Study On Optimization And Simulation Of Magnetic Stimulation System

Magnetic stimulation(MS) is a method for stimulating excitable tissue with an electric current induced by an external time-varying magnetic field. Having elucidated the principles of the generation and propagation of nerve excitation, a series of models relative to magnetic stimulation from circuits of magnetic stimulator to nerve fiber were given. Based on classical core conductor model, nonlinear Hodgkin-Huxley model and nonlinear CRRSS model under the induced electric field were derived to establish the relationship between nerve excitation and stimulator's circuit parameters. The systems of the derived nerve equations had elucidated the mechanism of magnetic stimulation: both the magnetic stimulation and the electric stimulation excite the cell membrane with electric current, and the difference lies in that the electric stimulation does that directly, but the magnetic stimulation does it with the electric current which is induced within the volume conductor by the time-varying applied magnetic field. As to the straight nerve fiber, it is the activating function, that is, the gradient of the component of induced electric field parallel to the axon(nerve), that plays the role of exciting nerve. Have elucidated the ways to calculate the distribution of induced electrical fields in the nerve fiber which parallel to coil plane by single loop stimulating coil without considering the section of the wire and the wire with rectangle section. The paper discussed exactly three types of respond states of magnetic stimulator system discharge circuit. And built a relationship between threshold respond of nerve and the circuit of magnetic stimulator. The result is used to optimize the design of magnetic stimulator, and was proved by activation function. The passive nerve fiber model can simulate the excitable nerve fiber's action extremely. And it is a useful tool to study the response of excitable nerves. With the respect of magnetic stimulation is electrical stimulation in fact, we establish a H-H model simulation used the tool of MATLAB's simulink. The model can simulate the responds of a nerve which was stimulated by a point current source. The model is the basis of study a magnetic stimulation.