Design of current source for multi-frequency simultaneous electrical impedance tomography
Design of current source for multi-frequency simultaneous electrical impedance tomography
复制标题
多频同步电阻抗断层扫描电流源设计
DOI：
10.1063/1.5004185
复制
发表时间：
2017-09-01
影响因子：
1.6
通讯作者：
Dong, Feng
中科院分区：
文献类型：
--
作者：
Han, Bing;Xu, Yanbin;Dong, Feng
多频电阻抗断层成像已从扫频方法发展到多频同时测量技术，该技术可以减少测量时间，并且在时变生物应用中越来越有吸引力。电流源的精度和稳定性是决定图像重建质量的关键因素。介绍了一种用于多频同步电阻抗成像系统的基于现场可编程门阵列的电流源。将基于反馈放大器AD844的经典电流镜与差分拓扑相结合，实现了一种新型电流源电路。通过峰值因子分析，得到了谐波正弦信号的最佳相位偏移量。通过仿真和实际测量，对该电流源的输出特性进行了评价。结果表明：（1）该电路的输出阻抗与Howland泵浦电路的输出阻抗进行了仿真比较，在低频下具有相当的性能。然而，所提出的电流源对电阻容差的要求较低，但在高频下性能更好。(2)在200 kHz以下的实际测量中，输出阻抗在1.3 M Ω以上，最高可达1 MHz的250 K Ω。(3)基于生物RC模型的实验已经实现。解调阻抗幅值和相位的平均误差分别为0.192%和0.139度。因此，所提出的电流源是宽带，生物相容性，和高精度，这表明了巨大的潜力，作为一个子系统中的多频电阻抗断层成像系统。出版社：AIP Publishing
Multi-frequency electrical impedance tomography has been evolving from the frequency-sweep approach to the multi-frequency simultaneous measurement technique which can reduce measuring time and will be increasingly attractive for time-varying biological applications. The accuracy and stability of the current source are the key factors determining the quality of the image reconstruction. This article presents a field programmable gate array-based current source for a multi-frequency simultaneous electrical impedance tomography system. A novel current source circuit was realized by combining the classic current mirror based on the feedback amplifier AD844 with a differential topology. The optimal phase offsets of harmonic sinusoids were obtained through the crest factor analysis. The output characteristics of this current source were evaluated by simulation and actual measurement. The results include the following: (1) the output impedance was compared with one of the Howland pump circuit in simulation, showing comparable performance at low frequencies. However, the proposed current source makes lower demands for resistor tolerance but performs even better at high frequencies. (2) The output impedance in actual measurement below 200 kHz is above 1.3 M Omega and can reach 250 K Omega up to 1 MHz. (3) An experiment based on a biological RC model has been implemented. The mean error for the demodulated impedance amplitude and phase are 0.192% and 0.139 degrees, respectively. Therefore, the proposed current source is wideband, biocompatible, and high precision, which demonstrates great potential to work as a sub-system in the multi-frequency electrical impedance tomography system. Published by AIP Publishing.