Human optic nerve DTI with EPI geometric distortion correction

Diffusion tensor imaging (DTI) of the human optic nerve presents challenges from geometric distortion in echo planar imaging (EPI) caused by magnetic field inhomogeneity and partial volume artifacts caused by confounding signals from surrounding fat and cerebrospinal fluid (CSF). A protocol for human optic nerve DTI was developed with geometric distortion correction and suppression of fat and CSF signals. This protocol was modified from a conventional DTI protocol to acquire images and field maps covering the whole brain including contiguous slices of the optic nerves. The technique was applied to healthy volunteers and multiple sclerosis (MS) patients with and without history of unilateral optic neuritis (ON). DTI measures of the optic nerves before and after distortion correction were compared. Means and standard deviations of these measures from different cohorts were reported.