Impedance Imaging Research Center and Department of Biomedical Engineering, Kyung Hee University, Korea.
Physiol Meas. 2011 Jul;32(7):835-49. doi: 10.1088/0967-3334/32/7/S08. Epub 2011 Jun 7.
We report the development of a new multi-frequency electrical impedance tomography (EIT) system called the KHU Mark2. It is descended from the KHU Mark1 in terms of technical details such as digital waveform generation, Howland current source with multiple generalized impedance converters and digital phase-sensitive demodulators. New features include flexible electrode configurations to accommodate application-specific requirements, multiple independent current sources and voltmeters for fully parallel operations, improved data acquisition speeds for faster frame rates and compact mechanical design. Given an electrode configuration, we can design an analog backplane in such a way that both current injections and voltage measurements can be done without using any switch. The KHU Mark2 is based on an impedance measurement module (IMM) comprising a current source and a voltmeter. Using multiple IMMs, we can construct a multi-channel system with 16, 32 or 64 channels, for example. Adopting a pipeline structure, it has the maximum data acquisition speed of 100 scans s(-1) with the potential to detect fast physiological changes during respiration and cardiac activity. Measuring both in-phase and quadrature components of trans-impedances at multiple frequencies simultaneously, the KHU Mark2 is apt at spectroscopic EIT imaging. In this paper, we describe its design, construction, calibration and performance evaluation. It has about 84 dB signal-to-noise ratio and 0.5% reciprocity error. Time-difference images of an admittivity phantom are presented showing spectroscopic admittivity images. Future application studies using the KHU Mark2 are briefly discussed.
我们报告了一种新型多频电阻抗断层成像（EIT）系统的开发，称为 KHU Mark2。它在技术细节上源自 KHU Mark1，例如数字波形生成、带有多个广义阻抗转换器的 Howland 电流源和数字相敏解调器。新功能包括灵活的电极配置，以适应特定应用的要求，多个独立的电流源和电压表用于完全并行操作，改进的数据采集速度以实现更快的帧率和紧凑的机械设计。给定一个电极配置，我们可以设计一个模拟背板，使得电流注入和电压测量都可以在不使用任何开关的情况下完成。KHU Mark2 基于一个阻抗测量模块（IMM），包括一个电流源和一个电压表。使用多个 IMM，我们可以构建一个具有 16、32 或 64 个通道的多通道系统，例如。采用流水线结构，它具有 100 扫描 s(-1)的最大数据采集速度，有可能在呼吸和心脏活动期间检测到快速的生理变化。KHU Mark2 同时测量多个频率的跨阻抗的同相和正交分量，适用于光谱 EIT 成像。在本文中，我们描述了它的设计、构建、校准和性能评估。它具有约 84 dB 的信噪比和 0.5%的互易误差。展示了光谱电导率图像的导纳体模型的时差图像。简要讨论了使用 KHU Mark2 的未来应用研究。
