Spengler Nils, While Peter T, Meissner Markus V, Wallrabe Ulrike, Korvink Jan G
IMTEK - Department of Microsystems Engineering, University of Freiburg, Freiburg, Germany.
Institute of Microstructure Technology (IMT), Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, Germany.
PLoS One. 2017 Aug 15;12(8):e0182779. doi: 10.1371/journal.pone.0182779. eCollection 2017.
A high NMR detection sensitivity is indispensable when dealing with mass and volume-limited samples, or whenever a high spatial resolution is required. The use of miniaturised RF coils is a proven way to increase sensitivity, but situations may arise where space restrictions could prevent the use of a small resonant coil, e.g., in the interior of the smallest practicable micro-coils. We present the use of magnetic lenses, denoted as Lenz lenses due to their working principle, to focus the magnetic flux of an RF coil into a smaller volume and thereby locally enhance the sensitivity of the NMR experiment-at the expense of the total sensitive volume. Besides focusing, such lenses facilitate re-guiding or re-shaping of magnetic fields much like optical lenses do with light beams. For the first time we experimentally demonstrate the use of Lenz lenses in magnetic resonance and provide a compact mathematical description of the working principle. Through simulations we show that optimal arrangements can be found.
在处理质量和体积受限的样品时，或者在需要高空间分辨率的任何情况下，高核磁共振（NMR）检测灵敏度都是必不可少的。使用小型化射频线圈是提高灵敏度的一种行之有效的方法，但可能会出现空间限制阻碍使用小型共振线圈的情况，例如在最小可行微线圈的内部。我们展示了一种磁透镜的应用，由于其工作原理，我们将其称为楞兹透镜，它可以将射频线圈的磁通量聚焦到更小的体积中，从而局部提高NMR实验的灵敏度——代价是总敏感体积减小。除了聚焦之外，这种透镜还能像光学透镜对光束那样，方便地对磁场进行重新引导或重塑。我们首次通过实验证明了楞兹透镜在磁共振中的应用，并对其工作原理给出了简洁的数学描述。通过模拟，我们表明可以找到最佳配置。
