Abstract

Mechanisms of UV laser ablation of biological tissue (aorta wall), which include thermal, mechanical, and photochemical effects, will be reported. Tissue optical properties were determined, followed by a quantitative study of laser energy transformation channels into heat generation, photochemical reactions, fluorescence, and reflectance. The role of photochemical decomposition was found to be minor (~1%) in comparison with thermal effects (~80%). The relative contribution of thermal explosion and mechanical stress in the mechanism of tissue ablation by means of XeCl and Nd:YAG laser pulses was investigated. Time-resolved acoustic signal detection and luminescence spectroscopy of ablation products with nanosecond resolution was utilized. Absolute pressure values in the irradiated tissue were measured. The peak pressure amplitude in tissue can reach several hundreds of atmospheres at threshold fluence by short laser pulse ablation, which is substantially higher than that in optically homogeneous aqueous solution. This observation indicates the important role of tissue microchromophore centers in the ablation process.

© 1992 Optical Society of America