Temperature Profiles in Spheres Due to Electromagnetic Heating

Abstract

This study predicts the steady state temperature rise in a homogeneous tissue sphere exposed to plane wave electromagnetic energy. The differential equation for heat transfer is solved, assuming heat transfer mechanisms of convection (due to blood flow), conduction, and évapotranspiration from the surface, The tissue heating is described by the specific absorption rate (SAR), which is a known function of the size and dielectric properties of the sphere and the frequency of the incident electromagnetic energy. We consider the limiting cases of irradiation at very low frequencies, very high frequencies, and intermediate frequencies. We propose the concept of convection length, over which distance in the SAR is effectively averaged to produce a smoothly varying temperature increase. The results of this study are used to predict the maximum temperature rise in the human head, produced by an incident electromagnetic plane wave.