Image navigators insensitive to B0 inhomogeneity for optimal prospective motion-corrected MRS

Motivation: Navigator-based prospective motion-corrected MRS is often performed with 2nd order shims optimized in the whole brain to prevent degradation of navigator images, resulting in suboptimal linewidth. Goal(s): Here, we report image-based prospective motion correction with 2nd order shims adjusted in the MRS voxel while maintaining good navigator image quality despite the strong B0 inhomogeneity outside the voxel. Approach: This was achieved by segmenting multislice spiral navigator images to reduce blurring artifacts from inhomogeneous B0 fields. Results: High-quality spectra with optimal linewidth were acquired in the presence of subject motion at 3T and 7T, demonstrating the feasibility of this new approach on clinical scanners. Impact: Image-based prospective motion correction with optimal localized B0 shim (1st and 2nd order) in the MRS voxel is feasible in the human brain at 3T and 7T.