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 typica