Application of a finite-difference technique to the human radiofrequency dosimetry problem.

A powerful finite-difference numerical technique has been applied to the human radiofrequency dosimetry problem. The method possesses inherent advantages over the method-of-moments approach in that its implementation requires much less computer memory. Consequently, it has the capability to calculate specific absorption rates (SARs) at higher frequencies and provides greater spatial resolution. The method is illustrated by the calculation of the time-domain and frequency-domain SAR responses at selected locations in the chest. The model for the human body is comprised of rectangular cells with dimensions of 4X4X6 cm and dielectric properties that simulate average tissue (2/3 muscle). Additionally, the upper torso (chest) is configured by both homogeneous and inhomogeneous models in which this region is subdivided into 20,736 cells with dimensions of 1X1X1 cm. The homogeneous model of the chest consists of cells with average tissue properties, and the calculated results are compared with measurements acquired from a homogeneous phantom model when the exposure frequency is 350 MHz. For the inhomogeneous chest model the lungs and surrounding region (ribs, spine, sternum, fat, and muscle) are modeled with as much spatial resolution as allowed by the 1X1X1 cm cells. Computed results from the inhomogeneous chest model are compared with the homogeneous model.