In the 1950s, a Corvette cost $2,900, watches glowed in the dark from radium-painted dials and shoppers slipped their shoe-clad feet into X-ray-generating fluoroscopes to check the fit.

Over time, some things have changed a lot (a new Corvette today costs almost $50,000), and other things, not so much. People agree that exposure to radiation from watches and shoe machines is risky, but we’re still exposing ourselves to needless radiation. Case in point: the low-level radiation from a typical CT scan.

Though no one knows exactly how much radiation exposure boosts your cancer risk, everyone from NASA to the American Cancer Society is pretty sure that exposure to any has some very small effect, and repeated exposure, well, that might be measurably harmful.

But according to a new study in the journal of the American Medical Association, 33 percent of you don’t know that CT scans produce radiation; and only 5 percent of you think a scan would increase your lifetime risk of getting cancer.

Fortunately, there are alternatives: Ultrasound or MRI may be used in place of a CT scan in specific instances — for example, to check for appendicitis (ultrasound) or to look at tendons and ligaments (MRI). What CT scans do best is see the chest and lungs, torn or damaged organs and broken bones.

And for those purposes, make sure the benefits you’re getting are greater than the risks. Ask — every time — “Do I need a CT scan, or is there an alternative imaging technique that would work as well?”

Be the informed patient.

Mehmet Oz, M.D., is host of “The Dr. Oz Show,” and Mike Roizen, M.D., is chief medical officer at the Cleveland Clinic Wellness Institute. To live your healthiest, visit sharecare.com. Distributed by King Features Syndicate, Inc.