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To avoid biopsies, doctors use non invasive medical techniques such as the computed tomography. Even that, the detection of the liver remains a big challenge because of the gray level and shape variations which depend on patients and acquisition modalites. In this work, we propose to create a 3D liver model in the training phase of 3D active shape model algorithm. This training model will be deformed according to any given 3D data for liver segmentation. The contribution of our work is the use of the Non-rigid registration with a B-spline registration on the training phase. We tested our method on an open access database (”3DIRCADb”) and on our database obtained from the radiology department of the National Oncology Institute of Tunis. Both data-sets showed the reliability of the method with an accuracy equal to 69.98% and 71.18% respectively for our database and ”3D-IRCADb”.

The paper focuses on the segmentation of magnetic resonance imaging (MRI) slices and 3D modelling of the temporomandibular joint disc in order to help physicians diagnose patients with dysfunction of the temporomandibular joint (TMJ). The TMJ is one of the most complex joints in the human body. The most common joint dysfunction is due to the disc. The disc is a soft tissue, which in principle cannot be diagnosed by the CT method. Therefore, a 3D model is made from the MRI slices, which can image soft tissues. For the segmentation of the disc in individual slices a new method is developed based on spatial distribution and anatomical TMJ structure with automatic thresholding. The thresholding is controlled by a genetic algorithm. The 3D model is realized using the marching cube method.

Tato práce se zabývá extrakcí iso-ploch ze skalárních datových množin obsahujících časově proměnnou síť. Taková data pocházejí například z numerických simulací proudění kapalin. Nedostatek zobrazovacíhc metod umožňujících práci s časově proměnnými sítěmi způsobil, že v existujících aplikacích bylo s každým časovým krokem zacházeno jako se samostatnou datovou množinou. Tato práce popisuje existující metody extrakce iso-ploch z časových proměnných skalárních dat se statickou sítí a poskytuje úvod do problematiky časově proměnných sítí. Rovněž je popsán úvodní výzkum v této oblasti a náš koncep dopočítávání konektivy mezi vrcholy sítí v sousedních časových hladinách. This work is focused on the iso-surfaces extraction from sca lar data sets with dynamic simulation mesh. Such data sets usually originate from Computational Fluid Dynamic (CFD) simulations, where moving boundaries of a simulation domain force a simulation mesh to change itself with each discrete time step. Up to now, each time step has been treated as a stand-alone entit y, because of lack of the methods capturing spatial and temporal coherency in data sets of such nature. The work covers the existing techniques for iso-surfaces extraction from time- varying scalar data sets with static mesh and provides an int roduction to the problematic of dynamic meshes and an overview of the initial research done. Finally our concept of handling data sets with time-varying meshes is described.

At present, many devices produce the volume data as their output. The well-known data acquisition tools are e.g. MRI, CT or PET scanners, which are used mainly in the medical field. The volume data can represent density, velocity, humidity etc. in the form of structured or unstructured grid. Scientists need to explore such data to study their inner properties and relations and to make decisions. The volume data visualization is a strong tool for such explorations. There are many methods for the volume data visualization. The volume rendering and the surface rendering approaches are governing two main visualization branches in this field. The volume rendering methods visualize the data as a whole. In the apart of that, the surface rendering methods are trying to find surfaces in the volume data and visualize them. The group of methods for the surface rendering contains also methods for the iso-surface extraction from the volume data. This thesis provides a reasonable overview of the main techniques that serve for the volume data acquisition as well as the state of the art in the field of the iso-surface extraction methods. The important methods are sensibly described together with appropriate references given and their difficulties, pros and cons are discussed as well. The offered work also concerns a research that was recently done and the outline of possible directions in which the future research can head towards.

Colloque avec actes et comité de lecture. internationale.; International audience; We present the Circular Incident Edge Lists (CIEL), a new data structure and a high-performance algorithm for generating a series of iso-surfaces in a highly unstructured grid. Slicing-based volume rendering is also considered. The CIEL data structure represents all the combinatorial information of the grid, making it possible to optimize the classical propagation from local minima paradigm. The usual geometric structures are replaced by a more efficient combinatorial structure. An active edges list is maintained, and iteratively propagated from an iso-surface to the next one in a very efficient way. The intersected cells incident to each active edge are retrieved, and the intersection polygons are generated by circulating around their facets. This latter feature enables arbitrary irregular cells to be treated, such as those encountered in certain computational fluid dynamics (CFD) simulations. Since the CIEL data structure solely depends on the connections between the cells, it is possible to take into account dynamic changes in the geometry of the mesh and in property values, which only requires the sorted extrema list to be updated. Experiments have shown that our approach is significantly faster than classical methods. The major drawback of our method is its memory consumption, higher than most classical methods. However, experimental results show that it stays within a practical range.

We show that contour trees can be computed in all dimensions by a simple algorithm that merges two trees. Our algorithm extends, simplifies, and improves work of S. P. Tarasov and M. N. Vyalyi [Construction of contour trees in 3D in O(nlogn) steps. In Proc. 14th Annu. ACM Sympos. on Comput. Geom., 68-75 (1998)] and of M. van Kreveld, R. van Oostrum, C. Bajaj, V. Pascucci and D. Schikore [Contour trees and small seed sets for isosurface traversal. In Proc. 13th Annu, ACM Sympos. Comput. Geom., 212-220 (1997)].

In this paper the GPU implementation of a real-time isosurface volume-rendering system is described in detail, which aims at autostereoscopic displays. Since autostereoscopic displays provide images for many views, and thus require different camera settings in each pixel, and even in the three color channels of a pixel, naive rendering approaches would slow down the rendering process by a factor of the number of views of the display. To maintain interactive rendering, our approach is image centric, that is, we independently set the eye position for each pixel and implement iso-surface ray-casting in the pixel shader of the GPU. To handle the different camera settings for different color channels, geometric and color computation processes are decomposed into multiple rendering passes. This solution allows rendering rates that are independent of the number of main views of the autostereoscopic display, i.e. we cannot observe speed degradation when real 3D images are generated.

The Centered Cubic Lattice method is used for an iso-surface extraction. This paper focuses on its comparison with other fundamental methods (Marching Cubes, Marching Tetrahedra) that are also used to extract an iso-surface from regular volume data. Iso-surfaces that are generated using above mentioned methods and mathematical data are compared due to area and volume approximation. The Hausdorff and RMS distances are also utilized for comparisons. Also all possible cell tessellations into 6 tetrahedra are discussed and analyzed. We think that such a comparison can be helpful to decide which of tested methods should be chosen when we have concrete demands concerning the iso-surface. Also newly developed methods can be compared with existing ones in the similar way.