Impact of fiber dispersion in collagenous soft tissue on diffusion MRI metrics

Motivation: Collagen fiber orientation and dispersion are important determinants of the mechanical behavior of soft tissues such as tendon. DTI can provide the bulk collagen fiber orientation of a voxel, but the quantitative relationship between the shape of the diffusion tensor and the intra-voxel fiber dispersion remains unclear. Goal(s): Determine the relationship between the diffusion tensor and intra-voxel collagen fiber dispersion of tendon via simulation. Approach: We simulated a diffusion MRI sequence within collagen fiber networks of known dispersion to determine the impact of fiber dispersion on diffusion MRI measurements. Results: Increased fiber dispersion is non-linearly associated with decreased axial diffusivity and fractional anisotropy. Impact: The relationships developed in this work will be used in subject- and tissue-specific DTI-based mechanical models of fibrous tissue. Such models can be used to predict mechanical behavior and the potential origins of failure.