Specific absorption rate analysis of a multi-layered arm model exposed to sinusoidal plane waves using FDTD method

Abstract

The Finite-Difference Time-Domain (FDTD) method is a powerful technique that employs the Yee algorithm to discretize and solve a computational space governed by a set of equations. On the other hand, Specific Absorption Rate (SAR) is a dosimetric parameter that measures the rate of change of the energy transferred to the biomaterial. This numerical study investigated the SAR of a multi-layered arm model using Maxwell’s Equations. First, a two-dimensional FDTD grid bounded by an absorbing boundary condition was constructed, and geometry was introduced. Then, a sinusoidal plane wave propagates through the vacuum until it eventually hits the material of interest. The electric field distribution is post-processed to analyze the energy transfer through each layer of tissue for both TE and TM polarizations. Simulation results have shown that SAR values exhibit sharp alterations at the junction of each tissue layer due to a large impedance mismatch at the interface between tissue layers. It also indicates the constructive and destructive interference of the reflected wave with the incident wave. The sudden rise and drop in the SAR values are due to large differences in mass density, permittivity, and conductivity at the junction between the two tissues. Cell size optimization is also crucial in obtaining accurate results. Temporal and spatial sizes are chosen based on the Courant condition and sampling theory requirement to attain numerical stability and accuracy.