This paper discusses the application of 3D solid volumetric Finite Element models to surgery simulation. In particular it introduces three new ideas for solving the problem of achieving real-time performance for these models. The simulation system we have developed is described and we demonstrate real-time deformation using the methods developed in the paper.

Modeling the deformation of human organs for surgery simulation systems has turned out to be quite a challenge. Not only is very little known about the physical properties of general human tissue but in addition, most conventional modeling techniques are not applicable because of the timing requirements of simulation systems. To produce a video-like visualization of a deforming organ, the deformation must be determined at rates of 10-20 times/s. In the fields of elasticity and related modeling paradigms, the main interest has been the development of accurate mathematical models. The speed of these models has been a secondary interest. But for surgery simulation systems, the priorities are reversed. The main interest is the speed and robustness of the models, and accuracy is of less concern. Recent years have seen the development of different practical modeling techniques that take into account the reversed priorities and can be used in practice for real-time modeling of deformable organs. This paper discusses some of these new techniques in the reference frame of finite element models. In particular, it builds on the recent work by this author on fast finite element models and discusses the advantages and disadvantages of these models in comparison to previous models.

This paper oers a new fast algorithm for non-rigid Viscous Fluid Registration of medical images that is at least an order of magnitude faster than the previous method by Christensen et al. [4]. The core algorithm in the uid registration method is based on a linear elastic deformation of the velocity eld of the uid. Using the linearity of this deformation we derive a convolution lter which we use in a scalespace framework. We also demonstrate that the 'demon'-based registration method of Thirion [13] can be seen as an approximation to the uid registration method and point to possible problems.

Abstract. This paper describes our recent work on real-time Surgery Simulation using Fast Finite Element models of linear elasticity [1]. In addition we discuss various improvements in terms of speed and realism.