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Tesi sul tema "2D reconstruction"
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1
Breton, Rodolphe. "Reconstruction inversible d'objets discrets 2D". Poitiers, 2003. http://www.theses.fr/2003POIT2305.
Testo completoAbstract (sommario):
Notre travail s'inscrit dans le cadre de la géométrie discrète, un domaine dans lequel les données manipulées sont discrètes. Ce domaine est souvent associé à celui de la géométrie euclidienne, plus classique. Il est possible de passer du modèle euclidien au modèle discret par une opération nommée discrétisation. L'opération réciproque est appellée reconstruction. Pour les besoins d'un logiciel de modélisation développé au laboratoire SIC, nous nous sommes attaché à réaliser une reconstruction de courbes discrètes standard 2D vérifiant des critères de réversibilité ß la discrétisation d'un objet discret reconstruit donne exactement l'objet discret d'origine ß, d'esthétique ß l'objet reconstruit est aussi proche que possible de ce qu'on attend intuitivement ß et d'unicité ß pour un objet discret donné, la reconstruction sera toujours la même. Notre méthode de reconstruction est basée sur un algorithme de reconnaissance de segments discrets nai͏̈fs conçu par J. Vittone mais utilise le modèle standard, plus adapté à la description de contours dans le modèle inter-pixelThe framework of our thesis is discrete geometry since we handle discrete objects. A Euclidean object can be converted into a discrete one by an operation of discretization. Conversely, the reconstruction allows us to obtain a discrete object from a Euclidean one. We created a reconstruction method for 2D discrete curves and implemented it in a modeling software developped in the SIC laboratory. This method satisfies three criteria : invertibility ß the discretization of the reconstructed object leads to the original discret object ß, aesthetics ß the reconstructed object is as close as possible to what we intuitively expect ß, unicity ß the reconstruction of a given discret object will always give the same Euclidean object. Our reconstruction method is based on an algorithm written by J. Vittone. Although this algorithm is designed to recognize naive discrete segments, we work with standard segments since it is well fitted to describe objects boundaries in the inter-pixel model
2
Huang, Hui. "Efficient reconstruction of 2D images and 3D surfaces". Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/2821.
Testo completoAbstract (sommario):
The goal of this thesis is to gain a deep understanding of inverse problems arising from 2D image and 3D surface reconstruction, and to design effective techniques for solving them. Both computational and theoretical issues are studied and efficient numerical algorithms are proposed.
The first part of this thesis is concerned with the recovery of 2D images, e.g., de-noising and de-blurring. We first consider implicit methods that involve solving linear systems at each iteration. An adaptive Huber regularization functional is used to select the most reasonable model and a global convergence result for lagged diffusivity is proved. Two mechanisms---multilevel continuation and multigrid preconditioning---are proposed to improve efficiency for large-scale problems. Next, explicit methods involving the construction of an artificial time-dependent differential equation model followed by forward Euler discretization are analyzed. A rapid, adaptive scheme is then proposed, and additional hybrid algorithms are designed to improve the quality of such processes. We also devise methods for more challenging cases, such as recapturing texture from a noisy input and de-blurring an image in the presence of significant noise.
It is well-known that extending image processing methods to 3D triangular surface meshes is far from trivial or automatic. In the second part of this thesis we discuss techniques for faithfully reconstructing such surface models with different features. Some models contain a lot of small yet visually meaningful details, and typically require very fine meshes to represent them well; others consist of large flat regions, long sharp edges (creases) and distinct corners, and the meshes required for their representation can often be much coarser. All of these models may be sampled very irregularly. For models of the first class, we methodically develop a fast multiscale anisotropic Laplacian (MSAL) smoothing algorithm. To reconstruct a piecewise smooth CAD-like model in the second class, we design an efficient hybrid algorithm based on specific vertex classification, which combines K-means clustering and geometric a priori information. Hence, we have a set of algorithms that efficiently handle smoothing and regularization of meshes large and small in a variety of situations.
3
Henrichsen, Arne. "3D reconstruction and camera calibration from 2D images". Master's thesis, University of Cape Town, 2000. http://hdl.handle.net/11427/9725.
