Coherent Control of Spin Dynamics to Improve Spectral and Spatial Resolution in NMR

在化学测量和成像项目的支持下，迈阿密大学的杰米·沃尔斯教授和他的团队正在努力开发具有成本效益的方法，以提高核磁共振（NMR）光谱的分辨率。核磁共振是一种强大而通用的工具，广泛用于学术、临床和工业研究。如果成功，这项工作将提高磁共振成像（MRI）的对比度，这是一种广泛用于临床诊断和其他成像应用的非侵入性工具。这反过来又可以改善癌症和其他难以发现的人体疾病的特征和诊断，以及提高固体（如骨骼）图像的空间分辨率。沃尔斯博士还在开发软件，使其他人能够模仿和扩展他的方法。从事这项研究的本科生和研究生接受核磁共振理论和实验方面的培训。在光谱学中，如果两个共振的频率不同，可以分辨它们，？？？？，大于单个共振的线宽。在核磁共振中，提高光谱分辨率是扩大核磁共振可解决问题范围的最重要挑战之一。PI小组最近发现，光谱分辨率的意想不到的改进可以实现(1)通过在固态系统中使用低功率射频激发，(2)通过使用延迟采集来突出由于傅立叶去相引起的光谱差异，这是线形的数学特性的结果，与潜在的自旋动力学和/或复杂性无关。或(3)在液态样品中存在部分相关的射频（RF）和磁场B0不均匀性的情况下产生多自旋有序。总的来说，这些结果表明了一种替代的和未探索的途径，可以提高NMR的光谱分辨率，这是本研究的基础。具体来说，沃尔斯小组正在开发脉冲序列，利用傅里叶减相的差异，以增强光谱中的尖锐光谱特征。这项工作需要理论和实验研究的性质，多自旋顺序，可以导致最佳线窄在液态核磁共振。它可以为固体和液态核磁共振应用中相干提高分辨率提供替代方法。除了提高固态MRI的空间分辨率外，这些改进还可以增强药物、复合糖和其他生物分子物种的光谱表征。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Measurement and Imaging Program, Professor Jamie Walls and his group at the University of Miami are working to develop cost-effective methods to improve the resolution of nuclear magnetic resonance (NMR) spectrometry, a powerful and versatile tool widely used in academic, clinical, and industrial research. If successful, this work will enable improved contrast in magnetic resonance imaging (MRI), a noninvasive tool widely used for clinical diagnostics and other imaging applications. This in turn could improve characterization and diagnosis of cancer and other difficult-to-detect ailments in the human body, as well as improving spatial resolution of images of solids such as bone. Dr. Walls is also developing software that will enable others to emulate and expand on his methods. Undergraduate and graduate students working on this research receive training in both theoretical and experimental aspects of NMR.In spectroscopy, two resonances can be resolved if their frequency difference, ????, is larger than the linewidths of the individual resonances. In NMR, improving spectral resolution is one of the most important challenges for extending the range of problems NMR can address. The PI's group recently discovered that unexpected improvements in spectral resolution could be achieved (1) by using low-power RF excitation in solid-state systems, (2) by using delayed-acquisition to highlight spectral differences due to Fourier dephasing, which is a result of the mathematical properties of the line shape and is independent of the underlying spin dynamics and/or complexity, or (3) by generating multispin-order in the presence of partially correlated radiofrequency (RF) and magnetic field B0 inhomogeneities in liquid-state samples. Collectively, these results suggest an alternative and unexplored route towards improving spectral resolution in NMR that forms the basis of this research. Specifically, the Walls group is developing pulse sequences that exploit differences in Fourier dephasing in order to enhance sharp spectral features in a spectrum. The work entails both theoretical and experimental investigations into the nature of the multispin-order that can lead to optimal line narrowing in liquid-state NMR. It can provide alternative methods for coherently improving resolution in both solid- and liquid-state NMR applications. These improvements can enhance spectroscopic characterization of pharmaceuticals, complex sugars, and other biomolecular species in addition to improving spatial resolution in solid-state MRI.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.