A Double-Quadrature Radiofrequency Coil Design for Proton-Decoupled Carbon-13 Magnetic Resonance Spectroscopy in Humans at 7T

PurposeCarbon-13 magnetic resonance spectroscopy (C-13-MRS) is challenging because of the inherent low sensitivity of C-13 detection and the need for radiofrequency transmission at the H-1 frequency while receiving the C-13 signal, the latter requiring electrical decoupling of the C-13 and H-1 radiofrequency channels. In this study, we added traps to the C-13 coil to construct a quadrature-C-13/quadrature-H-1 surface coil, with sufficient isolation between channels to allow simultaneous operation at both frequencies without compromise in coil performance. MethodsIsolation between channels was evaluated on the bench by measuring all coupling parameters. The quadrature mode of the quadrature-C-13 coil was assessed using in vitro Na-23 gradient echo images. The signal-to-noise ratio (SNR) was measured on the glycogen and glucose resonances by C-13-MRS in vitro, compared with that obtained with a linear-C-13/quadrature-H-1 coil, and validated by C-13-MRS in vivo in the human calf at 7T. ResultsIsolation between channels was better than -30 dB. The Na-23 gradient echo images indicate a region where the field is strongly circularly polarized. The quadrature coil provided an SNR enhancement over a linear coil of 1.4, in vitro and in vivo. ConclusionIt is feasible to construct a double-quadrature C-13-H-1 surface coil for proton decoupled sensitivity enhanced C-13-NMR spectroscopy in humans at 7T. Magn Reson Med 73:894-900, 2015. (c) 2014 Wiley Periodicals, Inc.