大腸におけるnarrow band imaging（NBI）観察の臨床意義について

Observation Using the Narrow Band Imaging (NBI) System During Colonoscopy

要旨　本稿では，1999年よりわれわれが開発してきた内視鏡の観察光の分光特性を狭帯域特性へ変更（短波長側にシフト）することで，病変の視認性や表面微細構造，毛細血管観察の向上を可能にしたnarrow band imaging（NBI）systemの大腸内視鏡検査における有用性について述べた．NBI systemの登場により，腫瘍の血管新生にもとづく病変の視認性の向上，毛細血管構築を中心とした従来の内視鏡では観察できなかった微小血管診断学が浮き彫りになってきた（endoscopic microangiology；EMA）．NBIを大腸内視鏡検査に導入することにより，腫瘍/非腫瘍の鑑別に要する色素観察が不要になるとともに（optical chromoendoscopy），capillary pattern（CP）観察により質的/量的診断が瞬時に可能となるだろう．また，NBIをはじめとしたinstrument-based chromoendoscopyとも言える新技術の開発に伴って，high-contrast endoscopyといった大きな概念として色素内視鏡はstain-basedとinstrument-basedに分ける必要性が出てくるものと考えられる．

　We reviewed NBI colonoscopy focusing on the observation of the magnification microvascular architecture of colorectal lesions and discussed the utility of detailed observation of the microvascular architecture for differential diagnosis during NBI colonoscopy. Angiogenesis is critical for the transition of premalignant lesions in a hyperproliferative state to the malignant phenotype. Therefore, diagnosis based on angiogenic or vascular morphologic changes might be ideal for early detection or diagnosis of neoplasms. In this review, we propose the term “meshed-like capillary” for the distinction between non-neoplastic and neoplastic lesions and the microvascular classification “capillary pattern : CP” for the differential diagnosis of colorectal lesions. We believe that the combined use of NBI optical chromoendoscopy and real chromoendoscopy decreases the time and cost of screening colonoscopy. To assess the feasibility and efficacy of using the NBI system, further studies are required for colorectal lesions and other lesions of the gastrointestinal tract.