Geometric distortion correction in EPI by phase labeling using sensitivity encoding (plus)

Geometric distortion induced by magnetic field inhomogeneity is an intrinsic problem for echo-planar imaging (EPI). Most of the existing correction techniques require separate field map scans in addition to the measurement scans. The effectiveness of these methods requires consistent patient position between these scans, thus inter-scan patient motions degrade the correction results. We propose a new method for geometric distortion correction in EPI that derives the field maps from the measurements themselves, without the need of additional field map scans. This method takes advantage of parallel imaging and k-space trajectory modification to generate multiple images for field mapping from a single measurement needed. The derived field maps are retrospectively applied to the measurements. The proposed method has been successfully demonstrated on combined k- space data that simulate the data from the modified k-space trajectories. These data were acquired from a phantom and a human brain.