Research On Method And Instrument Of The Multi-channel Brain Magnetic Stimulation

Magnetic stimulation is a new method for stimulating excitable tissue of human by using external time-varying magnetic fields. This technique has been applied in many fields such as academic research, diagnosis, therapy and so on. The typical process of magnetic stimulation is inducing the electric fields in human's body by using external magnetic fields, then the electric fields activate the excitable tissue. The stimulator is not directly contact on human's body during stimulation process, so the process is non-invasive, painless and it can be repeated easily. The skeleton is not a good conductor of electricity, but it won't attenuate the magnetic fields much. So, magnetic stimulation is more advantageous than the conventional stimulation methods.In order to overcome the limitation of the conventional magnetic stimulator, a multi-channel brain magnetic stimulator was developed in this paper. This device can stimulate several areas of brain simultaneously. The position and frequency of working coils can be controlled and the shape of magnetic fields can be adjusted by pre-defining the parameter of this stimulator. The stimulator will stimulate the target according to pre-defining automatically.In this paper, the magnetic fields that produced by a coil array was simulated by using the finite-element analysis software-ANSYS, and the character of magnetic fields, which produced by the multi-channel brain magnetic stimulator in different mode, can be described by this simulating result. The real magnetic field produced by the stimulator was also measured and the results showed that the calculation error is small. This study indicated that the simulation results can depict the real magnetic fields of multi-channel magnetic stimulator effectively, and it can be a reliable basis for designing and analyzing the magnetic stimulation experiments.Some stimulation experiments have been proceeded by using the multi-channel brain magnetic stimulator. The experimental results showed that the magnetic fields could stimulate the brain effectively, and could reach the anticipating result. A new method, which stimulates human brain alternatively by different frequencies and at different areas of the brain, was first used in this paper. And the complexity of EEG was used to observe the stimulation effect. The different effect between alternative and single stimulation on brain is researched in this paper, and the change of EEG's randomness was also studied.