Under the guidance of multimodality-ultrasound (US) fusion image, one of the three electrodes was placed across the portal vein branch near the tumor, and the other two electrodes were placed around the tumor through the previously planned approach path. After placement of electrodes, the temperature is maintained at 90-100 degrees Celsius for about 6-30 minutes depending on the size of the tumor, using the combined energy transfer mode that sequentially adds the bipolar mode and/or the monopolar mode.

Radiofrequency ablation is performed for peripherally located small hepatocellular carcinoma using combined energy delivery mode and triple cooled-wet electrodes. One of three electrodes is placed across the 4th or 5th portal vein branches near the target tumor which enables anatomical ablation of tumor.

Technical success addresses whether the index tumor was treated according to a predefined protocol and entirely covered by the ablation zone.

Local tumor progression, defined as the appearance of tumor foci at the margin of the ablation zone after the attainment of treatment success.

Post-radiofrequency ablation complications were defined as problems noted within 1 month after RFA as well as additional complications identified on follow-up imaging and judged to be likely caused by radiofrequency ablation.