Minimal number of sampling directions for robust measures of the spherical mean diffusion weighted signal: Effects of sampling directions, b-value, signal-to-noise ratio, hardware, and fitting strategy.
Minimal number of sampling directions for robust measures of the spherical mean diffusion weighted signal: Effects of sampling directions, b-value, signal-to-noise ratio, hardware, and fitting strategy.
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DOI：
10.1016/j.mri.2022.07.015
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发表时间：
2022-12
影响因子：
2.5
通讯作者：
Smith, Seth A.
中科院分区：
文献类型：
--
作者：
Schilling, Kurt G.;Palombo, Marco;O'Grady, Kristin P.;Combes, Anna J. E.;Anderson, Adam W.;Landman, Bennett A.;Smith, Seth A.
最近的几项多室弥散MRI研究和建模策略利用定向平均或球面平均弥散加权信号来研究中枢神经系统的组织微观结构。为了计算球面平均信号，大多数实验设计对大量的扩散加权方向进行采样，然而，对这些方向的子集进行采样可能会提高扫描效率，并使扫描时间减少或能够对更多的扩散加权进行采样。在这里，我们的目标是确定对球面平均信号进行鲁棒测量所需的最小梯度方向数。我们使用计算机模拟来表征测量的球面平均信号的变化作为梯度方向数量的函数，同时还研究了扩散加权（b值），信噪比（SNR），可用硬件和球面平均拟合策略的影响。然后，我们利用在大脑和脊髓中获得的经验数据来验证模拟，表明实验结果与模拟结果很好地吻合。我们通过提供一个直观的查找表来总结这些结果，以方便确定鲁棒球平均测量所需的最小采样方向数，并根据信噪比和实验条件给出建议。
Several recent multi-compartment diffusion MRI investigations and modeling strategies have utilized the orientationally-averaged, or spherical mean, diffusion-weighted signal to study tissue microstructure of the central nervous system. Most experimental designs sample a large number of diffusion weighted directions in order to calculate the spherical mean signal, however, sampling a subset of these directions may increase scanning efficiency and enable either a decrease in scan time or the ability to sample more diffusion weightings. Here, we aim to determine the minimum number of gradient directions needed for a robust measurement of the spherical mean signal. We used computer simulations to characterize the variation of the measured spherical mean signal as a function of the number of gradient directions, while also investigating the effects of diffusion weighting (b-value), signal-to-noise ratio (SNR), available hardware, and spherical mean fitting strategy. We then utilize empirically acquired data in the brain and spinal cord to validate simulations, showing experimental results are in good agreement with simulations. We summarize these results by providing an intuitive lookup table to facilitate the determination of the minimal number of sampling directions needed for robust spherical mean measurements, and give recommendations based on SNR and experimental conditions.
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