On the reproducibility of mri-dti based passive length changes and the added implications of quantitative mri

The versatile soft tissue contrast of magnetic resonance imaging (MRI) has enabled studying local strains in muscle fiber direction (Ef) as probed by diffusion tensor imaging (DTI). Recently, tracked fascicles of medial gastrocnemius (GM) muscle showed heterogeneous Ef distributions. As opposed to a uniform Ef expectation of the classical view-point, but in association to locations of e.g., neurovascular tracts. We analysed the reproducibility of the techniques used to quantify Ef, such as the effects of algorithm parameters, and applicability of various quantitative MRI (qMRI) metrics. Results showed reproducibility of previously reported Ef amplitudes in passive GM, in a different scanner and processing pipeline. The overall distribution pattern was easily reproduced and not sensitive to algorithm parameters, unlike Ef amplitudes. Variations in local tissue structure revealed by T1 have a significant predictive effect over mean Ef. Quantitative MRI shows promise to study the link between muscle structure and function.