Data from: Development of the corticospinal and callosal tracts from extremely premature birth up to 2 years of age

White matter tracts mature asymmetrically during development, and this development can be studied using diffusion magnetic resonance imaging. The aims of this study were i. to generate dynamic population-averaged white matter registration templates covering in detail the period from 25 weeks gestational age to term, and extending to 2 years of age based on DTI and fractional anisotropy, ii. to produce tract-specific probability maps of the corticospinal tracts, forceps major and forceps minor using probabilistic tractography, and iii. to assess the development of these tracts throughout this critical period of neurodevelopment. We found evidence for asymmetric development across the fiber bundles studied, with the corticospinal tracts showing earlier maturation (as measured by fractional anisotropy) but slower volumetric growth compared to the callosal fibers. We also found evidence for an anterior to posterior gradient in white matter microstructure development (as measured by mean diffusivity) in the callosal fibers, with the posterior forceps major developing at a faster rate than the anterior forceps minor in this age range. Finally, we report a protocol for delineating callosal and corticospinal fibers in extremely premature cohorts, and make available population-averaged registration templates and a probabilistic tract atlas which we hope will be useful for future neonatal and infant white-matter imaging studies.

脑白质束在发育过程中呈现不对称成熟的特征，该发育进程可通过扩散磁共振成像（diffusion magnetic resonance imaging）开展研究。本研究的目标如下：一是基于弥散张量成像（Diffusion Tensor Imaging，DTI）与各向异性分数（fractional anisotropy，FA），构建详细覆盖妊娠25周至足月、乃至2岁年龄段的动态群体平均脑白质配准模板；二是通过概率性纤维束追踪（probabilistic tractography）生成皮质脊髓束（corticospinal tracts）、大钳纤维束（forceps major）与小钳纤维束（forceps minor）的束特异性概率图谱；三是评估该神经发育关键时期内上述脑白质束的发育情况。本研究在所分析的纤维束中发现了不对称发育的证据：相较于胼胝体纤维，皮质脊髓束的成熟更早，但体积增长更为缓慢。此外，我们还发现，在以平均弥散率（mean diffusivity，MD）为衡量指标的胼胝体纤维脑白质微观结构发育过程中，存在前后梯度特征——在该年龄区间内，后部的大钳纤维束发育速度快于前部的小钳纤维束。最后，本研究报道了一套用于勾勒极早产队列中胼胝体与皮质脊髓束纤维的实验方案，并公开了群体平均配准模板与概率性纤维束图谱，以期为未来新生儿及婴幼儿脑白质成像研究提供参考与助力。