F.H. Chen, W. Yang, K. Yan, W. Wu, Y. Dai; Beijing/CN

Purpose
To evaluate the clinical value of contrast enhanced ultrasound (CEUS) for patients with liver malignancies in identifying the ablation range and designing the treatment protocol before radiofrequency ablation (RFA) treatment and to compare the efficacy of RFA after CEUS with the efficacy of RFA after fundamental ultrasonography (US) without contrast.

Material and methods
One hundred sixty-one patients with hepatocellular carcinoma (HCC) were suitable for percutaneous RFA and underwent US-guided RFA treatment. CEUS was performed for 77 patients pre-treatment (CEUS group) and fundamental US without contrast enhancement was performed for the remaining 84 patients pre-treatment (non-CEUS group). There were no significant differences in clinical data between the two groups; the average diameters of the lesions in CEUS group and non-CEUS group were (3.6±1.2) cm and (3.5±1.1) cm, respectively. CEUS group had 47 cases (61.0%) advanced-stage HCC and non-CEUS group had 49 cases (58.3%). Regular follow-up after treatment was performed using fundamental US and contrast-enhanced computed tomography (CECT) or CEUS (or both). No residue or local recurrence on CECT at least 6 months after treatment was classified as complete ablation.

Results
In the CEUS group, 77 cases with 105 lesions were treated with RFA. There were 59 lesions (56.2%) that were larger during the arterial phase and 49 lesions (46.7%) that had a more irregular shape during the arterial phase than in fundamental US. Feeding vessels were detected with CEUS in 37 of 52 lesions larger than 3.5 cm (71.1%). CEUS showed 16 small lesions (≤2.0 cm) in 10 cases, 5 of which had 5 hepatic distant recurrences after RFA which coexisted with liver cirrhosis. Another 5 cases had 11 satellite lesions around the main tumor. The average number of RFA sessions in the CEUS group and non-CEUS group were 1.2 and 1.5 respectively. During the 6 to 39 months of follow-up, the complete ablation rate in the CEUS group was significantly higher than that in the non-CEUS group (95.4% vs. 87.8%, P=0.042). The average survival time in the CEUS group was longer than that of non-CEUS group (34.2±1.2 months vs. 30.2±1.6 month, P=0.028).

Conclusion
CEUS is used to accurately identify the tumor invasive range and sensitively detect minute or satellite lesions and the feeding vessel of the tumor. CEUS provides important information and evidence for planning the RFA protocol and may improve the efficacy of RFA treatment of liver tumors.