A form-fitted three channel P-31, two channel H-1 transceiver coil array for calf muscle studies at 7 T

Abstract

PurposeTo enhance sensitivity and coverage for calf muscle studies, a novel, form-fitted, three-channel phosphorus-31 (P-31), two-channel proton (H-1) transceiver coil array for 7 T MR imaging and spectroscopy is presented. MethodsElectromagnetic simulations employing individually generated voxel models were performed to design a coil array for studying nonpathological muscle metabolism. Static phase combinations of the coil elements' transmit fields were optimized based on homogeneity and efficiency for several voxel models. The best-performing design was built and tested both on phantoms and in vivo. ResultsSimulations revealed that a shared conductor array for P-31 provides more robust interelement decoupling and better homogeneity than an overlap array in this configuration. A static B-1(+) shim setting that suited various calf anatomies was identified and implemented. Simulations showed that the P-31 array provides signal-to-noise ratio (SNR) benefits over a single loop and a birdcage coil of equal radius by factors of 3.2 and 2.6 in the gastrocnemius and by 2.5 and 2.0 in the soleus muscle. ConclusionThe performance of the coil in terms of B-1(+) and achievable SNR allows for spatially localized dynamic P-31 spectroscopy studies in the human calf. The associated higher specificity with respect to nonlocalized measurements permits distinguishing the functional responses of different muscles. Magn Reson Med 73:2376-2389, 2015. (c) 2014 Wiley Periodicals, Inc.