Resolving estimation uncertainties of chemical shift encoded fat‐water imaging using magnetization transfer effect

Purpose B 0 field inhomogeneity may cause significant errors in chemical shift encoding‐based fat‐water (F/W) separation. We describe a new approach to improve its robustness using novel B 0 field map pre‐estimation. Methods Our method exploits insensitivity of fat to magnetization transfer effect, which allows generating fat‐insensitive B 0 field priors with full or partial spatial support using a low‐resolution magnetization transfer‐weighted scan. The full prior can be employed by most F/W separation methods for initialization or data demodulation. We also propose a modified region‐growing algorithm in which the partial prior is utilized for its initial seeding. Results The magnetization transfer‐based B 0 priors significantly reduced F/W errors of three representative F/W separation methods in all cases. In cases with moderate B 0 inhomogeneity, the full prior allowed error‐free separation even with basic, voxel‐independent processing. When coupled with methods exploiting B 0 field smoothness, it significantly improved separation accuracy even in the presence of strong inhomogeneities. Seeding the region‐growing with the partial prior significantly improved performance of F/W separation, including cases with spatially disconnected tissues. Conclusion Magnetization transfer‐based B 0 field pre‐estimation provides valuable prior information for F/W separation, which may significantly improve its robustness at the expense of nominal (< 5%‐10%) scan time increase.