Geometric Quantification of Tendon Second Harmonic Images

Abstract. Tendons are composed of cells, blood vessels and extracellular matrix, intricately woven together to form a vital musculoskeletal connective tissue. There is a growing need for functional imaging of tendon, for example to provide non-invasive biochemical and biomechanical insight into injured, diseased or repairing tendon. This study describes the possibility of developing an magnetic resonance imaging (MRI) tool for tissue quality assessment. Near infrared-multiphoton laser scanning microscopy (NIR-MPLSM) was used to validate ultra-high field MRI-based distinctions between normal and damaged tendon. Using a novel interpretation framework based on intrinsic tissue geometry, tissue damage at the matrix level was quantified according to local and global geometric parameters. The tendon characteristic crimp waveform and matrix geometric regularity were disrupted by enzyme-digestion, potentially compromising the tissue mechanical properties. These findings suggest that different imaging modalities can reveal complementary and corresponding information about tendon structures at functionally relevant scales. The proposed framework provides a robust and quantifiable physiological description of tendon, which can be exploited for clinical tendon tissue classification, and related to in vivo MR imaging.