Surgical Simulation - Soft Tissue Modeling
Motivation: A biomechanical model of soft tissue derived from experimental measurements is critical for developing a reality-based model for minimally invasive surgical training and simulation. In our research, we have been focusing on developing a biomechanical model of the liver with the ultimate goal of using this model for local tool-tissue interaction tasks and providing feedback to the surgeon through a haptic display.
Project Highlights
- Ex vivo experiments on pig liver tissues: In actual deformation of soft-tissue during surgical intervention, the tissue is subject to tension, compression, and shear. Therefore, characterization of soft-tissue in all these three deformation modes is necessary. We have designed and built an experimental setup to carry out soft-tissue tension, compression, and pure shear experiments while capturing in real-time the image of the tissue undergoing deformation. Because in these ex vivo tests, boundary conditions are simple and under relatively precise control, the results can be used directly for the constitutive modeling.
- Using Digital Image Correlation (DIC) technique to measure strain field: In the tension and pure shear tests, the natural texture on the sample surface are excellent full-field marks for imaging. We use digital image correlation (DIC) technique to track these textures and calculate the strain. The accurate full-field strain field results give us more insight about the mechanical behavior of the tissues, which is desirable for the reality based modeling and simulation.
- Constitutive modeling of liver tissue: Based on the experimental result, a new combined logarithmic and Ogden strain energy was proposed and stress-strain relations were derived. This model is adequate to describe the full range of deformation for both compression and tension, and also good for low strain (<35%) deformation of pure shear.
Relevant publications:
- Zhan Gao, Kevin Lister, Jaydev P. Desai, “Constitutive Modeling of Liver Tissue: Experiment and Theory”, Second biennial IEEE/RAS-EMBS International Conference on Biomedical Robotics and Biomechatronics - BioRob, October 2008.