Thermal model for fast simulation during magnetic resonance imaging guidance of radio frequency tumor ablation.

Thermal ablation of a tumor with radio frequency (rf) energy from a small probe inserted into the solid tumor can be accomplished with minimal invasiveness under guidance with magnetic resonance imaging (MRI). A theoretical study is presented of 3D temperature distribution dynamics in tissue with rf heating to show the feasibility of fast numerical solution for repeated simulations during an ablation procedure. Model simulations are intended to be used during an ablation treatment together with temperature field images obtained by MR to predict the effect of alternative strategies of source heating and placement. A feature of the model is that it incorporates a heat source term that varies with distance from the rf probe to avoid the need for solving electric field equations. The effects of perfusion and internal cooling of the rf probe on the temperature distribution are simulated to show the model flexibility. Using a personal computer (PC), numerical solution of the model equations required 10 s to 2 min depending on the perfusion-temperature relationship. The results show the feasibility of using thermal model simulations in an iterative manner with MR images to help guide thermal ablation procedures in the clinical setting.