Neither doctors nor patients like uncertainty, and CT scanners and other imaging modalities are not only widely accessible but provide beautiful and precise images. Doctors worry about being sued if something turns up on some later CT scan, so they order one now, just in case. Also, some doctors own their own CT scanners, making a pretty penny with each scan. And as doctors’ physical examination skills wane, there’s a greater reliance on medical imaging. Even more reasons: CT scans often get repeated when a patient goes to one hospital because it saves doctors the hassle of communicating with another hospital’s medical records department. And it’s not only doctors: Patients are eager to get the newest high-tech imaging (thanks to direct-to-consumer marketing), and since medical insurance frequently covers these scans, neither party needs to worry about the financial consequences of ordering a test that’s being done for less-than-compelling reasons.
There are many well-meaning doctors who believe they’re doing the right thing by ordering unnecessary scans. I remember one woman, years ago, who’d been suffering from severe headaches for two months and was convinced she had a brain tumor. I was sure she didn’t—her exam was normal and the pattern of headaches corresponded to the increasing stress in her life. Ordering a CT scan didn’t make sense, although she desperately wanted one. But her obsession with brain cancer was making her sick—she’d missed many days of work because of overwhelming anxiety. So one day I relented. I figured that putting her mind at ease would outweigh any risks from radiation and the cost of the scan. The CT scan was negative, her headaches disappeared, she went back to work, and the story seemed to have a happy ending. In retrospect, I don’t think it was worth exposing her to radiation and possibly—and ironically—increasing her risk for cancer. (Another study out last month found that children under 15 who had two or three head CT scans had three times the risk of brain cancer; the overall risk was very small, but it was still a risk.)
A single CT scan can expose the body to about the same amount of radiation as 100 X-rays, and in some situations, up to 400. (See Table 3 in this study for a comparison of radiation doses of various imaging tests.) But it’s not like eating two slices of cheesecake and going for a long run the next day to burn off the calories: Radiation exposure from medical imaging is likely cumulative. According to Dr. Howard Forman, professor of diagnostic radiology at the Yale School of Public Health and a practicing emergency and trauma radiologist, the damage adds up: “It’s like cigarette smoking: More is worse, but no matter how few or many cigarettes you smoke, it’s harmful.”
The good news is that doctors and hospitals are starting to pay closer attention. Dr. Marilyn Goske, a professor of pediatric radiology at Cincinnati Children’s Hospital Medical Center and chairwoman of the Image Gently campaign, put it this way: “Look at the American car—it used to be a Cadillac with the big fins, and you didn’t pay attention to gas mileage. Now consumers are gas conscious. This is what’s happening in the CT world with increased emphasis on lowering radiation dose when possible.” In California, as of July 1, the dose of every CT scan must be documented in an electronic medical record. Forman offered a suggestion for the next step: a simply but strongly worded document that would be automatically generated every time a CT scan is ordered. “This patient has had four CT scans, each equal to x-number chest X-rays; we don’t know the definitive risk, but we know that patients with x times this exposure in Japan [after the atomic bombs] developed cancers.” At Southern New Hampshire Medical Center, Dr. Steven Birnbaum has created a sensible program to flag any patient under 40 who has had more than five CT scans for benign diagnoses. The message to doctors is to think about whether the next CT scan is truly necessary and to discuss the increased risk with the patient.
In the world of pediatrics, the numbers are already improving. One study of CT use in pediatric emergency rooms found that the number of CT scans in kids fell between 2008 and 2010. And there’s more research ahead: In response to the Institute of Medicine article, Dr. Eric Winer, chief scientific adviser and chair of the scientific advisory board for Susan G. Komen for the Cure, told me that his foundation is funding studies looking at how to minimize risks from ionizing radiation from imaging studies.
And what’s most important is that there is mounting pressure for doctors to justify the CT scans they order—not only to the radiologist who will perform and interpret the test, but to the patient. Websites of public education campaigns like Image Gently and Ultrasound First provide information to patients and health care professionals about the importance of “child-sizing” radiation doses, since children are much more vulnerable to effects from ionizing radiation (and have more years ahead of them to potentially develop cancers triggered by those very scans intended to help). There’s also the Image Wisely campaign, part of the broader Choosing Wisely campaign, which provides evidence-based recommendations for common scenarios. Many, not surprisingly, have to do with CT scan overuse.
Perhaps the simplest ways to protect ourselves and our children from the risks of unnecessary CT scans (and from appropriate but too-highly dosed CT scans) are these: Keep track of your imaging tests and share this list with any doctor recommending an imaging study (yes, there are apps for this), and don’t be too polite. The next time a doctor recommends a CT scan or any other imaging test, you shouldn’t assume it’s the only option. Ask if the result will change the treatment and whether there’s a safer way to get the necessary information. There’s a good chance your doctor hasn’t thought about it.
Correction, Aug. 2, 2012: This article originally stated that a researcher estimated that 6 percent of breast cancers would be caused by CT scans in a single year in the United States. The researcher actually estimated that of the total number of cancers caused by CT scans in a single year in the United States, 6 percent of them would be breast cancers.