Optimized Phase Cycling for Coherence Pathway Selection in Pi Echo Planar Imaging

Pi Echo Planar Imaging (PEPI) has a significantly reduced gradient duty cycle compared to FSE. It has a great potential for low field MRI where concomitant fields are significant. However, its application is limited due to the requirement of a near perfect refocusing pulse to avoid coherence pathway artifacts. In this work an optimized phase cycling scheme is proposed which minimizes coherence pathway contributions to the signal. This method has been validated in simulations and experiments showing a reduced sensitivity to flip angle compared to the conventional XY-16 method. Artifact-free 2D PEPI was achieved.