| Transcranial Magnetic Stimulation(TMS)is one of the mainstream nerve Stimulation technologies in brain science research and treatment.The main principle is to generate induced Magnetic field in the human brain with the help of large instantaneous pulse current to induce induced electric field and stimulate nerve cells for the purpose of treatment.H coil is a typical representative of deep transcranial magnetic stimulation coil,which mainly USES the principle of vector superposition to stimulate deep brain tissues.The current H coil is costly to develop and difficult to design,and the outline of H coil is mainly designed according to the standard head model,which is fixed by the induced magnetic field formed when the coil structure is fixed.However,since everyone’s head contour is different,and the lesion target area of many mental and neurological diseases is also different,it is of great significance to explore how to regulate the focusing performance and stimulation intensity of the intracranial induction field induced by the H coil while the output of the coil and the machine remains unchanged.In this paper,based on ANSYS finite element analysis software,the H-coil model based on the real head conductivity model is established,and high magnetic permeability,high conductivity model and comprehensive model of magnetic conductive block and conductive block are established at different positions.The parameters such as focus volume,focus position,stimulation intensity and depth characteristics of different models were compared and analyzed.The results show that after increasing the high magnetic permeability or the high conductivity model at different locations,the induced electric field intensity in the skull below the model can be significantly increased or decreased,while the other positions are less affected,and the focus volume of the H coil in the shallow cortex is reduced.The influence of the depth characteristics is not significant.Based on the results,the integrated model of the magnetic conductive block and the conductive block can be used to integrate the advantages of each model,significantly improve the intensity of the induced electric field at the position of the "window",and reduce the induced electric field strength of other regions,further improve the focusing characteristics of the H coil,while reducing damage to the shallow cortex,but slightly reduce the depth characteristics of the H coil,the effect is not obvious.In addition,this paper also carried out the exploration of the physical parameters,processing technology,shell and mold design of the coil winding,carried out the 8-coil,double cone coil and H-coil winding,built a magnetic field test platform,and three kinds of the coil is subjected to three-dimensional magnetic field test and comparative analysis.The results show that the 8-coil can be focused on a small area of the center of the coil,and the focusing performance is good,but the depth characteristics are poor.The focusing area of the double cone coil is larger than the 8-coil,but the depth characteristics are Better than the 8-coil,the H-coil will have a focus area on both sides of the head and the forehead part,which is less focused,but has the best depth characteristics.In summary,this paper proposes a scheme to adjust the inductive electric field focusing characteristics and stimulation intensity of the H coil induced by the H coil while the H coil is fixed without increasing the machine output,and explores the coil winding process.The basis of intracranial electric field regulation and development of transcranial magnetic stimulation H coil is provided. |
