自家蛍光内視鏡装置（AFI）による未分化型早期胃癌の診断

Autofluorescence Imaging Videoendoscopy System for Undifferenciated Type Early Gastric Cancer

要旨　内視鏡下で粘膜に励起光を照射し,発生する自家蛍光を捉えてリアルタイムに画像化するのが自家蛍光内視鏡装置（autofl uorescence imaging videoendoscopy system：AFI）である．当院にて2005年1月～2008年6月に内視鏡的粘膜下層はく離術，もしくは外科切除術が行われた未分化型早期胃癌115例のうち治療前評価にAFIが行われた46例を対象に，AFIの未分化型早期胃癌に対する診断能を，白色光観察（white light imaging：WLI）および色素観察（chromoendoscopy：CE）と比較検討した．周囲の背景粘膜との色調差が明瞭で容易に認識できた病変の割合は，AFI 76.1％，WLI 56.5％，CE 60.9％で，AFIが色調差を認識しやすい傾向があった（p＝0.120）．境界が全周性に明瞭に認識できた病変の割合は，AFI 52.2％，WLI 45.7％，CE 47.8％で差がなかった（p＝0.819）．上記46例のうちESD適応拡大の対象となりうる内視鏡的深達度がMかつUL陰性であった24例を対象に，病変の広がりに対する診断能を検討したところ，各観察法の正診率はAFI50％，WLI 33.3％，CE21.7％であった（p＝0.225）．AFIはWLIやCEと比較して病変と背景粘膜との色調差を認識しやすいため範囲診断の正診率を向上させる可能性はあったが，今回の限られた症例数での検討では有用性を明らかにできる程度ではなかった．

　Autofluorescence imaging videoendoscopy（AFI）systems are real-time imaging systems that capture autofluorescence produced by light excitation from submucosal layers using an endoscopic illumination. The diagnostic capability of AFI for undifferentiated early gastric cancer was evaluated in 46 of 115 cases of undifferentiated early gastric cancer treated by endoscopic submucosal dissection（ESD）or surgery from January 2005 to June 2008, in comparison with the results of white light imaging（WLI）and chromoendoscopy（CE）. The recognition rates of clear color differentiation between lesion and background were as follows : AFI, 76.1％ ; WLI, 56.5％ ; CE, 60.9％ . Thus, AFI showed the most distinct color differentiation（p＝0.120）. The recognition rates of the whole circumferential border line were as follows : AFI, 52.2％ ; WLI, 45.7％ ; CE, 47.8％ ; no significant differentiation was observed（p＝0.819）. In 24 cases with extended indication for ESD that had carcinoma within the mucosal layer and without ulcer（UL）among the 46 cases mentioned above, the rates of correct diagnosis for range of lesions were as follows : AFI, 50％ ; WLI, 33.3％ ; CE 21.7％（p＝0.225）. The results of the present study suggested that AFI may contribute to correct diagnosis for range of lesions because of its apparent color difference between background and lesion compared to WLI or CE. However, significant effectscould not be demonstrated in the limited sample number in the present study.