Testo completoAbstract (sommario):
Includes bibliographical references.A 3D reconstruction technique from stereo images is presented that needs minimal intervention from the user. The reconstruction problem consists of three steps, each of which is equivalent to the estimation of a specific geometry group. The first step is the estimation of the epipolar geometry that exists between the stereo image pair, a process involving feature matching in both images. The second step estimates the affine geometry, a process of finding a special plane in projective space by means of vanishing points. Camera calibration forms part of the third step in obtaining the metric geometry, from which it is possible to obtain a 3D model of the scene. The advantage of this system is that the stereo images do not need to be calibrated in order to obtain a reconstruction. Results for both the camera calibration and reconstruction are presented to verify that it is possible to obtain a 3D model directly from features in the images.
4
Zhao, Yajie. "3D Human Face Reconstruction and 2D Appearance Synthesis". UKnowledge, 2018. https://uknowledge.uky.edu/cs_etds/66.
Testo completoAbstract (sommario):
3D human face reconstruction has been an extensive research for decades due to its wide applications, such as animation, recognition and 3D-driven appearance synthesis. Although commodity depth sensors are widely available in recent years, image based face reconstruction are significantly valuable as images are much easier to access and store.
In this dissertation, we first propose three image-based face reconstruction approaches according to different assumption of inputs.
In the first approach, face geometry is extracted from multiple key frames of a video sequence with different head poses. The camera should be calibrated under this assumption.
As the first approach is limited to videos, we propose the second approach then focus on single image. This approach also improves the geometry by adding fine grains using shading cue. We proposed a novel albedo estimation and linear optimization algorithm in this approach.
In the third approach, we further loose the constraint of the input image to arbitrary in the wild images. Our proposed approach can robustly reconstruct high quality model even with extreme expressions and large poses.
We then explore the applicability of our face reconstructions on four interesting applications: video face beautification, generating personalized facial blendshape from image sequences, face video stylizing and video face replacement. We demonstrate great potentials of our reconstruction approaches on these real-world applications. In particular, with the recent surge of interests in VR/AR, it is increasingly common to see people wearing head-mounted displays. However, the large occlusion on face is a big obstacle for people to communicate in a face-to-face manner. Our another application is that we explore hardware/software solutions for synthesizing the face image with presence of HMDs. We design two setups (experimental and mobile) which integrate two near IR cameras and one color camera to solve this problem. With our algorithm and prototype, we can achieve photo-realistic results.
We further propose a deep neutral network to solve the HMD removal problem considering it as a face inpainting problem. This approach doesn't need special hardware and run in real-time with satisfying results.
5
Ren, Yuheng. "Implicit shape representation for 2D/3D tracking and reconstruction". Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:c70dc663-ee7c-4100-b492-3a85bf8640d1.
Testo completoAbstract (sommario):
This thesis develops and describes methods for real-time tracking, segmentation and 3-dimensional (3D) model acquisition, in the context of developing games for stroke patients that are rehabilitating at home. Real-time tracking and reconstruction of a stroke patient's feet, hands and the control objects that they are touching can enable not only the graphical visualization of the virtual avatar in the rehabilitation games, but also permits measurement of the patient's performs. Depth or combined colour and depth imagery from a Kinect sensor is used as input data. The 3D signed distance function (SDF) is used as implicit shape representation, and a series of probabilistic graphical models are developed for the problem of model-based 3D tracking, simultaneous 3D tracking and reconstruction and 3D tracking of multiple objects with identical appearance. The work is based on the assumption that the observed imagery is generated jointly by the pose(s) and the shape(s). The depth of each pixel is randomly and independently sampled from the likelihood of the pose(s) and the shape(s). The pose(s) tracking and 3D shape reconstruction problems are then cast as the maximum likelihood (ML) or maximum a posterior (MAP) estimate of the pose(s) or 3D shape. This methodology first leads to a novel probabilistic model for tracking rigid 3D objects with only depth data. For a known 3D shape, optimization aims to find the optimal pose that back projects all object region pixels onto the zero level set of the 3D shape, thus effectively maximising the likelihood of the pose. The method is extended to consider colour information for more robust tracking in the presence of outliers and occlusions. Initialised with a coarse 3D model, the extended method is also able to simultaneously reconstruct and track an unknown 3D object in real time. Finally, the concept of `shape union' is introduced to solve the problem of tracking multiple 3D objects with identical appearance. This is formulated as the minimum value of all SDFs in camera coordinates, which (i) leads to a per-pixel soft membership weight for each object thus providing an elegant solution for the data association in multi-target tracking and (ii) it allows for probabilistic physical constraints that avoid collisions between objects to be naturally enforced. The thesis also explore the possibility of using implicit shape representation for online shape learning. We use the harmonics of 2D discrete cosine transform (DCT) to represent 2D shapes. High frequency harmonics are decoupled from low ones to represent the coarse information and the details of the 2D shape. A regression model is learnt online to model the relationship between the high and low frequency harmonics using Locally Weighted Projection Regression (LWPR). We have demonstrated that the learned regression model is able to detect occlusion and recover them to the complete shape.
