5）AFI

Autofluorescence Imaging in Screening of Superficial Esophageal Cancer

要旨　消化管粘膜から生じる自家蛍光を内視鏡下にとらえ，モニター上に疑似カラー表示するのが自家蛍光電子内視鏡（AFI）である．AFIは正常の食道粘膜を緑色，癌を緑色と補色関係にあるマゼンタ色に描出し，癌の視認性を高めている．通常観察やnarrow band imagingに比べてAFIが最も癌を明瞭に描出できることもあるが，一方でglycogenic acanthosisや逆流性食道炎といった病変もAFIでマゼンタに近い色に描出されるので癌診断の特異度は低い．AFIの食道癌スクリーニングにおける有用性に関し多数例での検討が待たれる．

　An AFI（autofluorescence imaging）videoendoscopy system provides real-time pseudocolor images from computation of natural tissue fluorescence detected from endogenous fluorophores that are emitted by excitation light. Normal esophageal mucosa is usually displayed as green, while esophageal cancer is displayed as magenta on AFI. Although AFI can enhance the visualization of esophageal cancer, it is associated with a high false positive rate. AFI could be a useful modality for the screening of superficial esophageal cancer. However, a large-scale study to investigate the utility of AFI in the screening of esophageal cancer should be carried out before widespread use of AFI can be implemented.