Narrow band imaging: Application for early‐stage gastrointestinal neoplasia

Narrow‐band imaging (NBI) is an imaging technique for endoscopy using optical filters to narrow the bandwidth of spectral transmittance. Through this narrow spectrum, NBI contrasts surface structure and microvascular architecture of various lesions. In this article we focus on the application of NBI for early‐stage neoplasia in the esophagus, stomach and colon with a three‐step strategy of endoscopic diagnosis: (i) the detection of abnormality; (ii) the differentiation between non‐neoplasia and neoplasia; and (iii) staging for tumor extension and depth of invasion.