平田 健一郎, 伊東 佳澄, 三谷 正信, 辰口 治樹, 望月 環, 大内 博文, 那須 俊一, 荒明 洋, 吉田 茂夫, 福田 守道

Ken-ichiro HIRATA, Kasumi ITO, Masanobu MITANI, Haruki TATSUGUCHI, Tamaki MOCHIZAKI, Hirofumi OUCHI, Shun-ichi NASU, Hiroshi ARAAKE, Shigeo YOSHIDA, Morimichi FUKUDA

札幌医科大学機器診断部

Department of Ultrasound and M.E. , Sapporo Medical College Hospital

キーワード : Endoscopic ultrasound, Miniature probe scanner, Endosonography, High-frequency ultrasound

A new miniature probe scanner, Sonoprobe System, has been tested for ultrasonic scanning of the gastrointestinal tract. The system consists of a small 2×2 mm square transducer of 20 MHz frequency, a linear sweeping unit and an imaging unit with a CRT and image storage device.
The gastrointestinal tract is scanned with an operating videoendoscope which can accommodate the miniature probe scanner. Scanning is carried out using the sweeping unit, which consists of the manually driven linear runner, to assure constant movement of the scan head to yield a 17×16.5 mm B-mode image.
The resolutions of the system evaluated by custom made phantoms were 0.2 mm for the axial and approximately 1 mm in the lateral directions, respectively. The latter, azimuthal resolution, was considerably less because of the beam pattern characteristics of the probe used.
The high frequency transducer showed a considerable improvement in resolution compared to those obtained by the current EUS system. The image obtained from the gastric tissue in vitro showed 5 to 9 layers with varied echogenicities precisely coinciding to the tissue examined. In a normal stomach it showed a 5 layer structure, the third and fourth layers, immediately following the mucosa were the submucosa and muscularis propria and their thickness matched closely to those of the tissue section. On the other hand, the depth penetration of ultrasound in advanced cancer tissue was definitely lower than in normal tissue reflecting tissue alterations characteristic of carcinoma.
The new system clearly demonstrated increased resolution of tissue structures and hence it is suited for analysing gastric or colorectal malignancies in very early stages of the disease.