Quantification of collagen fiber organization using three-dimensional Fourier transform-second-harmonic generation imaging

We present three-dimensional Fourier transform-second-harmonic generation (3D FT-SHG) imaging, a generalization of the previously reported two-dimensional FT-SHG, to quantify collagen fiber organization from 3D image stacks of biological tissues. The current implementation calculates 3D preferred orientation of a region of interest, and classifies regions of interest based on orientation anisotropy and average voxel intensity. Presented are some example applications of the technique which reveal the layered structure of collagen fibers in porcine sclera, and estimates the cut angle of porcine tendon tissues. This technique shows promising potential for studying biological tissues that contain fibrillar structures in 3D.