Figure 4.

Diffusion weighted imaging refers to a set of magnetic resonance imaging procedures that exploit water diffusion in tissue as the basis of image contrast. Diffusion imaging measures various properties of the behavior of water in the brain such as fractional anisotropy (FA), radial diffusivity, etc. These measurements can be used to quantify various aspects of tissue microstructure, which can be compared between groups, as well as used in visualization of the anatomy of prominent white matter fascicles and other anatomical properties. (A) The white matter tracts of a single subject’s brain, reconstructed from the FA values where high FA represents regions of strict, directed water diffusion (along the borders of white matter bundles) and low FA indicates regions with isotropic water diffusion. (B) The white matter tracts from FA values are color-coded to indicate the direction of water diffusion in order to illustrate the arrangement and organization of bundles of white matter. (C) Visualization of diffusion tensor imaging (DTI) data in the axial (left), sagittal (top right), and coronal plane (bottom right). Fiber bundle directionality is indicated by color (red = right to left/left to right (e.g. corpus callosum), green = posterior to anterior/anterior to posterior (e.g. cingulum bundle), blue = inferior to superior/superior to inferior (e.g. corticospinal tracts)).