Diffusion tensor imaging of skeletal muscle--correlation of fractional anisotropy to muscle power.

PURPOSE: Recent DTI studies demonstrated the possibility of fiber geometry visualization in skeletal muscle. We tested for an association between muscle power and standard DTI parameters, e. g. fractional anisotropy.
MATERIALS AND METHODS: Maximal muscle power (Lmax) of the soleus muscle was determined in 11 healthy subjects. Subsequently DTI was performed and standard parameters (fractional anisotropy - FA, mean diffusivity - MD, parallel diffusivity - PD, radial diffusivity - RD) were extracted in an ROI of the soleus muscle.
RESULTS: We found a signficant association of Lmax with FA (neg. correlation: r = -0.85, p = 0.0015) and RD (pos. correlation r = 0.80, p = 0.047). There was no signficant association of MD or PD.
CONCLUSION: Maximum muscle power is an indirect measure of fiber type distribution. The correlation between muscle power and DTI parameters can be explained by differences in fiber diameter and differences in the intracellular microstructure of type-1 and type-2 fibers. DTI should be evaluated as a tool for non-invasive quantification of fiber type distribution in skeletal muscle. © Georg Thieme Verlag KG Stuttgart · New York.