Fig. 1. Definitions of parameters that determining the relative position between a pair of voxels (blue dots) in 3D GLCM

Fig. 2. 3D SHG images of collagen fibers within aortic intima and media of rats with different weeks of age (The left three columns show 2D images of collagen fibers at different depths from the inner surface of the vascular and the upper left digit indicates the depth value. The fourth column is the 3D reconstructed image. Scale bar: 100 μm)

Fig. 3. 3D SHG images of collagen fibers within aortic adventitia of rats with different weeks of age (The left three columns show 2D images of collagen fibers at different depths from the outer surface of the vascular and the upper left digit indicates the depth value. The fourth column is the 3D reconstructed image. Scale bar: 100 μm)

Fig. 4. 3D GLCM texture feature parameters derived from SHG images of aortic intima and media collagen fibers, which show significant differences among rats with different weeks of age (The red solid line indicates the median. "ns" denotes no significance, *: 0.01<P<0.05, **: 0.001<P<0.01, ***: 0.0001<P<0.001, ****: P<0.0001, one-way ANOVA and Tukey's multiple comparison test). (a) Correlation; (b) contrast; (c) entropy; (d) variance; (e) sum mean; (f) homogeneity

Fig. 5. 3D GLCM texture feature parameters derived from SHG images of aortic adventitia collagen fibers, which show significant differences among rats with different weeks of age (The red solid line indicates the median. *: 0.01<P<0.05, **: 0.001<P<0.01, one-way ANOVA and Tukey's multiple comparison test). (a) Homogeneity; (b) variance; (c) sum mean