Abstract
Collagen organization plays an important role in maintaining structural integrity and determining tissue function. Polarization-sensitive optical coherence tomography (PSOCT) is a promising noninvasive three-dimensional imaging tool for mapping collagen organization in vivo. While PSOCT systems with multiple polarization inputs have demonstrated the ability to visualize depth-resolved collagen organization, systems, which use a single input polarization state have not yet demonstrated sufficient reconstruction quality. Herein we describe a PSOCT based polarization state transmission model that reveals the depth-dependent polarization state evolution of light backscattered within a birefringent sample. Based on this model, we propose a polarization state tracing method that relies on a discrete differential geometric analysis of the evolution of the polarization state in depth along the Poincare sphere for depth-resolved birefringent imaging using only one single input polarization state. We demonstrate the ability of this method to visualize depth-resolved myocardial architecture in both healthy and infarcted rodent hearts (ex vivo) and collagen structures responsible for skin tension lines at various anatomical locations on the face of a healthy human volunteer (in vivo).
Highlights
Collagen, often organized in the form of fibers, is a structural protein widely distributed in biological tissue[1]
We note that the collagen orientation of glabella (Fig. 3g) is orthogonal to the direction of traditional Relaxed skin tension lines (RSTLs). While this may be a feature of the particular volunteer, there remains unanswered questions regarding the relationship between collagen fiber alignment and RSTLs. These results demonstrate the potential for the DDGbased polarization state tracing (PST) method to guide skin incision placement by visualization patient-specific RSTLs in vivo, further investigate collagen fiber orientation in normal and abnormal states of scar formation, and study collagen disorders of the skin such as Ehler’s Danlos syndrome and Scleroderma[37,38]
Differing from previous multiple input Jones matrix-based measurement[25,26], the discrete differential geometry (DDG)-based PST approach analyzes the trajectory of the depth evolution of a single input polarization state in the Stokes space
Summary
Often organized in the form of fibers, is a structural protein widely distributed in biological tissue[1]. While techniques, such as polarized light microscopy, have been utilized to image collagen fibers in an ex vivo setting, many require tissue sectioning procedures[6,7]. The field of view (FOV) (up to ~500×500 μm2) and imaging depth (up to ~200 μm) are often too limited to reconstruct macroscopic collagen organizations that reveal the functional architecture of the tissue. Tang et al Light: Science & Applications (2021)10:237 a technique capable of wide-field three-dimensional (3D) imaging of collagen structures in living tissue would provide rich information on how collagen organization relates to physiologic function
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