The thermal response of biological tissue subjected to short-pulsed irradiations

A combined transient radiation and hyperbolic heat conduction model is developed to simulate heat transfer of biological tissue subjected to short pulsed irradiations. For modeling the ultrafast radiation heat transfer, the Transient Discrete Ordinate Method (TDOM) is developed in the two-dimensional axisymmetric cylindrical coordinates. The hyperbolic conduction model is solved by MacCormack's scheme with error terms correction. One combination model of radiation and heat conduction is that the radiation transfer is initiated by short pulse train irradiating until millisecond time scale and heat conduction transfer is followed. The temperature always increases by the radiation transfer and the heat is dissipated to the surrounding tissue by the hyperbolic heat conduction. The typical characteristic of the hyperbolic conduction is the thermal wave propagation rather than thermal diffusion with indefinite speed. It is found that the maximum local temperatures are higher in the hyperbolic prediction than the parabolic prediction, which can be 7% higher in the modeled dermis tissue. After about 10 thermal relaxation times, thermal waves fade away and the predictions between the hyperbolic and parabolic models are closely consistent.;Other combination model is that radiation and conduction transfer always occurs together until a second time regime. The temperature prediction is compared with the experimental result provided by Dr. Kunal Mitra's group. Generally, the hyperbolic model combined with radiative heat transfer shows very similar result with the experimental data. It also shows high temperature increment near the laser deposition area compared with the parabolic model.;Own experimental study is conducted to evaluate the hyperbolic heat conduction phenomena. The fresh chicken tissue which is conserved the room temperature is suddenly contacted the ice block. Some of the results support the hyperbolic model by the temperature suddenly dropping rather that gradual temperature change.;The high absorbing tissue can enhance the radiation energy absorption and temperature increment is higher. The temperature increment is localized in the tissue surface region in the high scattering tissue. The focused laser beam played a role of temperature amplification around the focal region. The finer grid system is employed to catch up steep change of gradient of radiation energy absorption.