Narrow Band Imaging and Autofluorescence Imaging for the Detection and Optical Diagnosis of Colorectal Polyps

Colorectal cancer is the most common cancer in Singapore and polyps which are detected during screening colonoscopy are routinely removed. Conventional white light colonoscopy has a substantial miss-rate for polyps and limited accuracy in differentiating neoplastic from non-neoplastic polyps. Dye-based chromoendoscopy and more recent equipment-based image enhanced endoscopic techniques such as narrow-band imaging (NBI) and autofluorescence imaging (AFI) are promising tools to improve polyp detection and optical diagnosis. Current evidence suggests that NBI may not be superior compared to high definition white-light for polyp detection, but it achieves excellent accuracy in polyp characterisation, approaching that of histopathology. AFI is a wide area scanning modality which functions as a red-flag technique to improve polyp detection, although the evidence is still evolving. The ability to accurately characterise polyps with NBI and AFI will guide the management of polyps and in some cases, avoid unnecessary polypectomy and routine histopathology. This has potential to reduce associated costs and risks of polypectomy, and improves on overall efficiency of screening colonoscopy. The review will discuss the technology, current evidence and the issues relevant to the role of NBI and AFI for the detection and optical diagnosis of polyps in colorectal cancer screening.