Polarization-sensitive swept-source optical coherence tomography for investigating depth, birefringence, depolarization and orientation of collagen structure of human cervix tissue

Spontaneous preterm birth (sPTB) is one of the most serious causes of neonatal death. However, sPTB is unpredictable at present due to simplistic research. That cervix remodels progressively through collagen alterations plays an important role during gestation, but the study of cervical collagen structure has been limited by the lack of suitable observational method. Polarization-sensitive optical coherence tomography (PSOCT) is a functional extension of intensity-based OCT, which can noninvasively offer additional information, i.e., the light’s polarization state. Thus, the collagen properties of birefringence and depolarization can be obtained by a PSOCT in vivo. A PSOCT has been developed from our in-house swept-source (SS) OCT. In the PS-SS-OCT, a circularly polarized light is used to interact tissue and the backscattered light which carries sample’s polarization information is detected by two channels for measuring the horizontal and vertical polarization state respectively. Several human cervix tissues have been investigated by the PS-SS-OCT in vitro. The birefringence and depolarization information of cervical collagen can be obtained by processing the intensity and phase value of the two channels. Besides the birefringence and depolarization information, a conical beam scan strategy has been applied for exploring orientation of the collagen structure of human cervix. In the conical scan, the illumination beam streams into sample at a 45° of incidence angle, and the sample is imaged by acquiring successive B-scan over sample-rotation spans of 0-360°. Since probe of PSOCT can be easily integrated into a catheter or a hand-held probe, PSSS-OCT with a conical beam scan is an excellent candidate to identify cervical structure in clinical practice.