Navigator-Free Dynamic Phase Correction for Echo-Planar Imaging Based Functional MRI

Dan Xu¹, R. Scott Hinks¹, Bruce D. Collick

In echo-planar imaging based functional MRI, non-phase-encoded navigator echoes are sometimes collected to enable correction of temporal frame dependent even-odd-echo phase modulation. However, the navigator-based method assumes that the additional modulation that the center echoes experience is the same as that predicted by navigator echoes, which is not true when there is additional modulation building up across echoes. Therefore, the modulation of the center echoes would not be well corrected, leading to ghost drift. We propose a method to use scan data itself to more faithfully estimate the per-temporal-frame modulation than the navigator-based method, which significantly reduces ghost drift.