Epidermal cooling during pulsed laser treatment of selected dermatoses
The clinical objective in laser treatment of selected dermatoses such as port wine stain (PWS), hemangioma and telangiectasia is to maximize thermal damage to the blood vessels, while at the same time minimizing nonspecific injury to the normal overlying epidermis. 'Dynamic' cooling of skin, whereby a cryogen is sprayed onto the surface for an appropriately short period of time (on the order of tens of milliseconds), may offer an effective method for eliminating epidermal thermal injury during laser treatment. We present theoretical and experimental investigations of the thermal response of skin to dynamic cooling in conjunction with pulsed laser irradiation at 585 nm. Computed temperature distributions indicate that cooling the skin immediately prior to pulsed laser irradiation with a cryogen spurt of tetrafluoroethane is an effective method for eliminating epidermal thermal injury during laser treatment of PWS. Experimental results show rapid reduction of skin surface temperature is obtained when using tetrafluoroethane spurts of 20 - 100 ms duration. Successful blanching of PWS without thermal injury to the overlying epidermis is accomplished.