内視鏡的三次元超音波断層法（3D-EUS）による大腸疾患の検討

Use of Three-Dimensional Endoscopic Ultrasonography (3D-EUS) in the Diagnosis of Colorectal Diseases

要旨　オリンパス社製超音波三次元画像処理システムを用いて大腸疾患36病変に内視鏡的三次元超音波断層法(3D-EUS)を施行し，その有用性について検討した．本システムを用いて，ヘリカルモードから得られたラジアル画像とリニア画像の画像処理によって立体的な斜視構築像を形成した．癌18病変については術前深達度診断能を検討したが，正診率は全体では83％(15/18)であり従来のEUSによる成績とほぼ同等であった．粘膜下・壁外病変では腫瘍の局在や病変の拡がりが斜視構築像で明瞭に描出された．3D-EUSの使用によって，大腸疾患の病態の理解が更に容易となった．機種の改良により，今後ますます発展する診断方法と考えられた．

　An ultrasound 3D imaging system has been made by Olympus Co. Three-dimensional EUS (3D-EUS) images are obtained by an ultrasound 3D image processing unit using a newly developed ultrasonic probe which is 2.5 mm in diameter with a frequency of 20 MHz and a 360-degree scanning angle. Both radial and linear images are obtained by a scan using this 3D ultrasonic probe with an automatic movement in an outer sheath 3.4 mm in diameter. During a one-stroke movement, radial and linear scanning images are gained simultaneously. By this processing unit, stereoscopic images can be reconstructed from multiplane reconstruction images. This three-dimensional ultrasonic probe can be inserted in a larger-diameter forceps channel of a colonoscope. When a lesion is observed endoscopically, the 3D-EUS is examined by the water-filling technique. From August 1996 to October 1997, we performed 3D-EUS in 36 cases with colorectal diseases including 20 cases with cancer, 10 with submucosal or extralumina lesions, three with ulcerative colitis, and three with adenoma. The preoperative diagnosis of cancer invasion was investigated in 18 of 20 cases and these were confirmed histologically. The overall accuracy rate was 83%. Lymph nodes were clearly visualized by radial images and definitely differentiated from vessels particularly by the linear image. In case of rectal varices, the network of dilated vessels which spread through the wall of the rectum was able to be delineated precisely in the reconstructed stereoscopic image. Moreover, stereoscopic images are effective in understanding the extent of the lesions in cases of large tumors with cancers, extraluminar lesions and submucosal lesions. Using the 3D-EUS method, the pathological findings of colorectal diseases were recognized more easily and accurately in stereoscopic image. Further refinements of operability and capability of this system may make 3D-EUS a reliable diagnostic method for colorectal diseases.