Tumor ablation using radiofrequency (RF) energy is clinically used for treatment of various cancer types. During RF ablation, an electrode is inserted into a tumor under imaging-guidance, and the tumor is heated by RF electric current and cancer cells killed above temperatures of ~50 °C. One of the major factors affecting tissue temperature and ablation zone dimensions is tissue perfusion. To examine perfusion effects, we created Finite Element Method computer models of a clinically used RF ablation device, including temperature-dependent electrical and thermal tissue properties. Microvascular perfusion was modeled according to Pennes' Bioheat Equation, and was varied with temperature to include perfusion cessation due to coagulation at high temperatures. Microvascular perfusion rate was varied to represent variations between patients by +/-1 standard deviation based on prior data measured in humans. Macro-vascular perfusion was modeled by including a large vessel (10 mm diameter) in the model geometry, and assigning a convective heat transfer coefficient as a boundary condition at the vessel wall. The vessel resulted in local deviation of the ablation zone around the vessel, and resulted in a region of viable tissue near the vessel wall. Microvascular perfusion affected overall size and geometry of the ablation zone. Ablation zone volume for average microvascular perfusion was 20.1 cm³, and was 16.6 and 25.3 cm³ when perfusion rate was increased or reduced by 1 standard deviation. Both micro- and macrovascular perfusion considerably affect tissue temperature and ablation zone. Patient-specific data on perfusion would allow for more accurate estimates of ablation zone dimensions and improved treatment planning.

Date Published: 23 February 2009
PDF: 11 pages
Proc. SPIE 7181, Energy-based Treatment of Tissue and Assessment V, 71810R (23 February 2009); doi: 10.1117/12.808047

Published in SPIE Proceedings Vol. 7181:
Energy-based Treatment of Tissue and Assessment V
Thomas P. Ryan, Editor(s)