Cellular and vascular reactions in the liver to radio-frequency thermo-ablation with wet needle applicators: Study on juvenile domestic pigs

The aim of this animal experiment was to investigate the cellular and vascular reactions in the liver of juvenile domestic pigs produced by a radio-frequency thermoablation (RFTA) applicator perfused with saline solution. A total of 13 coagulation necroses were produced in the liver of 3 anesthetized domestic pigs using RFTA. The pigs were dissected and the coagulations examined. The mean macroscopical length and width of the coagulation zones with a hemorrhagic marginal zone after a 5-minute application time were 34.1 +/- 8 mm (22-46 mm) and 20.8 +/- 4 mm (12 +/- 28 mm) respectively. The sonographically determined diameters correlated significantly (r(length) = 0.741 and r(width) = 0.923). Three areas in the coagulation zones could be histologically distinguished: (1) central necrosis zone, (2) hemorrhagic marginal zone, (3) sublethal damage zone. Large vessels did not show any substantial changes after RFTA. Venous vessels less than 1 mm were completely thermally denatured or destroyed. Tumors in close proximity to large blood vessels can be treated by RFTA with 'wet electrodes'.