Thermolysis of port-wine-stain blood vessels: Diameter of a damaged blood vessel depends on the laser pulse length

Abstract

A thermal model of blood vessel damage during the laser treatment of port-wine stains (PWS) is presented. The model depends on the heat generation in a blood vessel caused by the absorption of laser light and the thermodiffusion of that heat through the dermis. The criterion of vessel injury adopted was an average vessel temperature of 70 °C. Results show that for a chosen combination of pulse length and radiant exposure, only blood vessels within a certain diameter range will be injured. This is in agreement with the pulse length selective photothermolysis criteria suggested previously by Anderson and Parrish (1). The Anderson and Parrish model relies on the cooling behaviour of instantaneously heated vessels, whereas the present study utilizes the heating of the vessel by a Gaussian temporal laser pulse profile. Predictions based on one blood vessel were verified in a skin model with multiple blood vessels by simulating vessel coagulation with a single laser treatment. The diameter of the blood vessels that are damaged during laser treatment of PWS depends on the laser pulse length.