Electromagnetic Probe and Driving Circuit Design for Micro Magnetic Stimulation of Small Animal Brains

Abstract

Magnetic stimulation is becoming more and more popular recently as a kind of medical treatment for brain function. By generating an alternating magnetic field from the electromagnetic probe, the induced electric field will be generated in a small region and stimulate a single or a group of neuron(s). A functional magnetic stimulation system consists of two parts: 1) electromagnetic probe/coil, and 2) magnetic stimulation circuit. For the electromagnetic probe, several possible structures for different application were discussed. For single neuron stimulation, magnetic probe with a sharp tip was investigated. Furthermore, an optimal shape for the sharp tip was determined by analytical calculation and COMSOL Multiphysics® finite element simulation. A prototype probe was fabricated and the induced electrical field of the probe was measured combining with the magnetic stimulation circuit and an electrical field detector. For brains of some small animals like rats, a cylindrical-shaped coil was studied and the optimized shape is determined by COMSOL Multiphysics® finite element simulation. For the magnetic stimulation circuit, a charging & control method was analyzed. Connected with a pulse generator and DC power source, the magnitude and pulse width are measured. The relationship between electronic and electromagnetic parameters was calculated and simulated with Multisim®. Furthermore, the application of an LR filter to suppress the noise was studied by calculation and simulation with Multisim®.