The healing power of light

If doctors could restore clogged arteries to health, heart-attack rates would plummet. MIT physicist Michael Feld thinks using light in sophisticated ways could bring this elusive goal closer.

The system he has in mind roughly resembles a benign version of the laser search-and-destroy machines featured in some computer games. The system’s probes, though, would be tiny enough to fit within the confines of a patient’s coronary artery.

Feld’s main collaborator is cardiologist John Kramer from the renowned Cleveland Clinic, and the pair recently passed a key milestone in their heart disease-related research.

The high-tech system Feld and Kramer have created is designed to diagnose danger spots in arteries. Using a technique called Raman spectroscopy, the researchers measure the spectrum, or frequency profile, of light scattered back from targets bathed in a laser beam. If the light’s from calcium, found in some artery buildups, it will have one kind of spectrum. If from cholesterol, it will have another.

In tests, the system proved virtually foolproof at gauging the chemical makeup of ailing arterial regions–a potential boon for doctors deciding how to treat diseased vessels. But getting to this stage wasn’t easy.

“The signals are incredibly weak,” notes Feld. “For every billion photons of light you put in, you get one back.” (Someone who had to send a billion e-mail messages to get a single response would have to transmit a message each second for almost 32 years.)

The researchers explored various approaches to measuring those rare light particles. The system they finally came up with does the job very efficiently. “It used to take 30 minutes to collect the data we need,” says Feld. “Now, we’ve gotten that down under a second.”

This opens the way for a catheter-mounted system that can be snaked through arteries around the heart, probing for signs of disease. Potential beneficiaries include people whose disease is so subtle conventional systems can’t find it.

“In some of the deadliest arterial conditions,” notes Feld, “the artery doesn’t narrow at all. A layer of decaying tissue has developed, though, and it can break down and cause a heart attack.”

Feld and Kramer haven’t abandoned their quest for a system that can both diagnose and treat disease. Lasers have been considered a risky choice for treating fragile tissues like coronary arteries but Feld says that’s mostly because of a lack of reliable targeting information. “People who’ve tried laser surgery in arteries haven’t had good feedback control,” he notes.

The proposed system would have, say, nine optical fibers in a bundle smaller around than a pencil lead. “You’d send a diagnostic pulse of light down each one,” he explains. “Based on the results, you could then transmit a stronger, therapeutic pulse through the fibers.”

For now, though, the researchers are trying to perfect their diagnostic system. And if it’s taken several years to get to this point, Feld sees the effort as well worth it.

“This research has led to several spinoffs,” he says. “We’re using the same technique to diagnose breast cancer and Alzheimer’s disease. We’re also using it to measure glucose and other chemicals in the blood without the need for a needle stick.”

Feld’s painstaking work, like that of most other MIT people working to defeat heart disease, has never generated big headlines. But many in the field think the future inroads against the disease are more likely to come from a series of smaller-scale advances than from stop-the-press breakthroughs. There’s also optimism the cumulative impact of such steps will be large.

Yet if major progress is all but assured, it will take time–a reality with implications not only for those who suffer from heart disease but also for researchers.

Cohen of the Harvard-MIT Division of Health Sciences and Technology has had first-hand experience of the need for patience. Trained as both a doctor and a physicist, he has appointments at Brigham & Women’s and Children’s hospitals as well as at MIT.

“There’s an immediate satisfaction you get from treating patients that you don’t get in research,” notes the faculty member who now focuses solely on lab work. “The time-scale for fulfillment in research is years rather than minutes. But you also have the chance to make truly significant contributions.”

by Richard Anthony « Previous | Next »

On Topic: health science+technology