Diffusion tensor MRI of the spinal cord

Apparent diffusion tensor (ADT) measurements on the spinal cord using a pul sed-field-gradient (PFG) multi-shot echo-planar imaging (EPI) sequence are presented. In a study of 10 healthy volunteers, the obtained rotationally i nvariant anisotropy information is compared to the results obtained by the rotationally dependent methods. The water diffusivity in the direction para llel to the fibers was found to be almost 2.5 times higher than the average diffusivity in directions perpendicular to the fibers and showed cylindric ally symmetric anisotropy characteristics. The influence of partial volume effects and the point spread function on the measured results was evaluated , and it was the concluded that a resolution of 1 mm in the read and phase directions is required to obtain unbiased values. Possible clinical implica tions were demonstrated by investigating the diffusion characteristics of 1 0 patients suffering from narrowing of the cervical canal. The changes in t he diffusion characteristics were found to be large enough to allow a robus t detection of diffusion changes in the spine, even in cases in which conve ntional T-2 and T-1 weighted images were unable to detect any lesion. (C) 2 000 Wiley-Liss, Inc.