Characterization and detection of hepatocellular carcinoma (HCC): comparison of the ultrasound contrast agents SonoVue (BR 1) and Levovist (SH U 508A) - von Herbay, A; Haeussinger, D; Gregor, M; Vogt, C (Ultraschall in der Medizin - European Journal of Ultrasound, 2007)