Department of Radiology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.
Division of Newborn Medicine, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.
Neuroimage. 2019 Jan 15;185:593-608. doi: 10.1016/j.neuroimage.2018.08.030. Epub 2018 Aug 30.
Altered structural fetal brain development has been linked to neuro-developmental disorders. These structural alterations can be potentially detected in utero using diffusion tensor imaging (DTI). However, acquisition and reconstruction of in utero fetal brain DTI remains challenging. Until now, motion-robust DTI methods have been employed for reconstruction of in utero fetal DTIs. However, due to the unconstrained fetal motion and permissible in utero acquisition times, these methods yielded limited success and have typically resulted in noisy DTIs. Consequently, atlases and methods that could enable groupwise studies, multi-modality imaging, and computer-aided diagnosis from in utero DTIs have not yet been developed. This paper presents the first DTI atlas of the fetal brain computed from in utero diffusion-weighted images. For this purpose an algorithm for computing an unbiased spatiotemporal DTI atlas, which integrates kernel-regression in age with a diffeomorphic tensor-to-tensor registration of motion-corrected and reconstructed individual fetal brain DTIs, was developed. Our new algorithm was applied to a set of 67 fetal DTI scans acquired from healthy fetuses each scanned at a gestational age between 21 and 39 weeks. The neurodevelopmental trends in the fetal brain, characterized by the atlas, were qualitatively and quantitatively compared with the observations reported in prior ex vivo and in utero studies, and with results from imaging gestational-age equivalent preterm infants. Our major findings revealed early presence of limbic fiber bundles, followed by the appearance and maturation of projection pathways (characterized by an age related increase in FA) during late 2nd and early 3rd trimesters. During the 3rd trimester association fiber bundles become evident. In parallel with the appearance and maturation of fiber bundles, from 21 to 39 gestational weeks gradual disappearance of the radial coherence of the telencephalic wall was qualitatively identified. These results and analyses show that our DTI atlas of the fetal brain is useful for reliable detection of major neuronal fiber bundle pathways and for characterization of the fetal brain reorganization that occurs in utero. The atlas can also serve as a useful resource for detection of normal and abnormal fetal brain development in utero.
胎儿大脑结构的改变与神经发育障碍有关。这些结构的改变可以通过弥散张量成像（DTI）在子宫内进行潜在检测。然而，子宫内胎儿脑 DTI 的采集和重建仍然具有挑战性。到目前为止，已经使用抗运动的 DTI 方法来重建子宫内胎儿 DTI。然而，由于胎儿运动不受限制且允许的宫内采集时间有限，这些方法的效果有限，通常会导致 DTI 噪声较大。因此，尚未开发出能够进行群组研究、多模态成像和计算机辅助诊断的图谱和方法。本文提出了第一个从子宫内弥散加权图像计算的胎儿脑 DTI 图谱。为此，我们开发了一种用于计算无偏时空 DTI 图谱的算法，该算法将核回归与运动校正和重建的个体胎儿脑 DTI 的仿射张量到张量配准相结合，以适应年龄。我们的新算法应用于一组 67 例来自健康胎儿的胎儿 DTI 扫描，每个胎儿在 21 至 39 周的妊娠期进行扫描。该图谱所描述的胎儿脑的神经发育趋势与之前的离体和子宫内研究以及与影像学等同的早产儿的结果进行了定性和定量比较。我们的主要发现表明，在第二个和第三个三个月期间，边缘纤维束的早期存在，随后是投射途径的出现和成熟（以 FA 的年龄相关性增加为特征）。在第三个三个月期间，关联纤维束变得明显。随着纤维束的出现和成熟，从 21 到 39 周的妊娠期，大脑皮质壁的放射状相干性逐渐消失。这些结果和分析表明，我们的胎儿脑 DTI 图谱可用于可靠地检测主要的神经元纤维束通路，并对子宫内发生的胎儿脑重组进行特征描述。该图谱还可作为子宫内检测正常和异常胎儿脑发育的有用资源。
