A woman, aged 75, with cirrhosis caused by hepatitis C had a routine ultrasound study for surveillance for hepatocellular carcinoma. A possible nodule was identified in segment VI but it was difficult to identify the contours or margins of the nodule. A contrast-enhanced ultrasound (US) study with perfluorobutane (Sonazoid®) showed no enhancement or washout of the nodule in either the vascular or Kupffer phases. Computed tomography (CT) during hepatic arteriography (CTHA) or arterial portography (CTAP) also failed to show a liver lesion (Figure 1, left and middle panel). In contrast, gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Primovist®)-enhanced magnetic resonance imaging (MRI) clearly revealed a low-signal nodule during the hepatobiliary phase (Figure 1, right). The appearance was consistent with either a dysplastic nodule or a well-differentiated hepatocellular carcinoma. As the nodule could not be detected on US or CT, we performed real-time virtual sonography synchronizing B-mode US images with the hepatobiliary phase of enhanced MRI which allowed for the same area to be displayed in real time as both MR and B-mode US images (Figure 2). Using this technique, the nodule was clearly visualized and an aspiration biopsy was performed. Histology revealed a well-to-moderately differentiated hepatocellular carcinoma that was treated by percutaneous radiofrequency ablation guided by real-time virtual sonography with contrast-enhanced MRI.

Radiofrequency ablation is widely used for the treatment of hepatocellular carcinoma. However, to achieve successful ablation, it is important to have a clear view of the margins of the nodule. Although most larger hepatocellular carcinomas are hypervascular, early carcinomas can be hypovascular and can be difficult to detect with contrast-enhanced US, contrast-enhanced CT or CT during hepatic arteriography. The recent introduction of contrast-enhanced MRI appears to have improved the detection of early liver tumors and may be helpful for the differentiation of early hepatocellular carcinoma from dysplastic nodules. Real-time virtual sonography is a system in which a B-mode US image can be synchronized with CT images. To our knowledge, this is the first report of the successful use of real-time virtual sonography with enhanced MRI for the detection and treatment of an early hepatocellular carcinoma. This technology may facilitate the diagnosis and treatment of hepatocellular carcinoma at an earlier stage.

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