Division of Neonatal and Developmental Medicine, Department of Pediatrics, Stanford University School of Medicine, Stanford, CA 94304, USA.
J Dev Behav Pediatr. 2010 May;31(4):346-56. doi: 10.1097/DBP.0b013e3181dcaa8b.
Diffusion tensor imaging (DTI) is a magnetic resonance imaging technique that allows for the visualization and characterization of the white matter tracts of the brain in vivo. DTI does not assess white matter directly. Rather, it capitalizes on the fact that diffusion is isotropic (equal in all directions) in cerebral spinal fluid and cell bodies but anisotropic (greater in one direction than the other directions) in axons that comprise white matter. It provides quantitative information about the degree and direction of water diffusion within individual units of volume within the magnetic resonance image, and by inference, about the integrity of white matter. Measures from DTI can be applied throughout the brain or to regions of interest. Fiber tract reconstruction, or tractography, creates continuous 3-dimensional tracts by sequentially piecing together estimates of fiber orientation from the direction of diffusion within individual volume units. DTI has increased our understanding of white matter structure and function. DTI shows nonlinear growth of white matter tracts from childhood to adulthood. Delayed maturation of the white matter in the frontal lobes may explain the continued growth of cognitive control into adulthood. Relative to good readers, adults and children who are poor readers have evidence of white matter differences in a specific region of the temporo-parietal lobe, implicating differences in connections among brain regions as a factor in reading disorder. Measures from DTI changed in poor readers who improved their reading skills after intense remediation. DTI documents injury to white matter tracts after prematurity. Measures indicative of white matter injury are associated with motor and cognitive impairment in children born prematurely. Further research on DTI is necessary before it can become a routine clinical procedure.
弥散张量成像（DTI）是一种磁共振成像技术，可用于可视化和描述大脑白质束的活体。DTI 并不直接评估白质。相反，它利用了这样一个事实，即扩散在脑脊髓液和细胞体中是各向同性的（在所有方向上相等），但在构成白质的轴突中是各向异性的（一个方向上比其他方向上更大）。它提供了关于磁共振图像中单个体积单位内水扩散程度和方向的定量信息，并且可以推断出白质的完整性。DTI 的测量可以应用于整个大脑或感兴趣的区域。纤维束重建，或束追踪，通过从单个体积单位内的扩散方向顺序拼接纤维方向的估计值来创建连续的三维束。DTI 增加了我们对白质结构和功能的理解。DTI 显示白质束从儿童期到成年期呈非线性增长。额叶白质的成熟延迟可能解释了认知控制在成年期的持续增长。与阅读良好的成年人相比，阅读能力较差的成年人和儿童在颞顶叶的特定区域有白质差异的证据，这表明大脑区域之间的连接差异是阅读障碍的一个因素。经过强化矫正后阅读能力提高的阅读困难者的 DTI 测量值发生了变化。DTI 记录了早产儿后白质束的损伤。与早产儿相关的运动和认知障碍与白质损伤的测量值相关。在 DTI 成为常规临床程序之前，还需要进一步的研究。
