Fieldmap-Free Retrospective Registration and Distortion Correction for EPI-based Diffusion-Weighted Imaging

Introduction Acquisition of a set Diffusion Weighted Images (DWIs) allows Diffusion Tensors and Tensor-derived quantities such as Fractional Anisotropy (FA) and Trace (TR) to be computed and used to infer the underlying white matter structure in the brain. DWIs are usually acquired with an echo-planar imaging (EPI) pulse sequence that produces images degraded by B0 field inhomogeneity, eddy current distortion and head motion. B0 distortion can be corrected using acquired fieldmaps [1], but these are typically unavailable in clinical studies, while eddy currents at acquisition time can be reduced, but not eliminated with gradient correction schemes [3]. In this work we evaluate a retrospective Fieldmap-Free method for B0, eddy current and motion correction in the context of EPI-based DWI and compare it to previous work that uses acquired fieldmaps and registration-based eddy current correction [2,4].