Goharian Mehran, Soleimani Manuchehr, Jegatheesan Aravinthan, Chin Kenrick, Moran Gerald R
Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, ON, Canada.
Ann Biomed Eng. 2008 Sep;36(9):1594-603. doi: 10.1007/s10439-008-9537-5. Epub 2008 Jul 16.
This paper describes the design of a multi-frequency Electrical impedance tomography (EIT) system, which provides a flexible mechanism for addressing up to 48 electrodes for imaging conductivity and permittivity distributions. A waveform generator based on a digital signal processor is used to produce sinusoidal waveforms with the ability to select frequencies in the range of 0.1-125 kHz. A software based phase-sensitive demodulation technique is used to extract amplitudes and phases from the raw measurements. Signal averaging and automatic gain control are also implemented in voltage and phase measurements. System performance was validated using a Cardiff-Cole Phantom and a saline filled cylindrical tank. The signal-to-noise ratio (SNR) using saline tank was greater than 60 dB and the maximum reciprocity error less than 4% for most frequencies. The common-mode rejection ratio (CMRR) was nearly 60 dB at 50 kHz. Image reconstruction performance was assessed using data acquired through a range of frequencies. This EIT system offers image reconstruction of both conductivity and permittivity distributions in three dimensions. The imaging results are presented in time difference and frequency difference imaging.
本文描述了一种多频电阻抗断层成像（EIT）系统的设计，该系统提供了一种灵活的机制，可用于处理多达48个电极，以成像电导率和介电常数分布。基于数字信号处理器的波形发生器用于产生正弦波形，能够在0.1 - 125 kHz范围内选择频率。基于软件的相敏解调技术用于从原始测量中提取幅度和相位。在电压和相位测量中还实现了信号平均和自动增益控制。使用加的夫 - 科尔体模和充满盐水的圆柱形水箱对系统性能进行了验证。使用盐水箱时，信噪比（SNR）大于60 dB，大多数频率下的最大互易误差小于4%。在50 kHz时，共模抑制比（CMRR）接近60 dB。使用通过一系列频率采集的数据评估图像重建性能。该EIT系统提供三维电导率和介电常数分布的图像重建。成像结果以时间差成像和频率差成像的形式呈现。
