Dangers of Having Too Many CT Scans

Some hospitals do more than needed, unnecessarily exposing you to cancer-causing radiation, Consumer Reports finds

Published: April 2014

If you have severe pain in your abdomen or chest, fall off your bike, or are in a car accident, there’s a good chance that you’ll undergo a CT scan. Those painless, quick tests can be lifesaving, by providing doctors detailed images of your bones, muscles, and even your blood vessels. But the tests pose risks, too, by exposing you to cancer-causing radiation. And our updated hospital Ratings show that some hospitals do more than they need to, exposing you to unnecessary risks.

Radiation risks

In the U.S., use of CT scans has grown more than three-fold since 1993 to an estimated 85 million each year. Many of those are no doubt done for good reasons. But over the last several years, researchers have grown increasingly worried about the radiation from all of those CT scans.

For example, a study in the Archives of Internal Medicine found that 29,000 future cancer cases in the U.S. could be linked to the CT scans done in just 2007. Children, who may be exposed to adult-sized radiation doses when they have a CT scan, are especially at risk. That’s because they are more sensitive to radiation and have more remaining years of life in which to develop a radiation-induced cancer.

Too many scans

Of course, no one is saying you should not get a CT scan when you really need it. But growing research suggests that sometimes doctors use doses that are higher than necessary. For example, a 2009 study in the Archives of Internal Medicine analyzed the radiation dosages delivered by 11 common CT scans at four San Francisco-area centers. Researchers found that the typical dose of radiation used for routine abdomen and pelvic CT scans was about 66 percent higher than necessary.

It’s also a problem when doctors order unnecessary scans. That sometimes happens in hospitals, particularly when doctors order so-called “double scans.” That means they first order a regular CT scan, and then a second with a contrast dye that can make certain areas more visible.

Sometimes doctors do that simply because they believe that’s faster and safer. “It’s a simpler decision to perform the scan without and with contrast since it supports the reasoning of, ‘If I do both, I cover all the bases for answering the question,’ ” said James R. Duncan, M.D., Ph.D., a professor of radiology at the Mallinckrodt Institute of Radiology at the Washington University School of Medicine in St. Louis.

But such double scans usually aren’t necessary. Probably less than 1 percent of patients undergoing chest CT scans should get double scans, our previous report found. Double scans of the abdomen are needed more frequently, often to define abnormalities in the liver, kidney, and pancreas, experts say.

What our Ratings show

Many hospitals now report information on the number of double chest and abdominal scans they perform to the Centers for Medicare and Medicaid Services. And we use that information in our hospital Ratings. (Read more about how we rate hospitals.)

Only 30 percent of the hospitals in our Ratings had double-scan rates of 5 percent or less in both categories, which is the cutoff we use for a top rating. Abdominal CT scans are particularly worrisome: 21 percent of hospitals in our Ratings earned our lowest Rating in that measure, performing double scans on more than 20 percent of their abdominal CT patients. Fewer hospitals had high rates of double chest CT scans: 7 percent of hospitals earned our lowest Rating in that measure.

What to do

Before ordering a CT scan, physicians should ask themselves, “How will the results of this CT scan change what I do?” Dr. Duncan said. “If it doesn’t change anything, then they are basically saying they are doing this to satisfy a curiosity.”

If your health care provider recommends that you or someone you care for have a CT scan, ask why it‘s needed, how the results will affect treatment, and if another imaging test that involves less radiation could be done. If a CT scan is the only option, ask the doctor to avoid double or repeat scans and to image only the necessary area. Request that the lowest effective dosage be used. And if your child is being scanned or you are a small person, ask the technologist to make sure the dosage has been dialed down. (Often a machine is set at a specific dose and has to be adjusted.) “If you’re a big adult, you need more radiation to get a quality image,” Dr. Duncan said. That’s not the case with a small woman or a child.

Finally, when choosing a hospital, use our Ratings to see how hospitals in your area compare in avoiding double scans and several other measures of hospital safety.

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