Numerical and experimental characterization of radiofrequency ablation in perfused kidneys

We develop a three-dimensional finite element model in order to predict the resulting temperature distribution of a radiofrequency ablation (RFA) treatment in human kidneys. Here, a strong cooling effect results from a high degree of blood perfusion, which is modeled via two different approaches. The influence of big blood vessels for treatments close to renal hilus is modeled by including a cylindrical cooling tube based on the renal artery (or vein) in the kidney model. The influence of the perfusion of small arterioles and capillaries is represented by Pennes' approach in the bioheat equation. The experimental validation is performed by an in vivo RFA treatment on porcine kidney. Prior to the in vivo measurements several ex vivo experiments on fresh kidneys are carried out as a plausibility check for the model. During the treatments temperature profiles are measured using thermocouples which are radially arranged around the RFA applicator trocar. The evaluated data for each sensor show a deviation between 0.01 and 12 % from the simulation results. The approach serves for the design of a preplanning tool for RFA treatment in the future.