Neurophysiology Department, GHU Paris Psychiatrie et Neurosciences, Sainte Anne Hospital, 1 rue Cabanis, F-75014 Paris, France.
Institute of Psychiatry and Neuroscience of Paris (IPNP), INSERM UMR 1266, F-75014 Paris, France.
Biomed Phys Eng Express. 2021 Aug 4;7(5). doi: 10.1088/2057-1976/ac177f.
. To measure the impact of skull-to-brain conductivity ratios on interictal spikes source localizations, using high resolution EEG (HR EEG). In previous studies, two ratios were mainly employed: 1/80 and 1/40. Consequences of the employed ratios on source localization results are poorly studied.. Twenty patients with drug-resistant epilepsy were studied using HR EEG (sixty-four scalp electrodes). For each patient, three-layers realistic head models based on individual MRI were elaborated using boundary element model. For each interictal spike, source localization was performed six times, using six skull-to-brain conductivity ratios (1/80, 1/50, 1/40, 1/30, 1/20 and 1/10), exploring all the spectrum of values reported in the literature. We then measured distances between the different sources obtained and between the sources and the anterior commissure (in order to estimate sources depth).. We measured a mean distance of 5.3 mm (sd: 3 mm) between the sources obtained with 1/40 versus 1/80 ratio. This distance increased when the discrepancy between the two evaluated ratios increased. We measured a mean distance of 14.2 mm (sd: 4.9 mm) between sources obtained with 1/10 ratio versus 1/80 ratio. Sources localized using 1/40 ratio were 4.3 mm closer to the anterior commissure than sources localized using 1/80 ratio.. Skull-to-brain conductivity ratio is an often-neglected parameter in source localization studies. The different ratios mainly used in the litterature (1/80 and 1/40) lead to significant differences in source localizations. These variations mainly occur in source depth. A more accurate estimation of skull-to-brain conductivity is needed to increase source localization accuracy.. ECD: equivalent current dipole; EIT: electric impedance tomography, HR EEG: High resolution Electroencephalography, IIS: Inter ictal spikes, MEG: Magnetoencephalography, MRI: Magnetic resonance imaging, mS/m: milli-Siemens/m, S/m: Siemens/m, SD: Standard deviation.
. 为了测量颅骨到大脑电导率比值对发作间期棘波源定位的影响，我们使用高分辨率脑电图（HR EEG）。在以前的研究中，主要使用了两种比值：1/80 和 1/40。 所使用的比值对源定位结果的影响研究甚少。.. 研究了 20 名耐药性癫痫患者，使用 HR EEG（64 个头皮电极）。对于每个患者，基于个体 MRI 使用边界元模型制作了三个层面的真实头颅模型。对于每个发作间期棘波，使用 6 种颅骨到大脑电导率比值（1/80、1/50、1/40、1/30、1/20 和 1/10）进行了 6 次源定位，探索了文献中报告的所有比值范围。然后我们测量了不同源之间的距离和源与前连合之间的距离（以便估计源的深度）。.. 我们测量到，使用 1/40 与 1/80 比值时，获得的源之间的平均距离为 5.3 毫米（标准差为 3 毫米）。当两个评估比值之间的差异增加时，这个距离会增加。我们测量到，使用 1/10 比值与 1/80 比值时，获得的源之间的平均距离为 14.2 毫米（标准差为 4.9 毫米）。使用 1/40 比值定位的源比使用 1/80 比值定位的源更靠近前连合，距离为 4.3 毫米。.. 颅骨到大脑电导率比值是源定位研究中经常被忽视的参数。文献中主要使用的比值（1/80 和 1/40）导致源定位存在显著差异。这些变化主要发生在源的深度上。需要更准确地估计颅骨到大脑的电导率，以提高源定位的准确性。.. ECD：等效电流偶极子；EIT：电阻抗断层成像，HR EEG：高分辨率脑电图，IIS：发作间期棘波，MEG：脑磁图，MRI：磁共振成像，mS/m：毫西门子/米，S/m：西门子/米，SD：标准差。
