NODDI: Practical in vivo neurite orientation dispersion and density imaging of the human brain
NODDI: Practical in vivo neurite orientation dispersion and density imaging of the human brain
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DOI：
10.1016/j.neuroimage.2012.03.072
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发表时间：
2012-07-16
期刊：
影响因子：
5.7
通讯作者：
Alexander, Daniel C.
中科院分区：
文献类型：
--
作者：
Zhang, Hui;Schneider, Torben;Alexander, Daniel C.
本文介绍了神经突方向分散和密度成像（NODDI），这是一种实用的扩散MRI技术，用于在临床MRI扫描仪上估计体内树突和轴突的微观结构复杂性。与来自扩散张量成像的标准指数（诸如分数各向异性（FA））相比，神经突的这种指数更直接地涉及脑组织微结构并且提供脑组织微结构的更特异性的标记。在临床扫描仪上将这些指数映射到整个大脑，为理解大脑发育和疾病提供了新的机会。所提出的技术通过将三室组织模型与针对临床可行性优化的双壳高角分辨率扩散成像（HARDI）协议相结合来实现这种映射。定义了一个表征神经突角度变化的方向分散指数。我们评估的方法在模拟和活的人脑使用临床3T扫描仪。结果表明，NODDI提供了合理的神经突密度和方向分散估计，从而解开两个关键因素FA，使每个因素单独分析。我们还表明，虽然取向分散可以估计只有一个单一的HARDI壳，神经突密度需要至少两个壳，可以更准确地估计与优化的双壳协议比替代的双壳协议。优化的协议需要大约30分钟来获取，使其能够包含在一个典型的临床设置。我们进一步表明，在每个壳中采样较少的方向可以将采集时间减少到10分钟，对估计的准确性影响最小。这证明了NODDI的可行性，即使是对时间最敏感的临床应用，如新生儿和痴呆症成像。(C)2012 Elsevier Inc. All rights reserved.
This paper introduces neurite orientation dispersion and density imaging (NODDI), a practical diffusion MRI technique for estimating the microstructural complexity of dendrites and axons in vivo on clinical MRI scanners. Such indices of neurites relate more directly to and provide more specific markers of brain tissue microstructure than standard indices from diffusion tensor imaging, such as fractional anisotropy (FA). Mapping these indices over the whole brain on clinical scanners presents new opportunities for understanding brain development and disorders. The proposed technique enables such mapping by combining a three-compartment tissue model with a two-shell high-angular-resolution diffusion imaging (HARDI) protocol optimized for clinical feasibility. An index of orientation dispersion is defined to characterize angular variation of neurites. We evaluate the method both in simulation and on a live human brain using a clinical 3T scanner. Results demonstrate that NODDI provides sensible neurite density and orientation dispersion estimates, thereby disentangling two key contributing factors to FA and enabling the analysis of each factor individually. We additionally show that while orientation dispersion can be estimated with just a single HARDI shell, neurite density requires at least two shells and can be estimated more accurately with the optimized two-shell protocol than with alternative two-shell protocols. The optimized protocol takes about 30 min to acquire, making it feasible for inclusion in a typical clinical setting. We further show that sampling fewer orientations in each shell can reduce the acquisition time to just 10 min with minimal impact on the accuracy of the estimates. This demonstrates the feasibility of NODDI even for the most time-sensitive clinical applications, such as neonatal and dementia imaging. (C) 2012 Elsevier Inc. All rights reserved.