Study On Magnetic Stimulator Design And Detection Of Induced Electromagnetic Field

Magnetic stimulation (MS) is a kind of stimulating technique for some excitable tissues in which a coil with a flow of time-varying current is extra corporeally place above the stimulating sit and generates a high-pulsed magnetic field while electric field is induced within the tissue. Induced eddy currents circulate, and if of sufficient amplitude and duration, can cause neuronal depolarization. Compared with other stimulations, MS is non-contact, non-invasive and no pain. It is these advantages that make it gaine much popularity in clinic within the last decade. On the other hand, there are still some problems technically, such as bad focusing of MS coil, low frequency, the power is too large for reaching MS threshold in existence MS instrument.This paper presents general guidelines for designing and constructing a magnetic stimulator. These guidelines cover theoretical concepts, hardware aspects and components required to build these system. The critical points discussed in this paper are based on key findings and difficulties encountered during the process of building the system. The magnetic field intensity in the central of a round coil is deduced and calculated. The paper focuses on a RLC model that produces the impulses in magnetic stimulator, and presents the way to calculate the parameters of the model. Some facts that influence magnetic field intensity are discussed. The parameters of elements of MS system are calculated in details. The paper expatiates key points such as elements choosing and notices in design in particular because magnetic stimulator is high voltage, large current device. A set of MS system that produces 2.5 Tesla pulsed magnetic field (8-shaped coil) and the highest working voltage is 2kV is developed. After debugged, it works smoothly. A set of induced magnetic field detection device is made. A 'point'detector is designed to minimize influence of the detector to distribution of induced magnetic field. Combined with oscilloscope, we obtain waveform of pulsed induced voltage. Round coil and 8-shaped coil are also designed and made. Experiments are carrying through using those coils, and Tesla meter detects the magnetic fields and the magnetic field detect device is made by myself. The experiments data reveal that the magnetic field changed with voltage linearly and the distributions of magnetic field ofthe two coils are tallied to those of theory calculation that adopted now.Getting approximately distribution of induced magnetic field of a half round coil.A simulation experiment to measure magnetic fields in brain is designed. The experiment data is unanimous to the FDTD theory analysis of brain. Development of magnetic stimulator in the paper bases further research for the future.