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13 May 1998 Pulsed holmium:YAG-induced thermal damage in albumen
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Proceedings Volume 3254, Laser-Tissue Interaction IX; (1998)
Event: BiOS '98 International Biomedical Optics Symposium, 1998, San Jose, CA, United States
The development of thermal damage during pulsed Holmium:YAG ((lambda) equals 2.12 micrometer, (tau) p equals 250 microseconds) irradiation of albumen was analyzed experimentally and numerically with the intent of validating the Arrhenius integral and investigating the influence of beam profile and dynamic changes in absorption. Fast flash videography was performed to document the transient development of coagulation during and after the laser pulse. A two-dimensional dynamic optical-thermal model was developed. The optical component involved a discretized Beer's law method in which absorption is a function of temperature. The thermal component was comprised of (1) a cylindrical coordinate (r,z) finite difference formulation of the heat conduction equation in which the output from the optical model was used as the source term and (2) a routine for calculating thermal damage using the Arrhenius relation. At the end of each time step, the temperature distribution was used to recalculate the absorption coefficient array, which in turn is used in the optical component. The model showed good agreement with experimental data and the literature. The Arrhenius integral was shown to be valid for the sub-vaporization pulsed laser regime. Experimental and numerical results indicated that spatial beam profile has a significant impact on thermal damage. Simulations predicted that at higher radiant exposures dynamic changes in absorption become more significant, accounting for a 10% increase in coagulation depth.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
T. Joshua Pfefer, Kin Foong Chan, Daniel X. Hammer, and Ashley J. Welch "Pulsed holmium:YAG-induced thermal damage in albumen", Proc. SPIE 3254, Laser-Tissue Interaction IX, (13 May 1998);

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