Dual-phase lag effects on thermal damage to biological tissues caused by laser irradiation.

A dual-phase lag (DPL) bioheat conduction model, together with the broad beam irradiation method and the rate process equation, is proposed to investigate thermal damage in laser-irradiated biological tissues. It is shown that the DPL bioheat conduction model could predict significantly different temperature and thermal damage in tissues from the hyperbolic thermal wave and Fourier's heat conduction models. It is also found that the DPL bioheat conduction equations can be reduced to the Fourier heat conduction equations only if both phase lag times of the temperature gradient (tau(T)) and the heat flux (tau(q)) are zero. This is different from the DPL model for pure conduction materials, for which it can be reduced to the Fourier's heat conduction model provided that tau(q)=tau(T). Effects of laser parameters and blood perfusion on the thermal damage simulated in tissues are also studied. The result shows that the overall effects of the blood flow on the thermal response and damage are similar to those of the time delay tau(T).