Computational Artifacts of the In Situ Electric Field in Anatomical Models Exposed to Low-Frequency Magnetic Field

An in situ (internal) electric field is used as a dosimetric quantity for human protection from low-frequency electromagnetic fields (lower than 5 MHz) under international safety standard/;guidelines. The IEEE standard uses a homogenous elliptical cross section to derive external field strength corresponding to an in situ field strength, while the International Committee on Non-Ionizing Radiation Protection (ICNIRP) guidelines use anatomical models to relate them. In the latter, “the 99th percentile value of the in situ electric field averaged over the cube of its side length of 2 mm” is used to represent the maximum in situ electric field. This metric was introduced to suppress computational artifacts that are inherent when using voxelized anatomical models, in which curved boundaries are discretized with a stair-casing approximation. To suppress the error, a few schemes have been proposed for treating the computational artifacts. In this study, the various schemes to suppress the artifacts are reviewed. Subsequently, a postprocessing method for determining the appropriate maximum in situ field strength is proposed. The performance of the proposed scheme is first verified by comparison with an analytical solution in a multilayered sphere. The method is then applied for different exposure scenarios in anatomically realistic human models where the volume under computation is also considered.