High-resolution cross-sectional imaging of the gastrointestinal tract using optical coherence tomography: In vitro study

Background/Purpose: Optical coherence tomography (OCT) is a novel biomedical imaging technique for noninvasive cross-sectional imaging in biological tissue with high spatial resolution (10-20 micrometers). OCT is similar to B-scan ultrasonography except that higher resolution is obtained by using infrared light rather than ultrasound. Another advantage is that OCT does not require acoustical coupling. We studied in vitro OCT imaging of the gastrointestinal (GI) tract and analyze the potential for endoscopic applications. Methods: Human GI tissue specimens harvested from surgical resections were used. Fresh specimens were imaged within 5 hours of resection (all but one specimen), or snap frozen in liquid nitrogen. Specimens were preserved on ice before study and imaged at room temperature. Specimens included esophagus (n=4), stomach (n=4), small bowel (n=3), and colon (n=6). After imaging, OCT scan locations were precisely marked using dye micro-injections, fixed, and prepared for routine histological processing. OCT images were compared with correlated H & E stained histological sections. Results: In all specimens, the mucosa and submucosa were clearly identified. Crypts (approximately 60-70 micrometers in diameter on histology slides) were visualized in all colonic specimens except one. The muscularis mucosae was demonstrated in 5 of 6 colonic specimens. Submucosal blood vessels were observec in 2 colonic specimens and 2 gastric specimens. A submucosal lymphocyte aggregation was observed in one colonic specimen. Due to the limited penetration of infrared light in tissue, the muscularis propria and serosa were not visualized. Conclusion: The resolution of OCT images of GI wall is sufficient to identify microscopic structures in the mucosa and submucosa such as crypts, blood vessels, and lymphocyte aggregations. Potentially, OCT would allow in vivo imaging at endoscopy of the microstructure of the mucosa and submucosa. This would be particularly useful in the detection and staging of small lesions such as early stage cancers.