- The Washington Times - Thursday, February 20, 2003

Laser light once was relegated to pulpy science-fiction yarns and dust-ups on television's "Star Trek."
Today, the narrow beams of light can be found in compact disc players, laser pointers and even the bar-code scanners at the local supermarket.
The medical community isn't immune to laser technology's promise. Laser treatments already exist to reduce wrinkles, remove tattoos and, more important, shrink life-threatening tumors. Soon, lasers also may be part of a doctor's diagnostic tool kit.
The first laser which stands for Light Amplification by Stimulated Emission of Radiation was created by American scientist T.H. Maiman in 1960.
Laser light is created by pumping the atoms of a set medium, which can be liquid, solid or gas, with energy. That, in turn, excites the atoms, which emit stored energy in the form of photons, a process called stimulated emission.
Light amplification occurs when the photons bounce between two parallel mirrors within the laser chamber, a process that causes further stimulated emissions. Some lasers generate power because of chemical or nuclear reactions.
Laser light differs from light emanating from, say, a flashlight in two key ways. Laser light is monochromatic, containing one specific wavelength, or color, while a flashlight beam emits a spectrum of hues. Laser beams also travel in one direction, whereas a generic light bulb, for example, casts light every which way. The laser's beams, as a result, can be far more powerful than a standard ray of light.
Power of light
Dr. Michael J. Manyak, chairman of George Washington University's department of urology, says a laser's power is derived chiefly from the amount of electrical energy introduced into it, not the medium through which it is passed.
Also crucial, particularly in the case of tumor-fighting lasers, is how efficiently the target absorbs the laser's wavelength. If the tissue in question is transparent or reflects that wavelength, far less energy will be absorbed by the target.
Laser light is classified on a scale of 1 through 5, with 5 being the most dangerous to humans if used improperly. A 5 would be a laser used to cut solid materials, such as diamonds. The average laser pointer, which operates via a small power source, would be classified as a 1, says Christopher C. Davis, a professor of electrical and computer engineering at the University of Maryland.
A grocery-store scanner, which poses no direct threat but shouldn't be stared at, would be a 2.
Laser light is generated through a variety of media. Solid-state lasers, such as the very first laser, which used a ruby crystal medium, are used widely, especially the neodymium-YAG laser, which has replaced the ruby-crystal versions because of its increased efficiency. Neodymium is a silverlike earth metal, and YAG is a synthetic hard aluminum garnet stone.
Solid-state lasers channel electrical energy through a solid material, such as a crystal. These lasers are used for many purposes, including cutting materials and printing and copying.
In gas lasers, Mr. Davis says, an electrical current is passed through a gas-filled tube, similar to a fluorescent light.
Helium-neon gas lasers emit a red light, he says, while carbon-dioxide lasers produce a strong infrared beam capable of slicing through hard material. These lasers can be used in everything from bar-code scanners to laser light shows. One form of gas lasers, excimer gas lasers, often are used in laser eye surgery in small pulses that do not create much heat.
Dye lasers, which use a liquid medium to manufacture laser light, are tunable, meaning the wavelength they generate can be adjusted. Doctors use dye lasers to remove birthmarks and stretch marks.
Mr. Davis says semiconductor or diode lasers, those found in computers and at the grocery checkout line, are among the most compact and power-efficient lasers available. They convert electrical energy into laser light using microchips as the medium. They can be found in CD players and laser printers.
Generally, a laser produces either pulsed or continuous-wave (CW) beams. Pulsed lasers deliver a burst of concentrated energy over a short period of time and are used in medical applications to vaporize tissue, a process called ablation.
CW lasers emit a steady light and are more commonly used for cutting, much like an optical scalpel, he says.
Lasers in medicine
The medical applications for laser light continue to expand. Laser treatment has helped remove birthmarks, whiten teeth and smooth out wrinkled skin.
More recently, doctors have begun treating both acne and its scarring effects with lasers. For the former, laser light can destroy the bacteria that causes acne, or, via laser heat treatments, it can attack the sebaceous glands that produce the oil that causes acne. Acne-scarred skin can be treated by heating and destroying the top layers of the skin.
Lasers also can stimulate the growth of collagen-producing cells, which can produce smoother skin.
One way lasers fight more serious conditions is through optical fiber networks, which, when directed properly, can blast away cancerous growths or break up painful kidney stones.
Dr. Manyak says a promising advance for medical laser applications will be coming to George Washington University Medical Center in April. Its planned diagnostic light technology program, known as optical coherence tomography, will immerse the patient in differing wavelengths of light via several different lasers, including diode and solid-state models, to help doctors assess the patient's overall health.
The procedure works like a standard body scan, but its proponents promise it delivers better image resolution.
By bouncing beams of light at the patient, doctors can learn about the body's blood flow, glucose content and oxygenation levels, plus whether any cancerous tissue is forming, Dr. Manyak says.
Body tissue can absorb, transmit or reflect laser light, letting doctors compare how a healthy body reacts to light as compared to an unhealthy one.
"An abnormal tissue may bend the light in a different way or absorb the light differently" than healthy tissue, he says.
Diomed, an Andover, Mass., firm, makes lasers for a variety of minimally invasive procedures, such as eliminating spider veins. It also produces lasers to battle tumors through photo dynamic therapy, says
John Welch, vice president of marketing at Diomed. In this therapy, doctors give cancer patients a photoreactive drug, which settles in the tumor tissue.
Then, the laser light is aimed at the tumor, which absorbs the pulses of light to reduce the tumor's size.
Another cosmetic problem lasers can treat is unwanted body hair. Dr. Bruce Ames, medical director for McLean-based Alase hair-removal services, says his firm uses a diode laser to whisk away hair.
Its laser, Lumenis' Light Shear model, is designed to be absorbed by certain colors, says Dr. Ames, whose company has six sites around the Washington area.
The dark brown melanin pigment found in the hair follicles attracts the laser light, which heats up the cells surrounding the hair follicles.
"When we heat them up to approximately 70 degrees centigrade [158 degrees Fahrenheit], it unravels the DNA in the cells … and they die," he says.
The process feels "like someone snapping a rubber band against your skin," Dr. Ames says.
That sensation would be worse if not for a series of cooling mechanisms to prepare the skin, including a cryogenic spray unleashed a fraction before the beam hits skin. Otherwise, the skin would blister under the steady stream of heat.
Lasers also help eye doctors with a range of eye conditions, from near-sightedness to cataracts to glaucoma.
Dr. Roy S. Rubinfeld, a surgeon with Washington Eye Physicians and Surgeons in Chevy Chase, says his lasers use cold ultraviolet beams to reshape corneas.
The laser in question, an argon-fluoride excimer laser, takes argon atoms and fluoride atoms and pumps them full of energy, he says. The atoms combine in a very unstable manner, then break apart, releasing energy that is harnessed to produce the laser beams.
"The lasers are extraordinarily accurate," Dr. Rubinfeld says. "Each pulse removes a quarter-micron of tissue… and a human hair is about 50 microns wide."


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