Diffusion Acquisition. Pushing the Boundaries.

Advanced acquisition methods for diffusion-weighted MRI are presented. First, an overview of the standard method, diffusion-weighted spin echo with single-shot echo planar imaging, is presented. The modularity of diffusion-weighted imaging (DWI) is defined, in which the image formation mechanism can largely be considered to be independent of the method of diffusion weighting. The reasons for the dominance of this method and its shortcomings are highlighted. Next, a range of alternative image formation methods are described in detail. These methods aim to improve the signal-to-noise ratio and/or spatial fidelity of images. Finally, possible mechanisms for imparting diffusion weighting to the MRI signal are described. Some diffusion-weighting schemes aim to improve the diffusion contrast, while others are intended to extract information that cannot easily be recovered from conventional protocols. Throughout, the costs and benefits of different methods are presented. © 2014 Elsevier Inc. All rights reserved.