Radiofrequency ablation (RFA) has become mainstream among non-surgical treatment modalities in clinical settings for the treatment of hepatocellular carcinoma. We have previously described the novel combination therapy of percutaneous ethanol injection and RFA (PEI-RFA) and reported that this combination therapy was more effective than RFA alone in terms of the induced volume of coagulated necrosis and the energy requirement for the treatment. RFA instruments are mainly divided into two types according to the electrode used, either the straight or expandable type electrode. Although PEI-RFA can be performed by either of the electrodes, there may be some important differences in PEI-RFA according to the type of electrode used. In the present study, the effect of using the straight or expandable electrode in PEI-RFA was evaluated by analyzing the ablation time, volume of coagulated necrosis, the energy requirement for ablation and the amount of injected ethanol into HCC. The comparative study showed that ablation time, total energy requirement and per unit volume of energy requirement for whole and marginal coagulated necrosis were significantly smaller in the group treated with the expandable electrode (E group) than those in the group treated with the straight electrode (S group). The volume of coagulated necrosis was similar between these groups. In group E, the amount of injected ethanol showed a positive correlation with the volume of coagulated necrosis and the size of the tumors. These results suggest that prior injection of ethanol works mainly by shortening the time and energy requirement for ablation in the time-lag PEI-RFA using the expandable electrode. Thus, prior injection of ethanol before RFA may make RFA treatment less invasive in the time-lag PEI-RFA using the expandable electrode as previously shown HCC cases treated with straight electrode.

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