title: Gradient preemphasis calibration in diffusion-weighted echo-planar imaging.
abstract: This article describes a method which enables fast and objective pulse-sequence-specific preemphasis calibration, using standard pulse sequences and system hardware. The method is based on a k-space measurement technique, and has been applied to single-shot, diffusion-weighted, spin-echo, echo-planar imaging (DW-SE-EPI), which is particularly sensitive to eddy-current-induced image distortions. The efficiency of the technique was demonstrated not only by the reduction of eddy-current fields to a negligible level using full preemphasis compensation, but also by the fact that adjustment of the slow time-base alone sufficed for the practical elimination of image distortions in the DW-SE-EPI images and the subsequent diffusion tensor maps (in a phantom and a human brain). By seeking to eliminate directly the effect of eddy-current-induced phase shifts during the EPI data collection, the method is free of the complications and restrictions associated with other eddy-current correction techniques for DW-SE-EPI (such as acquisition of additional calibration scans, intense postprocessing, extensive pulse-sequence modifications), making their use redundant.
authors.affiliation: Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, UK.
authors.forename: N G
authors.initials: NG
authors.lastname: Papadakis
authors.forename: K M
authors.initials: KM
authors.lastname: Martin
authors.forename: J D
authors.initials: JD
authors.lastname: Pickard
authors.forename: L D
authors.initials: LD
authors.lastname: Hall
authors.forename: T A
authors.initials: TA
authors.lastname: Carpenter
authors.forename: C L
authors.initials: CL
authors.lastname: Huang
mesh_terms: D001921:Brain / Q000033:anatomy & histology; D002138:Calibration; D017352:Echo-Planar Imaging / Q000295:instrumentation / Q000379:methods; D006801:Humans; D019047:Phantoms, Imaging