Without the JPL software, a technician would visually scan an ultrasound image on a computer screen and manually delineate the arterial wall by moving a mouse. This manual approach is subjective, hence findings from a single image can vary unpredictably. Seltzer says that in tests in which 100 patients were scanned once and then tested again a week later, the consistency of the thickness readings from one week to the next was four to ten times better with the software than with manual tracking. "When you come in on different days, you get the same result," he says.

Howard Hodis of the Keck School of Medicine at the University of Southern California, who conducted some of the clinical trials, says that "once patients see how thick their arteries are, there is much more incentive for them to change their lifestyle" by making alterations to their eating habits and exercise level.

The JPL-developed software has been licensed to a company called Medical Technologies International, which is now making it available to hospitals everywhere. The company's president, Gary Thompson, says he became interested in marketing the software after he learned firsthand how well it could reveal problems in patients who had no detectable symptoms.

Thompson says that he has a family history of heart disease, so when he turned 50, he paid for an expensive and exhaustive battery of tests--which he passed with flying colors. But weeks later, while running a marathon, he suddenly had a heart attack.

After recovering, he heard about the new software that was undergoing clinical trials, and he decided to give it a try. "I walked in, and I didn't tell them I had had a heart attack, didn't tell them anything about the family history," Thompson says. "In 15 minutes, after a $500 test, they told me, 'You need to see the doctor immediately.'"

Years later, clinical trials have now established that this was not an isolated event and that, as illustrated by Thompson's own experience, "in many cases, it will identify people who are at risk even when they are completely asymptomatic," he says. "For 40 percent of people who ultimately die of a heart attack, the first symptom is death. It happens all the time." Thompson hopes the new technology will help change that.