Polarization-sensitive optical coherence tomography (PS-OCT) and second harmonic generation (SHG) microscopy are
two imaging modalities with different resolutions, field-of-views (FOV), and contrasts, while they both have the
capability of imaging collagen fibers in biological tissues. PS-OCT can measure the tissue birefringence which is
induced by highly organized fibers while SHG can image the collagen fiber organization with high resolution. Articular
cartilage, with abundant structural collagen fibers, is a suitable sample to study the correlation between PS-OCT and
SHG microscopy. Qualitative conjecture has been made that the phase retardation measured by PS-OCT is affected by
the relationship between the collagen fiber orientation and the illumination direction. Anatomical studies show that the
multilayered architecture of articular cartilage can be divided into four zones from its natural surface to the subchondral
bone: the superficial zone, the middle zone, the deep zone, and the calcified zone. The different zones have different
collagen fiber orientations, which can be studied by the different slopes in the cumulative phase retardation in PS-OCT.
An algorithm is developed based on the quantitative analysis of PS-OCT phase retardation images to analyze the
microstructural features in swine articular cartilage tissues. This algorithm utilizes the depth-dependent slope changing
of phase retardation A-lines to segment structural layers. The results show good consistency with the knowledge of
cartilage morphology and correlation with the SHG images measured at selected depth locations. The correlation
between PS-OCT and SHG microscopy shows that PS-OCT has the potential to analyze both the macro and micro
characteristics of biological tissues with abundant collagen fibers and other materials that may cause birefringence.