CONTRAST ENHANCING AGENTS IN ULTRASONOGRAPHY - CLINICAL-APPLICATIONS

Introduction: As ultrasound remains a poorly sensitive method, echocon trast agents make a real difference. At least. 29 echocontrast agents are currently on trial worldwide; their chemical composition, mechanis ms of action and possible clinical applications are different. The sta te of the art of echocontrast agents is discussed: their established a pplications, those expected in the near future and finally their hypot hetical, ideal applications. Potential clinical applications: An extra vascular and a vascular domain can be considered. The former includes the gastrointestinal tract and body cavities-both the normal (bladder, uterus, tubes and so on) and the abnormal (abscesses, fistulas, peric ardium, peritoneum and so on) ones. Echocontrast agents can: (1) creat e or improve an acoustic window; (2) distend some organs and fill them with a liquid, with homogenous attenuation of the ultrasound beam; (3 ) displace the air-containing intestinal loops; (4) depict the walls, the shape and the contours of a normal or abnormal cavity; (5) detect abnormal communications, fistulas and drainages; and (6) evaluate the amount of fluid in the pleural, pericardial or peritoneal cavities. As for vascular applications, this domain sees the highest number of ech ocontrast agents on trial or on the market. The best know of them are : Levovist(TM) (Schering AG, Berlin, Germany), BR1 (Bracco, Milan, Ita ly) and EchoGen(R) (Abbott, USA). Ah these act by enhancing arteries, veins and capillaries. The clinical applications validated in clinical trials mainly regard studies in intracranial and neck vessels and the vascularity of upper and especially lower limbs of renal vessels. Tum or macrovascularity (and in the future, hopefully microvascularity) ca n also be studied in parenchymatous and/or glandular organs, as well a s in intra- and extra-abdominal parenchymatous organs in the periskele tal soft tissues. Clinical validation has also been obtained in the fo llow-up of tumors submitted to ablation therapy (chemoembolization, et hanol injection, thermal ablation) and in echocardiography, both for m orphological studies in the cardiac cavities and for the cardiac wall perfusion. Conclusions: In a subgroup of 513 out of 1275 patients exam ined Europe-wide, the contrast agent Levovist(TM) increased the diagno stic confidence from 27.4 +/- 22.5 to 77.2 +/- 22.5%. Such data encour age further trials to validate current preliminary results. (C) 1998 E lsevier Science Ireland Ltd. All rights reserved.