Hepatic bipolar radiofrequency ablation creates coagulation zones close to blood vessels: a finite element study

Radiofrequency (RF) ablation has become an important means of treatment of non-resectable primary and metastatic liver tumours. Recurrence of treated tumours is associated with cancer cell survival next to blood vessels. The paper examines the performance of classical monopolar, and two configurations of bipolar, RF ablation using a LeVeen ten-prong catheter. Finite element method models of monopolar and bipolar configurations were created at 5 mm distance from a vessel of the size of a typical portal vein (10 mm diameter). In one bipolar configuration, the probes were oriented in the same axial direction (asymmetric configuration); in the second bipolar configuration, the two probes were facing each other (symmetric configuration). The distribution of temperature and current density was analysed for three different flow conditions: normal flow, reduced flow due to portal hypertension and high flow. For normal flow, the distance between the formed coagulation zone and the blood vessel was 1.8 mm for monopolar, 1 mm for asymmetric bipolar, and 0.2 mm for symmetric bipolar, configurations. Symmetric bipolar RF ablation creates coagulation zones significantly closer to blood vessels compared with monopolar RF ablation. This may reduce tumour cell survival next to blood vessels and reduce recurrence rates.