Summary: Background : CT colonography was found to be sensitive and specific for detection of colonic polyps and colorectal cancer (CRC). Depending on the software used, CT colonography requires a certain amount of op...
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Summary: Background : CT colonography was found to be sensitive and specific for detection of colonic polyps and colorectal cancer (CRC). Depending on the software used, CT colonography requires a certain amount of operator interaction, which limits it's widespread usage. The goal of this papers is to present two novel automated techniques for displaying CT colonography: virtual dissection and automated colonic polyp detection. Methods : Virtual dissection refers to a technique where the entire colon is virtually stretched and flattened thus simulating the view on the pathologist's table.
Colonic folds show a ‘global outward bulging of the contour’, whereas colonic polyps exhibit the inverse (‘local inward bulging’). This feature is used to map areas of ‘local inward bulging’ with colours on 3D reconstructions. A cadaveric phantom with 13 artificially inserted polyps was used for validation of both techniques. Results : On virtual dissection all 13 inserted polyps could be identified. They appeared either as bumps or as local broadening of colonic folds. In addition, the automated colonic polyp detection algorithm was able to tag all polyps. Only 10 min of operator interaction were necessary for both techniques. Conclusions : Virtual dissection overcomes the shortcomings of CT colonography, and automated colonic polyp detection establishes a roadmap of the polyps. Zusammenfassung: Grundlagen : Die CT-Kolographie ermöglicht die Detektion von Kolonpolypen und kolorektalen Karzinomen. In Abhängigkeit von der verwendeten Software ist ein unterschiedlich großer Zeitaufwand notwendig, der die breite klinische Anwendung limitiert. Zweck der vorliegenden Arbeit ist die Präsentation zweier neuer Darstellungsverfahren für die CT-Kolographie: virtuelle Dissektion und automatische Detektion von Dickdarmpolypen. Methodik : Die virtuelle Dissektion ist eine Technik, bei der das gesamte Kolon aus den Spiral-CT-Daten extrahiert, artifiziell gestreckt, in seiner Längsrichtung aufge
This paper presents a set of algorithms to efficiently support geometric constraint satisfaction during engineering design. Based upon an incremental graph construction approach, these algorithms satisfy each new inse...
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This paper presents a set of algorithms to efficiently support geometric constraint satisfaction during engineering design. Based upon an incremental graph construction approach, these algorithms satisfy each new inserted constraint by exploiting the degrees of freedom of the involved geometric entities. The objective is to avoid satisfying the entire constraint set from scratch due to a new constraint insertion. A prototype system has been developed and is presented to demonstrate the flexibility gained by the proposed incremental algorithms.
The paper presents a skeleton-based approach for robust detection of perceptually salient shape features. Given a shape approximated by a polygonal surface, its skeleton is extracted using a three-dimensional Voronoi ...
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The paper presents a skeleton-based approach for robust detection of perceptually salient shape features. Given a shape approximated by a polygonal surface, its skeleton is extracted using a three-dimensional Voronoi diagram technique proposed recently by Amenta et al. Shape creases, ridges and ravines, are detected as curves corresponding to skeletal edges. Salient shape regions are extracted via skeleton decomposition into patches. The approach explores the singularity theory for ridge and ravine detection, combines several filtering methods for skeleton denoising and for selecting perceptually important ridges and ravines, and uses a topological analysis of the skeleton for detection of salient shape regions.
Interactive visualization of large digital elevation models is of continuing interest in scientific visualization, GIS, and virtual reality applications. Taking advantage of the regular structure of grid digital eleva...
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Interactive visualization of large digital elevation models is of continuing interest in scientific visualization, GIS, and virtual reality applications. Taking advantage of the regular structure of grid digital elevation models, efficient hierarchical multiresolution triangulation and adaptive level-of-detail (LOD) rendering algorithms have been developed for interactive terrain visualization. Despite the higher triangle count, these approaches generally outperform mesh simplification methods that produce irregular triangulated network (TIN) based LOD representations. In this project we combine the advantage of a TIN based mesh simplification preprocess with high-performance quadtree based LOD triangulation and rendering at run-time. This approach, called QuadTIN, generates an efficient quadtree triangulation hierarchy over any irregular point set that may originate from irregular terrain sampling or from reducing oversampling in high-resolution grid digital elevation models.
The new concept of parametrized bounding volumes for parametric objects is proposed to replace the common compact bounding volumes like axis aligned bounding boxes and parallelepipeds. Linear Interval Estimations (LIE...
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The new concept of parametrized bounding volumes for parametric objects is proposed to replace the common compact bounding volumes like axis aligned bounding boxes and parallelepipeds. Linear Interval Estimations (LIEs) are developed as a realization of the discussed ideas. Two reliable methods for the computation of LIEs are introduced based on a new understanding of the use of affine arithmetics and a special application of Taylor Models. The particular structure of LIEs allows an effective intersection test of LIEs with rays, boxes and other LIEs. The test gives besides of a possible location of the intersection in object space information about affected parts in the parameter spaces of the enclosed objects. A subdivision algorithm for the intersection of two parametric surface patches with remarkable experimental results is presented as a possible application.
We propose a framework for a complex visualization environment suitable for archaelogical applications. Given 2D and 3D data derived from appropriate acquisition processes, the scene is organized in a structure that c...
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ISBN:
(纸本)1581134479
We propose a framework for a complex visualization environment suitable for archaelogical applications. Given 2D and 3D data derived from appropriate acquisition processes, the scene is organized in a structure that can easily be incorporated into a database. Special care is taken on attributes such as time and likelihood of scientific hypothesises which are important for a correct interpretation of the excavation site. After a preprocessing step, the database content can directly be used to visualize the scene in a standalone virtual reality installation in a museum as well as on the internet.
Current feature modelling systems suffer from a number of shortcomings. One is that the meaning of features is often not adequately maintained during modelling, which implies that modelling is in essence only geometri...
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In current feature modeling systems, all dimensions in a model have to be fully specified by the user. It is desirable that systems become more flexible in this respect, i.e. that non-critical dimensions in a model ca...
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In current feature modeling systems, all dimensions in a model have to be fully specified by the user. It is desirable that systems become more flexible in this respect, i.e. that non-critical dimensions in a model can be declared as variant, and that the model can be automatically adjusted when this is appropriate. A method and an implementation to realize this will be described. The underlying feature model definition and validation approach will be introduced. Validation is done by a collection of constraint solvers. An overview of invalid situations in which automatic model adjustment can be applied will be given. The constraint solving scheme and, in particular, the automatic model adjustment strategies for different types of constraints will be elaborated. Applications in the areas of design by features, creating a member from a family of products, and feature conversion will be given. These will illustrate that automatic feature model adjustment is a very useful concept.
In current modeling systems, all dimensions in a model have to be fully specified by the user. It is desirable that systems become more flexible in this respect, i.e. that non-critical dimensions in a model can be dec...
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Behavioral modelling encompasses a number of processing requirements. These include the processing of any mental attributes, the perceived environment and the actions to be performed. These increase the load of any pr...
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