Shahidi A V, Guardo R, Savard P
Institut de génie Biomédical, Ecole Polytechnique, Montréal, Québec, Canada.
Ann Biomed Eng. 1995 Jan-Feb;23(1):61-9. doi: 10.1007/BF02368301.
A direct image reconstruction method of electrical impedance tomography (EIT) is evaluated using three-dimensional (3-D) finite element models of cylindrical and torso-shaped volume conductors. The cylindrical model is used to examine the effect of electrode configurations and the sensitivity to off-plane objects and to noise in the measured data. It is also used to validate the modeling procedures by comparison with experimental data acquired from a similar cylindrical tank filled with saline. Simulation results show only minor differences in performance between the various electrode configurations. In the second part, a realistic human thorax model constructed from CT images is used to evaluate monitoring of pulmonary edema by EIT. The conductivity, volume, and vertical position of an abnormal region in the lungs are varied to simulate the progress of edema. Dynamic EIT images are reconstructed from data computed for the inhomogeneous thorax (heart and lungs) as the reference set and a realistic amount of noise is added to reproduce the conditions in which the technique would be used in practice. Simulation results show that a 10 ml edema region with a conductivity equal to that of blood can be detected at a 40 dB signal-to-noise ratio (SNR). Detection of a smaller volume, in the order of 2 ml, should be possible by improving either the instrumentation to achieve 60 dB SNR or the performance of reconstruction algorithms.
利用圆柱形和躯干形状的体积导体的三维（3-D）有限元模型，对电阻抗断层成像（EIT）的一种直接图像重建方法进行了评估。圆柱形模型用于研究电极配置的影响以及对平面外物体和测量数据中噪声的敏感度。它还用于通过与从类似的装满盐水的圆柱形水箱获取的实验数据进行比较，来验证建模程序。模拟结果表明，各种电极配置之间的性能差异很小。在第二部分中，使用从CT图像构建的逼真的人体胸部模型来评估EIT对肺水肿的监测。改变肺部异常区域的电导率、体积和垂直位置以模拟水肿的进展。从为非均匀胸部（心脏和肺部）计算的数据重建动态EIT图像作为参考集，并添加实际量的噪声以再现该技术在实际应用中的条件。模拟结果表明，在40 dB的信噪比（SNR）下，可以检测到电导率与血液相等的10 ml水肿区域。通过改进仪器以达到60 dB的SNR或重建算法的性能，应该可以检测到更小体积（约2 ml）的水肿。