6
Li, Ci. "Automatic horse lameness detection through 2D to 3D reconstruction". Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-272126.
Testo completoAbstract (sommario):
Lameness is a condition that is difficult to treat in horses when discovered too late and is therefore a common cause for culling. Veterinarians often make a diagnosis based on their subjective experience. In this thesis, we investigate whether neural networks can do lameness detection of horses by using the 3D reconstructed model of the horses. We divide the problem into two parts. The first part is about the 3D model reconstruction of the horse in the videos and then we use neural networks to do lameness detection. We also perform experiments on human videos to test the generalization of our idea, reconstructing the 3D human model in the videos and doing action recognition with neural networks. The two frameworks we use are standard LSTM and LSTM with an attention mechanism. The results of the human experiments show that both networks can separate human actions given the 3D human model sequences and some specific joints are pointed out when doing the two-class action classification. The results of animal experiments preliminarily show that the information of the 3D horse model can be used to perform lameness detection and front-limb lameness is more comfortable for the networks to learn compared to hind-limb lameness.Hälta är ett svårbehandlat tillstånd hos hästar när det upptäcks för sent och är därför en vanlig orsak för avlivning. Veterinärer ställer ofta en diagnos baserat på deras subjektiva erfarenhet. I det här examensarbetet undersöker vi om neurala nätverk kan upptäcka hälta med hjälp av en 3D-rekonstruerad modell av hästar. Vi delar upp problemet i två delar. Den första delen handlar om rekonstruktion av 3D-modellen av hästen i filmerna och sedan använder vi neurala nätverk för att göra hältedetektering. Vi utför också experiment på mänskliga videor för att testa generaliseringen av vår idé, rekonstruerar den mänskliga 3D-modellen i videorna och utför handlingsigenkänning med neurala nätverk. De två sortens nätverk vi använder är ett standard LSTM-nätverk och ett LSTM-nätverk med en uppmärksamhetsmekanism. Resultaten från de mänskliga experimenten visar att båda nätverken kan separera mänskliga handlingar givet 3D-modeller och vissa relevanta kroppsdelar ges uppmärksamhet när man gör actionklassificering över två klasser. Resultaten av försöken på hästdata visar preliminärt att informationen i 3D-hästmodellen kan användas för att utföra hältedetektion och att det är lättare att detektera frambenshälta jämfört med att lära sig att detektera bakbenshälta.
7
Rolland, Franck. "Représentation tridimensionnelle et reconstruction 3D à partir de coupes 2D". Phd thesis, Grenoble 1, 1991. http://tel.archives-ouvertes.fr/tel-00339648.
