Continuous wave (CW) lasers, the first medical lasers to be used, continue to be effective, but are extremely operator dependent and can potentially result in significant risks, including scarring. In 1983, the theory of selective photothermolysis was introduced, which enabled physician-scientists to design lasers that were highly selective and safer to operate. These newer lasers are capable of affecting a specific target tissue without a high risk of scarring and pigmentary changes. They accomplish this task by producing a wavelength and pulse duration that is best absorbed by a specific target. However, not all modern lasers employ this theory and, therefore, may operate in either a CW, quasi-CW, pulsed, or Q-switched mode. CW lasers are least selective and tend to produce unwanted tissue damage and scarring through heat dissipation. Quasi-CW lasers attempt to limit unwanted thermal damage by producing a series of brief laser pulses or by the chopping of a CW beam; however, they still have a relatively high risk of causing nonspecific tissue damage and thermal injury. The pulsed and Q-switched systems adhere most closely to the principles of selective photothermolysis and result in the most selective destruction with the lowest risk of scarring and unwanted thermal diffusion. Of course, any laser system can potentially result in scarring and tissue damage; therefore, adequate operator education and skill are essential when utilizing medical lasers.

作者：C A, Nanni；T S, Alster

来源：Dermatologic surgery : official publication for American Society for Dermatologic Surgery [et al.] 1998 年 24卷 2期