Reduced field-of-view MRI using outer volume suppression for spinal cord diffusion imaging

Abstract

A spin-echo single-shot echo-planar imaging (SS-EPI) technique with a reduced field of view (FOV) in the phase-encoding direction is presented that simultaneously reduces susceptibility effects and motion artifacts in diffusion-weighted (DW) imaging (DWI) of the spinal cord at a high field strength (3T). To minimize aliasing, an outer volume suppression (OVS) sequence was implemented. Effective fat suppression was achieved with the use of a slice-selection gradient-reversal technique. The OVS was optimized by numerical simulations with respect to T1 relaxation times and B1 variations. The optimized sequence was evaluated in vitro and in vivo. In simulations the optimized OVS showed suppression to <0.25% and ∼3% in an optimal and worst-case scenario, respectively. In vitro measurements showed a mean residual signal of <0.95% ± 0.42 for all suppressed areas. In vivo acquisition with 0.9 × 1.05 mm2 in-plane resolution resulted in artifact-free images. The short imaging time of this technique makes it promising for clinical studies. © 2007 Wiley-Liss, Inc.