Symmetric block-matching registration for the distortion correction of Echo-Planar images

We introduce a new approach to correct geometric and intensity distortion of Echo Planar Images (EPI) from images acquired with opposite phase encoding directions. A new symmetric block-matching registration algorithm has been developed for this purpose relying on new adapted transformations between blocks and a symmetric optimization scheme to ensure an opposite symmetric transformation. We present results of our algorithm showing its ability to robustly recover EPI distortion while obtaining sharper results than the popular TOPUP algorithm.