Model-Based Force Control of a Steerable Ablation Catheter with a Custom-Designed Strain Sensor

The increasing popularity of catheter-based ablation therapy in treating cardiac arrhythmia has motivated researchers to seek new techniques to improve the accuracy and efficiency of such procedures. After guiding the catheter through the vessels into the heart chambers, precise positioning of the catheter tip and consistent tool/tissue contact force are the two factors that greatly affect the ablation outcome. Implementing force/position control of the catheter tip will improve the efficacy of cardiac ablation procedures immensely. This paper proposes a model-based force control system to ensure a desired contact force at the distal tip, without directly measuring the force applied at the tip. In this regard, it is studied how the displacement of the proximal handle of a common 7-Fr pull-wire ablation catheter relates to the change of angle at its distal tip. The resulting mapping together with a mapping that relates the forces at the distal tip to the tip shape are used in developing a control system that ensures a desired contact force at the tip. This paper also introduces an optical strain sensor that can be used without modification in the manufacture of present day ablation catheters. This strain sensor completes the feedback loop of the control system through integration with the shape to force model. Performance of the control system is evaluated experimentally and the results suggest that model-based control of steerable catheters is feasible for catheter ablation. The proposed control system can be employed on a conventional ablation catheter following a fairly simple calibration step.