Objective: Small-sized hepatocellular carcinomas are sometimes missed in the ultrasound examination of patients with liver cirrhosis. The coarse echo from the surrounding cirrhotic parenchyma makes the discrimination of the tumor image from the background difficult. To perform the radio frequency ablation therapy (RFA) on such hepatic tumors under ultrasound guidance, contrast-enhanced ultrasonography was therefore used to aid accurate placement of the therapeutic needle in the tumor.Methods: Three patients with hepatocellular carcinomas (mean: 1.5 cm in diameter), detected by helical CT but invisible to gray scale ultrasound examination, were treated with RFA under guidance of contrast-enhanced sonography. Under general or local anesthesia, 5 ml of Levovist (300 mg/dl) was administered intravenously with a bolus injection. A commercially available US system was used throughout (Acuson Sequoia 512; a Siemens Company, Mountain View, CA) in conjunction with a phased array convex probe (model 3C2; Siemens). The agent detection imaging (ADI) mode was used with an intermittent trigger of 1/250 msec. Examinations of either the hepatic arterial phase or the delayed phase (Kupffer phase) led to determination of the tumor location, followed by placement of the RFA needle.Results: Two of the three tumors could be visualized only in the arterial phase. The Kupffer cell imaging in those cases was of poor quality, probably because the function of microbubble uptake by Kupffer cells was disturbed in the severely cirrhotic liver. The remaining tumor was visualized in both the arterial and the delayed phase. With those images, the RFA needles were successfully placed in the center of the tumors in all the patients. The effectiveness of the RFA therapy was validated with a second contrast-enhancement ultrasonography as well as with helical CT.Conclusions: The contrast-enhanced ultrasonograpy proved to be a useful option for the local treatment of hepatic tumors by enhancing conspicuity of the lesions under ultrasound guidance. Especially in those cases in which only CT could be used to guide the needle insertion, the method described here was more cost-effective, saved time, and was technically easy to use. Objective: Small-sized hepatocellular carcinomas are sometimes missed in the ultrasound examination of patients with liver cirrhosis. The coarse echo from the surrounding cirrhotic parenchyma makes the discrimination of the tumor image from the background difficult. To perform the radio frequency ablation therapy (RFA) on such hepatic tumors under ultrasound guidance, contrast-enhanced ultrasonography was therefore used to aid accurate placement of the therapeutic needle in the tumor. Methods: Three patients with hepatocellular carcinomas (mean: 1.5 cm in diameter), detected by helical CT but invisible to gray scale ultrasound examination, were treated with RFA under guidance of contrast-enhanced sonography. Under general or local anesthesia, 5 ml of Levovist (300 mg/dl) was administered intravenously with a bolus injection. A commercially available US system was used throughout (Acuson Sequoia 512; a Siemens Company, Mountain View, CA) in conjunction with a phased array convex probe (model 3C2; Siemens). The agent detection imaging (ADI) mode was used with an intermittent trigger of 1/250 msec. Examinations of either the hepatic arterial phase or the delayed phase (Kupffer phase) led to determination of the tumor location, followed by placement of the RFA needle. Results: Two of the three tumors could be visualized only in the arterial phase. The Kupffer cell imaging in those cases was of poor quality, probably because the function of microbubble uptake by Kupffer cells was disturbed in the severely cirrhotic liver. The remaining tumor was visualized in both the arterial and the delayed phase. With those images, the RFA needles were successfully placed in the center of the tumors in all the patients. The effectiveness of the RFA therapy was validated with a second contrast-enhancement ultrasonography as well as with helical CT. Conclusions: The contrast-enhanced ultrasonograpy proved to be a useful option for the local treatment of hepatic tumors by enhancing conspicuity of the lesions under ultrasound guidance. Especially in those cases in which only CT could be used to guide the needle insertion, the method described here was more cost-effective, saved time, and was technically easy to use.