Testo completoAbstract (sommario):
L'objectif des travaux présentés dans ce mémoire est la représentation de formes tridimensionnelles ainsi que la reconstruction tridimensionnelle a partir de coupes sériées. Après avoir défini le cadre exact de la reconstruction tridimensionnelle a partir de coupes sériées, le premier chapitre analyse les différentes étapes et les méthodes généralement employées pour effectuer cette reconstruction. Les chapitre 2 et 3 s'attachent a la description et a la représentation de formes tant bidimensionnelles que tridimensionnelles. Le chapitre 3 developpe ainsi une methode de squelettisation tridimensionnelle permettant d'obtenir un squelette filaire. Le chapitre 4 est consacre a la description de deux méthodes de reconstruction tridimensionnelle opérant par inférence de formes. La methode utilisant l'inférence structurelle de graphes de la ligne médiane est ensuite développée. Elle passe par une nécessaire étape, chapitre 5, de mise en correspondance de graphes de la ligne médiane. Différentes méthodes de mise en correspondance sont présentées, finalement la methode procédant par recherche de cliques dans un graphe est développée. La construction du graphe de mise en correspondance est tout d'abord présentée, ensuite la recherche de cliques est abordée a l'aide de méthodes heuristiques de parcours (recuit simule et algorithmes génétiques). Le chapitre 6 développe le processus d'inférence de graphes de la ligne médiane mis en œuvre, il permet d'inférer des coupes intermediaires qui sont empilées pour finalement donner le volume tridimensionnel recherche. Le chapitre 7 est consacre a la présentation des divers résultats et de leurs conséquences, il présenté aussi d'autres applications possibles des différentes techniques developpees
8
Li, Yi. "Key issues of 2D/3D image reconstruction in electrical tomography". Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489019.
Testo completo
9
Dowell, Rachel J. (Rachel Jean). "Registration of 2D ultrasound images in preparation for 3D reconstruction". Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10181.
Testo completo
10
Cheng, Yuan 1971. "3D reconstruction from 2D images and applications to cell cytoskeleton". Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/88870.
Testo completoAbstract (sommario):
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, February 2001.Includes bibliographical references (leaves 121-129).
Approaches to achieve three dimensional (3D) reconstruction from 2D images can be grouped into two categories: computer-vision-based reconstruction and tomographic reconstruction. By exploring both the differences and connections between these two types of reconstruction, the thesis attempts to develop a new technique that can be applied to 3D reconstruction of biological structures. Specific attention is given to the reconstruction of the cell cytoskeleton from electron microscope images. The thesis is composed of two parts. The first part studies computer-vision-based reconstruction methods that extract 3D information from geometric relationship among images. First, a multiple-feature-based stereo reconstruction algorithm that recovers the 3D structure of an object from two images is presented. A volumetric reconstruction method is then developed by extending the algorithm to multiple images. The method integrates a sequence of 3D reconstruction from different stereo pairs. It achieves a globally optimized reconstruction by evaluating certainty values of each stereo reconstruction. This method is tuned and applied to 3D reconstruction of the cell cytoskeleton. Feasibility, reliability and flexibility of the method are explored.
(cont.) The second part of the thesis focuses on a special tomographic reconstruction, discrete tomography, where the object to be reconstructed is composed of a discrete set of materials each with uniform values. A Bayesian labeling process is proposed as a framework for discrete tomography. The process uses an expectation-maximization (EM) algorithm with which the reconstruction is obtained efficiently. Results demonstrate that the proposed algorithm achieves high reconstruction quality even with a small number of projections. An interesting relationship between discrete tomography and conventional tomography is also derived, showing that discrete tomography is a more generalized form of tomography and conventional tomography is only a special case of such generalization.
by Yuan Cheng.
Ph.D.
11
Wu, Wenchuan. "Acquisition and reconstruction methods for hybrid 2D/3D diffusion MRI". Thesis, University of Oxford, 2018. http://ora.ox.ac.uk/objects/uuid:b6de8931-3910-4342-acdb-4eac49263b2c.
