Industry continues to debate CT radiation exposure concerns
While some medical groups have issued warnings against overusing CT exams—especially for children—due to concerns for radiation exposure and increased cancer risk, some industry experts have expressed their concerns about frightening patients away from the invaluable tests.

"You don't want people to avoid getting a potentially life-saving diagnosis or therapy because they are afraid to get a CT scan," Arl Van Moore Jr., MD, a Charlotte, N.C.-based radiologist who chairs the American College of Radiology's board of chancellors, reported to The Washington Post. "When a scan is done the right way for the right reasons, the benefits clearly outweigh the risks of doing it."

According to a November 2007 study published in the New England Journal of Medicine (NEJM), CT scans could be responsible for as much as 2 percent of all cancers in the United States in the next 20 to 30 years due to radiation exposure. This news immediately sparked a debate about whether the increasingly ubiquitous tests are being overused, exposing millions of Americans to needless risk.

"The radiation doses from CT have been pretty clearly demonstrated to increase cancer risk," said David J. Brenner, PhD, DSc, a professor of radiation oncology at Columbia University who co-authored the NEJM study. "On an individual basis there's probably not a big risk, but a small cancer risk applied to an increasingly large population spells trouble down the road. That's the concern."

According to Brenner, it is estimated that more than 62 million CT scans are currently performed each year in the United States, as compared to approximately three million in 1980.

According to The Post, while the value of CT scans for screening remains the focus of debate, no one questions the value of the tests for allowing doctors to quickly diagnose a wide variety of health problems, including head injuries, heart problems, cancer, appendicitis, fractures and gallstones.

"CT is probably the biggest advance in diagnostic radiology that has ever occurred," Thomas Ohlhaber, deputy director of the Division of Mammography Quality and Radiation Programs at the FDA, told The Post. "Exploratory surgery that was common 10 or 15 years ago has virtually disappeared and all the risks associated with that have gone away because of CT. But nothing comes free of risks."

Because it would take decades to follow a large number of patients who have undergone CT scans to determine the exact risks posed by the exams, there are no direct data demonstrating the danger. But researchers have estimated the risk based on what is considered the best information available about the health effects of radiation—data collected from survivors of the atomic bombings of Hiroshima and Nagasaki, as well as exposure of nuclear plant and medical workers, according to The Post.

Using that information, experts have estimated that every 1,000 to 2,000 CT scans may produce one fatal cancer that would not have occurred otherwise.

"Twenty years from now we could see a huge bonus of cancer coming through because of indiscriminate use of CT today," Launders said. "That's the real issue people are worried about."

The Post reported that although the companies that make the CT machines have been developing new protocols designed to minimize radiation exposure, particularly for children, everyone agrees that the most prudent thing to do is to eliminate unnecessary use.

According to The Post, while there are scant hard data about how often CT scans are done needlessly, several experts estimated that perhaps one-third could be eliminated. There are many reasons CTs may be overused. Some CTs are full-body "virtual physicals" performed on people who appear perfectly healthy—a practice widely opposed by medical authorities.

Some doctors order the tests to stave off accusations that they withheld the most cutting-edge technology from their patients, The Post reported. In other cases, overuse results from worried patients and from parents demanding CT scans that may not be needed.

Other times doctors may not realize how many tests involving radiation patients have already undergone—information that could influence a doctor's decision—or may order a CT scan when other tests that do not involve radiation, such as a blood test, an MRI or an ultrasound, would suffice. "There are alternatives that are arguably just as good," Brenner said.

Patients can also take more responsibility for reducing the number of unnecessary scans, according to The Post. "If a patient walks in and says, 'Tell me what the dose is from this and tell me what the risk is,' they are going to make the doctor start thinking about it," Mettler said.