ヘリカルCTによる胆管癌の診断

Helical (spiral) CT Imaging of Bile Duct Cancer

要旨　ヘリカルCTとは，X線管球を高速で連続回転させ被検者のテーブルを一定の速度で移動させることにより得られるボリュームスキャンCTのことである．胆道においては，1回の呼吸停止（約20秒）で全胆道がスキャンできるので位相のずれがなく，小さな胆管癌や浸潤型胆管癌例でも確実に病巣部が描出できるようになってきた．また，優れた連続性のために多断面再構成像や3次元再構城像も従来のものより質が高い．それに伴い進展度診断能も進歩し，少なくとも漿膜を越え周囲組織に浸潤したものの診断においては最も信頼性が高いように思われる．しかし，壁深達度診断や壁内進展の診断については，まだその有用性が評価できる段階に至っていないのが現状である．

　Helical CT scanning, a volumetrical CT scan, has enabled us to scan the entire biliary tract during a single breath hold, so that even a small lesion of extrahepatic bile duct cancer has been able to be demonstrated. Additionally, high quality images of mutiple planner reconstruction (MPR) or three-dimentional reconsruction (3-D) were able to be obtained due to continuous data acquisition, and early phase images of dynamic CT could be acquired because of high-speed rotation of the scanner. Therefore, predictability of tumor extension into the adjacent tissues, especially invasion into the pancreatic parenchyma, is improving, but evaluation of the depth and intramural spread of the cancer is still difficult evan by means of helical CT scanning.

　On the basis of our data, it was conclued that helical CT is superior to conventional CT in detecting a tumor and evaluating the grade of the extramural extension of bile duct cancer.