The health risk posed by excessive CT scans

Nov 29 2007

Scientists in the United States have expressed concern about the number of computed tomography or CT scans now being performed.

They are suggesting that the 62 million CT scans done each year may be excessive and could in some cases cause cancer.

Researchers David Brenner and Eric Hall of Columbia University Medical Center in New York say even though CT scans save lives and speed up the diagnostic process, they may be responsible for 2 percent of all cancers in the next 20 to 30 years.

The two scientists believe doctors may be underestimating the radiation risk from CT scans and are ordering too many of them.

A CT scan can deliver 50 to 100 times more radiation than a conventional X-ray, depending on factors such as the site being examined and the machine being used.

Because their tissues are at least 10 times more sensitive to radiation than adults, children are more at risk from the scans and the long-term side effects have more time to appear.

The researchers say CT scans are particularly overused in looking for childhood appendicitis.

They also say a poll of physicians has revealed that perhaps one-third of the scans may be unjustified or an alternative technique, such as ultrasound would suffice.

However the researchers say it appears that as many as 20 million adults and more than 1 million children per year in the United States are being irradiated unnecessarily.

While they acknowledged that their is estimate based on the impressions of doctors they say research has yet to gauge the problem of unnecessary CT scans.

They were apparently shocked to discover how many doctors, particularly in emergency departments, had no idea of the magnitude of the doses or the potential risk that CT scans involve.

Brenner and Hall say it has been estimated that about 0.4 percent of all cancers in the United States may be attributable to the radiation from CT studies, but when this estimate is adjusted for current CT use, a more accurate number might be in the range of 1.5 to 2.0 percent once tumors from current exposures begin to appear.

They suggest that ultrasound and magnetic resonance imaging, or MRI, scans should be used instead of CT scans whenever possible.

Other suggestions include developing systems for discouraging doctors from performing unnecessary CT scans, reusing scans if patients are sent to another doctor or hospital, and urging patients, or their parents, to ask about the radiation risk involved in a CT scan.

Experts say the estimate is theoretical and doctors order CT scans because they can quickly spot a variety of potential problems that could be missed by other tests.

The American Cancer Society say concerns about excess exams and excess exposure, especially among pediatric patients, are appropriate.

The article is published in the New England Journal of Medicine.