Rullmann M, Anwander A, Dannhauer M, Warfield S K, Duffy F H, Wolters C H
Max Planck Institute for Human Cognitive and Brain Science, Leipzig, Germany.
Neuroimage. 2009 Jan 15;44(2):399-410. doi: 10.1016/j.neuroimage.2008.09.009. Epub 2008 Sep 24.
The major goal of the evaluation in presurgical epilepsy diagnosis for medically intractable patients is the precise reconstruction of the epileptogenic foci, preferably with non-invasive methods. This paper evaluates whether surface electroencephalography (EEG) source analysis based on a 1 mm anisotropic finite element (FE) head model can provide additional guidance for presurgical epilepsy diagnosis and whether it is practically feasible in daily routine. A 1 mm hexahedra FE volume conductor model of the patient's head with special focus on accurately modeling the compartments skull, cerebrospinal fluid (CSF) and the anisotropic conducting brain tissues was constructed using non-linearly co-registered T1-, T2- and diffusion-tensor-magnetic resonance imaging data. The electrodes of intra-cranial EEG (iEEG) measurements were extracted from a co-registered computed tomography image. Goal function scan (GFS), minimum norm least squares (MNLS), standardized low resolution electromagnetic tomography (sLORETA) and spatio-temporal current dipole modeling inverse methods were then applied to the peak of the averaged ictal discharges EEG data. MNLS and sLORETA pointed to a single center of activity. Moving and rotating single dipole fits resulted in an explained variance of more than 97%. The non-invasive EEG source analysis methods localized at the border of the lesion and at the border of the iEEG electrodes which mainly received ictal discharges. Source orientation was towards the epileptogenic tissue. For the reconstructed superficial source, brain conductivity anisotropy and the lesion conductivity had only a minor influence, whereas a correct modeling of the highly conducting CSF compartment and the anisotropic skull was found to be important. The proposed FE forward modeling approach strongly simplifies meshing and reduces run-time (37 ms for one forward computation in the model with 3.1 million unknowns), corroborating the practical feasibility of the approach.
对于药物治疗无效的患者，术前癫痫诊断评估的主要目标是精确重建致痫灶，最好采用非侵入性方法。本文评估基于1毫米各向异性有限元（FE）头部模型的表面脑电图（EEG）源分析能否为术前癫痫诊断提供额外指导，以及在日常临床实践中是否切实可行。利用非线性配准的T1加权、T2加权和扩散张量磁共振成像数据，构建了患者头部的1毫米六面体有限元容积导体模型，特别注重对头骨、脑脊液（CSF）和各向异性导电脑组织腔室进行精确建模。从配准的计算机断层扫描图像中提取颅内EEG（iEEG）测量的电极。然后将目标函数扫描（GFS）、最小范数最小二乘法（MNLS）、标准化低分辨率电磁断层扫描（sLORETA）和时空电流偶极建模反演方法应用于平均发作期放电EEG数据的峰值。MNLS和sLORETA指向单个活动中心。移动和旋转单个偶极拟合的解释方差超过97%。非侵入性EEG源分析方法定位在病变边界和主要接收发作期放电的iEEG电极边界。源方向朝向致痫组织。对于重建的浅表源，脑电导率各向异性和病变电导率的影响较小，而发现对高导电CSF腔室和各向异性颅骨进行正确建模很重要。所提出的有限元正向建模方法极大地简化了网格划分并减少了运行时间（在具有310万个未知数的模型中进行一次正向计算需要37毫秒），证实了该方法的实际可行性。
