Time‐dependent diffusion tensor imaging and diffusion modeling of age‐related differences in the medial gastrocnemius and feasibility study of correlations to histopathology
Vadim Malis, Usha Sinha, Edward Smitaman, Jed Keenan Lim Obra, Henning T. Langer, Agata A. Mossakowski, Keith Baar, Shantanu Sinha
Abstract
Abstract 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 2 ( t ), λ 3 ( t ), and D ⊥ ( t ); average of λ 2 ( t ) and λ 3 ( 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 3 ( t ) was significantly higher in the senior cohort for the range of diffusion times. RPBM fits to λ 2 ( 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 2 ( t ), λ 3 ( t ), and D ⊥ ( t ) (significant for fit to λ 3 ( t )). Fits of fiber diameter from RPBM to that from histology had the highest correlation for the fit to λ 2 ( t ). Conclusion The age‐related patterns in λ 2 ( t ) and λ 3 ( 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.