Full‐Field Assessment of Geometry and Collagenous Architecture of Porcine Valve Leaflets via Laser Micrometry and Quantitative Polarized Light Imaging

Figures

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  FIGURE 1. Depiction of a transverse section through the heart slightly above the level of the atrioventricular septum and a schematic of an aortic valve, as well as its leaflet microstructure. Based on diagrams from Piazza et al. [25] and Vogl et al. [26].

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  FIGURE 2. (A) Depiction of the laser micrometer set‐up. As the motorized stage moves the platform, the sample is scanned, and cross‐sectional thickness profiles are obtained and compiled to produce a 3D thickness profile. (B) Depiction of the QPLI set‐up. (C) Representative excised aortic valve leaflet. L: Left, R: Right. (D) Example of the warping process for a representative aortic valve leaflet with a map of unwarped thickness (raw data from laser scan, left) and warped thickness (processed to match sample orientation under QPLI, right).

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  FIGURE 3. Example of the regional analysis workflow. For each valve, full‐field contours of thickness, light intensity (S 0), and degree of linear polarization (DoLP) were divided radially into nine regions and regional means, standard deviations (not shown), and coefficients of variation were computed.

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  FIGURE 4. Thickness (mm), intensity (S 0), DoLP, and AoP plotted as a quiver plot, and for a representative aortic and pulmonary valve leaflet. Scale bars indicate 5 mm.

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  FIGURE 5. Full‐field distributions of the thickness (mm), S 0, and DoLP measured for all aortic and pulmonary leaflets (A). Spatial mean (B) and maximum (C) values of thickness, S 0, and DoLP. Statistical differences between aortic and pulmonary valve leaflets (as detected by a Welch's t‐test) are indicated by asterisks (*p < 0.05, **p < 0.01).

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  FIGURE 6. Correlation coefficient values for (A) S 0 and thickness, (B) DoLP and thickness, and (C) S 0 and DoLP for all aortic and pulmonary valve leaflets imaged. Statistical differences between aortic and pulmonary valve leaflets (as detected by a Welch's t‐test) are indicated by asterisks (*p < 0.05).

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  FIGURE 7. Percent area histograms for the representative aortic and pulmonary valve leaflets shown in Figure 4.

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  FIGURE 8. Two‐dimensional area histograms displaying the relationship between AoP and DoLP in the representative aortic and pulmonary valve leaflets from Figure 4.

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  FIGURE 9. Summary percent area distributions for thickness, S 0, and DoLP. Statistical differences between aortic and pulmonary valve leaflets (as detected by a Welch's t‐test) are indicated by asterisks (*p < 0.05, **p < 0.01).

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  FIGURE 10. Summary regional metrics (mean ± SD) of thickness and DoLP for aortic (left, n = 8) and pulmonary (right, n = 8) valve leaflets. Statistical differences between leaflet types (as detected by a Welch's t‐test) are indicated by asterisks (*p < 0.05, **p < 0.01, ***p < 0.001). Results are plotted on a representative valve geometry and are not drawn to scale.

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  FIGURE 11. Percent error from the warping code for the representative pulmonary valve leaflet shown in Figure 4.

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  FIGURE 12. Intensity (S 0), DoLP, angle (AoP), and thickness (mm) for a representative pulmonary valve leaflet before freezing (fresh) and after a freeze–thaw cycle (frozen and thawed). Pearson's (S 0, DoLP, and thickness) and circular (AoP) correlation coefficients between fresh and thawed images indicated negligible effects of a single freeze–thaw cycle on anisotropy or thickness (R > 0.75, p ≈ 0).