经颅磁刺激和脑电联合作用时电磁场分布的仿真研究

Simulation study of electromagnetic field distribution when combining TMS with EEG

目的:研究分析经颅磁刺激和脑电(TMS-EEG)联合作用时磁感应强度和感应电场强度的分布情况。方法:利用有限元多物理场仿真软件COMSOL,搭建3层同心球人头模型、TMS线圈模型和EEG电极模型,在TMS线圈的作用下,对比分析了有无脑电极时,人头模型当中磁感应强度和感应电场强度的不同。结果:取头部组织几个特殊位置点,放置脑电极后,各点处磁感应强度和感应电场强度均发生变化,磁感应强度最大变化达19.19%,感应电场强度最大变化达75.33%。添加脑电极后,人体头部组织YZ纵切面的最大磁感应强度降低7 mT,最大感应电场强度值降低0.6 V/m。大脑处的三维磁感应强度和感应电场强度均随着深度的增加而逐渐减小,放置脑电极后,脑组织中的最大磁感应强度值减少1.4 mT,最大感应电场强度值减少0.13 V/m。结论:经TMS-EEG联合作用时,在人头皮处放置脑电极会对电磁场的分布产生影响,间接影响TMS的治疗作用。

Objective To analyze the distributions of magnetic induction intensity and induced electric field intensity in the combined action of transcranial magnetic stimulation(TMS)and electroencephalogram(EEG).Methods The finite element multi-physics field simulation software COMSOL was used to model the 3-layer concentric spherical human head,TMS coil and EEG electrodes.The differences in magnetic induction intensity and induced electric field intensity of the human head model with and without brain electrodes are compared and analyzed in the presence of TMS coil.Results The magnetic induction intensity and the induced electric field intensity were changed at several specific points in the head after the placement of brain electrodes.The magnetic induction intensity had a maximum change up to 19.19%,and the maximum change in induced electric field intensity was 75.33%.After the placement of brain electrodes,the maximum magnetic induction intensity of YZ longitudinal section of human head was decreased by 7 mT,and the maximum induced electric field intensity was decreased by 0.6 V/m.Both the three-dimensional magnetic induction intensity and the induced electric field intensity at the brain were decreased gradually with the increase of depth.After the placement of brain electrodes,the maximum magnetic induction intensity and the maximum induced electric field intensity in the brain tissue were decreased by 1.4 mT and 0.13 V/m,respectively.Conclusion When TMS and EEG are combined,the placement of brain electrodes at the human scalp will change the electromagnetic field distribution,indirectly affecting the therapeutic effect of TMS.