Modeling Human-body Soft Tissues for Surgical Applications

1 Project Summary The goal of this research is to develop a general-purpose computational scheme for representing the geometry and physics of human-body soft-tissue structures and simulating their displacements and deformations in real-time when external forces are applied by surgical instruments. The ability to realistically model soft tissues on a computer has the potential to radically change the ways surgery is currently taught and practiced. Virtual environments simulating deformable tissues will allow medical students to extensively practice delicate operations and connrmed surgeons to retrain themselves and maintain their skills for infrequent operations. Soft-tissue simulations will become essential to plan and rehearse surgical operations. The on-line availability of the models will make it possible to give intra-operative assistance to the surgeons. It will enable the introduction of roboticized instruments that will perform operations, either automatically or in interaction with surgeons. Research on soft-tissue modeling will directly beneet domains such as robotics, where the modeling of environments containing deformable objects is increasingly important; computer vision, where the task of tracking objects undergoing continuous deformations is central to understanding image sequences; and computer graphics, especially for the animation of virtual characters. Previous research on soft-tissue modeling provides foundations on which the proposed research is based. In particular, as several researchers have suggested before, tissue structures will be modeled by meshes of point masses connected by elastic links, the so-called mass-spring elastic meshes. The research program includes both the theoretical development of a computational scheme based on the elastic mesh concept and the implementation/experimentation/evaluation of this scheme within a state-of-the-art virtual reality environment. The experiments will be conducted in the context of two applications: micro-anastomosis (the suturing of small blood vessels) and craniofacial surgery. This experimental eeort will be critical to the validation of the results. The unique features that this research expects to achieve are the following:-Modeling of complex tissue structures. Most existing models can only represent a tissue with uniform and isotropic elastic properties. Techniques will be developed to speciically model multiple adjacent soft tissues and their attachment to bones.-Realistic modeling of the mechanical response of individual tissues. To simplify computations a number of models assume linear elastic models. But human-body tissues are nonlinear and exhibit some hysteresis. These properties will be captured in the new modeling scheme.-Modeling changes in tissue topology. External forces may cause topological changes in tissue structures, such as tissue cutting or tearing and formation of new contacts. …