Hepatocellular Carcinoma: Contrast-Enhanced Sonography

In patients with chronic liver disease, sono-graphy and measurements of serum alpha-fetoprotein (αFP) levels are frequently used to screen for hepatocellular carcinoma (HCC). The sensitivity of sonography for HCC detection, however, in the end-stage cirrhotic liver is only 50% (Dodd et al., 1992). Furthermore, sonographic findings of HCC are variable and frequently nonspecific. Hepatocellular carcinoma is highly vascularized and often shows irregular neovascularization within the tumor. Therefore, detection and characterization of tumor vascularity are important in the differential diagnosis, the choice of treatment method, and assessment of the therapeutic response for HCC. Although color and power Doppler sonography are helpful in detecting vascularity of hepatic tumors, it has not proved satisfactory.

Since intravenous microbubble contrast agents including SH U 508A (Levovist; Schering AG, Berlin, Germany) for sonography have become available, many researchers have reported that contrast-enhanced sonography could be a promising technique for assessing post-treatment response of HCC (Bartolozzi et al., 1998; Choi, D. et al., 2000; Ding et al., 2001; Meloni et al., 2001; Solbiati et al., 1999; Youk et al., 2003b) as well as for making a correct diagnosis of HCC by observing tumoral vascularity (Choi et al., 2000a; Dill-Macky et al., 2002; Kim et al., 1998; Wen et al., 2004). Indeed, there is an increasing consensus that the use of contrast agents improves the ability of sonography to detect and characterize focal hepatic lesions. Levovist, one of the most popular sonographic contrast agents, is a suspension of galactose microparticles in sterile water. The microbubbles (2–8 μm in diameter, with a mean of 3 μm), which are stabilized in the microparticle suspension, can traverse the pulmonary capillary bed and diverse into whole blood circulation (Kim et al., 1998).