A 9-channel 1H, 3-channel 31P RF coil for metabolic calf muscle studies at 7 T

Motivation: Combined 1H/31P MRS allows the simultaneous investigation of oxidative and glycolytic metabolic processes in exercising muscle. Insufficient proton performance of typical double-tuned radiofrequency coils can be a limitation. Goal(s): To develop a 1H/31P calf coil with excellent proton performance and minimal compromises on 31P SNR. Approach: The proposed design combines three ¹H transceive dipoles, six ¹H receive-only loops and three 31P transceive loops. Results: The developed coil showed 3.3- and 1.3-times higher 1H SNR than double- and single-tuned reference coils, improved transmit performance and enables parallel imaging. The 31P SNR was 26 % below the reference, but with a larger field of view. Impact: The developed coil will enable advanced metabolic calf muscle studies, as it combines excellent 1H performance with the possibility of acquiring high-quality 31P spectra. Combining dipoles and loops is a powerful approach for building high-density coil arrays at ultra-high field.