Reciprocity Relations in Travelling Wave MRI

David Otto Brunner¹, Klaas Paul Pruessmann¹

NMR signal generation has been generally described by a generalized or gyrotropic reciprocity relation between sending and receiving port of the RF probe used. This reciprocity has been profoundly validated in experiments in which the spins reside within the near-field of the RF probe. In this work, verification and implications of NMR signal phases in travelling wave NMR setups are studied. It was found that the axial phase delay inside a wave guide used for excitation and detection coincides with the phase found in the NMR signal, confirming the reciprocity for long-range regimes of RF interaction.