Accelerated multi-shot diffusion imaging

Purpose To reduce image distortion in MR diffusion imaging using an accelerated multi-shot method. Methods The proposed method exploits the fact that diffusion-encoded data tend to be sparse when represented in the k _b-k_d space, where k_b and k_d are the Fourier transform duals of b and d, the b-factor and the diffusion direction, respectively. Aliasing artifacts are displaced toward under-used regions of the k_b-k_d plane, allowing nonaliased signals to be recovered. A main characteristic of the proposed approach is how thoroughly the navigator information gets used during reconstruction: The phase of navigator images is used for motion correction, while the magnitude of the navigator signal in k_b-k_d space is used for regularization purposes. As opposed to most acceleration methods based on compressed sensing, the proposed method reduces the number of k_y lines needed for each diffusion-encoded image, but not the total number of images required. Consequently, it tends to be most effective at reducing image distortion rather than reducing total scan time. Results Results are presented for three volunteers with acceleration factors ranging from 4 to 8, with and without the inclusion of parallel imaging. Conclusion An accelerated motion-corrected diffusion imaging method was introduced that achieves good image quality at relatively high acceleration factors. Magn Reson Med 72:324-336, 2014. © 2013 Wiley Periodicals, Inc.