Reliability and robustness of muscle architecture measurements obtained using diffusion tensor imaging with anatomically constrained tractography

To study muscle adaptation mechanisms, e.g. during growth, ageing or disease, reliable measurements of muscle architecture are required. Diffusion tensor imaging (DTI), combined with DTI tractography, can provide three-dimensional reconstructions of the architecture of whole human muscles. Here, we tested the inter-session reliability of a DTI method that uses anatomical constraints to ensure that fascicle reconstructions, like real muscle fascicles, have endpoints on aponeuroses. The intraclass correlation coefficient, averaged over four lower limb muscles, was 0.81 for measurements of fascicle length and 0.73 for pennation angle. We also showed that the use of anatomical constraints results in measurements which, unlike measurements from conventional DTI techniques, are quite robust to variations in arbitrarily selected stopping criteria for DTI tractography.