B1 inhomogeneity corrected APT MRI based on direct saturation removed omega plot model at 5 T

Motivation: B1 inhomogeneity correction is critical in CEST MRI. Reliable correction methods are desired. Goal(s): This study developed a B1 inhomogeneity correction method based on a direct saturation removed omega plot model and tested its performance in human brain APTw imaging at 5 T. Approach: Four healthy volunteers were scanned under four B1 levels. Corrected signal at nominal B1 was calculated from the omega plot model determined from either two or four B1 levels. Results: B1 inhomogeneity-induced artifact was shown on uncorrected APTw images, which was effectively mitigated after correction. Comparably homogeneous APTw maps were obtained between two and four B1 levels. Impact: The proposed method enables reliable B1 inhomogeneity correction from at least two B1 levels, providing an efficient way to improve quantitative CEST MRI, especially on high-field scanners.