Once-Futuristic Laser Becoming an Increasingly Common Medical Tool

BOSTON —  Julie Zuckerman slid into the dentist-type chair and donned a pair of dark protective goggles. She braced herself as a beam of laser light pulsed across the large, purplish birthmarks marring her young face.

Within weeks of the 10-minute procedure, the disfiguring “port wine stains” blemishing her forehead, cheek and ear, which had evoked stares from strangers all her life, would finally begin to fade.

“I am really excited about this,” said the 16-year-old Wilton, Conn., high school student. “It’s something I’ve lived with for so long. And now it’s gone, or soon it will be.”

The new treatment is one of the more recent examples of the increasingly common role lasers are playing in modern medicine.

Once considered futuristic, lasers of various kinds are becoming a more common sight in doctors’ offices, where they have become routine for the treatment of many medical problems.

“It’s no longer sort of a futuristic, hopeful concept. Based on the information we have today, the impact is real. In fact, it’s already started to happen,” said Dr. John Parrish of Wellman Laboratories at Massachusetts General Hospital in Boston.

Like High-Tech Scalpel

Primarily used as a more precise, high-tech scalpel, the greatest advantage of lasers is they are faster and cause less pain and scarring than the knife.

Eye doctors have been using lasers for years to reattach retinas and to remove blinding cataracts. Dermatologists commonly use lasers to remove growths, tattoos and, more recently, unsightly “spider veins.”

Throat surgeons rely on the precision of lasers for the delicate job of removing growths from vocal cords. Neurosurgeons employ lasers to spare precious brain cells when extracting tumors.

Gynecologists avoid pain, scarring and unnecessary damage to genital areas by using lasers to get rid of genital warts and precancerous lesions. A relatively new procedure in which a laser is used to perform hysterectomies and to treat endometriosis is also becoming more popular because it avoids major surgery and appears to reduce the incidence of recurrences.

Laser shot through fiber optic cables are replacing shock-wave machines to chip apart stones blocking urinary tracts. Similar techniques are also showing promise for treating hard-to-reach kidney stones and gallstones, researchers said.

“Lasers really have arrived in medicine,” said Dr. Barbara Gilchrest, director of the Laser Center at Boston University School of Medicine. “Many of the very routine procedures that are done couldn’t be performed if these weren’t available.”

Researchers are excited about new approaches in which lasers may be effective to help treat two of the most important medical problems: heart disease and cancer.

“It’s clear now that lasers are going to have a large impact on medicine,” said Parrish of Massachusetts General.

Everything absorbs light. The specific type of light absorbed determines its color. Lasers produce beams of light made up of pure wavelengths or colors. Since all the wavelengths are going in the same direction, they create intense energy. Various types of tissue absorb specific wavelengths of light depending on their color. By aiming a beam of light containing a pure wavelength of light, doctors can be very specific about the type of tissue destroyed.

‘Incredible Potential’

“Lasers have an incredible potential for specificity,” Gilchrest said. “For medical applications, it’s their greatest strength. You have the ability to hit a specific target.”

By destroying only a specific type of tissue, the amount of pain and scarring is reduced and healthy tissue can be spared.

A good example is the use of the laser to treat port wine stains like Zuckerman’s. Port wine stains are formed by abnormal, bloated blood vessels. Previous methods for removing the marks were painful and left scars because existing lasers could not be made specific enough to destroy only the blood vessels.

But a new type of laser, known as a tunable dye laser, can be adjusted to a wavelength that passes through the upper layers of skin without damaging them and only be absorbed by the dark red, abnormal blood vessels. The energy from the laser light coagulates the vessels, which die, are eventually absorbed into the skin and replaced by healthy, normal ones.

Among the most exciting, but still experimental, applications of lasers in medicine is for blasting open arteries that have been clogged by cholesterol.

Heart Attacks, Stroke

When vessels in the legs become clogged, they cause pain. Blocked vessels in the heart can cause heart attacks--the nation’s leading killer. In the neck, they can cause strokes.

