Danger: Body Scans

So-

called whole-body scans were originally used as a last-resort diagnostic tool to find hidden tumors in patients with cancer. But then the tests caught on among the healthy hypervigilant, who were drawn in growing numbers to walk-in clinics by aggressive TV and radio ads. In 2002, two years after Oprah Winfrey got scanned — and bubbled enthusiastically about the experience--32 million Americans shelled out as much as $1,000 apiece to get their bodies X-rayed in thin slices and reassembled into 3-D images detailed enough to show every blemish, scar and incipient tumor. The numbers are down slightly, owing to the economic downturn and, perhaps, repeated warnings that if you are relatively healthy, the scans will probably do you more harm than good.

But how much harm wasn't clear until last week, when a team of scientists at Columbia University reported in the journal Radiology precisely how much radiation you are exposed to in a single full-body scan. It turns out to be 100 times the radiation dose of a typical mammogram — or roughly equivalent to that received by Hiroshima survivors 1.5 miles away from the center of the atom bomb blast. According to David Brenner, lead author of the study, the risks associated with just one scan are relatively modest, likely to increase your chances of dying from a radiation-caused cancer to about 0.08%. But if you were to get scanned every year for 30 years, your risk of developing a radiation-related tumor would jump significantly, to about 1 in 50.

Most Americans are not getting annual scans — and now presumably even fewer will. Although full-body scans may still make sense for some patients, whatever information your doctor needs can usually be obtained by less extensive X rays — scanning just the kidney, for example, if what you are looking for is kidney cancer. Minimal scanning will also cut down on the chances that you'll find a growth that requires more invasive testing but turns out — and it usually does — to be perfectly benign.

There's a lesson here for all of us, doctors and patients alike: we should never order or submit to a high-tech medical test without weighing both the benefits and the risks.

Sanjay Gupta is a neurosurgeon and CNN medical correspondent