Computation of Induced Current Densities in the Human Body at Low Frequencies Due to Contact Electrodes Using the ADI-FDTD Method

We report the use of the alternating direction implicit (ADI) finite-difference time-domain (FDTD) method in a D-H formulation to compute induced current densities and recruitment volumes in the human body due to contact electrodes for human electromuscular incapacitation devices at frequencies below 200 kHz. A computational model resolution of 1 mm has been used for most of the human body model, including regions proximal to the electrode contact points, while a progressively coarser resolution up to 5 mm is utilized, according to an expanding grid scheme for body regions distant from the source, such as the lower extremities. Using quasi-static assumptions, discrete Fourier transforms have been used to average the electric field values at the desired frequencies for times much shorter than their time periods. The field values induced in the human body were then obtained as ratios with respect to the source, which can be scaled depending on the magnitude. This study suggests that the ADI-FDTD method can be used for the solution of low-frequency large-scale bioelectromagnetic problems. It is shown that, when used with quasi-static assumptions, Fourier series decomposition, and expanding grid, the D-H ADI-FDTD can be an effective computational bioelectromagnetics tool.