Enhancing measured diffusion anisotropy in gray matter by eliminating CSF contamination with FLAIR

In this work, the effect of fluid-attenuated inversion recovery (FLAIR) on measured diffusion anisotropy was investigated in gray matter. DTI data were obtained with and without FLAIR in six normal volunteers. The application of FLAIR was experimentally demonstrated to lead to a consistent increase in fractional anisotropy (FA) in gray-matter regions, which was attributed to suppressed partial volume effects from CSF. In addition to these experimental results, Monte Carlo simulations were performed to ascertain the effect of noise on the measured FA under the experimental conditions of this study. The experimentally observed effect of noise was corroborated by the simulation, indicating that the increase in the measured FA was not due to a noise-related bias but to an actual increase in diffusion anisotropy. This enhanced measurement of diffusion anisotropy can be potentially used to differentiate directionally dependent structure and tracking fibers in gray matter. (C) 2004 Wiley-Liss, Inc.