直腸pm癌の浸潤パターン―新しい画像診断的アプローチ

MR Imaging of Rectal Carcinoma Invading the Muscularis Propria

要旨　MR画像は，超音波内視鏡と同様にT2強調画像にて正常腸管壁の層構造を描出できる．また，大腸癌のMR画像は，腫瘍の発育様式や腫瘍の病理組織成分により異なるが，固有筋層に浸潤した癌の診断は，T2強調画像で高信号を示す粘膜下層の断裂が重要な所見である．筋層内に浸潤した癌の所見は，筋層の断裂，筋層の肥厚，腫瘍による筋層の置換，T2強調画像における筋層内のやや高信号を示す腫瘤に要約される．固有筋層を越えた癌の診断には，T1強調画像における腸管壁外側縁の不整な突出，ならびにT2強調画像における固有筋層外縦層の断裂が最も信頼できる所見である．MR画像は，超音波内視鏡と同様に治療法の選択に結びついた癌の深達度に役に立つ可能性が示唆された．

　We studied colorectal tumors with a high-resolution magnetic resonance (MR) imaging system to determine (1) MRI signal characteristics of these lesions, and the potential of MRI in (2) the tissue-diagnosis and (3) the evaluation of the cancer extension with intheintestinal wall.

　MRI can potentially visualize the layering structures of the normal intestine as clearly asendoscopic ultrasonography (EUS). Intramural tumor invasion confined to the intestinal wall was best evaluated in the T2 weighted image. Although the signal intensity of the colorectal tumors varied considerably depending on cellular components of the tumor, the most reliable MR finding of the cancer invading the muscle layer was the interruption of the submucosal layer. Carcinomatous invasion passed through the muscularis propria into the pericolonic fat tissue was well recognized as an irregular outer-contour of the muscle layer in T1 weighted image and as an interruption of the outer-longitudinal muscle layer in T2 weighted image.

　Our results corroborated the excellent utility of MRI in defining the internal structure of the colorectal wall. In cases of colonic carcinoma, MRI correlated well with the pathology in macroscopic growth pattern, depth of mural invasion, and other histologic features. We conclude that MR imaging is valuable in the clinical evaluation of rectal cancer.