Computations of SAR distributions for two anatomically based models of the human head using CAD files of commercial telephones and the parallelized FDTD code

A method for importing data from computer-aided design (CAD) files for a mobile telephone into finite-difference time-domain (FDTD) simulation software is described. Although the FDTD method is well suited for the bio-electromagnetic simulations and has become the method of choice for most researchers in this area, there may be some limitations to its use. Limitations include, the description of the source (e,g., the mobile telephone) and the fact that the FDTD method requires large amounts of memory and computational power. The size of the computational space is dependent upon both the physical size of the model and its resolution. Higher frequencies of operation require higher resolutions. This could place the solution of some problems outside the capabilities of the technique. Often the telephone has to be represented by a plastic covered metal box, which approximates the shape of the actual device. The paper addresses these problems. Wires and circuit boards inside the telephone can act as resonant elements if they are not shielded. This potential problem is also considered. The large problem size associated with high-resolution FDTD simulations is accommodated by the use of a parallel implementation of the FDTD method (run on an IBM SP-2). The techniques developed are used for two anatomically based head models that have been developed from magnetic resonance imaging (MRI) of two human subjects. The usefulness of the techniques developed and comparisons of the specific absorption rates (SARs) in the two models are discussed.