NMR Research Unit, University of Oulu, 90014 Oulu, Finland.
Oulu Functional NeuroImaging Group, Research Unit of Medical Imaging, Physics and Technology, Medical Research Center Oulu, University of Oulu and Oulu University Hospital, 90029 Oulu, Finland.
Anal Chem. 2020 Jul 21;92(14):9948-9955. doi: 10.1021/acs.analchem.0c01523. Epub 2020 Jul 2.
Restricted diffusion of fluids in porous materials can be studied by pulsed field gradient nuclear magnetic resonance (NMR) non-invasively and without tracers. If the experiment is repeated many times with varying diffusion delays, detailed information about pore sizes and tortuosity can be recorded. However, the measurements are very time-consuming because numerous repetitions are needed for gradient ramping and varying diffusion delays. In this paper, we demonstrate two different strategies for acceleration of the restricted diffusion NMR measurements: time-resolved diffusion NMR and ultrafast Laplace NMR. The former is based on time-resolved non-uniform sampling, while the latter relies on spatial encoding of two-dimensional data. Both techniques allow similar 1-2 order of magnitude acceleration of acquisition, but they have different strengths and weaknesses, which we discuss in detail. The feasibility of the methods was proven by investigating restricted diffusion of water inside tracheid cells of thermally modified pine wood.
多孔材料中受限流体的扩散可以通过脉冲场梯度核磁共振（NMR）非侵入式且无需示踪剂进行研究。如果实验重复多次，改变扩散延迟，就可以记录有关孔径和迂曲度的详细信息。然而，由于梯度上升和扩散延迟变化需要多次重复，因此测量非常耗时。在本文中，我们展示了两种加速受限扩散 NMR 测量的不同策略：时分辨扩散 NMR 和超快拉普拉斯 NMR。前者基于时分辨非均匀采样，而后者则依赖于二维数据的空间编码。这两种技术都可以实现类似的 1-2 个数量级的采集加速，但它们具有不同的优缺点，我们将详细讨论。通过研究热改性松木管胞内水的受限扩散，证明了这些方法的可行性。
