Cross-sectional imaging of colon cancer and ulcer-ative colitis using optical coherence tomography
Background/Purpose: Optical coherence tomography (OCT) is a novel biomedical imaging technique which enables obtain cross-sectional imaging in biological tissue with high spatial resolution (10-20 micrometers). OCT is analogous to B-scan ultrasonography except that much higher resolution is obtained by using infrared light rather than ultrasound. Preliminary results on gastrointestinal (GI) tissues have demonstrated that the resolution of OCT images of the GI wall is sufficient to identify microscopic structures in the mucosa and submucosa such as crypts of Lieberkühn, blood vessels, glands, and lymphocyte aggregation. However, data on diseased GI tissue are lacking. We studied in vitro OCT imaging of colon cancer (CA) and ulcerative colitis (UC) to evaluate feasibility of OCT in clinical use. Methods: Human GI tissue specimens harvested from surgical resections were used. Fresh specimens (n =14) were imaged within 5 hours of resection, or snap frozen in liquid nitrogen (n = 7). Specimens were preserved on ice before study and imaged at room temperature. Specimens included CA(n = 8), UC (n = 4), and normal colon (n = 9). After imaging, OCT scan locations were precisely marked, fixed, and prepared for routine histological processing. OCT images were compared with correlated H&E stained histological sections. OCT images of CA and UC were also compared with those of normal colon. The wave length of the light source used was 1300 nm and dynamic range was 107 dB. Results: Irregular glandular structures were seen in 5 of 7 CA specimens and these images were successfully correlated with corresponding histological sections. In UC specimens, there was disappearance of crypts associated with high backscatter in the mucosa seen. Although mascularis mucosae could be identified in UC specimens, this was less clear than in normal tissue. These findings seemed to be associated with inflammatory cell infiltration in the mucosa and submucosa. Conclusion: OCT can identify pathological morphological changes in the colon. Besides morphological changes, abnormal tissue may have different backscatter properties from normal tissue, which might be helpful in diagnosis. Potentially, OCT would allow precise in vivo evaluation of the mucosa and submucosa at endoscopy. This would be particularly useful to improve endoscopic diagnosis in situ and increase the yield of biopsy. Research was funded by the Olympus Optical Ltd., Tokyo, Japan, and Whitaker Foundation, Rosslin, VA.
Kobayashi, K; Izatt, JA; Kulkarni, MD; Sivak, MV
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