Fluorescence-based SMC and OCT endoscope to study aberrant crypt foci in the mouse colon

The accepted model of colorectal cancer assumes the paradigm that aberrant crypt foci (ACF) are the earliest events in tumorigenesis and develop into adenoma, which further develop into adenocarcinoma. Under this assumption, basic research and drug studies have been performed using ACF as substitute markers for fully developed carcinoma. While studies have shown a correlation between the number of ACF present and the presence of adenoma/adenocarcinoma, a causal relationship has yet to be determined. The mouse has shown to be an excellent model for colorectal cancer; however, the outcomes of such experiments require sacrifice and histologic examination of ex vivo tissue. To better utilize the mouse model to study ACF and adenoma development, an endoscope was constructed for non-destructive in vivo surface visualization, molecular imaging and cross-sectional imaging of the colon. Our system combines surface magnifying chromoendoscopy (SMC) and optical coherence tomography (OCT) to image colon microstructure. Sixteen mice, treated with the carcinogen azoxymethane, were imaged at 2 week intervals, to visualize carcinogenesis events. With this dual-modality system we are able to visualize crypt structure alteration over time as well as adenoma development over time.