标题： 微观各向异性估计的验证及临床可行双扩散编码MRI的噪声鲁棒性评估 显示英文标题

标题： Validation and noise robustness assessment of microscopic anisotropy estimation with clinically feasible double diffusion encoding MRI

摘要： 目的：双扩散编码（DDE）磁共振成像能够估计微观扩散各向异性，提供关于组织微结构的有价值信息。 一项最近的研究提出，通过假设高斯扩散，可以大大简化旋转不变的DDE指标的获取，通常使用球形“5设计”，从而减少采集时间，使其更符合临床环境。 在此，我们的目标是将新的最小采集方案与标准DDE 5设计进行验证，并量化所提出方法的噪声鲁棒性，以促进未来的临床应用。 方法：在9.4 T下对离体和活体大鼠大脑进行了DDE MRI实验，使用5设计和提出的最小设计，并考虑了采集次数的差异。 随后的微观部分各向异性（{\mu }FA）图在高达5000 s/mm2的b值范围内进行了比较。 通过分析计算和数值模拟研究了噪声鲁棒性。 结果：最小协议在准确性方面能够量化{\mu }FA，与通过更理论稳健的DDE 5设计获得的估计值相当。 发现{\mu }FA对噪声的敏感性在非线性方式上强烈依赖于组分各向异性和张量大小。 当{\mu }FA < 0.75或平均扩散率特别低时，需要非常高的信噪比（SNR）才能精确量化{\mu }FA。 结论：我们的工作支持在临床环境中使用DDE来量化微观扩散各向异性，但在使用DDE和典型临床SNR测量{\mu }FA时提出了此前被忽视的精度问题。 显示英文摘要

摘要： Purpose: Double diffusion encoding (DDE) MRI enables the estimation of microscopic diffusion anisotropy, yielding valuable information on tissue microstructure. A recent study proposed that the acquisition of rotationally invariant DDE metrics, typically obtained using a spherical "5-design", could be greatly simplified by assuming Gaussian diffusion, facilitating reduced acquisition times that are more compatible with clinical settings. Here, we aim to validate the new minimal acquisition scheme against the standard DDE 5-design, and to quantify the proposed method's noise robustness to facilitate future clinical use. Methods: DDE MRI experiments were performed on both ex vivo and in vivo rat brains at 9.4 T using the 5-design and the proposed minimal design and taking into account the difference in the number of acquisitions. The ensuing microscopic fractional anisotropy ({\mu}FA) maps were compared over a range of b-values up to 5000 s/mm2. Noise robustness was studied using analytical calculations and numerical simulations. Results: The minimal protocol quantified {\mu}FA at an accuracy comparable to the estimates obtained via the more theoretically robust DDE 5-design. {\mu}FA's sensitivity to noise was found to strongly depend on compartment anisotropy and tensor magnitude in a non-linear fashion. When {\mu}FA < 0.75 or when mean diffusivity is particularly low, very high signal to noise ratio (SNR) is required for precise quantification of {\mu}FA. Conclusion: Our work supports using DDE for quantifying microscopic diffusion anisotropy in clinical settings but raises hitherto overlooked precision issues when measuring {\mu}FA with DDE and typical clinical SNR.