Barrick Thomas R, Clark Chris A
Department of Clinical Neurosciences, St. George's Hospital Medical School, London SW17 0RE, UK.
Neuroimage. 2004 Jun;22(2):481-91. doi: 10.1016/j.neuroimage.2004.02.001.
The technique of diffusion tensor tractography utilizes directions of maximum diffusion to reconstruct pathways of white matter structures in the brain. Critically, successful tracking of these white matter pathways depends on well-defined maximal diffusion directional information. By examination of diffusion tensor field properties in the human brain, we demonstrate that the geometry of tracked pathways is influenced by points in the field where the maximum diffusion direction is poorly defined. In common with tensor fields describing other mathematical and physical phenomena, such as 3D surface differential geometry and gravitational fields, we refer to these points as singularities. Here we describe an automated procedure for detecting singularities and demonstrate that these occur where there is (i) fiber crossing, (ii) pathways passing close to one another within a voxel (partial volume effect), and (iii) noise propagation into low anisotropy regions. In order to highlight the relevance of singularities in tracking white matter structures, we determined their effect on computation of the cortico-spinal pathway.
扩散张量纤维束成像技术利用最大扩散方向来重建大脑中白质结构的路径。至关重要的是,这些白质路径的成功追踪取决于明确界定的最大扩散方向信息。通过检查人类大脑中的扩散张量场特性,我们证明了追踪路径的几何形状受场中最大扩散方向定义不明确的点的影响。与描述其他数学和物理现象的张量场(如三维表面微分几何和引力场)一样,我们将这些点称为奇点。在这里,我们描述了一种检测奇点的自动化程序,并证明这些奇点出现在以下情况:(i)纤维交叉;(ii)路径在体素内彼此靠近通过(部分容积效应);(iii)噪声传播到低各向异性区域。为了突出奇点在追踪白质结构中的相关性,我们确定了它们对皮质脊髓路径计算的影响。