Hyperbolic Heat Conduction In Pulsed Laser Irradiation Of Tissue

Abstract

The use of lasers for ablation of biological tissues is becoming common place in many medical and surgical applications. However, the complete nature of the ablation mechanism is yet to be understood. Many authors have contributed to the theoretical understanding and modeling of the thermodynamics of ablation process by a laser. Some examples are [LANGERHOLC,1979; VAN GEMERT et al., 1985; ARMON and LAUFER, 1986; MCKENZIE, 1986; PARTOVI et al., 1987; RASTEGAR et al., 1988]. In a previous theoretical work the effect of optical properties on the ablation process has been shown [RASTEGAR et al., 19881)]. The effect of variation of power and exposure time over a constant fluence delivered on the tissue volume removed and the damage incurred on the surrounding tissue is shown in figure 1 [ RASTEGAR et al., 1988a]. This shows that for a given fluence, as power is increased and exposure duration is decreased the change on the volume removed is not significant while the damage to the surrounding tissue is significantly lessened. However these results, and those of the above references, are based on Fourier's law of heat conduction which is valid for relatively low power CW laser irradiation. The interaction of short pulsed high power lasers with tissues manifests a different behavior and application of Fourier's heat conduction law becomes questionable. In particular, in some experimental observations application of pulsed lasers has shown no apparent thermal damage to the surrounding tissue.© (1989) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.