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'.