A metabolite‐specific 3D stack‐of‐spiral bSSFP sequence for improved lactate imaging in hyperpolarized [1‐13C]pyruvate studies on a 3T clinical scanner

PURPOSE: The balanced steady-state free precession sequence has been previously explored to improve the efficient use of nonrecoverable hyperpolarized 13 C magnetization, but suffers from poor spectral selectivity and long acquisition time. The purpose of this study was to develop a novel metabolite-specific 3D bSSFP ("MS-3DSSFP") sequence with stack-of-spiral readouts for improved lactate imaging in hyperpolarized [ 1- 13 C ]pyruvate studies on a clinical 3T scanner. METHODS: Simulations were performed to evaluate the spectral response of the MS-3DSSFP sequence. Thermal 13 C phantom experiments were performed to validate the MS-3DSSFP sequence. In vivo hyperpolarized [ 1- 13 C ], pyruvate studies were performed to compare the MS-3DSSFP sequence with metabolite-specific gradient echo ("MS-GRE") sequences for lactate imaging. RESULTS: Simulations, phantom, and in vivo studies demonstrate that the MS-3DSSFP sequence achieved spectrally selective excitation on lactate while minimally perturbing other metabolites. Compared with MS-GRE sequences, the MS-3DSSFP sequence showed approximately a 2.5-fold SNR improvement for lactate imaging in rat kidneys, prostate tumors in a mouse model, and human kidneys. CONCLUSIONS: Improved lactate imaging using the MS-3DSSFP sequence in hyperpolarized [ 1- 13 C ]pyruvate studies was demonstrated in animals and humans. The MS-3DSSFP sequence could be applied for other clinical applications such as in the brain or adapted for imaging other metabolites such as pyruvate and bicarbonate.