Ex situ quantification of the cooling effect of liver vessels on radiofrequency ablation.

PURPOSE: To quantify the cooling effect of hepatic vessels on liver radiofrequency (RF) ablation ex situ. METHODS: Bipolar RF applicators (diameter = 1.8 mm, electrode length = 30 mm) were inserted parallel to perfused glass tubes (diameter = 5 and 10 mm; flow = 250-1,800 ml/min) at distances of 5 and 10 mm in porcine livers ex vivo. RF ablation was performed at 30 W/15 kJ. RF lesions were analyzed by measuring the maximum (r (max)) and minimum radius (r (min)) and the lesion area. RESULTS: Glass tubes without flow showed no influence on RF lesions, whereas perfused glass tubes had a significant cooling effect on lesions. r (min) was reduced to 50% at 5 mm applicator-to-vessel distance and the lesion area was reduced from 407 to 321 mm(2) (p < 0.001). There was no significant influence of glass tube diameter or flow volume on any of the analyzed parameters. CONCLUSIONS: Cooling effects of intrahepatic vessels could be simulated in an ex situ model. Cooling effects should be taken into account in RF ablation within 10 mm distance to major liver vessels regardless of blood flow volume or vessel diameter. Surgical RF ablation with temporary blood flow occlusion should be considered in such constellations.