Gao W, Lin W, Chen Y, Gerig G, Smith J K, Jewells V, Gilmore J H
Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
AJNR Am J Neuroradiol. 2009 Feb;30(2):290-6. doi: 10.3174/ajnr.A1363. Epub 2008 Nov 11.
Diffusion tensor imaging (DTI) has been widely used to investigate the development of white matter (WM). However, information about this development in healthy children younger than 2 years of age is lacking, and most previous studies have only measured fractional anisotropy (FA). This study used FA and radial and axonal diffusivities in children younger than 2 years of age, aiming to determine the temporal and spatial development of axonal maturation and myelination of WM in healthy children.
A total of 60 healthy pediatric subjects were imaged by using a 3T MR imaging scanner. They were divided into 3 groups: 20 at 3 weeks, 20 at 1 year of age, and 20 at 2 years of age. All subjects were imaged asleep without sedation. FA and axial and radial diffusivities were obtained. Eight regions of interest were defined, including both central and peripheral WM for measuring diffusion parameters.
A significant elevation in FA (P < .0001) and a reduction in axial and radial diffusivities (P < .0001) were observed from 22 days to 1 year of age, whereas only radial diffusivity showed significant changes (P = .0014) from 1 to 2 years of age. The region-of-interest analysis revealed that FA alone may not depict the underlying biologic underpinnings of WM development, whereas directional diffusivities provide more insights into the development of WM. Finally, the spatial development of WM begins from the central to the peripheral WM and from the occipital to the frontal lobes.
With both FA and directional diffusivities, our results demonstrate the temporal and spatial development of WM in healthy children younger than 2 years of age.
扩散张量成像（DTI）已被广泛用于研究白质（WM）的发育。然而，缺乏2岁以下健康儿童这一发育过程的相关信息，并且之前的大多数研究仅测量了分数各向异性（FA）。本研究对2岁以下儿童使用FA以及径向和轴向扩散率，旨在确定健康儿童白质轴突成熟和髓鞘形成的时间和空间发育情况。
使用3T磁共振成像扫描仪对60名健康儿科受试者进行成像。他们被分为3组：3周龄组20名、1岁组20名和2岁组20名。所有受试者在未使用镇静剂的睡眠状态下进行成像。获取了FA以及轴向和径向扩散率。定义了8个感兴趣区域，包括中央和外周白质以测量扩散参数。
从22天到1岁，观察到FA显著升高（P <.0001）以及轴向和径向扩散率降低（P <.0001），而从1岁到2岁仅径向扩散率有显著变化（P =.0014）。感兴趣区域分析显示，仅FA可能无法描述白质发育的潜在生物学基础，而方向扩散率能为白质发育提供更多见解。最后，白质的空间发育从中央白质向外周白质开始，并从枕叶向额叶发展。
通过FA和方向扩散率，我们的结果证明了2岁以下健康儿童白质的时间和空间发育情况。
