a quantitative indicator obtained using diffusion-tensor MRI (DTI), reflecting the degree of directional dependence of the diffusion of water in the tissue. FA values range from 0 (fully isotropic diffusion, the same in all directions) to 1 (fully anisotropic diffusion, only in one direction). In the brain, high FA values are characteristic of white matter, where water diffuses more easily along axonal fibers than across them. FA is used to assess the integrity and cohesion of white matter; A decrease in the indicator is observed in multiple sclerosis, traumatic brain injuries, stroke and neurodegenerative diseases.