The Popular Test You Don’t Need

What's wildly popular but has a disturbing dark side? No, not embattled golfer Tiger Woods. We're talking about recent reports that high-tech CT (computerized tomography) scans raise your cancer risk more than anyone ever expected.

The use of CT scans (sometimes called CAT scans) has grown by leaps and bounds in the past 20 years. That's because they're painless, noninvasive, fast, and give doctors detailed images of everything from brain injuries and cancers to fractures, kidney stones, and ruptured appendixes. The scans are also credited with making exploratory surgery a thing of the past. So it's not hard to see why Americans and Canadians now get 75 million of them a year.

CT's dark side? A single scan can deliver 100 to 400 times more radiation than a traditional x-ray. A new National Cancer Institute study estimates that 29,000 cancers and 15,000 cancer deaths (more than the deaths from ovarian cancer) will be triggered by the CT scans done in 2007 alone. Meanwhile, the FDA is investigating more than 200 claims of scan-related radiation overdoses in California and elsewhere.

Does this mean you should avoid CT scans the way big-name sponsors are shunning Tiger? No, don't swing from scan-a-mania to scan-a-phobia. These tests can be lifesavers, provided you and your doctor use them only when the benefits outweigh the risks. Here's how to do that:

Ask, "Do I really need it, Doc?" Will a scan really provide vital info? Or can it be delayed, avoided, or replaced with a radiation-free alternative, such as an ultrasound or MRI? Ask. Up to 1 in 3 CT scans are unnecessary, say researchers in the United States and Canada. Top causes of scans you don't need: fear of lawsuits; ordering a repeat scan instead of getting records of one you've already had; and profits (docs or med centers may have a financial interest in the scanning equipment). Of course, if a CT is vital -- it's being used to guide cancer treatment, help diagnose a hip injury, or pinpoint an appendix about to burst -- get it if the doc feels no ultrasound or MRI alternative will do.

Be extra careful if you're female or a parent. Women are at higher risk because their breast and lung tissue is especially sensitive to radiation; kids (including teens), because their bodies are still growing. Be sure to ask if the scanner has been adjusted for your size and weight, and if technicians are using the lowest possible settings to get the images needed. Also ask for shields to protect breasts, ovaries, eyes, thyroid, or other areas.

Consider skipping calcium scans. Many hospitals and clinics offer CT scans that hunt for calcium in the arteries, a sign of heart disease. These coronary calcium scans can be useful for some people with heart disease or a history of heart attacks, but there's a reason most insurance policies don't cover them for everybody: There's no proof they help prevent heart attacks. Instead, most people just get unnecessary radiation.

Keep your own scan count. A handful of doctors and medical centers keep track of their patients' total scan count -- something we hope will be universal when electronic medical records are the norm. Meanwhile, keep track yourself, and let your doctor know the total so alternatives can be weighed. Not convinced? Try entering the info into the calculator at http://www.xrayrisk.com. You'll get an estimate of your cumulative radiation dose and increased cancer risk.