Specific absorption rate (SAR) revisited for the ellipsoidal model of a human body

Abstract

An unexplored procedure leading to a unified formulation of the average whole-body SAR, thus entirely covering the frequency spectrum of technical interest, is here described. The explanatory and referential example of an ellipsoid mimicking exposition of a standing man on a ground plane is adopted and an approximate closed form for the SAR is provided. In spite of the far-field condition which in principle applies to this investigation, the analysis starts from rigorously recognizing the near-field performances of the time average Poynting vector and goes on accordingly in modeling the induction mechanism. Therefore, the external dosimetry is preliminary assessed by using a quasistatic approach. This step is rather to be intended as an intermediate one with the aim of evaluating the SAR which, as a consequence, results subject to the same quasistatic conditions. Indeed, the approximation error affecting the calculation especially depends on the fact that the adopted biological model behaves as a perfect conductor externally to its boundary and internally as a dissipating dielectric body. On the whole, the continuous curves obtained in function of frequency are in fairly good agreement with available counterparts which, do not forget, are rather constructed by interpolation of discontinuous databases given using different models and spanning restricted frequency ranges. The only striking departure consists in the smoothed appearance of the curves related to this method against the presence of a resonance sharp peak arising elsewhere under specialized exposure conditions. In the light of this theory, the peak in question is hard to explain, except when the adopted corpulent ellipsoid is replaced with a more refined model.