Figure A1.

Diffusion imaging works by estimating the diffusivity of water along a set of directions (represented as arrows in the left column of images), sometimes at a number of magnetic gradient strengths (represented by colors on the left columns images). Upper Left: The directions are typical for a diffusion tensor imaging (DTI) scan where diffusion is all sampled at one gradient strength. Lower Left: The sampling scheme from diffusion spectrum imaging (DSI). This DSI scan samples 257 directions over a range of different gradient strengths. The effects of increased angular sampling resolution can be seen by comparing the resulting tractography based on the two diffusion sampling techniques (right column). In this example, we show tractography at a triple-crossing within the white matter of the parietal lobe. Upper Right: DTI-based tractography produces multiple spurious streamline bundles that do not cross. Lower Right: DSI-based resolves the triple crossing.