title: A hybrid strategy for correcting geometric distortion in echo-planar images.
abstract: A hybrid strategy for geometric distortion correction of echo-planar images is demonstrated. This procedure utilizes standard field mapping for signal displacement correction and the so-called reverse gradient acquisition for signal intensity correction. (The term reverse gradient refers to an acquisition of two sets of echo-planar images with phase encoding gradients of opposite polarity.) The hybrid strategy is applied to human brain echo-planar images acquired with and without diffusion-weighting. A comparison of the hybrid distortion corrected images to those corrected with standard field mapping only demonstrates much better performance of the hybrid method. A variant of the hybrid method is also demonstrated which requires the acquisition of only one pair of opposite polarity images within a set of images.
authors.affiliation: Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada; Department of Medical Imaging, University of Western Ontario, London, Ontario, Canada; Department of Lawson Health Research Institute, London, Ontario, Canada. Electronic address: ngelman@lawsonimaging.ca.
authors.forename: Neil
authors.initials: N
authors.lastname: Gelman
authors.affiliation: Department of Lawson Health Research Institute, London, Ontario, Canada.
authors.forename: Ally
authors.initials: A
authors.lastname: Silavi
authors.affiliation: Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada; Department of Lawson Health Research Institute, London, Ontario, Canada.
authors.forename: Udunna
authors.initials: U
authors.lastname: Anazodo
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology*; D017352:Echo-Planar Imaging / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: Diffusion weighted imaging; Echo planar imaging; Field mapping; Geometric distortion correction; Reverse phase encode gradient acquisition