Medical applications of polarization-sensitive optical coherence tomography

Abstract

Optical coherence tomography (OCT) technology can generate cross-sectional images of the scattering media such as biological tissues with spatial resolution as low as 1 ~ 10 mum. OCT uses a partial coherence Michelson interferometry that produces images similar to the ultrasound B-scans. There are many types of functional OCT technologies including polarization-sensitive OCT (PS-OCT), spectroscopic OCT, Optical Doppler Tomography (ODT), etc.PS-OCT produces not only the structural cross-sectional images but the functional images related to the tissue birefringence, phase retardation and depolarization of light reflected from deep tissue regions. Because the PS-OCT is sensitive to birefringent materials such as collagen, the PS-OCT has been studied as an optical diagnosis tool in skin, bone, cartilage, and tooth. In dermatology, OCT can generate useful images such as skin topology and basement membranes. It also can produce other useful images related to skin collagen morphologies and photoaging. We have also demonstrated that the PS-OCT can be applied to clinical problems such as wound healing monitoring of skin. Light depolarization due to multiple scattering is often considered as a negative effect during OCT image acquisition which prevents imaging of deep regions. In our study, we show that the scattering changes can be quantified using PS-OCT by measuring the axial variations of degree of polarization (DOP). Therefore, we suggest that the depolarization process can be used in a positive way. We have tested our hypothesis using various optical phantoms. Scattering changes often occur in pathologic conditions of human cervical tissues. We successfully applied our technique to in vitro diagnosis of cervical interepithelial neoplasm (CIN). It was found that the high-grade squamous intraepithelial lesions (H-SIL) including CIN-II, CIN-III, and Carcinoma in situ (CIS) can be diagnosed by DOP quantification with high sensitivity and specificity.