Computed tomography, or CT scans, were introduced in the 1970s. They allow doctors to see the inner workings of the human body through the use of multiple X-ray images. Their use has grown from 3 million a year in 1980 to more than 80 million today.
CT scans emit a powerful dose of radiation, in some cases equal to about 200 chest X-rays, or the amount most people would be exposed to from natural sources over seven years.
A dose like this can change the makeup of human tissue and create free radicals, molecules that can wreak havoc on human cells. Human bodies can often repair that damage – but not always. When they don’t, the damage can lead to cancer that can take from five to 60 years to develop, with risk that also depends on age and lifestyle.
“No one says that you should avoid a CT scan or other imaging test if you really need it, and the risk posed by any single scan is very small,” said Marvin M. Lipman, M.D., Consumer Reports chief medical adviser. “But the effect of radiation is cumulative, and the more you’re exposed, the greater your cancer risk.”
It’s essential, Lipman said, that consumers always ask doctors why they are ordering an imaging test and whether their health problem could be managed without one.
Doctors order millions of radiation-based imaging tests each year, but recent research shows that about one-third of these scans serve little if any medical purpose. Given the greater lifetime risk of cancer that comes with increased radiation, why is there so much overuse?
- Uniformed physicians. In a study of 67 doctors and medical providers caring for patients undergoing abdominal CT scans, fewer than half knew the scans could cause cancer. In another study, only 9 percent of 45 ER physicians said they knew CT scans increased cancer risk.
- Misinformed patients. Patients aren’t aware of the danger. A Consumer Reports survey of more than 1,000 adults found that less than one in six patients are told by their doctors about the radiation risks of medical imaging. Also many patients had mistaken assumptions about the risks. For example, almost as many – 17 percent – adults were very concerned about magnetic resonance imaging or MRIs, which doesn’t emit radiation, as were concerned about CT scans – 19 percent – which do emit radiation.
- Financial incentives. Most doctors are paid by volume, so they have an incentive to order tests. And many doctors have invested in radiology equipment or clinics. Research shows such physicians order far more CT scans and other imaging tests.
- Fear of lawsuits. Almost 35 percent of imaging tests are ordered mainly as a defense against lawsuits, not because of true medical need, according to a study presented at the 2011 meeting of the American Academy of Orthopedic Surgeons.
- Patient demand. If you or your child is in pain, it’s normal to want an imaging test to find out the cause. But that’s often not necessary or wise. Also, many back-pain sufferers, for example, ask their doctors for an X-ray or CT scan – and many doctors acquiesce – even though guidelines say such tests are only warranted if the pain lasts more than a month.
- Lack of regulation. About one-third of the people in the Consumer Reports’ survey assumed that laws strictly limit how much radiation a person can be exposed to during a CT scan. Unlike mammography, CT imaging doesn’t have any federal radiation limits. And, no national standards are in place for the training or certification of technologists who operate the machines.
Children and teens are particularly vulnerable to radiation. A 2013 Australian study looked at more than 680,000 people who had CT scans before the age of 20 and compared them with 10 million people younger than 20 who didn’t have a CT scan. It found that for every 10,000 young people scanned, 45 would develop cancer over the next 10 years, compared with 39 cancers among 10,000 people not screened.
Consumer Reports offers the following advice on what consumers can do before getting any radiation-based imaging tests done:
- Ask why the test is necessary.
- Check credentials of the facility and technicians.
- Get the right dose for your size.
- Ask for the lowest effective dose.
- Avoid unnecessary repeat scans.
The report on radiation overexposure is featured in the March 2015 issue of Consumer Reportsmagazine and is available at newsstands, local libraries, and www.ConsumerReports.org.