Motivation: For Chemical Exchange Saturation Transfer (CEST) imaging of human glioma at 7T, the contrast corresponding to the tumor area is often masked by the effects of B1+ inhomogeneity. Goal(s): Retrospective B1+ inhomogeneity correction using CEST data acquired using circularly polarized (CP) mode at multiple B1 levels can potentially reduce the image inhomogeneity. Approach: Using both spline and linear interpolation methods, contrast- and Z-spectrum-based corrections are tested on 7T CEST data from glioma patients. Results: The interpolation-based retrospective B1+ inhomogeneity correction has shown mixed effects for the CEST contrast. Impact: Retrospective correction for B1+ inhomogeneity has limited effects in improving CEST image quality acquired using CP mode at 7T, thus presenting a demand for alternative methods to archive homogeneous CEST contrast at time of acquisition.
Lan et al. (Tue,) studied this question.