Hallez Hans, Vanrumste Bart, Van Hese Peter, D'Asseler Yves, Lemahieu Ignace, Van de Walle Rik
Department of Electronics and Information Systems, Medical Image and Signal Processing (MEDISIP) Ghent University, Sint-Pietersnieuwstraat 41, 9000 Ghent, Belgium.
Phys Med Biol. 2005 Aug 21;50(16):3787-806. doi: 10.1088/0031-9155/50/16/009. Epub 2005 Jul 28.
Many implementations of electroencephalogram (EEG) dipole source localization neglect the anisotropical conductivities inherent to brain tissues, such as the skull and white matter anisotropy. An examination of dipole localization errors is made in EEG source analysis, due to not incorporating the anisotropic properties of the conductivity of the skull and white matter. First, simulations were performed in a 5 shell spherical head model using the analytical formula. Test dipoles were placed in three orthogonal planes in the spherical head model. Neglecting the skull anisotropy results in a dipole localization error of, on average, 13.73 mm with a maximum of 24.51 mm. For white matter anisotropy these values are 11.21 mm and 26.3 mm, respectively. Next, a finite difference method (FDM), presented by Saleheen and Kwong (1997 IEEE Trans. Biomed. Eng. 44 800-9), is used to incorporate the anisotropy of the skull and white matter. The FDM method has been validated for EEG dipole source localization in head models with all compartments isotropic as well as in a head model with white matter anisotropy. In a head model with skull anisotropy the numerical method could only be validated if the 3D lattice was chosen very fine (grid size < or = 2 mm).
许多脑电图（EEG）偶极子源定位的实现都忽略了脑组织固有的各向异性电导率，比如颅骨和白质的各向异性。在脑电图源分析中，由于未纳入颅骨和白质电导率的各向异性属性，因此对偶极子定位误差进行了研究。首先，使用解析公式在一个5层球头模型中进行模拟。测试偶极子放置在球头模型的三个正交平面中。忽略颅骨各向异性会导致偶极子定位误差平均为13.73毫米，最大为24.51毫米。对于白质各向异性，这些值分别为11.21毫米和26.3毫米。接下来，使用Saleheen和Kwong（1997年，《IEEE生物医学工程汇刊》44卷，800 - 9页）提出的有限差分法（FDM）来纳入颅骨和白质的各向异性。FDM方法已在所有隔室均为各向同性的头部模型以及具有白质各向异性的头部模型中用于脑电图偶极子源定位的验证。在具有颅骨各向异性的头部模型中，只有当3D晶格选择得非常精细（网格尺寸≤2毫米）时，该数值方法才能得到验证。
