Research on Hihg-Performance Electrical Impedance Tomography

电阻抗断层扫描（EIT）是一种能够可视化生命体中与解剖紊乱或生理活动相关的电阻抗分布及其变化的技术，可用于监测脑血流变化等生物状况。在这项研究中，我们开发了神经网络方法来解决通过在体表密集放置的一组电极测量的浅表电位分布来估计电导率分布的逆问题。为了提高电导率剖面的分辨率，当我们想要识别局部脑血流增量时，基于核磁共振的反褶积将被有效地使用；在这种情况下，应用动态正则化技术可以很好地改善逆问题的病态性。本文还提出了一种选择最佳分割指标的遗传算法，这是实现脑脊液、脑灰质和脑白质自动分割后，将MR数据整合到反卷积网络中的关键技术。我们研究的另一个课题是利用磁控四极法来监测大脑的脉动阻抗变化：我们对该系统进行了实验测试，以证明该方法在估计精神负荷测试期间的血光增量方面的有效性。我们现在计划通过对测量中获得的一系列数据进行反卷积，使磁场连续移动，从而提高磁控四极法的分辨率。

Electrical impedance tomography (EIT) is capable of visualizing the electrical impedance distribution and its changes related to the anatomical disorders or physiological activities in the living body, to be applied for monitoring the biological conditions such as blood-flow changes in the brain, swellings and urinary bladder content etc.In this research we developed neural network methods to solve the inverse problems in estimating the conductivity distribution from the superficial potential distribution measured via a set of electrodes densely placed on the body surface. For improving the resolution of the conductivity profile, MR-based deconvolution will be effective used when we want to identify the localized blood-flow increment in the brain ; in this case ill-posedness of the inverse problem can be well improved by applying the dynamic regularization technique. We also developed a GA method to select the best indices for MR segmentation, which is a key-technology for incorporating the MR data to the deconvolution network after segmenting the CSF,the gray-matter and the white-matter of the brain automatically.Another topic, we investigated is the use of magnetically controlled tetrapolar method to monitor the pulsatile impedance changes in the brain : we experimentally tested the system to prove the effectiveness of the method in estimating the blood-glow increment during the mental-loading tests.We are now planning to improve the resolution of magnetically controlled tetrapolar method by deconvolving the series of data obtained in the measurement with the magnetic field continuously shifted.