UC Irvine

A thermal model to predict the effects of laser parameters on the zone of thermal injury produced by laser ablation of biological tissue is presented. A dimensionless parameter based on the ablation velocity and the optical and thermal properties of the target is key in determining the resulting zone of thermal injury. The zone of thermal injury is minimized when this parameter, known as the Peclet number (Pe), is much larger than one. This occurs because the rapid movement of the ablation front prevents the diffusion of energy beyond the laser that absorbs the laser radiation. For Pe less than one, the slow movement of the ablation front allows for diffusion of energy away from the region of energy deposition and leads to larger zones of thermal injury. The model predictions are compared with data available in the literature. Deviations between the model predictions and published data are discussed and potential effects of pyrolysis, temporally varying pulse shapes and pulse repetition rates are explored.