Micro-Architectural Features of the in Vivo Human Optic Chiasm

Joelle E. Sarlls¹, Carlo Pierpaoli¹

Diffusion tensor images were acquired at sub-millimeter resolution, in-vivo, in the oblique plane of the optic nerves/chiasm/tracts. Acquiring data at sub-millimeter resolution dramatically reduces partial volume effects, allowing quantitative measures of the optic chiasm without CSF contamination and increased fiber coherence. In addition to the commonly calculated parameters of diffusion, measures of the diffusion ellipsoids shape were also calculated. We observe that there are not only architectural differences in the crossing and uncrossed fibers of the medial and latteral optic chiasm, but that the trajectory of crossing fibers may depend on their dorsal/ventral location in the chiasm as well.