- By Debra Witt
For the last decade, the number of computed topography, or CT, scans ordered for patients in the United States has risen each year by about 10 percent. CT scans use X-rays to generate images of cross-sections of the body and are employed for a variety of diagnostic needs. Advances in radiology allow doctors to use scans to quickly identify, and therefore better treat, everything from lung cancer and blood-vessel blockages to kidney stones and appendicitis.
But as scanning has become more routine, patient advocates and others in the medical community, including radiographers — the specialists who administer the scans — are asking if physicians are needlessly, even recklessly, exposing patients to unnecessary doses of radiation.
As more physicians have installed high-tech scanning equipment in their offices, critics charge that they have become prone to ordering unnecessary scans to recoup their investments. The more radiation used in a CT scan, the higher the quality of the image, but patient advocates say some doctors are too quick to use higher-radiation imaging as a form of "defensive medicine," to prevent misdiagnosis and its potential malpractice risk. On the other hand, many patients may be guilty of pushing doctors to prescribe scans in the belief that they'll provide the best insights modern medicine has to offer.
"Should patients be afraid every time their doctor sends them for a mammogram, CT scan or dental X-ray? No. The stress that fear causes is more harmful to their bodies than that one-time dose of radiation," says John Boone, a professor of radiology at the University of California-Davis, who has authored several studies investigating radiation exposure risks from medical tests. "Should they ask their doctor why they want this testing done and what they hope to gain? Absolutely. The sheer number of CT scans that are being performed each year — more than 70 million — highlights the need for a better understanding of the health risks of radiation exposure versus the benefits of enhanced diagnosis."
"The risk of getting cancer from medical radiation exposure is low," Boone says, "but it's not zero." A growing body of research is attempting to pin down the link between scanning and cancer. By some estimates, CT scanning is responsible for as much as 2 percent of all cancer cases in the United States. Radiation exposure can damage your DNA, which can lead to cancer 10 or more years later. However, it's difficult to pinpoint the exact cause of many cancers. And many of the studies being relied upon for analyses of radiation risk are based on research related to World War II atomic bomb survivors, who are unlike modern patients in that they were exposed to an immediate, massive dose of radiation, as opposed to several much smaller exposures over time.
Can You Limit Your Exposure?
Radiation exposure is measured in units called sieverts. One sievert would constitute a massive dose and cause acute radiation sickness; 10 sieverts is fatal. Most of the radiation we are exposed to is measured in microsieverts, or millionths of a sievert. To put it in perspective, we naturally absorb about 3,000 microsieverts of radiation every year from the environment alone. A traditional dental X-ray delivers five microsieverts; a standard chest X-ray, 100; and a mammogram, 400. CT scans, though, can deliver a dose of radiation up to 500 times stronger than standard x-rays. A virtual CT colonography comes with an average dose of 10,000 microsieverts; a CT scan of the abdomen and pelvis exposes patients to 15,000.
"It's very difficult for doctors and patients to concretely grasp the risks posed by medical radiation exposure. The numbers can be both complicated and confusing," says Dr. Ella Kazerooni, director of cardiothoracic radiology at the University of Michigan, who has worked with physicians groups to develop guidelines for safer screenings. "The studies that get reported in the news tend to talk about the risks of exposure, but not about the possible life-saving benefits of having the test."
Kazerooni urges doctors to take an evidence-based approach to imaging. Doctors shouldn't call for a CT scan, she advises, if it hasn't been shown in clinical trials to lead to a better outcome than available tests that don't involve radiation. For example, a recent study of the effectiveness of low-dose CT scans to detect lung cancer showed such clear, significant benefits that the project was stopped early. On the other hand, the use of CT scans to look for calcium buildup in coronary arteries is on the rise, she says, even though it has not been proven that the scans provide better data than ultrasound tests.
As patients, we can take some responsibility by questioning any test ordered by our physicians. What is the scan for? What will the doctor do with the information gleaned from it? What are the risks of having the scan? What are the risks if you don't have it, or if you wait to have it? Are there alternative tests that could provide the same information?
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"It's just crazy when I hear stories — and there are many of them — about people refusing a pre-operative CT scan out of fear of radiation," Boone says. "It's pretty important for your surgeon to know what's inside you before he or she cuts. But I also think it's pretty crazy for someone to get a CT scan for, say, headaches or belly aches before other diagnostic tools have been tried."
Tracking the number of CT scans, PET scans and X-rays you've had is important to help avoid overexposure from redundant exams. "It's not uncommon for different doctors to order essentially the same test," says radiographer James Johnston, dean of the College of Health Sciences and Human Services at Midwestern State University in Texas and a spokesperson for the American Society of Radiologic Technologists. "That's unnecessary exposure. Speak up and let each of your doctors know what the others have ordered and share the results."
There are national efforts to convince doctors to limit the overuse of scans and to empower patients to question them. The Choosing Wisely campaign, launched in 2012 by the ABIM Foundation, has brought together the leaders of groups representing more than 350,000 doctors to identify common tests and procedures that may be overused, unnecessary or potentially harmful to patients, including a range of scans.
"As Americans, we're hooked on technology," ABIM chief operating officer Daniel Wolfson recently told Next Avenue, "and not always with the accompanying evidence that it makes a difference. When patients know what is necessary and what's not, they can be less demanding."
Major equipment suppliers, like General Electric, Siemens and Philips, have also introduced new software packages that enable physicians to get high-quality scans using as much as 60 percent less radiation than current tests, although it will take time for such technology to filter through the nation's practices. "The technology isn't the problem," Johnston says.
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One more piece of advice: If you've been experiencing symptoms like severe headaches or abdominal pain for several days, seek the help of your primary care physician before the discomfort reaches the point where you need to head to the emergency room. "ER doctors are going to get you into the CT scan," Boone says. "It's their job to immediately rule out things like a stroke. At 1 A.M. in the ER, you will get a CT."