In vivo diffusion tensor imaging and tractography of human thigh muscles in healthy subjects.

OBJECTIVE: The aims of this study were to assess whether similar measurements of mean apparent diffusion coefficient and fractional anisotropy in muscles can be obtained with regions of interest drawn on cross-sectional diffusion tensor images and tractography and to assess whether water diffusivity in human thigh muscles is influenced by muscular compartment, age, and sex. SUBJECTS AND METHODS: Sixteen healthy volunteers (eight women, eight men) participated in this study. The right thigh of each subject was imaged with diffusion tensor imaging, and the mean apparent diffusion coefficient and fractional anisotropy values were calculated for each muscle of the quadriceps femoris and hamstrings. Fiber tracking was performed with a line propagation technique from the regions of interest drawn on cross-sectional diffusion tensor images.
RESULTS: The water diffusivity parameters obtained with tractography did not differ significantly from those obtained with diffusion tensor imaging in the three regions of interest evaluated in each muscle. The mean apparent diffusion coefficient of women (1.80 × 10⁻³ mm²/s) was similar to that of men (1.79 × 10⁻³ mm²/s). Women and men had identical fractional anisotropy values (0.26). The fractional anisotropy value in young volunteers (0.27) was similar to that in older subjects (0.26). The hamstrings had a lower mean apparent diffusion coefficient (1.64 × 10⁻³ mm²/s) than the quadriceps femoris (1.91 × 10⁻³ mm²/s), but the quadriceps femoris had a significantly lower fractional anisotropy value (0.25) than the hamstrings (0.28).
CONCLUSION: Our study showed that the water diffusivity values (mean apparent diffusion coefficient and fractional anisotropy) of the thigh muscles did not differ significantly with respect to sex or age of the subject. The quadriceps femoris and the hamstrings did have different mean apparent diffusion coefficient and fractional anisotropy values, which may reflect differences in hydration and muscular architecture.