改进型BMIT激励源设计及磁场分析

Improved Excitation Source Design and Magnetic Field Analysis of BMIT System

目的:设计一种符合人体电磁暴露安全标准要求的脑磁感应成像激励源,以满足临床应用中人体安全性的需要。方法:在该课题组前期工作的基础上,采用有源晶体振荡器作为振荡源,参照IEEEStdC95.1人体电磁暴露安全标准,计算、设计和实现3种激励线圈和激励电路,以产生符合安全标准的激励磁场,并对所产生的激励磁场进行初步测量和评估。结果:平面矩形聚焦线圈在线圈中心处10MHz、1MHz、200kHz最大磁感应强度分别为0.005、0.057、0.189T,沿着轴线方向磁场逐步衰减,且磁场由轴线方向两侧也逐步衰减,斜率分别约为0.0002、0.002、0.007T/cm。结论:测量区域内的场强均满足安全性要求。安全性激励源的实现为临床安全应用打下了良好的基础。

Objective To design an excitation source for brain magnetic induction tomography,which can produce a safety magnetic field within the standard of IEEE Std C95.1 for human brain and can meet the requirements of clinical application.Methods The active crystal oscillator was used to generate sinusoid signal.In order to produce safety and steady exciting magnetic field,three kinds of excitation coils and excitation circuits were designed.Induction coil was used to detect magnetic field intensity and evaluate the fields.Results The highest values of magnetic induction intensity near the center of the planar rectangular excitation coil were 0.005 T,0.057 T and 0.189 T at three frequencies of 10 MHz,1 MHz,200 kHz.The magnetic field intensity got lower and lower along with axial direction of the excitation coil.The attenuation rates were about 0.000 2 T/cm,0.002 T/cm and 0.007 T/cm from axes of the excitation coil to the both sides of the axes.Conclusion The magnetic field intensity meets the requirements of the standard for safety levels.The realization of safety excitation source may be of great help for further brain magnetic induction tomography clinical application.