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Cutting in deformable objects

By Han-Wen Nienhuys.


Flight simulators, such as the one on the picture, are used today to train pilots. This has many advantages, as it is much cheaper than a real plane and much safer when anything goes wrong. (Picture from NASA Glenn Research center, Controls and Dynamics Technology Branch)

Like pilots, surgeons have a great responsibility, and training surgeons is expensive, and can be dangerous or difficult. For example, minimally invasive procedures are difficult to learn: here, surgical instruments are introduced into the body through small apertures. There is little room for hand-eye coordination, and also little tactile feedback. It is difficult to learn how to perform such operations.

The aim of surgery simulation is to provide surgeons with virtual patients and surgical tools: tools and patients that respond realistically enough to be instructive.

Simulating surgery on-line is a challenging multidisciplinary problem: it brings together advanced software, special hardware, medicine and mathematics. The mechanics of living tissue are very complex, much more than structural materials such as steel or concrete. The amount of CPU time available is limited because of the interactive nature of the application. When a surgeon pushes virtual tissue, it should respond directly. To top that, handling the required 3D meshes is a hard task. All-in-all this a interesting problem, where real world applications, practical engineering and theoretical science meet.

(Picture from INRIA Projet Epidaure)

My research

To make such systems reality, one needs a lot of engineering background and have access to medical doctors, dedicated programmers and special purpose hardware. Our CS department is better known for its theoretical papers on computational geometry, so me doing this research here is a slightly paradoxical situation.

My way out of this paradox is to focus on "fundamental" questions for interactive surgery simulation systems. Note that fundamental is in quotes on purpose. Against the background of the involved disciplines---FEM modeling, mesh generation, nonlinear optimization and continuum mechanics -- the questions and problems to be addressed are mundane. Nevertheless, finding the simple solutions among all the advanced research in these rich fields, and integrating them into one coherent big answer was much harder than I imagined.

The basic premise for taking a fundamental stance, is that surgery involves the combination of a deforming object, and changes to that deforming object, in other words ``cutting in deformable objects.'' This means that the following ideas must be combined:



The results of my search for the big answer will hopefully be in my PhD. thesis, but some parts of it have been already been documented. A BibTeX bibliography file is available here.


Read these additional notes first.


This research is carried out at the Center for Geometry, Imaging and Virtual Environments of the Institute for information and computing sciences under auspices of the Dutch research school ASCI. Frank van der Stappen is the daily supervisor, Mark Overmars is the executive supervisor.

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