Displacement-based Model for Estimation of Contact Force Between RFA Catheter and Atrial Tissue with ex-vivo Validation

The goal of this study was to investigate the validity of a new contact model for sensor-less estimation of the contact force between RFA catheter and atrial tissue. To this end, a new nonlinear displacement-based model was proposed. Also, the model was formulated for forward and inverse problems and two solution schema were proposed. For assessing the model performance, two dynamic ex-vivo indentation tests were performed on a freshly excised porcine atrium, i.e. one with sinusoidal and one with triangular indentations. Results of the first test were used for parameter identification and verification of the model, while the second test was the benchmark for the model validation. Displacement range for both tests was 2±1mm, while the frequencies of indentations were 1, 1.5 and 2Hz for the sinusoidal, and 1.25Hz for the triangular indentation. From the sinusoidal test results, model parameters were identified using a particle-swarm optimization method. Using the optimized parameters, experimental forces were reconstructed. Error analysis revealed that the model was 91.5 % accurate in repeating the results of the sinusoidal test. Also, validation results showed an accuracy of 90.9% in model predictions of the contact force in the triangular test. Furthermore, the model could successfully capture the stress relaxation phenomenon, which is of high prominence in contact force control on atrial tissue. In conclusion, this investigation confirmed that the proposed contact model was valid in prediction of dynamic contact force with atrial tissue. Also, the proposed solution schema was fast-enough to be used in real-time surgical applications.