Radiofrequency ablation (RFA) is not feasible when hepatocellular carcinoma (HCC) is poorly defined or invisible on conventional gray-scale ultrasonography (GSUS). Recent introduction of contrast-enhanced ultrasonography (CEUS) helps diagnose HCC by showing its typical enhancement pattern. Objectives: The purpose of this study is to demonstrate the added value of CEUS as a RFA planning modality for HCC compared with conventional GSUS. Patients and Methods: A total of 64 HCCs from 57 patients

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... n:women = 41:16; mean age, 62.6) who had undergone GSUS and CEUS for RFA planning in 2011 were retrospectively reviewed. Ultrasound contrast agent was used for CEUS after conventional GSUS. The recorded images of GSUS and CEUS were reviewed retrospectively. On GSUS, the size, location, echogenicity, and margin of each HCC were reviewed. The visibility scores of HCC on GSUS and CEUS were measured using a 3-point scale. GSUS visibility score: score 1, definite nodule with well-defined margin; score 2, slightly hypo-/hyperechoic nodule with partial margin; score 3, isoechoic nodule without margin. CEUS visibility score: score 1, arterial enhancement; score 2, only delay washout; score 3, no arterial enhancement or washout. Results: The mean size of HCCs was 1.8 cm (range, 1.0 -4.8 cm). Among 64 HCCs, visibility score 1 were 37; score 2, 8; score 3, 19 on GSUS. By performing CEUS, 10 out of 19 HCCs with GSUS visibility score 3 showed CEUS visibility score 1. Seven out of 8 HCCs with GSUS visibility score 2 showed CEUS visibility score 1. Total 37 HCCs showed visibility score 1 on GSUS; whereas, 53 HCCs showed visibility score 1 on CEUS (57.8% vs. 82.8%). Conclusions: CEUS can be an effective RFA planning modality when a target HCC is invisible or questionable on GSUS.