Univ Rennes, INSERM, LTSI-U1099, F-35000, Rennes, France.
Neuroelectrics Barcelona, Barcelona, Spain.
Biomed Phys Eng Express. 2023 Jun 2;9(4). doi: 10.1088/2057-1976/acd385.
Intracranial electrodes are used clinically for diagnostic or therapeutic purposes, notably in drug-refractory epilepsy (DRE) among others. Visualization and quantification of the energy delivered through such electrodes is key to understanding how the resulting electric fields modulate neuronal excitability, i.e. the ratio between excitation and inhibition. Quantifying the electric field induced by electrical stimulation in a patient-specific manner is challenging, because these electric fields depend on a number of factors: electrode trajectory with respect to folded brain anatomy, biophysical (electrical conductivity / permittivity) properties of brain tissue and stimulation parameters such as electrode contacts position and intensity. Here, we aimed to evaluate various biophysical models for characterizing the electric fields induced by electrical stimulation in DRE patients undergoing stereoelectroencephalography (SEEG) recordings in the context of pre-surgical evaluation. This stimulation was performed with multiple-contact intracranial electrodes used in routine clinical practice. We introduced realistic 3D models of electrode geometry and trajectory in the neocortex. For the electrodes, we compared point (0D) and line (1D) sources approximations. For brain tissue, we considered three configurations of increasing complexity: a 6-layer spherical model, a toy model with a sulcus representation, replicating results from previous approaches; and went beyond the state-of-the-art by using a realistic head model geometry. Electrode geometry influenced the electric field distribution at close distances (∼3 mm) from the electrode axis. For larger distances, the volume conductor geometry and electrical conductivity dominated electric field distribution. These results are the first step towards accurate and computationally tractable patient-specific models of electric fields induced by neuromodulation and neurostimulation procedures.
颅内电极在临床上用于诊断或治疗目的，特别是在耐药性癫痫（DRE）等疾病中。可视化和量化通过此类电极传递的能量对于理解产生的电场如何调节神经元兴奋性（即兴奋与抑制之比）至关重要。以患者特异性方式量化电刺激引起的电场具有挑战性，因为这些电场取决于许多因素：电极相对于折叠脑解剖结构的轨迹、脑组织的生物物理（电导率/介电常数）特性以及刺激参数，例如电极接触的位置和强度。在这里，我们旨在评估各种生物物理模型，以在接受立体脑电图（SEEG）记录的 DRE 患者中评估电刺激引起的电场，这些患者正在进行术前评估。这种刺激是使用常规临床实践中使用的多接触颅内电极进行的。我们在新皮层中引入了电极几何形状和轨迹的逼真 3D 模型。对于电极，我们比较了点（0D）和线（1D）源近似。对于脑组织，我们考虑了三种越来越复杂的配置：6 层球形模型、具有沟回表示的玩具模型，复制了先前方法的结果；并通过使用逼真的头部模型几何形状超越了最新技术。电极几何形状会影响距离电极轴 3 毫米以内的电场分布。对于较大的距离，容积导体几何形状和电导率主导电场分布。这些结果是朝着准确且可计算的神经调节和神经刺激程序引起的电场的患者特异性模型迈出的第一步。
