ABSTRACT Purpose To implement and evaluate chemical exchange saturation transfer (CEST) at ultra‐high field on a whole‐body 11.7 T scanner using parallel transmission (pTx). Methods Tailored pTx CEST saturation pulses were optimized to achieve a spatially uniform target B 1 + while satisfying SAR and power constraints either defined by conservatively defined radio‐frequency (RF) power limits or by a virtual observation point (VOP)–based framework. The resulting pulse performance at 11.7 T was assessed through numerical simulations and compared against corresponding designs at 7 T. The proposed saturation pulses were integrated into a two‐dimensional multi‐slice EPI sequence. Experimental testing of the sequence was performed in vitro using metabolite‐doped phantoms and in vivo in four healthy volunteers. Results The pTx pulse designs optimized under VOP‐based SAR constraints at 11.7 T achieved comparable performance to 7 T designs despite higher intrinsic B 1 + inhomogeneity. In vitro experiments validated the sequence implementation and confirmed detection of the targeted metabolites. In vivo experiments demonstrated acceptable saturation homogeneity (nRMSE ≤ 12.1%) in a slab of thickness 1 cm, with only minimal additional improvement achieved through B 1 + post‐processing correction. Across the cohort, robust gray matter–white matter contrast was consistently observed for multiple CEST contrasts. Conclusion VOP‐based SAR‐constrained pTx CEST saturation pulse design enabled robust and reproducible contrast at 11.7 T by effectively mitigating B 1 + inhomogeneities while remaining within safety limits, facilitating translation to future in vivo clinical research applications.
Ressam et al. (Fri,) studied this question.