Testo completoAbstract (sommario):
Diffusion magnetic resonance imaging (MRI) has been increasingly used in neuroscience studies, particularly for mapping white matter tracts in the brain. Typically, diffusion MRI is acquired using a two-dimensional (2D) single-shot echo planar imaging sequence, which allows rapid acquisition and reduced sensitivity to subject motion. However, conventional 2D diffusion MRI faces many limitations, such as long TR (repetition time) which lead to low SNR (signal-to-noise ratio) efficiency, and long scan times with advanced diffusion protocols which usually require a large number of diffusion directions and/or b values. These limitations become more acute at high spatial resolution. Three-dimensional (3D) methods have also been developed for diffusion MRI, but they are not widely used for acquiring data in vivo due to the challenges in subject motion. Hybrid 2D/3D methods, including 3D multi-slab acquisition and simultaneous multi-slice acquisition, have been recently proposed to address the limitations of conventional 2D and 3D methods. However, 3D multi-slab acquisition faces the problem of slab boundary artefacts, which could decrease the image quality and propagate into diffusion quantifications. Simultaneous multi-slice acquisition would suffer from significant noise amplification when in-plane under-sampling is also applied. The work in this thesis seeks to develop acquisition and reconstruction methods to improve hybrid 2D/3D diffusion MRI. A new method is proposed to correct slab boundary artefacts in 3D multi-slab imaging, which jointly estimates the slab profile and underlying image using a nonlinear reconstruction. Correction results demonstrate superior performance compared with previously proposed methods. A k-q acquisition and reconstruction approach is developed to accelerate diffusion MRI based on Gaussian process methods. Here, we target improvements to simultaneous multi-slice imaging, demonstrating high acceleration factors in combination with in-plane under-sampling. Combinations of hybrid 2D/3D acquisitions with the ultra-high field of 7T are also investigated, which could enable high resolution diffusion MRI without substantially compromising SNR. The methods developed in this work are expected to improve the data quality and scan efficiency of diffusion MRI.
12
Rolland, Franck Montanvert Annick. "Représentation tridimensionnelle et reconstruction 3D à partir de coupes 2D". S.l. : Université Grenoble 1, 2008. http://tel.archives-ouvertes.fr/tel-00339648.
Testo completo
13
Islam, Md Monowarul, e Muftadi Ullah Arpon. "Image Reconstruction Techniques using Kaiser Window in 2D CT Imaging". Thesis, Linnéuniversitetet, Institutionen för fysik och elektroteknik (IFE), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-94135.
Testo completoAbstract (sommario):
The traditional Computed Tomography (CT) is based on the Radon Transform and its inversion. The Radon transform uses parallel beam geometry and its inversion is based on the Fourier slice theorem. In practice, it is very efficient to employ a back-projection algorithm in connection with the Fast Fourier Transform, and which can be interpreted as a 1-D filtering across the radial dimension of the 2-D Fourier plane of the transformed image. This approach can easily be adapted to windowing techniques in the frequency domain, giving the capability to reduce image noise. In this work we are investigating the capabilities of the so called Kaiser window (giving an optimal trade-off between the main lobe energy and the sidelobe suppression) to achieve a near optimal trade-off between the noise reduction and the image sharpness in the context of Radon inversion. Finally, we simulate our image reconstruction using MATLAB software and compare and estimate our results based on the normalized Least Square Error (LSE). We conclude that the Kaiser window can be used to achieve an optimal trade-off between noise reduction and sharpness in the image, and hence outperforms all the other classical window function in this regard.
14
North, Peter R. J. "The reconstruction of visual appearance by combining stereo surfaces". Thesis, University of Sussex, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362837.
Testo completo
15
Villota, Juan Carlos Perafán. "Adaptive registration using 2D and 3D features for indoor scene reconstruction". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3139/tde-17042017-090901/.
