Development of a Proton-Frequency-Transparent Birdcage Radiofrequency Coil for In Vivo C-13 MRS/MRSI Study in a 3.0 T MRI System

Abstract

A proton-frequency-transparent (PFT) birdcage RF coil that contains carbon-proton switching circuits (CPSCs) is presented to acquire C-13 MR signals, which, in turn, enable H-1 imaging with existing H-1 RF coils without being affected by a transparent C-13 birdcage RF coil. CPSCs were installed in the PFT C-13 birdcage RF coil to cut the RF coil circuits during H-1 MR imaging. Finite-difference time-domain (FDTD) electromagnetic (EM) simulations were performed to verify the performance of the proposed CPSCs. The performance of the PFT C-13 birdcage RF coil with CPSCs was verified via phantom and in vivo MR studies. In the phantom MR studies, H-1 MR images and C-13 MR spectra were acquired and compared with each other using the C-13 birdcage RF coil with and without the CPSCs. For the in vivo MR studies, hyperpolarized C-13 cardiac MRS and MRSI of swine were performed. The proposed PFT C-13 birdcage RF coil with CPSCs led to a percent image uniformity (PIU) reduction of 1.53% in the proton MR images when compared with the case without it. FDTD EM simulations revealed PIU reduction of 0.06% under the same conditions as the phantom MR studies. Furthermore, an SNR reduction of 5.5% was observed at C-13 MR spectra of corn-oil phantom using the PFT C-13 birdcage RF coil with CPSCs compared with that of the C-13 birdcage RF coil without CPSCs. Utilizing the PFT C-13 birdcage RF coil, C-13-enriched compounds were successfully acquired via in vivo hyperpolarized C-13 MRS/MRSI experiments. In conclusion, the applicability and utility of the proposed 16-leg low-pass PFT C-13 birdcage RF coil with CPSCs were verified via H-1 MR imaging and hyperpolarized C-13 MRS/MRSI studies using a 3.0 T MRI system.