Fernandez-Corazza Mariano, Turovets Sergei, Muravchik Carlos H
Annu Int Conf IEEE Eng Med Biol Soc. 2020 Jul;2020:1440-1443. doi: 10.1109/EMBC44109.2020.9175254.
Electrical Impedance Tomography (EIT) can be used to estimate the electrical properties of the head tissues in a parametric approach. This modality is called parametric EIT or bounded EIT (bEIT). Typical bEIT protocols alternate between several current injection patterns with two current injection electrodes each: one source and one sink ("1-to-1"), while the rest of the electrodes measure the resulting electric potential. Then, one value of conductivity per tissue (e.g. scalp and/or skull) is estimated independently for each current injection pair. With these protocols, it is difficult to obtain local estimates of the skull tissue. Thus, the grand average of the estimates obtained from each pair is assigned to each tissue modeling them as homogeneous. However, it is known that these tissues are inhomogeneous within the same subject. We propose the use of current injection patterns with one source and many sinks ("1to-N") located at the opposite side of the head to build individual and inhomogeneous skull conductivity maps. We validate the method with simulations and compare its performance with equivalent maps generated by using the classical "1-to-1" patterns. The map generated by the novel method shows better spatial correlation with the more conductive spongy bone presence.Clinical Relevance- The novel bEIT protocol allows to map individual head models with spatially resolved skull conductivities in vivo and non-invasively for use in electroencephalography (EEG) source localization, transcranial electrical stimulation (TES) dose calculations and TES pattern optimization, without the risk of ionizing radiation associated with computed tomography (CT) scans.
电阻抗断层成像（EIT）可用于通过参数化方法估计头部组织的电学特性。这种模式被称为参数化EIT或有界EIT（bEIT）。典型的bEIT协议在几种电流注入模式之间交替，每种模式有两个电流注入电极：一个源电极和一个汇电极（“1对1”），而其余电极测量产生的电势。然后，针对每个电流注入对独立估计每个组织（例如头皮和/或颅骨）的一个电导率值。使用这些协议很难获得颅骨组织的局部估计。因此，将从每个对获得的估计值的总体平均值分配给每个组织，并将它们建模为均匀的。然而，已知这些组织在同一受试者体内是不均匀的。我们建议使用一个源电极和多个位于头部相对侧的汇电极的电流注入模式（“1对N”）来构建个体的、不均匀的颅骨电导率图。我们通过模拟验证了该方法，并将其性能与使用经典“1对1”模式生成的等效图进行了比较。新方法生成的图与更具导电性的海绵骨存在显示出更好的空间相关性。临床相关性——这种新的bEIT协议允许在体内非侵入性地绘制具有空间分辨颅骨电导率的个体头部模型，用于脑电图（EEG）源定位、经颅电刺激（TES）剂量计算和TES模式优化，而没有与计算机断层扫描（CT）相关的电离辐射风险。
