Role of narrow band imaging in endoscopic submucosal dissection

Narrow band imaging (NBI) is a new image enhancement system employing optic digital methods to enhance images of blood vessels on mucosal surfaces, allowing improved visualization of mucosal surface structures. Studies have progressed over the last several years, and the clinical usefulness has been demonstrated. NBI has become frequently applied for preoperative diagnosis before endoscopic submucosal dissection (ESD) of digestive tract cancers, as well as for assessment of the range of ESD for en-bloc resection of large lesions. Consensus has been reached with regard to the usefulness of NBI for detecting micro-lesions of esophageal squamous cell carcinoma indicated for ESD, for the diagnosis of the range and depth. NBI has also been attracting attention for diagnosing gastric cancer based on the observation of micro blood vessels on the mucosal surface and mucosal surface microstructures. The usefulness of NBI has been reported in relation to various aspects of colon cancer, including diagnoses of the presence, quality, range, and depth of lesions. However, as NBI has not surpassed diagnostic methods based on magnifying observation combined with the established and widely employed dye method, its role in ESD is limited at present. Although NBI is very useful for the diagnosis of digestive tract cancers, comprehensive endoscopic diagnosis employing the combination of conventional endoscopy including dye spraying, EUS, and NBI may be important and essential for ESD.