Received: 13.10.2008 Accepted: 30.10.2008 J Gastrointestin Liver Dis March 2009 Vol.18 No 1, 103-108 Address for correspondence: Larisa Săndulescu University of Medicine and Pharmacy Petru Rares Str. no 2 Craiova, Romania E-mail: larisasandulescu@yahoo.com CLINICAL IMAGING The Role of Real-time Contrast-Enhanced and Real-time Virtual Sonography in the Assessment of Malignant Liver Lesions Larisa Săndulescu, Adrian Săftoiu, Daniela Dumitrescu, Tudorel Ciurea Research Center of Gastroenterology and Hepatology, University of Medicine and Pharmacy Craiova, Romania Abstract Contrast enhanced ultrasound has recently been introduced and is recommended in daily practice in many circumstances, mainly for the detection and characterization of focal liver lesions. Also, contrast enhanced ultrasound has the potential of becoming the primary liver-imaging modality, preceding CT or MR, for the diagnosis of hepatocellular carcinoma in patients with cirrhosis, detection of liver metastases in oncology patients and guidance and assessment of the outcome of percutaneous tumor ablation procedure. Recently, a new imaging technique that combines in real-time, transabdominal ultrasound with CT or MR, has been introduced in clinical practice. Real-time virtual sonography uses a magnetic positioning system attached to the ultrasound probe in order to calculate the spatial position and to display both imaging methods in real-time. Benefits include an increased diagnostic confidence, direct comparison of the lesions using different imaging modalities, more precise monitoring of interventional procedures and reduced radiation exposure. We describe the role of real-time contrast-enhanced and real-time virtual sonography in the assessment of malignant liver lesions. Keywords Real-time contrast-enhanced ultrasound – malignant liver lesions – hybrid imaging – real-time virtual sonography. Contrast enhanced ultrasound (CEUS) The development of microbubble contrast agents has had a major impact on the role of ultrasound in the liver, particularly for focal lesions. As a result of their double blood supply provided by the hepatic artery and portal vein, focal liver lesions present a complex temporal and spatial picture of increased and reduced contrast [1]. The guidelines published in 2008 by the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) clearly defined the indication and recommendations for the use of contrast agents in liver ultrasound investigation [2]: 1. characterization of focal liver lesions (benign versus malignant); 2. guidance and monitoring local ablative treatment, and 3. measuring the hepatic transit time and studying the hepatic vessels. 1. Characterization of malignant liver lesions Hypo-enhancement of solid lesions (darker than the surrounding liver) in the late phase characterizes malignancies [2]. Recognition of hepatocellular carcinomas (HCC) in liver cirrhosis is difficult if the echo texture is very inhomogeneous due to the presence of regenerative nodules and architectural changes caused by extensive fibrosis. The progression from a regenerative nodule to a frank HCC is characterized by loss of visualization of portal tracts and development of new arterial vessels, which become the dominant blood supply in HCC lesions [3-5]. This arterial neoangiogenesis is the landmark of HCC and is the key for imaging diagnosis [6-8]. Several reports have shown that CEUS is the perfect tool to detect arterial neoangiogenesis in HCC [9, 10-12]. Typical features of hepatocellular carcinoma in cirrhotic liver show strong, early, complete enhancement in the arterial phase [Fig. 1a], while macroregenerative nodules are iso-enhancing with liver parenchyma. In other cases, basket pattern, chaotic vessels or rim-like enhancement can be detected in HCC lesions. Selective arterial enhancement on CEUS has been observed in 91-96% of HCC lesions [13, 14]. In subsequent phases, most hepatocellular carcinomas have a wash-out pattern and become hypo-enhanced in the parenchimal phase (Fig. 1b,c). Both the 2005 EASL conference on HCC and the AASLD practice guidelines have recommended the further