Polarization-resolved second harmonic generation (PSHG) microscopy enables label-free, high-resolution imaging of collagen architecture in biological tissues. To make this technique more accessible, the authors introduce CollagenFitJ, a user-friendly plugin for the open-source FIJI platform. Designed around the cylindrical symmetry model of collagen, CollagenFitJ performs fast, pixel-wise quantification of collagen structure from PSHG image stacks, outputting orientation, anisotropy, and molecular susceptibility ratio maps.

The cover image illustrates the plugin’s ability to analyze PSHG datasets from various collagen-containing tissue types. The method’s robustness is enhanced by embedded fitting assessment metrics and local statistical descriptors of structural dispersion and randomness. This work appears in the article by R. Hristu et al., “CollagenFitJ, a FIJI plugin for the quantification of collagen in polarization-resolved second harmonic generation image sets,” Adv. Photonics Nexus 4(3), 037001 (2025). doi: 10.1117/1.APN.4.3.037001.