Diffusion-weighted magnetic resonance imaging (DWI or DW-MRI) is
the use of specific MRI sequences as well as software that generates images
from the resulting data that uses the diffusion of water molecules to generate
contrast in MR images. It allows the mapping of the diffusion process of
molecules, mainly water, in biological tissues, in vivo and non-invasively.
Molecular diffusion in tissues is not random, but reflects interactions with
many obstacles, such as macromolecules, fibers, and membranes. Water molecule
diffusion patterns can therefore reveal microscopic details about tissue
architecture, either normal or in a diseased state.