A finite-difference model provides computer simulations of laser ablation, depicting a dynamic process of surface dessication, temperature rise, carbonization, and explosive subsurface vaporization, which repeats cyclically. The model considers the role of changing tissue optical properties, thermal diffusion, surface water evaporation, water diffusion, tissue dessication, transient carbonization, subsurface explosive vaporization. The parameters of the model were adjusted to yield an ablation velocity, vabl (mm/s), which matched a typical experimental value from the literature. Then the effect of each parameter on vabl was examined by plotting vabl versus variation in that one parameter while holding all other parameters constant. The major factors influencing vabl appear to be the threshold for explosive vaporization [ Qth (J/cm 3 )] and the rate of carbonization expressed in terms of its optical absorption [ \deltaµacarb)/\delta t cm -1 s -1 ]. The ablation process is dynamic not constant, but the average ablation velocity can be adequately modeled as the simple boiling of water caused by heat deposition in a 2-5 µ m time-averaged thickness of carbonized tissue.
S. L. Jacques, "Finite-difference model for laser ablation with emphasis on the role of carbonization and explosive vaporization," SPIE Proceedings of Laser-Tissue Interaction V, edited by S. L. Jacques, 2134A, 372-382 (1994).