RF coil design for accurate parallel imaging on 13 C MRSI using 23 Na sensitivity profiles

To develop a coil-based method to obtain accurate sensitivity profiles in C MRI at 3T from the endogenous Na. An eight-channel array is designed for C MR acquisitions. As application examples, the array is used for two-fold accelerated acquisitions of both hyperpolarized C metabolic imaging of pig kidneys and the human brain. A flexible coil array was tuned optimally for C at 3T (32.1 MHz), with the coil coupling coefficients matched to be nearly identical at the resonance frequency of Na (33.8 MHz). This is done by enforcing a high decoupling (obtained through highly mismatched preamplifiers) and adjusting the coupling frequency response. The SNR performance is compared to reference coils. The measured sensitivity profiles on a phantom showed high spatial similarity for C and Na resonances, with average noise correlation of 9 and 11%, respectively. For acceleration factors 2, 3, and 4, the obtained maximum g-factors were 1.0, 1.1, and 2.6, respectively. The Na profiles obtained in vivo could be used successfully to perform two-fold acceleration of hyperpolarized C 3D acquisitions of both pig kidneys and a healthy human brain. A receive array has been developed in such a way that the C sensitivity profiles could be accurately obtained from measurements at the Na frequency. This technique facilitates accelerated acquisitions for hyperpolarized C imaging. The SNR performance obtained at the C frequency, compares well to other state-of-the-art coils for the same purpose, showing slightly better superficial and central SNR.