Mapping of strain-induced diffusivity changes in biological tissues using magnetic resonance

The effect of strain on diffusion tensor magnetic resonance images of muscles was investigated using numerical simulations and animal experiments. For numerical simulations, a muscle fiber was modeled as a 50 /spl times/ 50-/spl mu/m /sup 2/ square with strains ranging from -0.5 to 1.0. The effective diffusion coefficient monotonically increased with an increase in strain. Changes in the mean diffusivity (MD) were below 1%, while strain caused an increase in the fractional anisotropy (FA). Diffusion tensor images of the frog gastrocnemius muscle were obtained with and without compression in the direction perpendicular to the muscle fibers. A decrease in the effective diffusion coefficient was observed in the direction parallel to the compression.