Nossin-Manor Revital, Card Dallas, Raybaud Charles, Taylor Margot J, Sled John G
Diagnostic Imaging, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada; Neurosciences and Mental Health, Research Institute, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada.
Diagnostic Imaging, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada.
Neuroimage. 2015 May 15;112:30-42. doi: 10.1016/j.neuroimage.2015.02.051. Epub 2015 Feb 27.
The magnetization transfer ratio (MTR) and diffusion tensor imaging (DTI) correlates of early brain development were examined in cohort of 18 very preterm neonates (27-31 gestational weeks) presenting with normal radiological findings scanned within 2weeks after birth (28-32 gestational weeks). A combination of non-linear image registration, tissue segmentation, and voxel-wise regression was used to map the age dependent changes in MTR and DTI-derived parameters in 3D across the brain based on the cross-sectional in vivo preterm data. The regression coefficient maps obtained differed between brain regions and between the different quantitative MRI indices. Significant linear increases as well as decreases in MTR and DTI-derived parameters were observed throughout the preterm brain. In particular, the lamination pattern in the cerebral wall was evident on parametric and regression coefficient maps. The frontal white matter area (subplate and intermediate zone) demonstrated a linear decrease in MTR. While the intermediate zone showed an unexpected decrease in fractional anisotropy (FA) with age, with this decrease (and the increase in mean diffusivity (MD)) driven primarily by an increase in radial diffusivity (RD) values, the subplate showed no change in FA (and an increase in MD). The latter was the result of a concomitant similar increase in axial diffusivity (AD) and RD values. Interpreting the in vivo results in terms of available histological data, we present a biophysical model that describes the relation between various microstructural changes measured by complementary quantitative methods available on clinical scanners and a range of maturational processes in brain tissue.
在18名极早产儿（孕龄27 - 31周）队列中，研究了出生后2周内（孕龄28 - 32周）影像学检查正常的早期脑发育的磁化传递率（MTR）和扩散张量成像（DTI）相关性。基于横断面体内早产儿数据，采用非线性图像配准、组织分割和体素回归相结合的方法，在三维空间中绘制全脑MTR和DTI衍生参数随年龄的变化。不同脑区和不同定量MRI指标获得的回归系数图存在差异。在整个早产儿脑中观察到MTR和DTI衍生参数有显著的线性增加和减少。特别是，脑壁的分层模式在参数图和回归系数图上很明显。额叶白质区（板下带和中间带）的MTR呈线性下降。虽然中间带的各向异性分数（FA）随年龄意外下降，且这种下降（以及平均扩散率（MD）的增加）主要由径向扩散率（RD）值增加驱动，但板下带的FA无变化（MD增加）。后者是轴向扩散率（AD）和RD值同时类似增加的结果。根据现有的组织学数据解释体内结果，我们提出了一个生物物理模型，该模型描述了临床扫描仪上可用的互补定量方法测量的各种微观结构变化与脑组织中一系列成熟过程之间的关系。
