Effect of Surface Cooling and Blood Flow on the Microwave Heating of Tissue

The one-dimensional heat transport equation has been solved for a semi-infinite plane of tissue irradiated by microwave radiation, to determine the effects of thermal convection due to blood flow and transfer of heat from the tissue surface into space on the steady-state temperature distribution in the tissue. For microwaves in the 1 to 10-GHz range, the effective heating depth is 1 to 2 cm, and can be much deeper than the penetration depth of the radiation in the tissue. The position of the maximum tissue temperature can be varied by a centimeter or so by cooling the surface. The results suggest that microwave irradiation of simulated biomaterials is not likely to provide accurate estimates of the actual microwave-induced temperature distribution in tissue.