A monotone multigrid solver for two body contact problems in biomechanics

The purpose of the paper is to apply monotone multigrid methods to static and dynamic biomechanical contact problems. In space, a finite element method involving a mortar discretization of the contact conditions is used. In time, a new contact-stabilized Newmark scheme is presented. Numerical experiments for a two body Hertzian contact problem and a biomechanical application are reported

Computer annual

xii+412hlm.;28c

Volume Rendering Mathematical Models and Algorithmic Aspects

In this paper various algorithms for rendering gaseous phenomena are reviewed. In computer graphics such algorithms are used to model natural scenes containing clouds, fog, ames and so on. On the other hand displaying three dimensional scalar datasets as cloudy objects has become an important technique in scienti c visualization. Our emphasis is on this latter subject of so-called direct volume rendering. All algorithms will be discussed within the framework of linear transport theory. The equation of transfer is derived. This equation is suitable to describe the radiation eld in a participating medium where absorption, emission, and scattering of light can occur. Almost all volume rendering algorithms can be shown to solve special cases of the equation of transfer. Related problems like the mapping from data values to model parameters or possible parallelization strategies will be discussed as well.

Visualization and 3D-Interaction for Hyperthermia Treatment Planning

In regional hyperthermia extensive numerical simulations are required for optimizing individual cancer therapy treatments. To take full advantage of such simulations a therapy planning system is needed. In this paper we discuss a new hyperthermia planning system, focussing on its visualization and 3D-interaction functionality. Our software, called HyperPlan, assists the whole treatment planning process with state-of-the-art numerics and visual controlling techniques. Its flexible design allows it to be used in both hyperthermia research and clinical practice. Introduction Planning systems are well established in conventional radiotherapy. They have also proved to be essential for hyperthermia treatment planning. In this paper we deal with regional hyperthermia that employs radiofrequency waves to heat up the tumor region non-invasively. The goal is to locally achieve temperatures higher than 41C ffi without affecting healthy tissue. Numerical simulations can help to optimize an indi..

Fast LIC with Piecewise Polynomial Filter Kernels

. Line integral convolution (LIC) has become a well-known and popular method for visualizing vector fields. The method works by convolving a random input texture along the integral curves of the vector field. In order to accelerate image synthesis significantly, an efficient algorithm has been proposed that utilizes pixel coherence in field line direction. This algorithm, called "fast LIC", originally was restricted to simple box-type filter kernels. Here we describe a generalization of fast LIC for piecewise polynomial filter kernels. Expanding the filter kernels in terms of truncated power functions allows us to exploit a certain convolution theorem. The convolution integral is expressed as a linear combination of repeated integrals (or repeated sums in the discrete case). Compared to the original algorithm the additional expense for using higher order filter kernels, e.g. of B-spline type, is very low. Such filter kernels produce smoother, less noisier results than a box filter. Th..

Weighted Labels for 3D Image Segmentation

Segmentation tools in medical imaging are either based on editing geometric curves or on the assignment of region labels to image voxels. While the first approach is well suited to describe smooth contours at subvoxel accuracy, the second approach is conceptually more simple and guarantees a unique classification of image areas. However, contours extracted from labeled images typically exhibit strong staircase artifacts and are not well suited to represent smooth tissue boundaries. In this paper we describe how this drawback can be circumvented by supplementing region labels with additional weights. We integrated our approach into an interactive segmentation system providing a well-defined set of manual and semi-automatic editing tools. All tools update both region labels as well as the corresponding weights simultaneously, thus allowing one to define segmentation results at high resolution. We applied our techniques to generate 3D polygonal models of anatomical structures