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

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 hardwar