Low-field nuclear magnetic resonance and polarized noble gases

核磁共振(核磁共振)和核磁共振成像(MRI)是使科学家、工程师和医生能够研究各种问题的技术，从微妙的原子、分子和化学过程到人体的结构和功能。通常，它们需要使用强大的磁铁来极化样品或对象。这相当于对齐样品中的原子核；根据经验，磁场越大，信号或图像就越好。因此，这项提案中描述的研究寻求探索另一个极端：在非常弱的磁场中的核磁共振和核磁共振。虽然这看起来可能适得其反，但确实有方法可以在不诉诸大磁场的情况下极化某些原子。例如，我使用激光来极化稀有气体元素家族中某些成员的原子核，如氦。一旦极化，我就可以使用我实验室开发的低场MRI系统对这种气体进行成像--这是世界上为数不多的几个这样的设备之一。如果吸入这种气体，就可以生成肺部的图像。我们已经证明了追求这项技术有很好的理由，但它还没有准备好商业化或临床使用。他说，我们将进行的研究分为两类，这两类密切相关，但动机和结果截然不同。在第一类中，我们将研究在获得图像或其他形式的核磁共振数据时操纵原子和检测信号的新方法。这将帮助我们理解、量化和优化我们从低场--有时是高场--核磁共振/核磁共振实验中提取的信息；实际上，实现实际应用。在第二类中，我们将与其他物理学家合作，进行一个非常复杂的磁共振实验，在这个实验中，样品是极化中子(亚原子粒子)和极化氦原子的气体混合物，温度接近绝对零度。这项实验将以极高的灵敏度探测中子的结构，并有望挑战描述物质性质的理论。

Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI) are techniques that enable scientists, engineers, and doctors to study diverse problems, ranging from subtle atomic, molecular, and chemical processes to the structure and function of the human body. Ordinarily, they require the use of powerful magnets that polarize the sample or subject. This amounts to aligning the nuclei of atoms in the sample; as a rule of thumb, the larger the magnetic field is, the better the signal or image will be.     The research described in this proposal seeks to explore the other extreme: NMR and MRI in very-weak magnetic fields. While this might seem counter-productive, methods do exist for polarizing certain atoms without resorting to a large magnetic field.  For example, I use lasers to polarize the nuclei of certain members of the noble gas family of elements, such as helium. Once polarized, I am able to image this gas using a low-field MRI system that was developed in my laboratory - one of only a handful of such devices worldwide. If this gas is inhaled, an image of the lungs can be generated. We have already shown that there are good reasons for pursuing this technology, but it is not yet ready for commercialization or clinical use.     The research that we will undertake to perform falls into two categories that are intimately related, yet have radically different motivations and outcomes. In the first category, we will investigate new ways of manipulating atoms and detecting signals as images or other forms of NMR data are acquired. This will help us to understand, quantify, and optimize the information that we extract from low-field - and in some cases high field - NMR/MRI experiments; in effect, to realize practical applications.  In the second category, we will collaborate with other physicists to perform a very complex magnetic resonance experiment in which the sample is a gaseous mixture of polarized neutrons (a subatomic particle) and polarized helium atoms at temperatures close to absolute zero. This experiment will probe the structure of the neutron with exquisite sensitivity, and is expected to challenge theories that describe the nature of matter.