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Travelling-wave nuclear magnetic resonance


Nuclear magnetic resonance1,2 (NMR) is one of the most versatile experimental methods in chemistry, physics and biology3, providing insight into the structure and dynamics of matter at the molecular scale. Its imaging variant—magnetic resonance imaging4,5 (MRI)—is widely used to examine the anatomy, physiology and metabolism of the human body. NMR signal detection is traditionally based on Faraday induction6 in one or multiple radio-frequency resonators7,8,9,10 that are brought into close proximity with the sample. Alternative principles involving structured-material flux guides11, superconducting quantum interference devices12, atomic magnetometers13, Hall probes14 or magnetoresistive elements15 have been explored. However, a common feature of all NMR implementations until now is that they rely on close coupling between the detector and the object under investigation. Here we show that NMR can also be excited and detected by long-range interaction, relying on travelling radio-frequency waves sent and received by an antenna. One benefit of this approach is more uniform coverage of samples that are larger than the wavelength of the NMR signal—an important current issue in MRI of humans at very high magnetic fields. By allowing a significant distance between the probe and the sample, travelling-wave interaction also introduces new possibilities in the design of NMR experiments and systems.

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Figure 1: Working principles of traditional and travelling-wave NMR.
Figure 2: Demonstration of travelling-wave NMR in an aqueous 10% ethanol solution.
Figure 3: Example of wave impedance matching in travelling-wave MRI.
Figure 4: In vivo results.
Figure 5: Travelling-wave MRI of very large samples.


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We thank N. van den Berg and A. Trabesinger for discussions. We are also grateful to P. Boesiger for his leading role in creating the 7T facility. This work was funded in part by the Swiss National Science Foundation (Project 116400) and by the Velux Foundation. Technical support from Philips Healthcare is also gratefully acknowledged.

Author Contributions D.O.B.: basic concept, antenna design and construction, bench experiments, magnetic resonance experiments, manuscript. N.D.Z.: conceptual considerations, assistance with antenna design, assistance with bench and magnetic resonance experiments, editing. J.F.: conceptual considerations, FDTD models, radio-frequency safety validation, editing. J.P.: FDTD models. K.P.P.: conceptual considerations, assistance with magnetic resonance experiments, manuscript, supervision.

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Correspondence to Klaas P. Pruessmann.

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Brunner, D., De Zanche, N., Fröhlich, J. et al. Travelling-wave nuclear magnetic resonance. Nature 457, 994–998 (2009).

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