PERCUTANEOUS TISSUE ABLATION BY RADIOFREQUENCY THERMAL-ENERGY AS A PRELIM TO TUMOR ABLATION

Porcine hepatic tissue was ablated in vitro and in vivo with radiofrequency (RF) energy applied through various percutaneous probes. Ultrasound was used for guidance. The technique was assessed for potential use to ablate tumours percutaneously. Tissue ablation was performed in two porcine cadaver and six live piglet livers in various experiments, three RF generators with either bipolar gold probes, 18-22 gauge modified angiocath needles, titanium curved and spiral 0.018'' guidewires, three-pronged grabber baskets, and/or a thermistor (temperature-controlled) probe were used to induce the RF effect with simultaneous assessment by real-time ultrasound. Gross and microscopic analysis of the liver was undertaken after acute sacrifice of the animals. The hepatic tissue that surrounded the probe after RF energy application became increasingly echogenic sonographically. The size of the echogenic area on ultrasound corresponded to the size of the thermal lesion on gross and microscopic examination. Thermal lesions up to 2 cm were created. The size of the thermal lesion was proportional to the surface area of the probe, the shape of the probe, the generator power, and the length of time that the RF energy was applied. The thermistor probe permitted improved contact and control by preventing central charring, cavitation, and boiling of the tissue that occasionally was observed with other probes. Percutaneously applied radiofrequency energy using US-guidance and monitoring is a feasible method to ablate hepatic tissue.