FULL ARTICLE Evaluation of oral mucosa collagen condition with cross-polarization optical coherence tomography Natalia Gladkova 1 , Elena Kiseleva 1 , Natalia Robakidze 2 , Irina Balalaeva 3 , Maria Karabut 3 , Ekaterina Gubarkova 1 , and Felix Feldchtein 4 1 Nizhny Novgorod State Medical Academy, Nizhny Novgorod, Russia 2 Northwestern State Medical University, St.-Petersburg, Russia 3 Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, Russia 4 Dental Photonics Inc., MA, USA Received 29 March 2012, revised 30 May 2012, accepted 8 June 2012 Published online 4 July 2012 Key words: Cross Polarization Optical Coherence Tomography (CP OCT), oral mucosa, collagen, image analysis. 1. Introduction Optical coherence tomography (OCT) has been used in dentistry for more than a decade [1–3]. The ma- jority of dental OCT studies were performed using time domain OCT, and later with frequency domain OCT systems [4, 5]. Multiple publications are avail- able on time domain polarization sensitive OCT (PS-OCT) where hard dental tissues were primarily studied [6–9]. Birefringence-related phase retardation and ran- dom depolarization are two principal macroscopic polarization phenomena occurring in the light propa- gating in biotissues that have an impact on OCT images. Birefringence in biotissues is observed in structures regularly oriented in the direction non- parallel to light propagation direction. An example of such anisotropic structures is highly organized tendon collagen fibers. The polarization of the back- reflected wave depends on the cumulative impact of # 2012 by WILEY-VCH Verlag GmbH& Co. KGaA, Weinheim Journal of BIOPHOTONICS Early View publication on www.wileyonlinelibrary.com (issue and page numbers not yet assigned; citable using Digital Object Identifier – DOI) The goal of the research was analysis of the effect of col- lagen condition in formation of cross-polarized CP OCT images. We used of the CP OCT technique for studying collagen condition on an example of oral mucosa. Spe- cial histologic picrosirius red (PSR) staining of cheek mu- cosa specimens was used with subsequent assessing of the result of collagen staining in polarized light. High correlation (r ¼ 0.692, p ¼ 0.0001) between OCT signal standard deviation (SD) in cross-polarized images and brightness of PSR stained collagen fibers in cheek muco- sa specimens was demonstrated in patients with inflam- matory intestine and oral mucosa diseases. We have found that the OCT signal SD in cross-polarized images reflects two boundary conditions of collagen disorganiza- tion, namely, loss of fiber properties at active inflamma- tion which attenuates the signal and fibrosis that occurs due to synthesis of a new remodeled collagen which am- plifies the OCT signal. Selecting an ROI for OCT signal SD measurement in cross-polarization at Crohn’s disease (a) and ROI for measuring brightness in PSR stained images of histologi- cal specimens in Crohn’s disease (b). Bars: white – 1 mm, yellow – 0.5 mm. * Corresponding author: e-mail: natalia.gladkova@gmail.com, Phone: +7(831)-419-55-86, Fax: +7(831)-465-41-13 J. Biophotonics 1–10 (2012) / DOI 10.1002/jbio.201200059