Correlation of endoscopic optical coherence tomography with histology

Optical Coherence Tomography (OCT) is a noninvasive optical imaging technique that allows high-resolution cross-sectional imaging of tissue microstructure. We have recently developed a system for endoscopic OCT (EOCT) to examine the gastrointestinal tract of humans in vivo. Compared to endoscopic ultrasonic devices it offers a higher resolution (10-20 μm) and does not require coupling gels or fluids. EOCT may lead to a versatile tool for biopsy site selection or optical biopsy itself. The EOCT unit is comprised of an interferometer unit with a high speed scanning reference arm and an endoscopically compatible radially scanning probe as the sample arm. Fast data acquisition allows real-time display (4-8 fps). Temporal averaging for speckle reduction and a transformation to correct nonlinear scanning were included in the EOCT control software, both in real-time. During in vivo clinical trials, we have observed the structure of the mucosa and submucosa in several gastrointestinal organs as well as glands, blood vessels, pits, villi and crypts. The purpose of this study was to correlate images acquired in vitro with EOCT to corresponding histological sections. EOCT images were obtained on fresh specimens (<1 h), which were then fixed in formalin and submitted for standard histology. Tissues examined were normal specimens of stomach, ileum, colon and rectum. It was shown that the thickness of the mucosa correlates well with the first bright layer in EOCT. The R2-value was determined to be 0.69. The submucosa and the muscularis propria could be identified. Furthermore, we were able to show the effect of pressure on the tissue on the visible details in the EOCT images.