great benefit, it can also have the potential to cause real and significant risk.”
Indeed, in a study recently published in The Lancet, scientists found that otherwise healthy children who had multiple CT scans — after falls, accidents or to diagnose infection — were three times more likely to develop brain tumors and four times more likely to be diagnosed with leukemia later on, compared with children who were exposed to less radiation.
In the current study, Smith-Bindman and her team analyzed the medical records of patients enrolled in six large managed care systems throughout the U.S. Previous studies of rates of advanced medical imaging use have focused on people insured by Medicare, suggesting that increasing use of these expensive scans was driven in part by the fee-for-service insurance model that rewards doctors for ordering more tests. But Smith-Bindman and her colleagues found the same increases in privately insured populations in which doctors are paid a salary or fixed rate and have little financial incentive to test more.
So why the soaring rates? Part of the reason is medical: advanced imaging tests are a powerful way to diagnose internal injuries following a major trauma or accident without having to do surgery. The scans can also identify hidden causes of illness, such as infections in the abdomen that cause patients vague pain that isn’t obviously triggered by anything the physician can see.
Another powerful reason: the fear of malpractice lawsuits. Because CT scanning technology is ubiquitous, and because it is so effective, many doctors order the tests as a fail-safe, to protect themselves in case they might have missed some potentially life-threatening condition. In fact, many patients come to the doctor expecting to be scanned, and feel they haven’t been provided adequate care if their doctors don’t order a CT.
“We’ve lowered our threshold, so now we use [CT] so frequently and for any reason that we probably tipped the balance toward using it more than is clinically indicated or necessary,” says Smith-Bindman. It’s often easier for a doctor to order an imaging test than it is to spend more time with the patient discussing his or her symptoms to determine whether the test is really necessary, she says.
Many experts say that the doses of radiation required by advanced imaging technologies like CT scans have come down in the past decade, but Smith-Bindman says more studies are needed to confirm that. In the meantime, both patients and doctors can be more proactive in reversing the screening trend. Patients can ask doctors about alternative tests that don’t involve radiation, such as ultrasound, particularly for children. To diagnose cases of appendicitis in youngsters, for example, ultrasound may be sufficient, and could spare children from the added exposure to radiation from a CT scan.
Doctors can help reduce CT scan overuse by limiting the number of unnecessary “repeat” scans, which are ordered when images can’t be easily shared from one facility to the next — electronic health records should help control such extra testing.
And finally, particularly when it comes to monitoring cancer patients, physicians can be more judicious about exactly how often they need to image patients to check for recurrent growths. “The images have gotten so much better, that we see much more,” says Smith-Bindman. “And we see so much that we don’t know what to do about half of it. If things are so small that we can’t tell what it is, we have to be more willing to say it’s probably nothing and not follow it up with such frequent scanning.”
Given that modern patients and doctors want to be as informed as possible, it’s not going to be easy to counter the expectation for more and more testing. With the potential long-term risks associated with exposure to CT radiation, however, experts warn that it’s high time we step back and make sure that each scan is necessary and can provide a justifiable health benefit.
The current study was published in the Journal of the American Medical Association.