The use of computed tomography (CT) scans as a diagnostic tool has grown explosively over the past 25 years — from 3 million in 1980 to 62 million last year in the U.S. alone.

Now we're getting worrisome news about cancer because CT scans expose people to much larger doses of radiation than conventional x-rays.

Should you be worried? Let's look at the pros and cons of this remarkable tool.

The standard 64-slice CT scanner can detect 90 percent of coronary artery blockages and rule out major blockages in 83 percent of patients tested.

And as the technology continues to improve, CT scans could potentially eliminate many of the 1.3 million invasive cardiac catheterizations now done each year in the U.S. Some experts even suggest using CT scans as an alternative to cardiac exercise stress testing done on a treadmill.
 
But this remarkable technology has one sizable drawback: Even though CT scans provide more information than conventional x-rays, they also expose people to much larger doses of radiation. Radiation causes permanent damage to DNA and increases the risk of cancer. And that damage doesn't go away; on the contrary, it accumulates over a person's lifetime.

For example, an abdominal CT scan exposes the stomach to about 40 times more radiation than a conventional x-ray of the stomach. And a recent New England Journal of Medicine report estimated that radiation exposure from current use of CT scans may eventually become responsible for 1.5 percent to 2 percent of all cancers. Most physicians, and even many radiologists, underestimate the radiation exposure from a CT scan.

Troubling, too, are the 4 million or so CT diagnostic scans performed on U.S. children each year. Children are more sensitive to radiation damage and have the potential of developing radiation-induced cancer over many more years of life than do adults. 

So what should you do? Most of us probably have little cause to worry about our past or future CT scans greatly increasing our risk of cancer. Nevertheless, I think we would all be wise to ask our doctors what they expect to learn from, or do with, the results of that CT scan they've recommended for us or our children.

Personally, I would think twice right now about having a CT scan to determine whether my coronary arteries are obstructed. Since a blockage can still be present in nearly 20 percent of people with a negative CT scan, a doctor might still wish to proceed with invasive coronary angiography or, if the suspicion of a blockage is great, repeat the CT scan later.

If you have the choice, you might wish to wait for the next generation of CT scanning equipment. The new 320-slice CT machines, although not yet available, are five times more powerful than current 64-slice machines and will undoubtedly provide even more useful diagnostic information.