E Mesa, J F Ramirez, P Boulanger and J W Branch (2011). Experimental Characterization of Material Properties to Simulate Needle Indentation Into Soft Tissues. In 6th Canadian Student Conference on Biomedical Computing and Engineering, 5 pages, London, Ontario, Canada. May 2011. Robats Institute.

Surgical needle insertion has an important role in applications such as biopsies, neurosurgery and tumor ablation, and many studies have been carried out to simulate these types of procedures. The realistic simulation of tool-tissue interactions is required for the development of surgical simulators, and accurate biomechanical tissue models are determinant in their effectiveness. Previous works had characterized soft tissue properties; however, it is missing an appropriated validation of the results. In this paper, we used several hyperelastic models to replicate mechanical behavior of a silicone rubber under an indentation test. An uniaxial compression test was performed on the phantom tissue, with mechanical properties similar to brain, to estimate the parameters of the models using an optimization algorithm. The best fitted model is then used to validate the parameters in a FEM simulation of needle indentation comparing with experimental measurements. We found that the second order Reduced Polynomial model showed to be a good agreement for the material behavior (R-squared = 0.9922) and was stable for all strains. The simulation results of needle indentation using that material model gave us an R-squared error of 0:9613 with respect to the experimental values. Finally, we validated the used of an Optical Tracking system as a tool for measuring the position of the needle in real time. We compare those measures with the ones given by the stepper motor and we obtained an R-squared of 0.9999.

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