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

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 T 1 relaxation times and B 1 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 mm 2 in‐plane resolution resulted in artifact‐free images. The short imaging time of this technique makes it promising for clinical studies. Magn Reson Med 57:625–630, 2007. © 2007 Wiley‐Liss, Inc.