This proof-of-concept exploratory study demonstrates the feasibility of deriving a quantitative, three-dimensional metric of collagen organisation from MADI-derived vector fields to enhance ACL visualisation beyond conventional tractography alone. The FC metric was sensitive to local deviations in mesoscopic scale collagen alignment under controlled conditions. Additionally, FC revealed biologically plausible patterns in human ACLs. In particular, a centrally located band of uniform collagen organisation was observed in healthy tissue, consistent with literature describing native ACL mid-substance structure[10,16,17]. The absence of this band in injured ligaments, and its partial re-emergence following reconstruction, may suggest loss and potential restoration of native collagen organisation.

Although FC did not directly localise focal tear regions, the presence or absence of organised collagen structure may provide an indirect marker of ligament integrity. Overlaying FC colour maps onto streamline tractography produced intuitive hybrid visualisations that preserved fibre pathway context while highlighting local organisational changes.

For radiologists, this approach offers a non-invasive tool to assess ACL integrity beyond conventional MRI[1-3]. The presence of the central band may indicate healthy collagen organisation, while its absence could flag potential injury requiring closer evaluation (Figure 6). By providing a clear, quantitative 3D visualisation of collagen structure, FC maps may improve triage, enhance diagnostic confidence, and help prioritise cases for further investigation.

With further validation, this approach may complement conventional MRI by supporting radiological assessment of subtle ACL injury, post-operative evaluation, and surgical decision-making. Future work will focus on validation in larger cohorts and assessment of clinical usability.