Igney C H, Watson S, Williams R J, Griffiths H, Dössel O
Institut für Biomedizinische Technik, Universität Karlsruhe (TH), Kaiserstr 12, 76131 Karlsruhe, Germany.
Physiol Meas. 2005 Apr;26(2):S263-78. doi: 10.1088/0967-3334/26/2/025. Epub 2005 Mar 29.
In this study the performance of a planar array for magnetic induction tomography (MIT) was investigated and the results of measurements to determine the precision and sensitivity of the sensor were undertaken. A planar-array MIT system utilizing flux-linkage minimization for the primary field has been constructed and evaluated. The system comprises 4 printed excitation coils of 4 turns which were shielded, 8 surface-mount inductors of inductance 10 microH as sensor, mounted such that in principle no primary-field flux threads them, and a calibration coil to produce a strong primary field. The excitation current was multiplexed via relays to drive the excitation and reference coils. The noise values were similar in real and imaginary components in the lower frequencies and the factor to which the primary field could be reduced was greatest in the nearest coil. Methods for determining the true real and imaginary components and for flux-linkage minimization for the primary field for variations in channel sensitivities are described and the results of measurements of the system's noise and drift are given. A SNR of 47 dB was observed at 4 MHz when a 0.3 Sm-1 saline filled tank of dimensions 20 cmx20 cmx10 cm was placed centrally over the array. Finally, images were reconstructed from measurements of saline samples in a free space background, with the samples moved past the array in 21 1 cm steps to emulate mechanical scanning of the array. The image reconstruction characteristics of the planar array in conjunction with the reconstruction technique employed are discussed.
在本研究中，对用于磁感应断层成像（MIT）的平面阵列性能进行了研究，并开展了测量以确定传感器的精度和灵敏度。构建并评估了一种利用初级场磁通链最小化的平面阵列MIT系统。该系统包括4个4匝的印刷励磁线圈（已屏蔽）、8个电感为10微亨的表面贴装电感器作为传感器（安装方式使得原则上没有初级场磁通穿过它们）以及一个用于产生强初级场的校准线圈。励磁电流通过继电器进行多路复用，以驱动励磁线圈和参考线圈。在较低频率下，实部和虚部的噪声值相似，且在最靠近的线圈中，初级场能够降低的系数最大。描述了确定真实实部和虚部以及针对通道灵敏度变化使初级场磁通链最小化的方法，并给出了系统噪声和漂移的测量结果。当一个尺寸为20 cm×20 cm×10 cm、电导率为0.3 S/m的充满盐水的水箱放置在阵列中心上方时，在4 MHz处观察到信噪比为47 dB。最后，从自由空间背景下盐水样本的测量结果重建图像，样本以1 cm的步长从阵列旁经过，以模拟对阵列的机械扫描。讨论了平面阵列的图像重建特性以及所采用的重建技术。
