Current projects
Multiresolution nonlinear finite element aprroach to real-time simulation of soft tissue deformation with haptic feedback
Several surgical simulators have been presented with the purpose of improving the teaching and rehearsing of surgical skills simulating key steps of laparoscopic and open operations. Modelling soft tissue deformation with force-feedback remains a major problem to be solved in order to provide a realistic immersion in the virtual environment. One of the most studied methods for simulating soft tissue deformation is the Finite Element Method (FEM). We have developed a new hierarchical approach to FEM that allows for rendering of the complex mechanical and physiological behaviour of human organs in real-time with force feedback. Integration into surgical simulators such as Laparoscopic Cholecystectomy and Appendectomy is possible by using realistic models of the human anatomy involved such as liver, gallbladder and appendix, and concentrating on key surgical tasks such as grasping and cutting. Volumetric tetrahedral meshes have been employed providing information about the inside of the object, thus enabling operations such as cutting. The FEM hierarchy consists of different levels of detail of the underlying object mesh, with a coarse structure for the part of the object that is far away from the area of contact and a more refined one where the contact between the virtual tool and the object is taking place. This approach produces a real time and high quality simulation. Due to the non-linear behaviour of human organs, we have implemented a non-linear model taking into account different physical parameters dependent on time and space. Better realism has been achieved by integrating force-feedback that gives the user the tactile feeling of the human organ and its deformation.
Study of the fidelity and realism of VR based surgical simulators
Laparoscopic virtual reality simulation has been investigated during the last years with several prototypes and commercial products developed. Nevertheless, little work has been done towards understanding the requirements of these simulators and the degree of fidelity they need to be an effective educational tool. As part of this study we will define a taxonomy of different simulation components and capabilities, with six main groups: sensorial fidelity, mechanical fidelity, physiological fidelity, procedural guides, interaction metaphors and didactic resources. This taxonomy will then be applied to study how different commercial simulators make use of the varios components to train a range of skills. This first step is needed in order to identify which components are more important to train different training objectives and the degree of realism required to achieve certain educational objective with a specific task. The second part of our work will consist on the selection of a relevant educational objective in minimally invasive surgery. This will be followed by the design and implementation of a virtual task to achieve the chosen objective. Finally, we will study how the chosen objective is achieved with the different degrees of realism in the virtual task and investigate the relationship between different educational objectives and varying degrees of realism.
