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Combined prospective and retrospective correction to reduce motion‐induced image misalignment and geometric distortions in EPI
Author(s) -
Ooi Melvyn B.,
Muraskin Jordan,
Zou Xiaowei,
Thomas William J.,
Krueger Sascha,
Aksoy Murat,
Bammer Roland,
Brown Truman R.
Publication year - 2012
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.24285
Subject(s) - distortion (music) , computer science , rigid body , artificial intelligence , shim (computing) , computer vision , reference frame , orientation (vector space) , physics , frame (networking) , medicine , mathematics , geometry , surgery , computer network , amplifier , telecommunications , bandwidth (computing) , classical mechanics , erectile dysfunction
Despite rigid‐body realignment to compensate for head motion during an echo‐planar imaging time‐series scan, nonrigid image deformations remain due to changes in the effective shim within the brain as the head moves through the B 0 field. The current work presents a combined prospective/retrospective solution to reduce both rigid and nonrigid components of this motion‐related image misalignment. Prospective rigid‐body correction, where the scan‐plane orientation is dynamically updated to track with the subject's head, is performed using an active marker setup. Retrospective distortion correction is then applied to unwarp the remaining nonrigid image deformations caused by motion‐induced field changes. Distortion correction relative to a reference time‐frame does not require any additional field mapping scans or models, but rather uses the phase information from the echo‐planar imaging time‐series itself. This combined method is applied to compensate echo‐planar imaging scans of volunteers performing in‐plane and through‐plane head motions, resulting in increased image stability beyond what either prospective or retrospective rigid‐body correction alone can achieve. The combined method is also assessed in a blood oxygen level dependent functional MRI task, resulting in improved Z ‐score statistics. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.