Aspects of NMR reciprocity and applications in highly conductive media
Aspects of NMR reciprocity and applications in highly conductive media
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核磁共振互易性及其在高导电介质中的应用
DOI：
10.1002/cmr.a.21466
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发表时间：
2018
影响因子：
0.6
通讯作者：
Jerschow, Alexej
中科院分区：
文献类型：
--
作者：
Ilott, Andrew J.;Jerschow, Alexej
在核磁共振波谱和核磁共振的背景下，互易原理为从发射的射频场方向图确定接收灵敏度提供了一种方便的方法。核磁共振的互易原理最初是由Hoult等人（J Magn son. 1976;24:71）描述的，它与更广泛的洛伦兹互易原理和天线理论中的类似定理有关。互易原理的一个常见应用是，对于用于发送和检测的单个线圈，可以假设发送和接收场相等。这方面也是应用定理可能遇到的一些概念性困难的地方。例如，是否应该使用复共轭场进行检测，或者是否应该在旋转坐标系或实验室坐标系中应用定理，这些问题可能会引起相当大的混乱。我们试图在这里提供一个有用的讨论互惠原则的应用，以澄清一些混淆的问题。特别是，我们避免使用在这方面经常提到的“负旋转框架”，因为我们认为它不必要地使问题复杂化。此外，我们还讨论了该定理对导电样品，特别是金属的磁共振实验的影响。
In the context of NMR spectroscopy and MRI, the principle of reciprocity provides a convenient method for determining the reception sensitivity from the transmitted rf field pattern. The reciprocity principle for NMR was originally described by Hoult et al (J Magn Reson. 1976;24:71) and is related to the broader Lorentz reciprocity principle and similar theorems from antenna theory. One frequent application of the reciprocity principle is that for a single coil used for both transmission and detection, the transmit and receive fields can be assumed to be equal. This aspect is also where some of the conceptual difficulty of applying the theorem may be encountered. For example, the questions of whether one should use the complex conjugate field for detection or whether one should apply the theorem in the rotating frame or in the laboratory frame may give rise to considerable confusion. We attempt here to provide a helpful discussion of the application of the reciprocity principle in such a way as to clarify some of the confounding questions. In particular, we avoid the use of the “negatively rotating frame,” which is frequently mentioned in this context, since we consider it to unnecessarily complicate the matter. In addition, we also discuss the implications of the theorem for magnetic resonance experiments on conducting samples, and metals, in particular.