脑EIT中边界电压随颅内电阻率扰动变化情况的仿真研究

Simulation Study of the Variation of Boundary Voltages in Brain EIT Caused by Resistivity Disturbance inside Cranium

由于脑部高电阻率的颅骨的存在,电阻抗断层成像(EIT)测量时,由颅内电阻率分布的改变导致边界电压的变化量与不含颅骨的目标不同。参照人脑部的解剖图谱,制作了一个由7 300多个电阻构成的脑部电阻率分布仿真模型。基于该模型的仿真结果显示:颅骨和脑脊液的存在使边界电压动态范围由17倍增至28倍。当目标中心占成像区域空间分辨率在0.09、电阻率分辨率在0.25时,归一化的边界电压平均变化量和最大变化量分别比均匀模型小11.4倍和8.3倍。根据这些结果,可以认为脑EIT硬件系统需至少能够识别出相对满量程的0.01%的边界电压变化,才能探测出这种电阻率变化。

Because of the existence of the high resistivity skull,the variations of the boundary voltages which are caused by the resistivity changes inside the target area are different to that with non skull object during EIT measurement. In order to study these variations,a simulation model which consists of 7300 resistors was established based on the anatomical atlas of the human head.Simulation results based on this model shown that the existence of the skull and CSF caused the dynamic range of boundary voltages increased from 17 to 28 times.As the skull and CSF was considered,the resulted average and the maximal normalized boundary voltage changes decreased by 11.4 and 8.3 times respectively when the spatial resolution is 0.09 and the conductivity resolution is 0.25.Based on those results,we think that the hardware of brain EIT should be able to measure 0.01% of the boundary voltages changes compared with their full scale ranges（FSR） so that it can detect the resistivity disturbance like this.