Quantitative Assessment of Colorectal Cancer Progression: a Comparative Study of Linear and Nonlinear Microscopy Techniques

BACKGROUND AND AIMS Colorectal cancer (CRC) is a disease that can be prevented if is diagnosed and treated at pre-invasive stages. Thus, the monitoring of colonic cancer progression can improve the early diagnosis and detection of malignant lesions in the colon. This monitoring should be performed with appropriate image techniques and be accompanied by proper quantification to minimize subjectivity. We have monitored the mice CRC progression by image deconvolution, two-photon emission fluorescence (TPEF) and second harmonic generation (SHG) microscopies and present different quantization indices for diagnosis. METHODS The Azoxymethane (AOM) / dextran sodium sulfate (DSS) protocol was used. 35 eight-week old male BALB/cCmedc mice were used and distal colon segments were dissected at day zero and fourth, eighth, sixteen, and twenty weeks after injection. These segments were observed with linear and nonlinear optical microscopies and several parameters were used for quantification. RESULTS Crypt diameter higher than 0.08 mm and increased fluorescence signal intensity in linear images; as well as aspect relation above 0.7 and altered organization reflexed by high-energy values obtained from SHG images, away from those obtained in normal tissues. CONCLUSION The combination of linear and nonlinear signals improve the detection and classification of pathological changes in crypt morphology/distribution and collagen fiber structure/arrangement. In combination with standard screening approaches for CRC, the proposed methods improve the detection of the disease in its early stages, thereby increasing the chances of successful treatment.