Enlargement of thermal ablation zone by the combination of ethanol injection and radiofrequency ablation in excised bovine liver.

The efficacy of radiofrequency ablation (RFA) and RFA with concurrent ethanol injection (EI-RFA) was compared. RFA (3-cm-electrode) was applied to bovine liver using three types of RFA equipment; Radionics, RITA and Radio Therapeutics Corporation (RTC). For EI-RFA, 5 ml of 99.5% ethanol was injected around the electrode. A total number of 40 RFA and EI-RFA treatments were performed. We compared RFA with EI-RFA by examining the size, shape of ablation zone, treatment time, power, and needle tip temperature. Liver specimens were examined for pathological changes. EI-RFA produced a larger zone of ablation than RFA alone using Radionics and RITA (Radionics, 35.3+/-7.4 cm(3) vs 23.2+/-7.7 cm(3), p<0.05; RITA, 30.7+/-10.3 cm(3) vs 19.7+/-4.7 cm(3), p<0.05), corresponding to shortest diameters of coagulation zone (Radionics, 3.7+/-0.4 cm vs 3.0+/-0.4 cm, p<0.05; RITA, 3.8+/-0.4 cm vs 3.1+/-0.3 cm, p<0.01). However, a larger ablation zone was not seen with the RTC device. The ablated volume per energy and the ablated volume per current density administered were greater with EI-RFA than with RFA using Radionics (p<0.05). The shape of the ablated zone changed from ellipsoid to spherical with EI-RFA using Radionics. No pathological differences between RFA and EI-RFA samples were detected. For a given amount of energy and current administered, ethanol injection caused a better ablation effect, in terms of the size and shape of the ablated zone, than RFA with Radionics and RITA equipment.