Spatiotemporal changes in diffusivity and anisotropy in fetal brain tractography,Human Brain Mapping

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Spatiotemporal changes in diffusivity and anisotropy in fetal brain tractography
Human Brain Mapping ( IF 3.5 ) Pub Date : 2021-09-06 , DOI: 10.1002/hbm.25653
Fedel Machado-Rivas ₁ , Onur Afacan ₁ , Shadab Khan ₁ , Bahram Marami ₁ , Clemente Velasco-Annis ₁ , Hart Lidov ₂ , Simon K Warfield ₁ , Ali Gholipour ₁ , Camilo Jaimes ₁

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Population averaged diffusion atlases can be utilized to characterize complex microstructural changes with less bias than data from individual subjects. In this study, a fetal diffusion tensor imaging (DTI) atlas was used to investigate tract-based changes in anisotropy and diffusivity in vivo from 23 to 38 weeks of gestational age (GA). Healthy pregnant volunteers with typically developing fetuses were imaged at 3 T. Acquisition included structural images processed with a super-resolution algorithm and DTI images processed with a motion-tracked slice-to-volume registration algorithm. The DTI from individual subjects were used to generate 16 templates, each specific to a week of GA; this was accomplished by means of a tensor-to-tensor diffeomorphic deformable registration method integrated with kernel regression in age. Deterministic tractography was performed to outline the forceps major, forceps minor, bilateral corticospinal tracts (CST), bilateral inferior fronto-occipital fasciculus (IFOF), bilateral inferior longitudinal fasciculus (ILF), and bilateral uncinate fasciculus (UF). The mean fractional anisotropy (FA) and mean diffusivity (MD) was recorded for all tracts. For a subset of tracts (forceps major, CST, and IFOF) we manually divided the tractograms into anatomy conforming segments to evaluate within-tract changes. We found tract-specific, nonlinear, age related changes in FA and MD. Early in gestation, these trends appear to be dominated by cytoarchitectonic changes in the transient white matter fetal zones while later in gestation, trends conforming to the progression of myelination were observed. We also observed significant (local) heterogeneity in within-tract developmental trajectories for the CST, IFOF, and forceps major.

中文翻译：

胎儿脑束显像中扩散率和各向异性的时空变化

总体平均扩散图谱可用于表征复杂的微观结构变化，其偏差小于来自个体受试者的数据。在这项研究中，胎儿扩散张量成像 (DTI) 图谱用于研究 23 至 38 周胎龄 (GA) 体内基于束的各向异性和扩散性变化。具有典型发育胎儿的健康怀孕志愿者在 3 T 下成像。采集包括使用超分辨率算法处理的结构图像和使用运动跟踪切片到体积配准算法处理的 DTI 图像。来自个体受试者的 DTI 用于生成 16 个模板，每个模板都特定于一周的 GA；这是通过与年龄核回归相结合的张量到张量微分形可变形配准方法来实现的。进行确定性纤维束成像以勾勒出大钳、小钳、双侧皮质脊髓束 (CST)、双侧额枕下束 (IFOF)、双侧下纵束 (ILF) 和双侧钩束 (UF)。记录所有区域的平均分数各向异性 (FA) 和平均扩散率 (MD)。对于束的子集（大钳、CST 和 IFOF），我们手动将束图划分为符合解剖结构的段，以评估束内的变化。我们在 FA 和 MD 中发现了特定于区域的、非线性的、与年龄相关的变化。在妊娠早期，这些趋势似乎主要由瞬时白质胎儿区的细胞结构变化主导，而在妊娠后期，观察到符合髓鞘形成进展的趋势。

更新日期：2021-11-01

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