Ultra-Low Field Nuclear Magnetic Resonance
Ultra-Low Field Nuclear Magnetic Resonance
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发表时间：
2018
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通讯作者：
Kiwoong Kim
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作者：
Kiwoong Kim
目前，微特斯拉核磁共振技术引起了许多超导量子干涉器件(SQUID)研究小组的兴趣。通过施加微特斯拉(MT)磁场而不是传统核磁共振/磁成像(MRI)中的几特斯拉磁场，我们可以用生物和化学材料来观察新的物理，从而我们可以利用新的性质来开发有用的临床应用和新的科学分析工具。在这样一个低场下，质子的Larmor频率太低，不能产生足够的法拉第感应来感应检测，因此，我们使用低T_c的SQUID传感器来检测信号。SQUID在施加强磁脉冲的恶劣环境中的操作在技术上是棘手的，因此，我们可以说Mt-NMR处于SQUID技术的前沿。微弱的样品极化，鱿鱼拾取线圈中的磁通爬行噪声，以及磁屏蔽室(MSR)墙壁上持续的涡流，限制了灵敏检测核磁共振信号的能力。作为这些问题的解决方案，我们分别引入了动态核极化(DNP)、超导磁滞和一种新的MSR设计。这些突破性的技术应该会改善核磁共振系统的性能，并使应用范围扩大。此外，可以利用低磁场中的特殊物理性质来寻找SQUID核磁共振技术的新应用。在这篇手稿中，我们介绍了几个mt-核磁共振的具体应用：用于材料识别的强耦合区域的2D核磁共振谱，用于癌症测绘的T1增强对比磁共振，带有DNP的非场循环核磁共振，以及生物磁共振。
Currently, micro-Tesla nuclear magnetic resonance (NMR) is attracting the interests of many research groups dealing with superconducting quantum interference device (SQUID) technology. By applying a micro-Tesla (mT) magnetic field rather than a several Tesla magnetic field in conventional NMR/magnetic imaging (MRI), we can observe new physics with bioand chemical materials so that we can utilize the new properties to develop useful clinical applications and new scientific analysis tools. Under such a low field, the Larmor frequency of protons is too low to generate sufficient Faraday induction to be detected inductively; hence, we utilize low-Tc SQUID sensors to detect the signal. SQUID operation in a harsh environment where strong magnetic pulses are applied is technically tricky; thus, we can say that mT-NMR is on the forefront of SQUID technology. Weak sample polarization, flux-creeping noise in a SQUID pick-up coil, and long-lasting eddy currents along the walls of a magnetically shielded room (MSR) limit the ability to detect sensitively NMR signals. As solutions for those problems, we introduce dynamic nuclear polarization (DNP), superconductive magnetic hysteresis, and a new design of an MSR, respectively. These breakthrough techniques should improve the performance of the NMR system and enable the range of applications to be widened. In addition, particular physical properties in a low magnetic field can be utilized to find new applications of the SQUID NMR technology. In this manuscript, we introduce several mT-NMR specific applications: the 2D NMR spectrum in a strongly coupled region for material identification, T1-enhanced contrast MRI for cancer mapping, non-field-recycling NMR with DNP, and biomagnetic resonance.