High-Speed Structured Polarized Light Imaging of Bovine Heart Valve Leaflet Dynamics

Collagen is the primary load-bearing component in connective tissues, and its organization dictates the biomechanical properties and functions of the tissue. Polarized light imaging has been an effective tool for characterizing collagen organization. Recently, with the integration of structured light illumination (SLI), structured polarized light imaging (SPLI) has enabled quantification of collagen fiber orientation in the superficial layers of thick tissues with higher specificity and accuracy. However, SPLI typically requires 12 images to perform depth discrimination and collagen quantification, limiting its application in imaging tissue dynamics. To overcome this limitation, we developed a high-speed SPLI system that can perform continuous tracking and quantification of tissue deformation at 75 frames per second (FPS). High-speed SPLI was achieved by pairing a polarization camera with a rolling image processing technique. We evaluated the performance of high-speed SPLI on a bovine heart valve leaflet under uniaxial deformation. We were able to continuously track and quantify collagen fiber orientation at 75 FPS, with improved accuracy due to effective depth discrimination using SLI. Additionally, we demonstrated that reflectance with SLI is more sensitive to local collagen deformation compared to imaging without SLI, offering a complementary perspective for studying the dynamics of collagenous tissues.