DYNAMIC EPIDERMAL COOLING DURING PULSED-LASER TREATMENT OF PORT-WINE STAIN - A NEW METHODOLOGY WITH PRELIMINARY CLINICAL-EVALUATION

Background and Design: The clinical objective in the treatment of a pa tient with port-wine stain (PWS) undergoing laser therapy is to maximi ze thermal damage to the PWS, while at the same time minimizing nonspe cific injury to the normal overlying epidermis. With dynamic cooling, the epidermis can be cooled selectively. When a cryogen spurt is appli ed to the skin surface for an appropriately short period of time (on t he order of tens of milliseconds), the cooling remains localized in th e epidermis, while leaving the temperature of the deeper PWS vessels u nchanged. Results: Comparative measurements obtained by a fast infrare d imaging detector demonstrated that the surface temperature prior to laser exposure could be reduced by as much as 40 degrees C using the d ynamic cooling technique. No skin surface textural changes were noted on PWS test sites cooled with a 20- to 80-millisecond cryogen spurt af ter flashlamp-pumped pulsed dye laser (FLPPDL) exposure (lambda=585 nm ; tau(p)=450 microseconds) at the maximum light dosage possible (10 J/ cm(2)). In contrast, epidermal necrosis occurred on the uncooled sites after such exposure. Six months after laser exposure, clinically sign ificant blanching on the cooled sites indicates laser photothermolysis of PWS blood vessels did occur. Conclusions: Our preliminary experime nts demonstrate the feasibility of selectively cooling the normal over lying epidermis without affecting the temperature of the deeper PWS ve ssels. Furthermore, protection of the epidermis from thermal injury, p roduced by melanin light absorption at clinically relevant wavelengths , can be achieved effectively. An additional advantage of dynamic epid ermal cooling is reduction of patient discomfort associated with FLPPD L therapy. Further studies are under way to determine an optimum strat egy for applying this dynamic cooling technique during pulsed laser tr eatment of patients with PWS and others with selected dermatoses (derm al melanocytic lesions and tattoos).