Huynh Khoi Minh, Kim Jaeil, Chen Geng, Wu Ye, Shen Dinggang, Yap Pew-Thian
Biomedical Engineering Department, University of North Carolina, Chapel Hill, USA.
Department of Radiology and BRIC, University of North Carolina, Chapel Hill, USA.
Comput Diffus MRI. 2019;2019:183-191. doi: 10.1007/978-3-030-05831-9_15. Epub 2019 May 3.
The human brain develops very rapidly in the first years of life, resulting in significant changes in water diffusion anisotropy. Developmental changes pose significant challenges to longitudinally consistent white matter tractography. In this paper, we will introduce a method to harmonize infant diffusion MRI data longitudinally across time. Specifically, we harmonize diffusion MRI data collected at an earlier time point to data collected at a later time point. This will promote longitudinal consistency and allow sharpening of fiber orientation distribution functions (ODFs) based on information available at the later time point. For this purpose, we will introduce an approach that is based on the method of moments, which allows harmonization to be performed directly on the diffusion-attenuated signal without the need to fit any diffusion models to the data. Given two diffusion MRI datasets, our method harmonizes them voxel-wise using well-behaving mapping functions (i.e., monotonic, diffeomorphic, etc.), parameters of which are determined by matching the spherical moments (i.e., mean, variance, skewness, etc.) of signal measurements on each shell. The mapping functions we use is isotropic and does not introduce new orientations that are not already in the original data. Our analysis indicates that longitudinal harmonization sharpens ODFs and improves tractography in infant diffusion MRI.
人类大脑在生命的最初几年发育非常迅速，导致水扩散各向异性发生显著变化。发育变化给纵向一致的白质纤维束成像带来了重大挑战。在本文中，我们将介绍一种方法，用于纵向协调婴儿扩散磁共振成像（MRI）数据。具体而言，我们将早期时间点收集的扩散MRI数据与后期时间点收集的数据进行协调。这将促进纵向一致性，并基于后期时间点可用的信息锐化纤维方向分布函数（ODF）。为此，我们将介绍一种基于矩量法的方法，该方法允许直接对扩散衰减信号进行协调，而无需对数据拟合任何扩散模型。给定两个扩散MRI数据集，我们的方法使用表现良好的映射函数（即单调、微分同胚等）逐体素地对它们进行协调，其参数通过匹配每个壳层上信号测量的球矩（即均值、方差、偏度等）来确定。我们使用的映射函数是各向同性的，不会引入原始数据中不存在的新方向。我们的分析表明，纵向协调可锐化ODF并改善婴儿扩散MRI中的纤维束成像。
