Radiofrequency thermal ablation: increase in lesion diameter with continuous acetic acid infusion

To evaluate the influence of continuous infusion of acetic acid 50% during radiofrequency ablation (RFA) on the size of the thermal lesion produced.

Radiofrequency (RF) was applied to excised bovine liver by using an expandable needle electrode with 10 retractable tines (LeVeen Needle Electrode, RadioTherapeutics, Sunnyvale, CA) connected to a commercially available RF generator (RF 2000, RadioTherapeutics, Sunnyvale, CA). Experiments were performed using three different treatment modalities: RF only (n = 15), RF with continuous saline 0.9% infusion (n = 15), and RF with continuous acetic acid 50% infusion (n = 15). RF duration, power output, tissue impedance, and time to a rapid rise in impedance were recorded. The ablated lesions were evaluated both macroscopically and histologically.

The ablated lesions appeared as spherical or ellipsoid, well-demarcated pale areas with a surrounding brown rim with both RF only and RF plus saline 0.9% infusion. In contrast, thermolesions generated with RF in combination with acetic acid 50% infusion were irregular in shape and the central portion was jelly-like. Mean diameter of the coagulation necrosis was 22.3 +/- 2.1 mm (RF only), 29.2 +/- 4.8 mm (RF + saline 0.9%) and 30.7 +/- 5.7 mm (RF + acetic acid 50%), with a significant increase in the RF plus saline 0.9% and RF plus acetic acid 50% groups compared with RF alone. Time to a rapid rise in impedance was significantly prolonged in the RF plus saline 0.9% and RF plus acetic acid 50% groups compared with RF alone.

A combination of RF plus acetic acid 50% infusion is able to generate larger thermolesions than RF only or RF combined with saline 0.9% infusion.