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

PURPOSE: To develop a coil‐based method to obtain accurate sensitivity profiles in (13)C MRI at 3T from the endogenous (23)Na. An eight‐channel array is designed for (13)C MR acquisitions. As application examples, the array is used for two‐fold accelerated acquisitions of both hyperpolarized (13)C metabolic imaging of pig kidneys and the human brain. METHODS: A flexible coil array was tuned optimally for (13)C at 3T (32.1 MHz), with the coil coupling coefficients matched to be nearly identical at the resonance frequency of (23)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. RESULTS: The measured sensitivity profiles on a phantom showed high spatial similarity for (13)C and (23)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 (23)Na profiles obtained in vivo could be used successfully to perform two‐fold acceleration of hyperpolarized (13)C 3D acquisitions of both pig kidneys and a healthy human brain. CONCLUSION: A receive array has been developed in such a way that the (13)C sensitivity profiles could be accurately obtained from measurements at the (23)Na frequency. This technique facilitates accelerated acquisitions for hyperpolarized (13)C imaging. The SNR performance obtained at the (13)C frequency, compares well to other state‐of‐the‐art coils for the same purpose, showing slightly better superficial and central SNR.