Criteria of pressure and thermal damage during laser irradiation of port wine stains: Which is dominant to vascular lesions?

Abstract

Abstract Port wine stains (PWSs) are congenital dermal vessel proliferations mainly treated with laser therapy. The complete removal of the vessel lesions is rarely achieved because of a lack of discriminatory analysis of the two competitive laser damages to blood vessels, namely, pressure damage and thermal damage. Unlike complete vessel constriction, which is caused by thermal damage that can be measured by temperature-related integral Ω, vessel rupture results from pressure damage, which has been seldom studied. In this study, the rupture potential index based on wall pressure (RPIP) was calculated as the ratio of locally acting pressure to the pressure threshold. RPIP\u202f>\u202f1 and Ω\u202f>\u202f103 were adopted as benchmarks to judge pressure damage (vessel rupture) and thermal damage (complete vessel constriction), respectively. A computational fluid dynamics simulation was carried out to provide the temperature and pressure field in the PWS vessel model during irradiation by 595\u202fnm pulsed dye laser (PDL) or 1064\u202fnm Nd:YAG laser. Numerical results showed that for the 595\u202fnm laser, vessels constantly underwent rupture. The area of high RPIP determined the degree of rupture by predicting the large and multiple rupture locations of the vessel. By contrast, for the 1064\u202fnm laser, complete constriction was the main damage type. To a single vessel of 100\u202fμm diameter, the optimized laser parameters were E\u202f=\u202f10\u202fJ/cm2 with tp\u202f=\u202f6\u202fms for 595\u202fnm PDL and E\u202f=\u202f180\u202fJ/cm2 with tp\u202f=\u202f6\u202fms 1064\u202fnm for Nd:YAG laser.