High‐resolution deuterium metabolic imaging of the human brain at 9.4 T using phase‐cycled balanced SSFP spectral–spatial acquisitions

Abstract Purpose The aim was to improve the sensitivity and robustness against B 0 inhomogeneities of deuterium metabolic imaging (DMI) using phase‐cycled balanced SSFP (bSSFP) methods at 9.4 T. Methods We investigated two variants of phase‐cycled bSSFP acquisitions, namely uniformly weighted multi‐echo and acquisition‐weighted chemical shift imaging (CSI) to improve the SNR of DMI in the brain after oral 6,6′‐ 2 H 2 ‐glucose intake. Phase‐cycling was introduced to reduce the off‐resonance sensitivity of bSSFP, incurring a moderate SNR loss. Two SNR optimal methods for obtaining metabolite amplitudes from the phase‐cycled bSSFP data were proposed. The SNR performance of the two bSSFP variants was compared with the SNR‐optimized vendor's standard CSI. Additionally, in vivo T 1 and T 2 of deuterium metabolites were estimated. Results High‐resolution whole‐brain dynamic DMI maps were obtained for all acquisitions. The CSI variant of phase‐cycled bSSFP achieved an average SNR increase of 16% and 25% for glucose and glutamate + glutamine (Glx), respectively, compared to the SNR‐optimized vendor's standard CSI. Phase‐cycling improved the bSSFP metabolite estimation and provided additional spectral encoding at the cost of a 10% to 20% SNR loss. Compared to the CSI variant of bSSFP acquisition, the multi‐echo variant exhibited up to 35% lower SNR performance because of uniform k‐space weighting and less efficient readout. However, it achieved higher resolutions than acquisition‐weighted CSI protocols and showed several qualitative improvements. Conclusion We demonstrated the feasibility of using two phase‐cycled bSSFP acquisitions for off‐resonance insensitive high‐resolution 6,6′‐ 2 H 2 ‐glucose DMI studies in the human brain. bSSFP acquisitions have potential to improve the sensitivity of DMI despite the SNR loss of phase‐cycling and other human scanner constraints.