SAR calculations from 20 MHz to 6 GHz in the University of Florida newborn voxel phantom and their implications for dosimetry

摘要

This paper presents Finite-Difference Time-Domain, FDTD calculations of SAR in the University of Florida newborn female model. The newborn model is based upon a surface representation of the organs of the body, using non-uniform rational B-spline surfaces, NURBS. The surface model can then be converted into voxels at any resolution required. This flexibility allows the preparation of voxel models at 2-, 1- and 0.5 mm to investigate the effect of resolution on dispersion and the choice of SAR averaging algorithms as the frequency increases up to 6 GHz. The added advantage of the newborn model is that it is relatively small and so FDTD calculations can be made tractable at the very fine resolution of 0.5 mm. A comparison is made between the calculated external electric fields required to produce the basic restriction on whole-body averaged SAR and the ICNIRP reference levels for public exposure. At 250 MHz, the whole body resonance, the ICNIRP reference level does not provide a conservative estimate of the whole-body averaged SAR restriction. The reference level is also breached in the range 700 to 2450 MHz by all of the irradiation geometries considered.