Narrowed or blocked blood passages are often treated with a method known as balloon angioplasty. A tiny balloon is inserted into the artery and inflated to reopen the passageway. In more serious cases, the blocked artery is replaced with a new artery in so-called bypass surgery.

Laser researchers have already begun using fiber optics and lasers to blast through the blockages in both legs and heart arteries.

Dr. Timothy Sanborn, an associate professor of medicine at Mount Sinai School of Medicine in New York, developed a device already approved by the Food and Drug Administration.

A fiber optic cable about the diameter of a strand of fine spaghetti is inserted into the body through a small incision in the groin and snaked to the blocked artery using X-rays to guide it. The doctor shoots an argon laser through the fiber, which is tipped with a tiny metal cap that heats up and bores through the blockages.

Helps Avoid Surgery

Several thousand patients have already undergone the procedure in leg arteries, a condition for which an estimated 300,000 people are treated each year. The procedure could help avoid surgery for patients whose arteries are so clogged that conventional balloon angioplasty is impossible, Sanborn said. Arteries opened with the laser may stay open longer also, he said. At least one-quarter of arteries reopened with balloon angioplasty eventually close up again.

Sanborn has treated about 100 patients with blocked heart arteries with this method. Although it is too early to tell how effective the approach is, early results are promising, he said. About 500,000 Americans undergo balloon angioplasty procedures or bypass operations for blocked heart arteries each year.

Dr. James Livesay, an associate surgeon at the Texas Heart Institute in Houston, has been experimenting with a carbon dioxide laser to open up clogged heart arteries in patients who also undergo bypass surgery. A 1985 study involving 35 patients found the approach to be about 90% effective in opening the passageways, he said.

“Most people in the field think these devices have a way to go before there is enough safety and efficacy to do it (routinely),” Livesay said.

Dr. Frank Litvack, director of the cardiac catheterization laboratory at Cedars-Sinai Medical Center in Los Angeles, has been using an Excimer laser in leg arteries. He said he expects the treatment to gain FDA approval within a year.

Tried on Heart Arteries

Although the use of the laser for opening leg arteries is now being done in more than 200 centers in the United States, only about 20 laboratories have tried the approach on heart arteries.

Heart arteries are narrower and more curved than leg arteries, making it more difficult to reach the blockages. In addition, if the laser misses the blockage and hits the artery wall, the results would be more serious.

To reduce such risks, many researchers are experimenting with improved methods of aiming the laser.

Dr. Martin Leon, co-director of the cardiac catheterization laboratory at National Institutes of Health in Bethesda, Md., is one of the researchers trying to develop improved methods of aiming the laser. He has developed a dual laser system that uses one laser to aim and the other to destroy the blockage.

“We were discouraged that even the best laser systems still created problems because we could not direct the beam correctly to prevent it from perforating the vessel,” Leon said. “You’ve got to have a way of targeting the beam.”

Like the other approaches, a tiny plastic tube about half the diameter of a standard pencil is inserted into a groin vessel and snaked to the blocked artery under X-ray guidance. The tube contains two tiny fiber optic cables through which separate lasers are shot.

Reflects ‘Signature’

The first laser is a low-intensity, helium-cadmium laser that reflects back a “signature or fingerprint” light spectrum through the system to a computer, which analyzes the response to determine if the tissue being hit is normal or abnormal tissue, Leon said.

The computer then sends a signal to the second high-powered pulsed dye laser instructing it whether to fire, based on whether the signal from the first laser indicated that the tissue was abnormal, he said. The second laser breaks up the blockage.

Leon has used the system to treat 10 patients with blocked leg arteries, achieving success in eight out of 10 of the patients. Of two heart patients treated so far, the laser made its way through one blockage and partially through the second. But the system’s fibers are too stiff, making it too difficult to negotiate many of the turns necessary to reach heart arteries, Leon said. He hopes to get FDA approval for more flexible catheters and to resume testing.

Leon said he doubts that laser angioplasty will ever completely replace balloon angioplasty, but it may enable some patients who would have otherwise required surgery to avoid it.

Meanwhile, the first wide-scale study of a new form of cancer treatment involving lasers, known as photodynamic therapy, is just getting under way.