Value of post-vascular phase (Kupffer imaging) by contrast-enhanced ultrasonography using Sonazoid in the detection of hepatocellular carcinoma

We evaluated the sensitivity and specificity of post-vascular phase (Kupffer imaging) by contrast-enhanced ultrasonography (CEUS) using perflubutane microbubbles (Sonazoid) in comparison with conventional B-mode ultrasonography (US) for the detection of hepatocellular carcinoma (HCC) nodules. A total of 100 treatment-na < ve HCC patients admitted at our hospital between December 2007 and June 2009 were consecutively enrolled. The sensitivity and specificity of conventional and contrast-enhanced US were evaluated on a liver segment basis using dynamic CT as a reference standard. Movie files of conventional and enhanced US were stored separately for each segment (e.g., lateral, medial, anterior, and posterior) and reviewed randomly by two blinded readers. A total of 138 HCC nodules (mean diameter 20.3 mm) were detected in 123 of 400 segments. Detection sensitivity of B-mode US was 0.837 for reader A and 0.846 for reader B, and that of CEUS was 0.732 for reader A and 0.831 for reader B. Specificity of B-mode US was 0.902 for reader A and 0.949 for reader B, and that of CEUS was 0.986 for reader A and 0.978 for reader B. CEUS false positives were mainly due to misidentification of hepatic cysts. A significant proportion of false-negative nodules are hyperechoic in B-mode US, likely because echogenicity hampers visualization of the defect in Kupffer imaging. Kupffer imaging by CEUS with Sonazoid showed very high specificity but rather mediocre sensitivity for HCC detection. CEUS is highly suitable for confirmatory diagnosis of HCC; however, caution should be exercised in reaching a diagnosis based only on CEUS.