In vivo imaging of the time-dependent apparent diffusional kurtosis in the human calf muscle

PurposeTo evaluate the time dependency of apparent diffusion coefficient D-app and apparent diffusional kurtosis K-app in vivo in the human calf. Materials and MethodsDiffusion-weighted images of five healthy male volunteers were acquired using a 1.5T MR scanner. A stimulated echo sequence with echo planar imaging readout was used with diffusion gradients oriented along the three main axes. Mixing times (TM) of 100, 300, 500, and 700 ms and b-values ranging from 0 to 5600 s/mm(2) were used. D-app and K-app were determined. ResultsD(app) and K-app decreased with increasing TM. As an example for absolute values, D-app of the tibialis anterior drops from 1.18 0.04 m(2)/ms (TM = 100 ms) to 0.86 +/- 0.02 m(2)/ms (TM = 700 ms) (P = 0.001) and K-app from 0.38 +/- 0.06 to 0.32 +/- 0.03 (P = 0.046) for a diffusion weighting along the left-right direction. K-app was smaller than 0.43 in all muscles and at all TMs. ConclusionThe clearly observed time-dependence of D-app and K-app is an indicator of restricted diffusion in muscle tissue and may thus be a promising marker to investigate alterations of the microstructure. Compared to typical kurtosis values in white matter tissue of the brain, the kurtosis in muscle tissue is much smaller, which we attribute to the absence of the almost impermeable myelin sheath. J. Magn. Reson. Imaging 2015;41:1581-1590. (c) 2014 Wiley Periodicals, Inc.