颅骨对磁感应断层成像信号检测影响的仿真与实验研究

Simulation and Experimental Research on the Impact of Skull in Magnetic Induction Tomography Signal Detection

采用仿真和实验研究颅骨对磁感应断层成像(MIT)信号检测的影响。使用Comsol软件建立3层球形仿真颅脑模型,仿真计算颅骨电导率对MIT信号检测的影响。使用螺线管线圈、后置电路及数据接收仪器搭建单通道磁感应信号测量实验系统,利用琼脂和Na Cl溶液制作与真实颅脑电导率分布相近的脑出血分层模型,模型外径为158 mm;最后采用有颅骨和无颅骨两种模型,测量无病变及不同病变位置情况下MIT信号的相位变化,模型中心与检测线圈相距85 mm。实验结果显示,在无病变和病变分别位于X-Y平面上坐标为(-40,0)、(0,0)和(40,0)的位置时,有、无颅骨数据的幅值比例分别为0.57、0.59、0.42、0.61,其中,坐标点(-40,0)代表Y轴左侧距离激励线圈45 mm的位置,坐标点(40,0)代表Y轴右侧距离接收线圈45 mm的位置。当病变存在时,有、无颅骨数据的变化趋势均为:病变位于坐标点(-40,0)时最大,病变位于坐标点(40,0)时次之,病变位于坐标点(0,0)时最小。实验结果表明,颅骨对MIT信号的数据大小有衰减作用,但不影响数据的变化趋势,提示在实际应用中结合高精度检测设备,可实现颅内病变的无创、无接触图像监测。

The aim of this paper is to study the effect of skull to magnetic induction tomography（ MIT） signal detection through simulation and experiments. Firstly,a spherical brain model of three layers was established using Comsol software to simulate the effects of the skull conductivity to MIT signal detection. And then a multichannel magnetic induction tomography experimental system which consists of solenoid coil,rear circuit and data receiving apparatus was established,and a hierarchical model of cerebral hemorrhage was made of agar and Na Cl solution which has a similar conductivity distribution with the real brain. The diameter of the model is 158 mm. Finally,in the two models with skull and without skull,the phase change of no lesion and different locations of simulating lesions were measured. The distance between the model center and detection coil is 85 mm. From the results,what can be seen is that,when the model with no lesion and lesions were on the coordinates of（- 40,0）,（ 0,0） and（ 40,0） of the X-Y plane,the proportion of the phase change between the models with and without skull is 0. 57,0. 59,0. 42,0. 61 respectively. The coordinates of（- 40,0） and（ 40,0） represent the position which has a distance of 45 mm from incentive coil to y axis and a distance of45 mm from Y axis to incentive coil respectively. When there is a lesion,the change trend of the data in the model with and without skull is same,which means that the maximum appears on the coordinate of（- 40,0）,the second appears on the coordinate of（ 0,0）,and the smallest appears on the coordinate of（ 40,0）. The results show that,the skull has an effect of attenuation on the size of MIT signals,but the changing trend ofmeasured data is not changed. The results also indicate that the image detection of intracranial lesions can be achieved without a record and contact using high precision hardware detection system in practical applications.