IEE原理と臨床応用を俯瞰する―NBI・TXI・RDI―

Principles, mechanism, and clinical applications of IEE: narrow band imaging (NBI), texture and color enhancement imaging (TXI) and red dichromatic imaging (RDI)

要旨

2020年に新規画像強調内視鏡（image enhanced imaging：IEE）であるtexture and color enhancement imaging（TXI）とred dichromatic imaging（RDI）が上市された。TXIは構造・色調・明るさの3要素を最適化したデジタル法IEEである。病変部と非病変部の色差が増加するため，早期胃癌・早期食道癌・大腸ポリープなどの視認性を向上させることが報告されている。TXIが実際に消化管癌拾い上げ診断能を向上させるか否かは，今後の前向き比較研究で明らかとなる。RDIはヘモグロビン吸収率の低い2つの狭帯域光と高い狭帯域光を組み合わせた光デジタル法IEEで，深部血管や出血点の視認性が向上し，ESDや静脈瘤治療に臨床応用されている。第三世代narrow band imaging（NBI）（EVIS X1）は中遠景でも十分な光量があり，非拡大NBI観察による表在型消化管腫瘍拾い上げ診断能の向上が期待される。

　In 2020, two new image-enhanced endoscopy (IEE), texture and color enhancement imaging (TXI), and red dichromatic imaging (RDI), were introduced to the market. TXI is a digital IEE that optimizes three factors: structure, color tone, and brightness. It has been reported that TXI improves the visibility of early gastric cancer, early esophageal cancer, and colorectal polyps because of the increased color difference between lesions and surrounding mucosa. Whether or not TXI actually improves the ability to detect gastrointestinal cancers will be elucidated in future prospective comparative studies. RDI is an optical-digital IEE that combines narrow-band lights of high hemoglobin absorption to improve the visibility of deep vessels and bleeding points, and it has been clinically applied to ESD and treatments for varix. The third-generation NBI (EVIS X1) has sufficient light intensity even in the mid- to distant-view, and is expected to improve the ability for detecting superficial gastrointestinal tumors through unmagnified NBI observation.