Magnetic Resonance Imaging RF Coils Systems Testing and Measurement

Abstract – The radio-frequency (RF) detection coil is a transducer device that excites the nuclear magnetic resonance (NMR) signal and then detects it in the magnetic resonance spectroscopy (MRS) measurement. The signal-to-noise (SNR), spatial and temporal resolution, spatial uniformity, and the efficiency with which RF excitation power is used and lost to the measurement sample are all dependent on the RF coil’s performance. The success of the MRS measurement is largely determined by the proper choice and application of the RF detection coil. There are many coil design choices available and we need to fit the best options for the specific application. Among coil design choices there are transmission line coils, wire coils (surface coils, volume coils), TEM coils. The types of surface coils are single loop solenoids, multiple-loop arrays, and the types of volume coils solenoids, crossed pairs, saddle pairs, phased arrays, cage coils, Litz coils. TEM coils are coaxial lines, strip lines, and microstrips. TEM coils can be capacitively shortened and tuned; half-wave trans-mission line resonators are similar to the slotted tube resonator but with a number of practical features that lend themselves to modern utility. Typical features are where the center conductor ‘rungs’ of these coils generate a highly uniform field like rungs of a birdcage. The TEM coil can be double-tuned by tuning alternating rungs to alternating Larmor frequencies of the desired nuclei. The Larmor or precessional frequency in MRI refers to the rate of precession of the magnetic moment of the proton around the external magnetic field.

Reference

9783031586996. Aluf, Advanced Microwave RF Antennas and Circuits, Nonlinearity Applications in Engineering, Springer, Edition 2, 2025, In two Volumes, ISBN: 978-3-031-58699-6, EAN: 9783031586996.

              https://link.springer.com/book/9783031586996