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

Background: We evaluated the sensitivity and specificity of post-vascular phase (Kupffer imaging) by contrastenhanced ultrasonography (CEUS) using perflubutane microbubbles (Sonazoid) in comparison with conventional B-mode ultrasonography (US) for the detection of hepatocellular carcinoma (HCC) nodules. Methods: A total of 100 treatment-näive 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. Results: 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. Conclusions: 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.