Biomedical subjects

Martin Rumpf

Publications and source records attributed to Martin Rumpf.

5 recordsLinked to original sources

PubMed2005

An adaptive level set method for interactive segmentation of intracranial tumors.

BACKGROUND: Meaningful segmentation of intracranial lesions can be of assistance for planning open navigated microneurosurgical procedures, as well as for radiotherapy. Meaningful segmentation, however, may be hampered by lack of computational power. The respective segmentation method should be based on state-of-the-art mathematical tools, and it should be suitable for real applications. METHODS: A three-dimensional computational method for interactive segmentation of intracranial tumors is presented. It is based on a front propagation method, in which the evolving front gradually approaches the boundary of a given segment. It generates and remembers the entire evolution of the interface. The segment boundary is chosen from a one parameter family. User interaction is realized by selecting "seed points" inside the object/lesion. External evolution velocity regulates the segmentation process, while approaching the boundary. Adaptively resolved grids ensure computational efficiency for larger segments. The resolution is steered by an image-based indicator, which allows coarse representation of the solution in low-frequency regions, but high resolution along suspected edges of the image. RESULTS: Model-based segmentation was performed on the imaging data of n = 12 patients and the results compared with manual segmentation of the same tumors. The method allowed for basic segmentation in all tumors <3 minutes. This increased 2-4 fold in four irregular tumors, where discrepancies existed in comparison with manually performed segmentation. DISCUSSION: The implicit formulations of this method establish methodical and topological flexibility in three dimensions. It is thus suitable for the segmentation of objects with non-sharp boundaries such as intracranial tumors.

Algorithms↗

PubMed2004

A new software for prediction of femoral neck fractures.

Femoral neck fractures are an important clinical, social and economic problem. Even if many different attempts have been carried out to improve the accuracy predicting the fracture risk, it was demonstrated in retrospective studies that the standard clinical protocol achieves an accuracy of about 65%. A new procedure was developed including for the prediction not only bone mineral density but also geometric and femoral strength information and achieving an accuracy of about 80% in a previous retrospective study. Aim of the present work was to re-engineer research-based procedures and develop a real-time software for the prediction of the risk for femoral fracture. The result was efficient, repeatable and easy to use software for the evaluation of the femoral neck fracture risk to be inserted in the daily clinical practice providing a useful tool for the improvement of fracture prediction.

Bone Density↗

PubMed2004

Processing textured surfaces via anisotropic geometric diffusion.

A multiscale method in surface processing is presented which carries over image processing methodology based on nonlinear diffusion equations to the fairing of noisy, textured, parametric surfaces. The aim is to smooth noisy, triangulated surfaces and accompanying noisy textures-as they are delivered by new scanning technology-while enhancing geometric and texture features. For an initial textured surface a fairing method is described which simultaneously processes the texture and the surface. Considering an appropriate coupling of the two smoothing processes one can take advantage of the frequently present strong correlation between edge features in the texture and on the surface edges. The method is based on an anisotropic curvature evolution of the surface itself and an anisotropic diffusion on the processed surface applied to the texture. Here, the involved diffusion tensors depends on a regularized shape operator of the evolving surface and on regularized texture gradients. A spatial finite element discretization on arbitrary unstructured triangular grids and a semi-implicit finite difference discretization in time are the building blocks of the corresponding numerical algorithm. A normal projection is applied to the discrete propagation velocity to avoid tangential drifting in the surface evolution. Different applications underline the efficiency and flexibility of the presented surface processing tool.

Algorithms↗

PubMed1997

Exploring invariant sets and invariant measures.

We propose a method to explore invariant measures of dynamical systems. The method is based on numerical tools which directly compute invariant sets using a subdivision technique, and invariant measures by a discretization of the Frobenius-Perron operator. Appropriate visualization tools help to analyze the numerical results and to understand important aspects of the underlying dynamics. This will be illustrated for examples provided by the Lorenz system. (c) 1997 American Institute of Physics.

Journal Article↗

PubMedDate not supplied

Robust feature detection and local classification for surfaces based on moment analysis.

The stable local classification of discrete surfaces with respect to features such as edges and corners or concave and convex regions, respectively, is as quite difficult as well as indispensable for many surface processing applications. Usually, the feature detection is done via a local curvature analysis. If concerned with large triangular and irregular grids, e.g., generated via a marching cube algorithm, the detectors are tedious to treat and a robust classification is hard to achieve. Here, a local classification method on surfaces is presented which avoids the evaluation of discretized curvature quantities. Moreover, it provides an indicator for smoothness of a given discrete surface and comes together with a built-in multiscale. The proposed classification tool is based on local zero and first moments on the discrete surface. The corresponding integral quantities are stable to compute and they give less noisy results compared to discrete curvature quantities. The stencil width for the integration of the moments turns out to be the scale parameter. Prospective surface processing applications are the segmentation on surfaces, surface comparison, and matching and surface modeling. Here, a method for feature preserving fairing of surfaces is discussed to underline the applicability of the presented approach.

Algorithms↗