新しい画像検査・診断法と今後の展開―体外式超音波：造影超音波を含めて

Novel Diagnostic Imaging/Examination and its Development-Transabdominal Ultrasound of Gastrointestinal Diseases ― Including Ultrasound Contrast Imaging

要旨　造影超音波を含めた体外式超音波法（以下US法）の各種消化管疾患に対する診断的意義について述べた．US法による消化管の診断にはスクリーニングとしての場合と精査手段としての場合の2つがあり，それぞれ少しずつ見かたが異なっている．しかしながら，いずれも異常像を描出した場合には，その病理像あるいは病態生理を類推しながら，できる限り分析的に解析する点は共通するところである．US法により消化管における炎症から腫瘍まで幅広く診断可能であるが，さらに近年の超音波造影剤の開発や低音圧モニター下間欠送信を用いたflash echo imaging法の開発により従来のドプラ法では評価できなかった細径かつ低流速の血流評価が可能となってきた．これらの技術の進歩により生体下での腫瘍性病変のvascularityの評価，瘢痕性狭窄と炎症性狭窄との鑑別，炎症性腸疾患における活動性の指標などが非侵襲的に評価可能であり，臨床的有用性が大きい．内視鏡やX線診断等の従来の診断法にこれらのUS法を加えることで，より適切な治療方針の決定や病態生理の把握に役立つものと考えられる．

　The diagnostic significance of transabdominal ultrasound (US) including ultrasound contrast imaging for a variety of gastrointestinal diseases was reported. As diagnostic methods for diseases of the gastrointestinal tracts by US, there are two types, that for screening purpose and that for precise investigational purpose, with only a small difference between them in terms of observational method. However, if both of them visualize an abnormal finding, it is common to investigate them analytically as much as possible, analogizing its pathological image or pathophysiology. It is possible to diagnose the gastrointestinal tracts extensively from inflammation to tumor by the use of the US method. Furthermore, development of ultrasound contrast agent and development of the flash echo imaging method using intermittent pulse transmission under low mechanical index imaging have enabled us to evaluate blood flow in micro vessels and at low flow velocity, which foctors are difficult to evaluate by conventional Doppler ultrasound. Advancement in these technologies enables evaluation of vascularity in neoplastic lesions in vivo, differentiation between fibrotic stenosis and inflammatory stenosis, and non-invasive evaluation of the index of activity in inflammatory bowel disease. These data are useful clinically. Adding these US methods to conventional diagnostic methods including endoscopy and radiological diagnosis may be useful for determining more appropriate treatment strategies and for the understanding of pathophysiology.

　1) Department of Endoscopy, Hiroshima University Hospital, Hiroshima, Japan