Measurement of Collagen and Smooth Muscle Cell Content in Atherosclerotic Plaques Using Polarization Sensation Optical Coherence Tomography Seemantini K. Nadkarni, Mark C. Pierce, B. Hyle Park, Johannes F. de Boer, Peter Whittaker, Brett E. Bouma, Jason E. Bressner, Elkan Halpern, Stuart L. Houser, Guillermo J. Tearney We investigated a recently developed technique termed polarization-sensitive optical coherence tomography (PSOCT) for evaluating collagen and smooth muscle cell (SMC) content in atherosclerotic plaques. Polarization-sensitive optical coherence tomography images were obtained from human cadaveric aortas, and the spatially averaged PSOCT birefringence was measured. A high positive correlation was observed between PSOCT birefringence and total collagen content in all plaques and in fibrous caps of necrotic core fibroatheromas. Polarization-sensitive optical coherence tomography birefringence demonstrated a strong positive correlation with thick collagen fiber content and SMC density. Our results demonstrate that PSOCT provides information about plaque collagen and SMC content, which are important indicators of rupture risk.