Automated multi-atlas labeling of the fornix and its integrity in alzheimer´s disease

Alzheimer´s disease is the most common form of dementia. Diffusion imaging provides information on white matter integrity not available with standard MRI, revealing additional information on how Alzheimer´s disease affects the brain. Here we implemented and tested a multi-atlas labeling algorithm to segment the fornix and a point-correspondence tract matching scheme to assess fiber integrity in the fornix in diffusion MRI from 210 participants scanned as part of the Alzheimer´s Disease Neuroimaging Initiative. Various diffusion-derived measures were used to relate fornix degeneration to cognitive decline. On 3D parametric tract models, mean diffusivity (MD) was more sensitive to group differences than fractional anisotropy (FA). Compared to previous studies, we mapped diffusion information along the fornix, yielding 3-D maps of degenerative changes along the tract in people with different stages of Alzheimer´s disease.