Multiple-Wave-Vector Diffusion-Weighted NMR

Abstract Since their introduction by Stejskal and Tanner, pulsed-field-gradient diffusion-weighted NMR experiments have been applied to characterize condensed matter ranging from liquids and rocks to biological tissue in vivo . In spite of their outstanding success, for example, in biomedical research and clinical diagnosis, the technique faces some inherent limitations, for instance the inability to detect diffusion anisotropy present on a microscopic scale in a macroscopically isotropic sample. Thus, the interest in an extended version of the diffusion-weighted NMR experiment where two (or more) diffusion-weighting periods are applied successively in a single acquisition has emerged in the past few years. Such experiments, sometimes referred to as two- or multiple-wave-vector experiments, have been shown to be a promising tool to investigate diffusion in confined geometries. They are able to assess information difficult or impossible to achieve with standard diffusion-weighting experiments and, thus, may help to provide deeper insight into the sample's microstructure. In this work, current developments in the theoretical modelling of multiple-wave-vector experiments and recent experimental results demonstrating the potential of the technique are summarized.