First results of endoscopic applications of optical coherence tomography for in vivo studies of human mucosa in respiratory, gastrointestinal, urinary and genital tracts are presented. A novel endoscopic OCT (EOCT) system has been created that is based on the integration of a sampling arm of an all-optical-fiber interferometer into standard endoscopic devices using their biopsy channel to transmit low-coherence radiation to investigated tissue. We have studied mucous membranes of esophagus, larynx, stomach, urinary bladder, uterine cervix and body as typical localization for carcinomatous processes. Images of tumor tissues versus healthy tissues have been recorded and analyzed. Violations of well-defined stratified healthy mucosa structure in cancered tissue are distinctly seen by EOCT, thus making this technique promising for early diagnosis of tumors and precise guiding of excisional biopsy.

The purpose of this study was to understand the capabilities and utility of optical coherence tomography (OCT) in characterizing tissue in patients with precancer and cancer of the uterine cervix and vulva. OCT is an optical technique that uses low-coherence interferometer to develop a two-dimensional image of optical scattering from internal tissue microstructure. This study was designed to develop diagnostic criteria. Women undergoing colposcopic evaluation secondary to an abnormal Papanicolaou smear or visualized grossly abnormal vulvar lesion comprised the study population. Under colposcopic visualization, the OCT device was applied to normal regions in all patients and abnormal areas when present, and images were captured. Each subject then underwent multiple directed biopsies. Images were then reviewed and compared with matched histology. A total of 50 women were recruited for the study. Of the 50 patients evaluated, 18 had cervical intraepithelial neoplasia (CIN) II,III, 14 had CIN I, 13 had metaplasia/inflammation, two had invasive squamous cell carcinoma of the cervix, and three had a diagnosis of Paget's disease of the vulva. Analysis of the OCT images showed a repetitive pattern that represented normal squamous epithelium of the cervix in 100% of the normal biopsies. Images of the 18 patients with histologically proven CIN II,III showed an unstructured homogeneous highly backscattering region with fast attenuation of the signal in 16 (89%) of the patients. OCT is a new approach for the early identification of cervix and vulvar malignancies. Using information inherent to the returning photon signals from tissue, early morphological and light-scattering changes can be detected during tumorigenesis. It has the potential to be a true optical biopsy. If diagnostically comparable to a biopsy, then clearly the ability of OCT to provide a point of service diagnosis would serve a significant advantage.

We report results of application of our endoscopic optical coherence tomography (EOCT) system in clinical experiments to image human internal organs. Based on the experience of studying more than 100 patients, we make first general conclusions on the place and capabilities of this method in diagnosing human mucous membranes. It is demonstrated that EOCT can serve for several clinical purposes such as performing directed biopsy, monitoring functional states of human body, guiding surgical and other treatments and monitoring post-operative recovery processes. We show that applications of OCT are more informative in the case of internal organs covered by epithelium separated from underlying stroma by a smooth basal membrane and therefore concentrate on the results of the EOCT study of three internal organs, namely of larynx, bladder, and uterine cervix. Finally, we report first examination of internal organs in abdomen with the use of laparoscopic OCT.

A numerical algorithm based on a small-angle approximation of the radiative transfer equation (RTE) is developed to reconstruct scattering characteristics of biological tissues from optical coherence tomography (OCT) images. According to the algorithm, biological tissue is considered to be a layered random medium with a set of scattering parameters in each layer: total scattering coefficient, variance of a small-angle scattering phase function, and probability of backscattering, which fully describe the OCT signal behavior versus probing depth. The reconstruction of the scattering parameters is performed by their variation to fit the experimental OCT signal by the theoretical one using a time-saving genetic algorithm. The proposed reconstruction procedure is tested on model media with known scattering parameters. The possibility to estimate scattering parameters from OCT images is studied for various regimes of OCT signal decay. The developed algorithm is applied to reconstruct optical characteristics of epithelium and stroma for normal cervical tissue and its pathologies, and the potential to distinguish between the types of pathological changes in epithelial tissue by its OCT images is demonstrated.

This work is dedicated to the development of the OCT system with angiography for everyday clinical use. Two major problems were solved during the development: compensation of specific natural tissue displacements, induced by contact scanning mode and physiological motion of patients (eg, respiratory and cardiac motions) and online visualization of vessel cross-sections to provide feedback for the system operator.