Most of the storefront enterprises that not long ago were pitching elaborate 3-D "multislice" CT scans to the worried well have disappeared. Once scanned, most people didn't come back for rechecks. Or, in many cases, patients discovered that suspicious spots and shadows weren't worth worrying about—but only after subjecting themselves to further tests, some of them painful.

The underlying technology held bright promise, however. And now, according to radiologists surveyed in Chicago at this week's annual meeting of the Radiological Society of North America, multislice scanning is closing in on the point where it could replace procedures long employed for evaluating the heart, colon, lungs, and other parts of the body for disease.

"Things are changing fast," says Elliot Fishman, director of diagnostic imaging at Johns Hopkins Hospital. "I'll probably get my head taken off for saying this, but I think multislice scanning will be widespread within five years."

That's because scanners are producing images with detail and dimensionality unimaginable just a few years ago. The latest scanners, from manufacturers such as Siemens, GE, Philips, and Toshiba, produce 64 X-ray slices of tissue per second as the X-ray generator spins around the patient. Each slice is as thin as 0.75 millimeters—less than 1/30 inch. While a large number of thin slices requires a higher slug of radiation than a smaller number of thicker slices, researchers are developing ways to lower the dose.

Powerful software, moreover, can display images in 3-D and distinguish between types of tissue. To get a better look at a patient's blood vessels for evidence of abnormalities, for example, the radiologist can strip away bones, ligaments, and other structures that get in the way. Recently, a surgeon sent Fishman a patient about to undergo a biopsy because of a tumor in his pancreas apparent on a conventional CT image. Using a 64-slice CT scanner, Fishman removed irrelevant tissue from the image and discovered that the surgeon had been about to drive a biopsy needle into an aneurysm—a ballooned-out section of an artery. "The patient would have died," says Fishman.

Multislice scanners can be as valuable for what they rule out as for what they find. In a study published this summer in the Journal of the American College of Radiology, scanning was almost 100 percent successful in identifying emergency room patients who had not had a heart attack. That spared up to 40 percent of those who arrived at the ER from the trauma, time, pain, and expense of tests and possible hospital admission.

The new scanners are being snapped up, thanks to price tags only slightly higher than for previous versions (and to the human tendency to want what the hospital across town has, observes Leonard Berlin, head of radiology at Rush North Shore Medical Center in Skokie, Ill.). Learning and applying their full capabilities is daunting and time consuming, however. Based on conversations with manufacturers, Fishman estimates that 20 percent of radiologists with 64-slice scanners are exploiting them to the fullest extent. But that will change, he says.

"We're developing tools that give us the opportunity to really change things."