Calculation of electric fields in conductive media

A method is presented, based upon finite-difference forms of Laplace's equation, for the iterative calculation of three-dimensional electric field distributions in electrically conductive media. The method, while generally applicable to any conductive media, will be presented with emphasis on its use for the prediction of power density in tissue when radio-frequency hyperthermia is utilized in the treatment of cancer. A computer code which performs these calculations has been written in BASIC so that is may be adapted to relatively inexpensive desktop computers for use in treatment planning. Example calculations of the distributions of electric potential, gradient, and power density with specific electrode configurations are presented. Applications and limitations of the technique are discussed.