Optical Imaging Techniques for the Detection of Esophageal Neoplasia in Barrett’s Esophagus
Richards-Kortum, Rebecca Rae
Doctor of Philosophy
The main objective of this research was to develop a two-stage optical imaging platform to improve detection of cancer in Barrett’s esophagus (BE). BE caused by chronic reflux and patients with BE are at a higher risk for developing esophageal adenocarcinoma (EAC). However, neoplasia in BE is often unidentifiable under standard endoscopy, and studies have shown nearly half of early cancers can go unidentified by this method. Widefield imaging (resolves ~100 microns) allows efficient surveillance of large BE segments. Two widefield imaging techniques were identified to improve contrast between benign and abnormal lesions during an ex vivo 15 patient feasibility study. Cross-polarized imaging (CPI) reduced specular reflection and improved vascular contrast. Vital-dye fluorescence imaging (VFI) using topically-applied proflavine improved visualization of glandular pattern. Moreover, relevant pathologic features visible during VFI were seen in corresponding histology slides as well as high resolution images of the same sites. Based on these results, a cap-based Multispectral Digital Endoscope (MDE) was designed and built. The MDE can image in three different imaging modes: white light imaging, CPI, and VFI. Modifications to a Pentax EPK-i video processor and a Pentax endoscope were made to incorporate these imaging modes into one system. A 21 patient in vivo pilot study with 65 pathologically correlated sites demonstrated the feasibility of using this system in vivo; image criteria were developed to classify neoplasia with a sensitivity and specificity of 100% and 76% respectively. High resolution imaging (resolves ~2-5 micron) may verify the disease presence in suspicious areas identified using widefield techniques. 2-NBDG, a fluorescent metabolic marker, was used as to identify neoplastic biopsies. In a study with 21 patients yielding 38 pathologically correlated biopsies and 158 image sites, 2-NBDG imaging allowed classification of cancerous biopsies with a sensitivity of 96% and specificity of 90%. The unique contributions of these results is the development of a multimodal cap-based endoscopic system to identify suspicious areas in BE, and using a metabolic marker to verify the presence of disease. This application extends beyond esophageal cancer detection and may be explored for cancer detection in other organ sites characterized by columnar epithelium.