PET（PET/CT）による大腸腫瘍性病変の診断

Diagnosis of Colorectal Tumors Using PET (PET/CT)

要旨　大腸癌はFDGが良好に集積する腫瘍の1つである．しかし，PETは空間分解能に劣るため，早期癌の検出には限界がある．一方，PET/CTではこの弱点が改善され，病変の解剖学的位置が明瞭になるので有用性が向上する．臨床的には局所診断というよりも転移診断，再発診断への有用性が高く，特に予期せぬ部位への転移や再発診断においては，ほかの画像診断に比べて優れている．PET/CTに造影CTを加えると，さらに有用性が高まる．また，PET/CTにCT angiographyや仮想内視鏡などの三次元画像を組み合わせると新たな“術前マッピング”として有用な画像情報を得ることができる．

　Colorectal cancer is one of the tumors that show strong accumulation of FDG. But due to the limitation of spatial resolution, early cancer is difficult to be detected on PET. As this weak point is defeated on PET/CT to clarify anatomical location, clinical usefulness is remarkably improved. PET or PET/CT is effective for detecting metastases and recurrence rather than evaluation of primary tumor, especially for finding unexpected lesions in comparison with other imaging modalities. PET/CT using contrast material further improves clinical efficacy, and PET/CT combined with CT angiography or virtual endoscopy enables us to obtain new three dimensional images which are valuable for preoperative mapping.