Closed-Form Solution Concomitant Field Correction Method for Echo Planar Imaging on Head-only Asymmetric Gradient MRI System

The spatial encoding gradient field used in MRI always includes spatially-varying higher order fields known as concomitant fields. Different from conventional gradient systems whose concomitant fields only contain 2nd-order spatial dependency, some emerging MRI platforms employ asymmetric gradient system, whose concomitant fields also include zero- and first-order spatial dependencies. The first-order terms cause further image distortion and echo shift in echo planar imaging (EPI). In this work, we develop a generalized waveform pre-emphasis framework to correct first-order concomitant fields for arbitrary axial-coronal oblique EPI acquisitions on a head-only asymmetric gradient system, and provide closed-form mathematical expressions for determining pre-emphasis factors.

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