Calculation of electric fields induced in the human knee by a coil applicator

Calculations are presented of the induced electric fields and current densi ties in the cartilage of the knee produced by a coil applicator developed f or applying pulsed magnetic fields to osteoarthritic knees. This applicator produces a sawtooth-like magnetic field waveform composed of a series of 2 60-mus pulses with a peak to peak magnitude of approximately 0.12 mT in the cartilage region. The simulations were performed using a recently develope d 3 dimensional finite difference frequency domain technique for solving Ma xwell's equations with an equivalent circuit model. The tissue model was ob tained from the anatomically segmented human body model of Gandhi. The temp oral peak electric field magnitude was found to be -153 mV/m, averaged with in the medial cartilage of the knee for the typical dB/dt excitation levels of this coil. The technique can be extended to analyze other excitation wa veforms and applicator designs. (C) 2001 Wiley-Liss, Inc.