Is Cerebral Microvascular Flow Anisotropic - Preliminary Evidence from Multi-Directional Diffusion Weighted Perfusion MRI

Anitha K. Priya¹, Lirong Yan¹, Danny J. J. Wang¹

Perfusion Tensor Imaging has been introduced recently to demonstrate anisotropic microvascular flow. In the present study, a multi-directional diffusion-weighted arterial spin labeling (DW-ASL) sequence was performed with a post-labeling delay of 1.2s and a b value of 50s/mm2 to derive the directional information of capillary flow. Fractional anisotropy values were relatively high throughout the brain but were significantly greater in white matter than in gray matter. The primary eigenvectors showed random patterns in the brain. The largely isotropic microvascular flow or perfusion observed in this study implies that a single ASL scan may be enough to quantify cerebral perfusion.