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Laser

Surgery (nd:yag, Co2, Holmium, Erbium)

Lasers have a variety of applications in the field of medicine. Using laser beams whose wavelength is absorbed strongly, surgeons can cut and remove tissue with great precision by vaporizing it, with little damage to the surrounding tissue. The systems are used in minimally-invasive surgical techniques such as angioplasty (removing plaque from artery walls) and lithotripsy (the destruction of kidney stones in the bladder), in which a hair-thin optical fiber feeds light into the body through a tiny incision; the small opening required for the fiber results in reduced scarring and shorter healing times. In a technique called photorefractive keratectomy, lasers are routinely used to correct myopia and astigmatism. Other medical applications include removal of birthmarks, tattoos, and small varicose veins from the skin; welding tissue and sealing blood vessels during surgery; or resurfacing skin to minimize wrinkles or sun damage.

Cutting-edge researchers are using visible and infrared lasers to increase bloodflow to oxygen-starved regions of the heart, to visually detect cancer cells on the skin's surface, or to image through the skin to monitor bloodflow or detect cancerous regions. In a technique called photodynamic therapy, laser light activates a drug that accumulates in certain types of tumors, causing the drug to destroy the cancerous tissue. A sophisticated diagnostic technique called spectroscopy takes advantage of the fact that cancerous tissue reflects light differently than non-cancerous tissue, allowing doctors to identify skin cancer and cervical cancer. A laser-based optical mammography system is even under development.

Resources

Books

Hecht, Jeff. Laser Pioneers. New York: Academic Press, 1992.

Hecht, Jeff. Understanding Lasers. New York: IEEE Press, 1994.

Keller, Gregory, et al. Lasers in Aesthetic Surgery. New York: Thieme Medical Pub., 2001

Laurence, Clifford L. The Laser Book. Englewood Cliffs, NJ: Prentice Hall, 1986.

Niemz, Markolf H. Laser-Tissue Interactions: Fundamentals and Applications. 2nd ed. Berlin: Springer Verlag, 2002.

Stevens, Lawrence. Laser Basics. Englewood Cliffs, NJ: Prentice Hall, 1985.

Verdeyen, Joseph. Laser Electronics. Englewood Cliffs, NJ: Prentice Hall, 1994.


Iain A. McIntyre

KEY TERMS

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Absorption

—The destruction of a photon when its energy is used by an atom to jump from a lower energy level to a higher level.

Coherent light

—A light beam where the phase difference between any two points on a line perpendicular to the direction of propagation is constant with time.

Optical cavity

—An optical structure formed by at least two mirrors in which a light beam can be made to circulate in such a way that it retraces the same path every round trip.

Phase

—The term phase is used when comparing two or more optical waves. If the waves are at the same point in their cycle at the same moment in time, they are said to be "in phase."

Photon

—The particle associated with light. A photon is emitted by an atom when the atom undergoes a shift in internal energy from a high state to a lower state: the excess energy is carried off by the photon.

Stimulated emission

—A process of emitting light in which one photon stimulates the generation of a second photon which is identical in all respects to the first.

Additional topics

Science EncyclopediaScience & Philosophy: Laser - Background And History to Linear equationLaser - Background And History, How It Works, Stimulated Emission, Oscillation, Solid State Lasers, Gas Lasers - Applications