Prospective motion correction in 2D multishot MRI using EPI navigators and multislice‐to‐volume image registration

Purpose Prospective motion correction reduces artifacts in MRI by correcting for subject motion in real time, but techniques are limited for multishot 2‐dimensional (2D) sequences. This study addresses this limitation by using 2D echo‐planar imaging (EPI) slice navigator acquisitions together with a multislice‐to‐volume image registration. Methods The 2D‐EPI navigators were integrated into 2D imaging sequences to allow a rapid, real‐time motion correction based on the registration of three navigator slices to a reference volume. A dedicated slice‐iteration scheme was used to limit mutual spin‐saturation effects between navigator and image data. The method was evaluated using T 2 ‐weighted spin echo and multishot rapid acquisition with relaxation enhancement (RARE) sequences, and its motion‐correction capabilities were compared with those of periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER). Validation was performed in vivo using a well‐defined motion protocol. Results Data acquired during subject motion showed residual motion parameters within ±0.5 mm and ±0.5°, and demonstrated a substantial improvement in image quality compared with uncorrected scans. In a comparison to PROPELLER, the proposed technique preserved a higher level of anatomical detail in the presence of subject motion. Conclusions EPI‐navigator‐based prospective motion correction using multislice‐to‐volume image registration can substantially reduce image artifacts, while minimizing spin‐saturation effects. The method can be adapted for use in other 2D MRI sequences and promises to improve image quality in routine clinical examinations. Magn Reson Med 78:2127–2135, 2017. © 2017 International Society for Magnetic Resonance in Medicine.