Phase-Labeled Reference EPI for Frequency-Segmented Inhomogeneity Corrections (PREFICS)

Mario Zeller¹, Alexander Mller¹, Dietbert Hahn¹, Herbert Kstler¹

Artifacts induced by field inhomogeneities in non-Cartesian EPI acquisitions typically cannot be corrected by simple pixel-shifting. Instead, conjugate phase based methods can be applied. These methods require the acquisition of a separate gradient-echo field map. The acquisition of such a map is relatively time-consuming, as multiple radiofrequency pulses are applied. In this work, a method is described, which allows deriving the field map from a phase-labeled reference EPI scan comprising of only two fast EPI acquisitions. With this map, geometric distortions arising in non-Cartesian EPI can be successfully corrected.