Virtual chromoendoscopy systems enhances specific characteristics of the lining of the large bowel such as surface patterns and mucosal vasculature. This theoretically increases the detection of pre-cancerous tissue compared to high definition white light endoscopy alone. Narrow-band imaging or NBI (Olympus, Tokyo, Japan), Blue Laser (Fujinon, Tokyo, Japan) and OE scan (Pentax, Tokyo, Japan) use optical light filters to select particular narrow spectrums of red, green and blue light with a relative decrease in the proportion of red light. The Fujinon Intelligent Chromo-Endoscopy (FICE) system uses post hoc computer algorithms, applying different filters to the stored endoscopic images and enabling a theoretically endless number of combinations of filters that can be used. The Pentax I-SCAN system also allows post hoc modification of the images. It provides the ability to enhance the mucosal surface to better highlight mucosal changes.