Numerical treatment of boundary conditions at points connecting more than two electrically distinct regions

Points of intersection of three or more lossy dielectric regions (i.e. tissues) often occur in anatomical cross‐sections of the human body obtained with CT‐scans. The boundary conditions for the electric and magnetic fields require special attention at these points, in contrast to points of connectin of only two tissues, thus posing a problems for numerical methods involved with calculating the electromagnetic fields in tissue. In this paper, a simple theoretical analysis, which exposes the dominant analytic behaviour near such points, is followed. The derived analytic behaviour is numerically enforced via a special basis function which is compatible with the finite element method. Results are shown which indicate that the special basis preserves the analytic behaviour while maintaining grid resolution that is typical of the overall mesh.