THE EFFECT OF LASER PARAMETERS ON THE ZONE OF THERMAL-INJURY PRODUCEDBY LASER-ABLATION OF BIOLOGICAL TISSUE

A thermal model to predict the effect of laser parameters on the zone of thermal injury produced by laser ablation of biological tissue is p resented. The model suggests that the Peclet number based on the optic al penetration depth of laser radiation is the key parameter in determ ining the resulting zone of thermal injury. We show that the zone of t hermal injury is minimized for Peclet numbers greater than one since t he transport of energy via conduction beyond the ablation front is min imized. We also show that for Peclet numbers less than one, larger zon es of thermal damage are unavoidable regardless of the laser pulse dur ation. The predictions of the model are compared with data available i n the literature. Deviations between the model predictions and publish ed data are discussed and the potential effects of the model assumptio ns, optical scattering, pyrolysis, temporal pulse shape, pulse duratio n, irradiance and pulse repetition rate are explored.