Modeling bimodal vessel effects on radio and microwave frequency ablation zones.

A bench liver model is presented that separates the thermal and electrical effects of large blood vessels within radio and microwave frequency ablation boundaries. The model includes a cylindrical tissue environment with a 5 mm vessel placed parallel to and 15 mm way from either a Covidien Energy-based Devices Evident MW Ablation Percutaneous Antenna or a CoolTip RF Ablation Single Electrode Kit. An array of fiber optic thermal probes is used to monitor radial temperature profile on the vessel and non-vessel sides of the ablation zone. Circulating blood exhibits higher electrical conductivity than surrounding liver tissue and provides a significant means for transport of thermal energy. Data from the thermal probes indicate key performance differentiators between MW and RF ablation modalities when they are used next to large blood vessels clarifying the difference between thermal and electrical energy sink. The results suggest RFA is susceptible to both the thermal and electrical energy sink effects of large vasculature while MWA is only susceptible to thermal sink. Ablation zone boundaries were distorted on both the vessel and non-vessel sides with RFA whereas with MWA only the vessel side is affected.