Experimental Measurements and Numerical Modeling Validation of Temperature Distribution in Tissue Medium During Short Pulse Laser Irradiation

The objective of this paper is to analyze the temperature distributions and heat affected zone in skin tissue medium when irradiated with either a collimated or a focused laser beam from a short pulse laser source. Single-layer and three-layer tissue phantoms containing embedded inhomogeneities are used as a model of human skin tissue having subsurface tumor. Q-switched Nd:YAG laser is used in this study. Experimental measurements of axial and radial temperature distribution in the tissue phantom are compared with the numerical modeling results. For numerical modeling, the transient radiative transport equation is first solved using discrete ordinates method for obtaining the intensity distribution and radiative heat flux inside the tissue medium. Then the temperature distribution is obtained by coupling the bio-heat transfer equation with either hyperbolic non-Fourier or parabolic Fourier heat conduction model. The hyperbolic heat conduction equation is solved using MacCormack’s scheme with error terms correction. It is observed that experimentally measured temperature distribution is in good agreement with that predicted by hyperbolic heat conduction model. The experimental measurements also demonstrate that converging laser beam focused directly at the subsurface location can produce desired high temperature at that location as compared to that produced by collimated laser beam for the same laser parameters.