Gradient preemphasis calibration in diffusion-weighted echo-planar imaging.
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.
Papadakis
N G
NG
Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, UK.
Martin
K M
KM
Pickard
J D
JD
Hall
L D
LD
Carpenter
T A
TA
Huang
C L
CL
D001921:Brain / Q000033:anatomy & histology; D002138:Calibration; D017352:Echo-Planar Imaging / Q000295:instrumentation / Q000379:methods; D006801:Humans; D019047:Phantoms, Imaging