Computation of the potential distribution in a four-layer anisotropic concentric spherical volume conductor

A method for solving the potential distribution in a multilayer anisotropic concentric spherical volume conductor, which has recently been described in the literature, has been tested and found to be numerically unstable. In this paper it is demonstrated how these numerical difficulties can be avoided. Moreover, the method is extended by lifting the previously imposed restriction on the innermost region to be isotropic. A convergence criterion for determining the required number of terms in the final series expansion is proposed. The influences of radial and tangential conductivity values of the skull and brain tissue on the dipole-induced potential are investigated.