Reconstruction of High Resolution 3D Objects from Incomplete Images and 3D Information

To this day, digital object reconstruction is a quite complex area that requires many techniques and novel approaches, in which high-resolution 3D objects present one of the biggest challenges. There are mainly two different methods that can be used to reconstruct high resolution objects and images: passive methods and active methods. This methods depend on the type of information available as input for modeling 3D objects. The passive methods use information contained in the images and the active methods make use of controlled light sources, such as lasers. The reconstruction of 3D objects is quite complex and there is no unique solution- The use of specific methodologies for the reconstruction of certain objects it’s also very common, such as human faces, molecular structures, etc. This paper proposes a novel hybrid methodology, composed by 10 phases that combine active and passive methods, using images and a laser in order to supplement the missing information and obtain better results in the 3D object reconstruction. Finally, the proposed methodology proved its efficiency in two complex topological complex objects

Reconstruction 3D des artères coronaires à partir d'images angiographiques pour la visualisation en ligne des anévrismes

RESUME La maladie de Kawasaki est une pathologie pediatrique provoquant un dereglement immunitaire. Elle entra^ne une in ammation des vaisseaux sanguins de moyen et grand calibres. Chez environ 30% des patients non traites apparaissent une in ammation des arteres coronaires, qui se manifeste par l'apparition d'anevrismes et peut mener, par la suite, a un deces par infarctus du myocarde. Ces anevrismes sont diagnostiques par un examen angiographique en injectant dans les arteres du patient un produit de contraste reactif aux rayons X. Les anevrismes sont alors observables sur les dierentes sequences d'images 2D acquises a dierents angles de vue a l'aide d'un C-arm biplan. Ces images permettent une evaluation qualitative, mais ne sont pas susantes pour pouvoir attester correctement de la geometrie 3D, parfois complexe, des anevrismes. Ceci oblige les medecins a multiplier le nombre de vues angiographiques, ce qui entra^ne sur-irradiation du patient aux rayons X. Une solution que nous proposons dans ce projet est d'eectuer une reconstruction 3D des arteres coronaires a l'aide des images angiographiques. L'objectif de cet outil est d'^etre rapide et automatique an de pouvoir ^etre utilise dans le cadre d'un examen angiographique. L'acquisition d'une nouvelle image ne se fera que si la reconstruction actuelle est insusante pour le medecin et necessite plus d'informations, permettant ainsi de rationaliser le nombre de vues au minimum necessaire. Les algorithmes de stereoscopie, couramment utilises pour la reconstruction 3D des arteres coronaires, ne permettent pas une reconstruction d'un volume en simpliant la plupart du temps l'artere a sa ligne centrale et rayons. De plus, le temps de mise en correspondance entre les images ne permet pas une utilisation iterative au cours de l'examen angiographique. An d'obtenir une reconstruction 3D volumique des arteres coronaires, nous avons choisi de nous pencher sur la technique de Forme a partir de la silhouette. Cette methode permet a partir de silhouettes d'un objet placees dans les dierentes vues de reconstruire cet objet volumiquement. Cette technique presente l'avantage de ne pas ^etre limitee dans le nombre de vues pouvant ^etre utilise et permet d'obtenir la forme de l'objet, ce qui se pr^ete tres bien a notre desir de visualiser la geometrie 3D de l'anevrisme. Nous appliquons donc dans ce memoire cette methode a des silhouettes d'arteres coronaires, obtenues apres segmentation de ces m^emes arteres. La reconstruction par voxels de Forme a partir de la silhouette presente l'avantage d'^etre rapide et automatique (pas de mise en correspondance des images a eectuer). Ainsi, la reconstruction par voxels consiste a tester chaque voxel d'une grille 3D avec la condition suivante : si la projection dans les plans detecteurs du centre du voxel appartient a l'interieur d'une silhouette pour chaque vue alors ce voxel appartient a la reconstruction. Dans un premier temps, nous testons la methode Forme a partir de la----------ABSTRACT Kawasaki disease is an immune dysfunction that typically aects children under the age of ve and causes in ammation of large and medium sized vessels. Kawasaki disease may cause the in ammation of coronary arteries that lead to aneurysms and heart attacks. Aneurysms can be observed by an angiographic examination. A contrast agent is injected into the patient's arteries through a catheter and serves to accentuate the arteries when radiographs are taken. Several image sequences of the arteries from dierent viewpoints are taken by means of a biplanar C-arm. These images allow a qualitative evaluation but, due to the high degree of overlapping structures that occurs in the 2D X-ray images, an aneurysm's often complex 3D geometry cannot be usually assessed correctly. As a result, the clinician must take several image series from dierent viewpoints, which leads to patient over-irradiation when unnecessary views are acquired. The solution proposed in this work is to create a 3D reconstruction of the coronary arteries from the angiographic images. The reconstruction method must be fast and automatic in order to be used during an angiographic examination. Also, we should be able to integrate newly acquired views to the existing 3D reconstruction, and new images should be taken only if the current reconstruction is not yet sucient for the physician, thereby restricting the number of view to the minimum required. Furthermore, the 3D reconstruction made "on the y" should provide hints as to which new viewing angle to use. Such an iterative approach could also contribute toward reducing the number of angiographic views. The current state of the art in 3D reconstruction of coronary arteries invariably exploits stereoscopic vision algorithms. These approaches generally do not yield volume-based reconstructions since they simplify the artery to a centerline and radii, which is too coarse to represent the geometry of an aneurysm. Moreover, the stereo matching step is too time consuming to be integrated in an iterative procedure during an angiographic examination. To obtain a volume-based 3D reconstruction of the coronary arteries, we decided to focus on the technique called Shape from Silhouette (SFS). This method generates the volume-based reconstruction of an object from its silhouettes as seen from dierent orientations. The advantages are that an unlimited number of views can be used and that the reconstructed shape is suitable for our application, i.e. visualizing the geometry of the aneurysm. In addition, the SFS approach is fast and automatic (no stereo matching between images to perform). We apply this method on the silhouettes of coronary arteries, which are rst segmented from the angiographic images. The 3D reconstruction then consists in testing each voxel in a 3D grid under the following condition: if the projection of the centre of the voxel on the detector plane lies within the silhouette for each view, then the given voxel belongs to the reconstru

Active modelling of virtual humans

This thesis provides a complete framework that enables the creation of photorealistic 3D human models in real-world environments. The approach allows a non-expert user to use any digital capture device to obtain four images of an individual and create a personalised 3D model, for multimedia applications. To achieve this, it is necessary that the system is automatic and that the reconstruction process is flexible to account for information that is not available or incorrectly captured. In this approach the individual is automatically extracted from the environment using constrained active B-spline templates that are scaled and automatically initialised using only image information. These templates incorporate the energy minimising framework for Active Contour Models, providing a suitable and flexible method to deal with the adjustments in pose an individual can adopt. The final states of the templates describe the individual’s shape. The contours in each view are combined to form a 3D B-spline surface that characterises an individual’s maximal silhouette equivalent. The surface provides a mould that contains sufficient information to allow for the active deformation of an underlying generic human model. This modelling approach is performed using a novel technique that evolves active-meshes to 3D for deforming the underlying human model, while adaptively constraining it to preserve its existing structure. The active-mesh approach incorporates internal constraints that maintain the structural relationship of the vertices of the human model, while external forces deform the model congruous to the 3D surface mould. The strength of the internal constraints can be reduced to allow the model to adopt the exact shape of the bounding volume or strengthened to preserve the internal structure, particularly in areas of high detail. This novel implementation provides a uniform framework that can be simply and automatically applied to the entire human model