Computation of induced fields in the human torso at low frequencies due to contact electrodes using the ADI-FDTD method

The Alternating-Direction Implicit (ADI) Finite-Difference Time-Domain (FDTD) method allows larger time steps than the traditional explicit method by bypassing the Courant limit, thus leading to shorter simulation times. In this paper, the use of the ADI-FDTD method in D-H formulation, to compute low-frequency induced fields due to contact electrodes in the human body is reported. Since the frequency is low (120 KHz), quasi-static assumptions have been used to reduce the number of time steps required. An averaging scheme based on Discrete-Fourier Transforms (DFT) have been used to obtain the ratio of the induced field magnitudes to the source, which can then be scaled for any applied signal magnitude.