<qa>  What is NBI called?Narrow band imaging NBI is a technique that relies on light filters to improve contrast for the smallest blood vessels in the bowel lining which shows up precancerous areas as they have a richer vascular network. It is sometimes described as digital chromoendoscopy as the images produced are similar to chromoendoscopy, but it is much simpler and quicker to use. With magnification it allows assessment of the fine mucosal surface pattern pit pattern of lesion which allows and assessment of their likelihood of being precancerous. Autofluorescence endoscopy uses short wavelength light and light filters to produce a false colour image of the bowel lining where polyps stand out. These techniques have been used with some success in the oesophagus and stomach but little work is available for the colon. 