Department of Radiology, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
Neuroscience. 2013 Feb 12;231:1-12. doi: 10.1016/j.neuroscience.2012.11.038. Epub 2012 Dec 3.
Diffusion tensor imaging (DTI) provides information regarding white matter microstructure; however, macroscopic fiber architectures can affect DTI measures. A larger brain (fiber tract) has a 'relatively' smaller voxel size, and the voxels are less likely to contain more than one fiber orientation and more likely to have higher fractional anisotropy (FA). Previous DTI studies report left-to-right differences in the white matter; however, these may reflect true microscopic differences or be caused purely by volume differences. Using tract-based spatial statistics, we investigated left-to-right differences in white matter microstructure across the whole brain. Voxel-wise analysis revealed a large number of white matter volume asymmetries, including leftward asymmetry of the arcuate fasciculus and cingulum. In many white matter regions, FA asymmetry was positively correlated with volume asymmetry. Voxel-wise analysis with adjustment for volume asymmetry revealed many white matter FA asymmetries, including leftward asymmetry of the arcuate fasciculus and cingulum. The voxel-wise analysis showed a reduced number of regions with significant FA asymmetry compared with analysis performed without adjustment for volume asymmetry; however, the overall trend of the results was unchanged. The results of the present study suggest that these FA asymmetries are not caused by volume differences and reflect microscopic differences in the white matter.
弥散张量成像（DTI）提供了关于白质微观结构的信息；然而，宏观纤维结构会影响 DTI 测量结果。较大的大脑（纤维束）具有“相对”较小的体素大小，并且体素不太可能包含多个纤维方向，而更有可能具有更高的分数各向异性（FA）。以前的 DTI 研究报告了白质的左右差异；然而，这些差异可能反映了真正的微观差异，或者纯粹是由体积差异引起的。使用基于束的空间统计学，我们研究了整个大脑的白质微观结构的左右差异。体素分析揭示了大量白质体积不对称，包括弓状束和扣带回的左侧不对称。在许多白质区域，FA 不对称性与体积不对称性呈正相关。在考虑体积不对称性调整的体素分析中，发现了许多白质 FA 不对称性，包括弓状束和扣带回的左侧不对称。与不进行体积不对称性调整的分析相比，体素分析显示具有显著 FA 不对称性的区域数量减少；然而，结果的总体趋势没有改变。本研究的结果表明，这些 FA 不对称性不是由体积差异引起的，而是反映了白质的微观差异。
