Figure 2.

Diffusion reveals the underlying microstructure of the tissue.

The diffusion of a drop of ink on isotropic (left) or anisotropic (right) fibrous tissue is Gaussian and can be modeled with an ellipse. The main axis of this ellipse (horizontal axis in this case) defines the main direction of the fibers that form the tissue. The ratio between the main and the secondary axis defines the degree of anisotropy of the paper. Similarly, diffusion in the white matter tissue is modeled with an ellipsoid in diffusion tensor imaging experiments. This figure was inspired by Dr Gordon Kindlmann (University of Chicago).