Bagshaw Andrew P, Liston Adam D, Bayford Richard H, Tizzard Andrew, Gibson Adam P, Tidswell A Thomas, Sparkes Matthew K, Dehghani Hamid, Binnie Colin D, Holder David S
Department of Clinical Neurophysiology, University College London, UK.
Neuroimage. 2003 Oct;20(2):752-64. doi: 10.1016/S1053-8119(03)00301-X.
Electrical impedance tomography (EIT) is a recently developed technique which enables the internal conductivity of an object to be imaged using rings of external electrodes. In a recent study, EIT during cortical evoked responses showed encouraging changes in the raw impedance measurements, but reconstructed images were noisy. A simplified reconstruction algorithm was used which modelled the head as a homogeneous sphere. In the current study, the development and validation of an improved reconstruction algorithm are described in which realistic geometry and conductivity distributions have been incorporated using the finite element method. Data from computer simulations and spherical or head-shaped saline-filled tank phantoms, in which the skull was represented by a concentric shell of plaster of Paris or a real human skull, have been reconstructed into images. There were significant improvements in image quality as a result of the incorporation of accurate geometry and extracerebral layers in the reconstruction algorithm. Image quality, assessed by blinded subjective expert observers, also improved significantly when data from the previous evoked response study were reanalysed with the new algorithm. In preliminary images collected during epileptic seizures, the new algorithm generated EIT conductivity changes which were consistent with the electrographic ictal activity. Incorporation of realistic geometry and conductivity into the reconstruction algorithm significantly improves the quality of EIT images and lends encouragement to the belief that EIT may provide a low-cost, portable functional neuroimaging system in the foreseeable future.
电阻抗断层成像（EIT）是一种最近开发的技术，它能够利用外部电极环对物体的内部电导率进行成像。在最近的一项研究中，皮质诱发反应期间的EIT在原始阻抗测量中显示出令人鼓舞的变化，但重建图像存在噪声。使用了一种简化的重建算法，该算法将头部建模为一个均匀的球体。在当前的研究中，描述了一种改进的重建算法的开发和验证，其中使用有限元方法纳入了真实的几何形状和电导率分布。来自计算机模拟以及球形或头部形状的充满盐水的水箱模型（其中颅骨由巴黎石膏同心壳或真实人类颅骨表示）的数据已被重建为图像。由于在重建算法中纳入了精确的几何形状和脑外层，图像质量有了显著提高。当使用新算法重新分析先前诱发反应研究的数据时，由不知情的主观专家观察者评估的图像质量也有了显著提高。在癫痫发作期间收集的初步图像中，新算法生成的EIT电导率变化与脑电图发作期活动一致。将真实的几何形状和电导率纳入重建算法显著提高了EIT图像的质量，并让人相信在可预见的未来EIT可能会提供一种低成本、便携式的功能神经成像系统。
