[Radiofrequency ablation of the liver in vitro: increasing the efficacy by perfusion probes]

Percutaneous radiofrequency interstitial thermal ablation is a new method in local tumour therapy. The aim of this study was to define the relations between the variable parameters and local efficacy in vitro and to evaluate optimal parameter combinations for this system. Furthermore, we studied the feasibility of increasing the volume of destroyed tissue using perfusion electrodes.

Thermal lesions were produced with radiofrequency in ex vivo pig livers. In separate experiments the parameters wattage (5-30 watts), exposure time (1-15 minutes) and tip exposure were varied. The resulting areas of tissue necrosis coagulation were measured; in 30 of 90 cases the macroscopic findings were compared to the histological findings.

Lesion size correlated with tip exposure, wattage and procedure duration up to 10 minutes. For a tip exposure of 2 cm (3 cm) the maximal lesion volume was 18.8 cm3 (33.2 cm3) at a wattage of 20 watts (30 watts) and a procedure duration of 10 minutes. The maximal cross- (length-) diameter of these lesions was 3 cm (4 cm) for 2 cm tip exposure and 3.6 cm (4.9 cm) for 3 cm tip exposure.

The parameters wattage, procedure duration and tip exposure affect the size of lesions created with radiofrequency under ex vivo conditions. Perfusion electrodes make it possible to produce larger lesions than described for non-perfused electrodes. The ablation of hepatic neoplasms up to a size of 3 cm seems to be possible with a single electrode.