UC Davis, Department of Neurology and Center for Neuroscience, Sacramento, CA 95817, USA.
Magn Reson Imaging. 2012 Oct;30(8):1111-22. doi: 10.1016/j.mri.2012.04.004. Epub 2012 Jun 12.
Characterizing the diffusion properties of cortical tissue is complicated by intersubject variability in the relative locations of gyri and sulci. Here we extend methods of measuring the average diffusion properties of gyral and sulcal structures after they have been aligned to a common template of cortical surface anatomy. Diffusion tensor image (DTI) data were gathered from 82 young subjects and co-registered with high-resolution T1 images that had been inflated and co-registered to a hemispherically unified spherical coordinate system based on FreeSurfer. We analyzed fractional anisotropy (FA), mean diffusivity (MD) and the novel quantity of cortical primary diffusion direction (cPDD) at five surfaces parallel to the white/gray junction, spanning approximately 5 mm from the pial surface into white matter. FA increased with increasing depth, whereas MD and cPDD were reduced. There were highly significant and reliable regional differences in FA, MD and cPDD as well as systematic differences between cortical lobes and between the two hemispheres. The influence of nearby cortical spinal fluid (CSF), local cortical curvature and thickness, and sulcal depth was also investigated. We found that FA correlated significantly with cortical curvature and sulcal depth, while MD was strongly influenced by nearby CSF. The measurement of FA, MD and cPDD near the cortical surface clarifies the organization of fiber projections to and from the cortex.
描述皮质组织的扩散特性很复杂，因为脑回和脑沟在不同个体间的相对位置存在差异。在这里，我们扩展了在将脑回和脑沟结构对齐到皮质表面解剖学的共同模板后，测量其平均扩散特性的方法。从 82 名年轻受试者中收集了扩散张量图像（DTI）数据，并与经过膨胀和以半球统一球坐标系统配准的高分辨率 T1 图像进行了配准，该系统基于 FreeSurfer。我们分析了五个与白质/灰质交界处平行的表面上的分数各向异性（FA）、平均扩散度（MD）和皮质原始扩散方向（cPDD）的新型量，这些表面大约从脑皮层表面延伸到白质 5 毫米。FA 随着深度的增加而增加，而 MD 和 cPDD 则减少。FA、MD 和 cPDD 存在高度显著和可靠的区域差异，以及皮质叶之间和两个半球之间的系统差异。还研究了附近皮质脑脊液（CSF）、局部皮质曲率和厚度以及脑沟深度的影响。我们发现 FA 与皮质曲率和脑沟深度显著相关，而 MD 则受到附近 CSF 的强烈影响。在皮质表面附近测量 FA、MD 和 cPDD，可以阐明到和来自皮质的纤维投射的组织。
