Combined prospective and retrospective correction to reduce motion-induced image misalignment and geometric distortions in EPI

Melvyn B. Ooi, Jordan Muraskin, Xiaowei Zou, William J. Thomas, Sascha Krueger, Murat Aksoy, Roland Bammer, Truman R. Brown
2012 Magnetic Resonance in Medicine  
Despite rigid-body realignment to compensate for head motion during an echo-planar imaging (EPI) time-series scan, non-rigid 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 non-rigid components of this motionrelated image misalignment. Prospective rigid-body correction, where the scan-plane orientation is dynamically updated to
more » ... track with the subject's head, is performed using an active marker setup. Retrospective distortion correction is then applied to unwarp the remaining non-rigid 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 EPI time-series itself. This combined method is applied to compensate EPI 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 BOLD fMRI task, resulting in improved Z-score statistics.
doi:10.1002/mrm.24285 pmid:22499027 pmcid:PMC3402592 fatcat:cwjxeo3m4rdhrohwnevbxka34i