Sparse and optimal acquisition design for diffusion MRI and beyond
Sparse and optimal acquisition design for diffusion MRI and beyond
复制标题
DOI：
10.1118/1.3700166
复制
发表时间：
2012-05-01
期刊：
影响因子：
3.8
通讯作者：
Meyerand, M. Elizabeth
中科院分区：
文献类型：
--
作者：
Koay, Cheng Guan;Oezarslan, Evren;Meyerand, M. Elizabeth
目的：弥散磁共振成像（MRI）与功能性MRI相结合，为科学家无创地研究人类大脑的结构和功能连接提供了一个全新的前景-人类连接体，这是迄今为止无法实现的。与其他成像方式一样，弥散MRI数据本身就有噪声，采集耗时。此外，可以作为预测模型的人类连接体的忠实表示需要强大且准确的数据分析管道。本文的重点是该管道的关键部分之一-特别是，扩散MRI多壳采集及其他的稀疏和最佳采集（SOA）设计的开发。方法：作者提出了一种新的稀疏多壳捕获和准多壳捕获的最优性准则，扩散磁共振成像中的壳设计和一种新颖有效的半随机适度贪婪组合搜索策略，设计或配置。最优性标准的目标有三个：首先，最大化每个壳中扩散测量的均匀性，这相当于角度测量中的最大不相干性;其次，最大化每条径向线周围扩散测量的覆盖范围，以实现多壳采集的径向测量中的最大不相干性;最后，当所有壳层都重合时，如在单壳层采集的情况下，在极限情况下确保扩散测量方向的最大均匀性。在评估各种采集设计的稳定性中所采取的方法是基于设计矩阵的条件数和A-最优测度。结果：即使对于给定的扩散梯度方向集合的不同配置的数量通常非常大-例如，对于一组144个扩散梯度方向，在10（232）的数量级中，发现所提出的搜索策略在找到最佳配置方面是有效的。发现正方形设计是最稳健的（即，在不同的实验条件下具有稳定的条件数和A-最优测量）。在相同的性能评价下，平方设计被认为是更强大的比广泛使用的采样计划类似的三维径向MRI和扩散谱imaging（DSI）.Conclusions：稀疏多壳采集和quasimultiple-shell设计在扩散MRI和有效的搜索策略，找到最佳的配置已经开发了一种新的最优性标准。结果是非常有前途的，有趣的，实用的扩散MRI采集。(C)2012年美国医学物理学家协会。[http：//dx.doi.org/10.1118/1.3700166]
Purpose: Diffusion magnetic resonance imaging (MRI) in combination with functional MRI promises a whole new vista for scientists to investigate noninvasively the structural and functional connectivity of the human brain-the human connectome, which had heretofore been out of reach. As with other imaging modalities, diffusion MRI data are inherently noisy and its acquisition time-consuming. Further, a faithful representation of the human connectome that can serve as a predictive model requires a robust and accurate data-analytic pipeline. The focus of this paper is on one of the key segments of this pipeline-in particular, the development of a sparse and optimal acquisition (SOA) design for diffusion MRI multiple-shell acquisition and beyond.Methods: The authors propose a novel optimality criterion for sparse multiple-shell acquisition and quasimultiple-shell designs in diffusion MRI and a novel and effective semistochastic and moderately greedy combinatorial search strategy with simulated annealing to locate the optimum design or configuration. The goal of the optimality criteria is threefold: first, to maximize uniformity of the diffusion measurements in each shell, which is equivalent to maximal incoherence in angular measurements; second, to maximize coverage of the diffusion measurements around each radial line to achieve maximal incoherence in radial measurements for multiple-shell acquisition; and finally, to ensure maximum uniformity of diffusion measurement directions in the limiting case when all the shells are coincidental as in the case of a single-shell acquisition. The approach taken in evaluating the stability of various acquisition designs is based on the condition number and the A-optimal measure of the design matrix.Results: Even though the number of distinct configurations for a given set of diffusion gradient directions is very large in general-e.g., in the order of 10(232) for a set of 144 diffusion gradient directions, the proposed search strategy was found to be effective in finding the optimum configuration. It was found that the square design is the most robust (i.e., with stable condition numbers and A-optimal measures under varying experimental conditions) among many other possible designs of the same sample size. Under the same performance evaluation, the square design was found to be more robust than the widely used sampling schemes similar to that of 3D radial MRI and of diffusion spectrum imaging (DSI).Conclusions: A novel optimality criterion for sparse multiple-shell acquisition and quasimultiple-shell designs in diffusion MRI and an effective search strategy for finding the best configuration have been developed. The results are very promising, interesting, and practical for diffusion MRI acquisitions. (C) 2012 American Association of Physicists in Medicine. [http://dx.doi.org/10.1118/1.3700166]