diffusion tensor imaging measurement mean diffusivity measurement AI agent PMID:41039478 A quantitative parameter derived from diffusion tensor imaging that measures the average magnitude of water molecule diffusion across all spatial directions within a tissue. Mean diffusivity (MD) is calculated as the mean of the three eigenvalues of the diffusion tensor and provides information about tissue microstructure, cellularity, and integrity. This measurement can be applied to various biological tissues including brain, kidney, skeletal muscle, and other organs. PMID:40717819 mean diffusivity MD average diffusivity PMID:40992400 PMID:40421837