A novel fast split-echo multi-shot diffusion-weighted MRI method using navigator echoes.

Abstract

Difficulties in obtaining diffusion-weighted images of acceptable quality using conventional hardware and in a reasonable time have hindered the clinical application of diffusion-weighted magnetic resonance imaging (DWI). Diffusion-weighted fast spin-echo (FSE) sequences offer the possibility of fast DWI on standard hardware without the susceptibility problems associated with echoplanar imaging. However, motion in the presence of diffusion-sensitizing gradients can prevent fulfilment of the Meiboom Gill phase condition, leading to destructive interference between echo components and consequent signal losses. A recently proposed single-shot FSE sequence employed split-echo acquisition to address this problem. However, in a segmented FSE sequence, phase errors differ between successive echo trains, causing "ghosting" in the diffusion-weighted images that are not eliminated by split-echo acquistion alone. A DWI technique is presented that combines split-echo acquisition with navigator echo phase correction in a segmented FSE sequence. It is shown to be suitable for diffusion measurements in vivo using standard hardware.