Uda Satoshi, Matsui Mie, Tanaka Chiaki, Uematsu Akiko, Miura Kayoko, Kawana Izumi, Noguchi Kyo
Department of Psychology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan.
Dev Neurosci. 2015;37(2):182-94. doi: 10.1159/000373885. Epub 2015 Mar 17.
Diffusion tensor imaging (DTI), which measures the magnitude of anisotropy of water diffusion in white matter, has recently been used to visualize and quantify parameters of neural tracts connecting brain regions. In order to investigate the developmental changes and sex and hemispheric differences of neural fibers in normal white matter, we used DTI to examine 52 healthy humans ranging in age from 2 months to 25 years. We extracted the following tracts of interest (TOIs) using the region of interest method: the corpus callosum (CC), cingulum hippocampus (CGH), inferior longitudinal fasciculus (ILF), and superior longitudinal fasciculus (SLF). We measured fractional anisotropy (FA), apparent diffusion coefficient (ADC), axial diffusivity (AD), and radial diffusivity (RD). Approximate values and changes in growth rates of all DTI parameters at each age were calculated and analyzed using LOESS (locally weighted scatterplot smoothing). We found that for all TOIs, FA increased with age, whereas ADC, AD and RD values decreased with age. The turning point of growth rates was at approximately 6 years. FA in the CC was greater than that in the SLF, ILF and CGH. Moreover, FA, ADC and AD of the splenium of the CC (sCC) were greater than in the genu of the CC (gCC), whereas the RD of the sCC was lower than the RD of the gCC. The FA of right-hemisphere TOIs was significantly greater than that of left-hemisphere TOIs. In infants, growth rates of both FA and RD were larger than those of AD. Our data show that developmental patterns differ by TOIs and myelination along with the development of white matter, which can be mainly expressed as an increase in FA together with a decrease in RD. These findings clarify the long-term normal developmental characteristics of white matter microstructure from infancy to early adulthood.
扩散张量成像（DTI）通过测量白质中水分子扩散各向异性的大小，近来已被用于可视化和量化连接脑区的神经束参数。为了研究正常白质中神经纤维的发育变化以及性别和半球差异，我们使用DTI对52名年龄在2个月至25岁之间的健康人进行了检查。我们采用感兴趣区域法提取了以下感兴趣的神经束（TOIs）：胼胝体（CC）、海马扣带束（CGH）、下纵束（ILF）和上纵束（SLF）。我们测量了分数各向异性（FA）、表观扩散系数（ADC）、轴向扩散率（AD）和径向扩散率（RD）。使用局部加权散点图平滑法（LOESS）计算并分析了各年龄组所有DTI参数的近似值及其增长率变化。我们发现，对于所有TOIs，FA随年龄增长而增加，而ADC、AD和RD值随年龄增长而降低。增长率的转折点大约在6岁。CC中的FA大于SLF、ILF和CGH中的FA。此外，CC压部（sCC）的FA、ADC和AD大于CC膝部（gCC），而sCC的RD低于gCC的RD。右半球TOIs的FA显著大于左半球TOIs的FA。在婴儿中，FA和RD的增长率均大于AD的增长率。我们的数据表明，不同TOIs的发育模式以及随白质发育的髓鞘形成情况各不相同，这主要表现为FA增加而RD降低。这些发现阐明了从婴儿期到成年早期白质微观结构的长期正常发育特征。
