Endoscopic imaging and size estimation of colorectal adenomas in the multiple intestinal neoplasia mouse

Background: The scientific potential of animal models of carcinogenesis has not been fully realized because of our limited ability to monitor tumor growth in vivo. Objective: To develop an endoscopy-based protocol for the accurate estimation of adenoma size in vivo from images obtained during colonoscopy. Design: To compare estimates of lesion size acquired during endoscopy with those obtained from magnetic resonance imaging (MRI) and at necropsy. Setting: A small-animal imaging facility. Subjects: Adenomatous polyposis coli multiple intestinal metaplasia Fox Chase Cancer Center mice that develop multiple colorectal adenomas. Methods: The mice received colonoscopic examination by using a rigid endoscope, and high-resolution images of colon adenomas were captured by using a charge-coupled-device camera. Lesion size was estimated by comparing the dimensions of the adenoma relative to a reference rod by using a novel geometric construction. The resulting areas were compared with estimates from MRIs and validated at necropsy. Main Outcome Measurements: Cross-sectional area of colon adenomas. Results: The cross-sectional area of 20 adenomas was measured in vivo during colonoscopy and compared with the size as measured at necropsy, which yielded a Pearson correlation coefficient of 0.94 (P = 6.52 × 10^-9). Assessment of interoperator variability, when using measurements from 11 adenomas, yielded a Pearson correlation coefficient of 0.85 (P = 4.35 × 10^-3) and demonstrated excellent reproducibility. Limitations: Only the distal colon could be viewed, and endoscopic measurements were 2-dimensional. Conclusions: An endoscopic method for the reliable measurement of colorectal adenomas in vivo was established. The application of this technique to mouse models of colon carcinogenesis will provide unique insight into the dynamics of adenoma growth.