Design optimization of stimulation coil system for nerve stimulation

Magnetic stimulation therapy without pain is being studied as an alternative to electrical stimulation therapy with pain. This paper presents a novel coil arrangement including the two sub-coils besides the main coil. This scheme results in the desired flux distribution penetrating more deeply into the tissue. Each optimal coil current and the optimal sub-coil location are derived with the aid of numerical magnetic field analysis. The derivation is carried out by means of the genetic algorithm combined with the finite element method. Moreover, the authors incorporate the circuit equations with the above methods. The results suggest that the magnetic stimulation with plural coils is effective for the pudendal nerve in the deep site.