Time-dependent diffusion tensor imaging and diffusion modeling of age-related differences in the medial gastrocnemius and feasibility study of correlations to histopathology.

PURPOSE

Implement STEAM-DTI to model time-dependent diffusion eigenvalues using the random permeable barrier model (RPBM) to study age-related differences in the medial gastrocnemius (MG) muscle. Validate diffusion model-extracted fiber diameter for histological assessment.

METHODS

Diffusion imaging at different diffusion times (Δ) was performed on seven young and six senior participants. Time-dependent diffusion eigenvalues (λ (t), λ (t), and D (t); average of λ (t) and λ (t)) were fit to the RPBM to extract tissue microstructure parameters. Biopsy of the MG tissue for histological assessment was performed on a subset of participants (four young, six senior).

RESULTS

λ (t) was significantly higher in the senior cohort for the range of diffusion times. RPBM fits to λ (t) yielded fiber diameters in agreement to those from histology for both cohorts. The senior cohort had lower values of volume fraction of membranes, ζ, in fits to λ (t), λ (t), and D (t) (significant for fit to λ (t)). Fits of fiber diameter from RPBM to that from histology had the highest correlation for the fit to λ (t).

CONCLUSION

The age-related patterns in λ (t) and λ (t) could tentatively be explained from RPBM fits; these patterns may potentially arise from a decrease in fiber asymmetry and an increase in permeability with age.