Abstract

Based on the assumption that the maximum irradiance allowed during laser treatment of port wine stains is limited by the temperature rise at the dermoepidermal junction (DEJ), we theoretically investigated how much the irradiance could be increased by dynamically cooling the skin surface. The heat condution equation was solved numerically in cylindrical coordinates using a skin model composed of four layers. The laser-light absorption was calculated using Monte Carlo simulations. The transient thermal behaviour of the skin was modelled when cooling with water at a temperature of 0°C and with liquid nitrogen at a temperature of -196°C. With cooling, an increase in the maximum irradiance by a factor 2.33.6 was theoretically permitted depending on the irradiation time, wavelength and mode of cooling. The corresponding increase in vessel selective damage depth was predicted to be 0.4-0.5 mm.

© 1996 IEEE