Distortion correction for a double inversion-recovery sequence with an echo-planar imaging readout

• Published in: Magnetic resonance imaging Vol. 26; no. 7; pp. 943 - 953
• Main Authors: Meara, Simon J.P, Embleton, Karl V, Parker, Geoffrey J.M
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 01.09.2008
• Subjects: Brain Mapping - methods; Distortion correction; Double inversion-recovery; Echo-planar imaging; Echo-Planar Imaging - methods; Humans; Image Enhancement - methods; Image Processing, Computer-Assisted - methods; Magnetic Resonance Imaging - methods; MRI; Radiology; Reversed-gradient method; Double inversion-recovery; Distortion correction; Echo-planar imaging; MRI; Reversed-gradient method
• ISSN: 0730-725X; 1873-5894
• DOI: 10.1016/j.mri.2008.02.007

Abstract A double inversion-recovery (DIR) sequence with an echo-planar imaging (EPI) readout can be used to image selectively the grey matter of the brain, and this has previously been applied to improve the sensitivity of the statistical analysis of functional magnetic resonance imaging (fMRI) data. If a procedure were to be implemented to remove the distortions that are inherent in the EPI-based fMRI data set, then a similar technique would have to be applied to the DIR-EPI image also to ensure that it matches the geometry of the functional data. A comparison of candidate methodologies for correcting distortions in DIR-EPI images, based on the reversed-gradient method, is presented. A corrected image could be calculated from two DIR-EPI images acquired with k -space traversal in opposite directions, but that method was not able to cope with the large regions of low signal intensity corresponding to the nulled white matter. It was found that the optimal procedure to apply the reversed-gradient method to DIR-EPI images was to acquire two additional EPI images (without the two inversion pulses) with opposite-direction k -space traversal; the distortion-correction information calculated from those EPI images was then applied to the DIR-EPI data.