Reproducible liver CEST Imaging at 7 T with B1+ shimming

Motivation: While most chemical exchange saturation transfer (CEST) studies focus on the brain, liver CEST imaging is promising and requires further investigation. Goal(s): To explore the feasibility and reproducibility of CEST imaging in the human liver at 7T with B1+ shimming. Approach: Datasets were obtained in five healthy volunteers on a 7T whole-body imager. Static parallel transmission (pTx, i.e. B1+ shimming) was applied to locally maximize the B1+ efficiency. MTRRex CEST contrasts of amide, guanidino and exchange-relayed nuclear Overhauser effect (rNOE) signals were quantified. Results: Amide and rNOE MTRRex values demonstrated reproducibility across all subjects - coefficients of variation were 9.8% and 7.5% correspondingly. Impact: In this study, to the best of our knowledge, we have successfully demonstrated for the first time the robust and reliable acquisition of relaxation-compensated CEST contrasts (i.e., MTRRex of amide, rNOE and guanidino) of the human liver at ultra-high fields.