Detection of Microscopic Diffusion Anisotropy in the Living Human Brain

Marco Lawrenz¹, Jrgen Finsterbusch¹

Anisotropy measures derived from DTI reflect a mixture of cell eccentricity and their orientation distribution within the voxel which hampers their informative value. For instance, a vanishing FA in brain white matter is consistent with the absence of eccentric cells like neurons but also with a uniform orientation distribution of neuronal fibers. Here, it is shown that double-wave-vector diffusion-weighting experiments can detect the diffusion anisotropy on a microscopic level in the living human brain. In particular, it is demonstrated that the microscopic anisotropy can also be observed in regions-of-interest that are macroscopically isotropic, i.e. with a FA value of 0.