De Lucia M, Parker G J M, Embleton K, Newton J M, Walsh V
Department of Medical Physics, University College London, London, UK.
Neuroimage. 2007 Jul 15;36(4):1159-70. doi: 10.1016/j.neuroimage.2007.03.062. Epub 2007 May 23.
We evaluate and discuss the relevance of fiber anisotropy in estimating the effect of transcranial magnetic stimulation (TMS) on the human brain. Finite element simulations were carried out on a three-dimensional model of the head that included anisotropic conductivity information derived from diffusion tensor imaging (DTI). The results show that anisotropy has minor effects both on the position of the main locus of activation and on its intensity. It has considerably more effect on the spatial distribution of the induced electric field, yielding differences of the order of 10% of the maximum induced field. Moreover the area affected by magnetic stimulation is slightly larger when we include fiber anisotropy in the calculations than in an isotropic model. We also show that the induced field observed in the anisotropic model does not always align with the local fiber orientation but rather follows specific patterns of parallelity. These findings will help to improve the estimation of the areas involved in magnetic stimulation.
我们评估并讨论了纤维各向异性在估计经颅磁刺激（TMS）对人脑影响方面的相关性。在一个包含从扩散张量成像（DTI）得出的各向异性电导率信息的头部三维模型上进行了有限元模拟。结果表明，各向异性对激活主要位点的位置及其强度的影响较小。它对感应电场的空间分布影响要大得多，产生的差异约为最大感应场的10%。此外，当我们在计算中纳入纤维各向异性时，受磁刺激影响的区域比在各向同性模型中略大。我们还表明，在各向异性模型中观察到的感应场并不总是与局部纤维方向一致，而是遵循特定的平行模式。这些发现将有助于改进对磁刺激所涉及区域的估计。
