Proton-decoupled carbon magnetic resonance spectroscopy in human calf muscles at 7 T using a multi-channel radiofrequency coil

(13)C magnetic resonance spectroscopy is a viable, non-invasive method to study cell metabolism in skeletal muscles. However, MR sensitivity of (13)C is inherently low, which can be overcome by applying a higher static magnetic field strength together with radiofrequency coil arrays instead of single loop coils or large volume coils, and (1)H decoupling, which leads to a simplified spectral pattern. (1)H-decoupled (13)C-MRS requires RF coils which support both, (1)H and (13)C, Larmor frequencies with sufficient electromagnetic isolation between the pathways of the two frequencies. We present the development, evaluation, and first in vivo measurement with a 7 T 3-channel (13)C and 4-channel (1)H transceiver array optimized for (1)H-decoupled (13)C-MRS in the posterior human calf muscles. To ensure minimal cross-coupling between (13)C and (1)H arrays, several strategies were combined: mutual magnetic flux was minimized by coil geometry, two LCC traps were inserted into each (13)C element, and band-pass and low-pass filters were integrated along the signal pathways. The developed coil array was successfully tested in phantom and in vivo MR experiments, showing a simplified spectral pattern and increase in signal-to-noise ratio of approximately a factor 2 between non-decoupled and (1)H-decoupled spectra in a glucose phantom and the human calf muscle.