Characterization of Small Focal Liver Lesions Using Real-time Contrast-Enhanced Sonography

OBJECTIVE The purpose of this study was to assess the diagnostic performance of real-time contrast-enhanced sonography in characterization of small focal liver lesions (FLLs; < or = 3.0 cm in diameter). METHODS Two hundred small FLLs in 200 patients were examined by contrast-enhanced sonography using a contrast-specific mode of contrast pulse sequencing and a sulfur hexafluoride-filled microbubble contrast agent. The sonographic images were reviewed by 2 independent readers. A 5-point confidence level was used to discriminate malignant from benign FLLs, and specific diagnoses were recorded. The diagnostic performances were evaluated by receiver operating characteristic (ROC) analysis, and the interobserver agreement was analyzed by weighted kappa statistics. RESULTS After review of contrast-enhanced sonography, ROC analysis revealed significant improvement in differentiating between malignant and benign small FLLs that the areas under the ROC curve were 0.856 at baseline sonography versus 0.954 at contrast-enhanced sonography for reader 1 (P < .001) and 0.857 versus 0.954 for reader 2 (P = .003). The sensitivity, negative predictive value, and accuracy for both readers also improved significantly after contrast agent administration (all P < .001). A better result of specific diagnosis was obtained (38.5% [77/200] at baseline sonography versus 80.5% [161/200] at contrast-enhanced sonography for reader 1 and 34.5% [69/200] versus 80.5% [161/200] for reader 2; both P < .001) after contrast agent administration, and a better interobserver agreement was achieved (kappa = 0.425 at baseline sonography versus 0.716 at contrast-enhanced sonography). CONCLUSIONS Real-time contrast-enhanced sonography improves the diagnostic performance in small FLLs compared with baseline sonography.