Development electric impedance CT using magnetic field

本研究提出了一种利用磁场四极电路实现生物电阻抗断层成像的方法。在此基础上，制作了实验装置，并利用生物材料的电学模型进行了模型实验。该仪器由恒流源、电磁铁心及其驱动电路、压差检测电路组成。检测到的电压值通过D/A转换器输入计算机。利用直线电机移动磁场，由步进电机实现测量方向的旋转。这些动作是由计算机控制的。为了从电压差数据中得到模型中的电导分布，采用了最小残差法。研究了计算次数和初始值的设置方法。结果表明：1)通过设置计算次数的条件，比较所有测量方向在固定计算次数下的计算次数，可以减少总的计算次数；2)以测量方向θ；i-1；gt；的最终电导值作为θ；&lt；i-gt；计算次数的初始值，也可以减少计算次数。3)在图像中重建模型旋转和电导的部分变化。4)研究表明，三维阻抗CT的实现方法是将测量的x-y平面沿z轴方向移动来实现的，利用该方法建立实用的阻抗CT需要具有更高的空间灵敏度和更短的电压差数据采集时间。

In this study, a realizing method of a bio-electrical impedance tomography (EIT) by the tetrapolar circuit using magnetic field was proposed. Based on this method, an instrument was made and model experiments were performed suing some electric model of the bio-substance. This instrument consists of a constant current source, an electromagnetic core and its driving circuit, detection circuit of voltage difference. The detected voltage values are inputted into a computer using D/A converter. The magnetic field is moved using a linear motor and the rotation of measurement direction is performed by a stepping motor. These actions are controlled by a computer. To get the distribution of conductance in the model from voltage difference data, the least residual method was used. Setting method of calculation number and initial value were studied. The obtained results are as follows;1)The total calculation number can be decreased by setting a condition for calculation number, comparing that of obtained under a constant calculation number for all measurement directions.2)By using the final conductance value obtained at the measurement direction θ_<i-1> as initial value at θ_<i-> calculation number can be also decreased.3)The model rotation and the partial change in conductance were reconstructed in the image. Therefore, it is considered that the proposed realization method of CT has a high sensibility for change in conductance.4)It was shown that three dimensional impedance CT would be realized by moving the measuring x-y plane in z-axis direction.To establish a practical impedance CT by this method, it is necessary to get a higher spatial sensibility and a more brief time of acquiring voltage different data.