A Pilot Study on Linking Tissue Mechanics with Load-Dependent Collagen Microstructures in Porcine Tricuspid Valve Leaflets

Figures

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  Figure A1. Demonstration of the pSFDI modality to capture the CFA: (a) an experimental photo of a representative TV leaflet specimen mounted to the BioTester system, with a defined region of interest as delimited by the red box, and (b) the quantified intensity-θpolarizer relationship of a selected pixel point (see the red dot in (a)), together with the fitting of the 3-term Fourier series in Equation (A2) to the acquired data for predicting the collagen fiber orientation angle θfiber. (c) The quantified DOA throughout the ROI, and (d) vector plots of the quantified θfiber with an increasing level of visualization grid.

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  Figure A2. 3 × 3 grid comparisons of the predicted θfiber : (a) between unloaded and equibiaxial loading, (b) between unloaded and radially-dominate loading, and (c) between unloaded and circumferentially-dominate loading. (d) Comparison of the predicted DOA among all the states for the TVAL specimen of heart #1.

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  Figure A3. 3 × 3 grid comparisons of the predicted θfiber : (a) between unloaded and equibiaxial loading, (b) between unloaded and radially-dominate loading, and (c) between unloaded and circumferentially-dominate loading. (d) Comparison of the predicted DOA among all the states for the TVPL specimen of heart #1.

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  Figure A4. 3 × 3 grid comparisons of the predicted θfiber : (a) between unloaded and equibiaxial loading, (b) between unloaded and radially-dominate loading, and (c) between unloaded and circumferentially-dominated loading. (d) Comparison of the predicted DOA among all the states for the TVSL specimen of heart #1.

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  Figure 1. (a) The porcine TV was dissected to retrieve the three TV leaflets for use in (b) biaxial mechanical testing. (c) A side view of the combined pSFDI-biaxial testing system, displaying optical components, mounted tissue specimen, and mechanical testing components. (d) TV leaflet strips from the effective testing region were used for histological analyses.

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  Figure 2. 3 × 3 grid sub-regions used for analyzing the spatial variations in the quantified load-dependent fiber orientation angle and the degree of optical anisotropy (DOA) for the anterior leaflet (TVAL), the posterior leaflet (TVPL), and the septal leaflet (TVSL) tissue specimens. (TC: circumferential tension, TR: radial tension, PPC: post-preconditioning).

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  Figure 3. Representative heart #1 quantifications, as follows: (left) membrane tension (T) versus tissue stretch (λ) results of biaxial testing experiments (subscripts C and R stand for the circumferential and radial directions, respectively), (middle) histology-based evaluations of tissue’s morphology and constituents, and (right) the pSFDI-quantified collagen fiber architecture for: (a) the TVAL, (b) the TVPL, and (c) the TVSL specimens. In the right column, the dash lines represent the predicted fiber orientation angle and the colormaps denote the DOA.

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  Figure 4. Comparisons of the load-dependent collagen fiber architecture for the entire tissue’s ROI described in Table 1. (see the right column in Figure 3a–c): (a) the predicted DOA, (b) the predicted θfiber between unloaded and equibiaxial loading (TC:TR= 1:1), (c) the predicted θfiber between unloaded and radially-dominate loading (TC:TR= 0.5:1), and (d) the predicted θfiber between unloaded and circumferentially-dominated loading (TC:TR= 1:0.5).

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  Figure 5. 3 × 3 grid comparisons of (a) the predicted θfiber, and (b) the predicted DOA in the unloaded state for the TVAL, TVPL, and TVSL specimens from heart #1.