virtual endoscopyの現状と展望―大腸微細病変の描出能について

Present Status and Future View on Virtual Endoscopy-Depiction of Minute Lesions in the Large Intestine with CT Colonography

要旨　CT colonographyによる大腸小病変の発見能および表面型病変の描出性について検討した．注腸で病変が指摘された54症例を対象にして，CT colonography，大腸鏡および注腸X線検査の診断能を比較した．大腸鏡で確認できた病変79病変中，CTで描出できたのは72病変（91％）であった．しかし，0.5cm以下でCTによって指摘した135病変中大腸鏡で確認できたのは43病変（32％）で偽陽性が多数みられた．大腸表面型病変の描出については大きさ1.0cmのⅡc型早期癌が明瞭に描出できた．CT colonographyは臨床応用がまだ始まったばかりであるが，今後，装置の改良のみならず画像処理やコンピュータ支援診断などソフト面の進歩も期待できるので，近い将来，注腸や大腸鏡と並んで大腸スクリーニング検査の一環を担う可能性がある．

　CT colonography is a new imaging technique using helical CT. We studied the efficacy of CT colonoscopy in the detection of small polyps and depiction of superficial lesions.

　Concerning the detection of small polyps, we studied 54 patients with abnormality checked by barium enema. Conventional colonoscopy revealed 79 lesions (5 advanced carcinomas, 4 superficial-type adenomas and 70 polyps) . CT colonography identified all 5 carcinomas, 3 of the 4 superficial lesions and 43 of the 45 polyps that were 0.5 cm or smaller in diameter, 18 of 22 polyps that were 0.6 to 0.9 cm, and all 3 polyps that were 1.0 cm or more in diameter. There were 92 false positive polyps that were 0.5 cm or smaller in diameter.

　On a superficial lesion, we could depict a superficial depressive type early colonic carcinoma 1.0 cm in diameter, using very thin-slice CT equipment.

　In conclusion, CT colonography has a high sensitivity for detection of small polyps and sufficient capability for depiction of superficial lesions. CT colonography may be suitable for screening examinations of the large intestine.