Automatic control of finite element models for temperature-controlled radiofrequency ablation.
BACKGROUND
The finite element method (FEM) has been used to simulate cardiac and hepatic radiofrequency (RF) ablation. The FEM allows modeling of complex geometries that cannot be solved by analytical methods or finite difference models. In both hepatic and cardiac RF ablation a common control mode is temperature-controlled mode. Commercial FEM packages don't support automating temperature control. Most researchers manually control the applied power by trial and error to keep the tip temperature of the electrodes constant.


METHODS
We implemented a PI controller in a control program written in C++. The program checks the tip temperature after each step and controls the applied voltage to keep temperature constant. We created a closed loop system consisting of a FEM model and the software controlling the applied voltage. The control parameters for the controller were optimized using a closed loop system simulation.


RESULTS
We present results of a temperature controlled 3-D FEM model of a RITA model 30 electrode. The control software effectively controlled applied voltage in the FEM model to obtain, and keep electrodes at target temperature of 100 degrees C. The closed loop system simulation output closely correlated with the FEM model, and allowed us to optimize control parameters.


CONCLUSIONS
The closed loop control of the FEM model allowed us to implement temperature controlled RF ablation with minimal user input.
Haemmerich
Dieter
D
Division of Pediatric Cardiology, Medical University of South Carolina, 165 Ashley Ave,, Charleston, SC 29425, USA. haemmer@musc.edu
Webster
John G
JG
D000465:Algorithms; D000818:Animals; D001185:Artificial Intelligence; D001831:Body Temperature; D006348:Cardiac Surgical Procedures / Q000379:methods*; D017115:Catheter Ablation / Q000379:methods*; D003198:Computer Simulation; D005246:Feedback; D020342:Finite Element Analysis; D006321:Heart / Q000503:physiopathology*; D006801:Humans; D008955:Models, Cardiovascular; D025321:Surgery, Computer-Assisted / Q000379:methods*; D013696:Temperature