Testo completoAbstract (sommario):
Pairwise alignment between point clouds is an important task in building 3D maps of indoor environments with partial information. The combination of 2D local features with depth information provided by RGB-D cameras are often used to improve such alignment. However, under varying lighting or low visual texture, indoor pairwise frame registration with sparse 2D local features is not a particularly robust method. In these conditions, features are hard to detect, thus leading to misalignment between consecutive pairs of frames. The use of 3D local features can be a solution as such features come from the 3D points themselves and are resistant to variations in visual texture and illumination. Because varying conditions in real indoor scenes are unavoidable, we propose a new framework to improve the pairwise frame alignment using an adaptive combination of sparse 2D and 3D features based on both the levels of geometric structure and visual texture contained in each scene. Experiments with datasets including unrestricted RGB-D camera motion and natural changes in illumination show that the proposed framework convincingly outperforms methods using 2D or 3D features separately, as reflected in better level of alignment accuracy.O alinhamento entre pares de nuvens de pontos é uma tarefa importante na construção de mapas de ambientes em 3D. A combinação de características locais 2D com informação de profundidade fornecida por câmeras RGB-D são frequentemente utilizadas para melhorar tais alinhamentos. No entanto, em ambientes internos com baixa iluminação ou pouca textura visual o método usando somente características locais 2D não é particularmente robusto. Nessas condições, as características 2D são difíceis de serem detectadas, conduzindo a um desalinhamento entre pares de quadros consecutivos. A utilização de características 3D locais pode ser uma solução uma vez que tais características são extraídas diretamente de pontos 3D e são resistentes a variações na textura visual e na iluminação. Como situações de variações em cenas reais em ambientes internos são inevitáveis, essa tese apresenta um novo sistema desenvolvido com o objetivo de melhorar o alinhamento entre pares de quadros usando uma combinação adaptativa de características esparsas 2D e 3D. Tal combinação está baseada nos níveis de estrutura geométrica e de textura visual contidos em cada cena. Esse sistema foi testado com conjuntos de dados RGB-D, incluindo vídeos com movimentos irrestritos da câmera e mudanças naturais na iluminação. Os resultados experimentais mostram que a nossa proposta supera aqueles métodos que usam características 2D ou 3D separadamente, obtendo uma melhora da precisão no alinhamento de cenas em ambientes internos reais.
16
Chung, Heeteak. "In vivo dose reconstruction using a 2D dosimeter via transit dosimetry". [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0024695.
Testo completo
17
Law, Kwok-wai Albert, e 羅國偉. "3D reconstruction of coronary artery and brain tumor from 2D medical images". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B31245572.
Testo completo
18
MIGEON, BRUNO. "Reconstruction 2d et 3d d'os longs des membres par traitement d'images echographiques". Orléans, 1993. http://www.theses.fr/1993ORLE2025.
Testo completoAbstract (sommario):
L'objet de cette these est la reconstruction 3d des os longs des membres a partir de coupes paralleles successives reconstruites par tomographie ultrasonore. L'originalite du travail au niveau de la reconstruction 2d reside dans le developpement de methodes de tomographie ultrasonore en mode reflexion par traitement d'images radiales (acquises avec des sondes echographiques classiques). Pour cela un systeme d'acquisition permettant d'obtenir plusieurs images radiales par plan de coupe et pour plusieurs plans de coupes paralleles successifs a ete realise. Le traitement des images permet la segmentation des structures recherchees et l'extraction de leurs contours, moyennant la resolution d'un certain nombre de problemes et de cas particuliers. La reconstruction 3d consiste a donner un sens a la scene volumique obtenue en etablissant des liens de connexion entre les differents contours extraits, afin de comprendre la scene comme un ensemble d'objets distincts. Il est ensuite possible de faire une representation 3d par facettes planes via une etape de triangulation, et meme par listes de voxels grace a une methode originale d'interpolation de contours. La visualisation 3d permet ensuite de representer les structures sous n'importe quel angle de vue par des techniques classiques, avec rendu realiste grace a l'utilisation d'un modele d'ombrage
19
Sun, Jingchuan. "Structural studies of the SARS virus Nsp15 endonuclease and the human innate immunity receptor TLR3". Diss., Texas A&M University, 2005. http://hdl.handle.net/1969.1/3811.
Testo completoAbstract (sommario):
Three-dimensional (3D) structural determination of biological macromolecules is not only critical to understanding their mechanisms, but also has practical applications. Combining the high resolution imaging of transmission electron microscopy (TEM) and efficient computer processing, protein structures in solution or in two-dimensional (2D) crystals can be determined. The lipid monolayer technique uses the high affinity binding of 6His-tagged proteins to a Ni-nitrilotriacetic (NTA) lipid to create high local protein concentrations, which facilitates 2D crystal formation. In this study, several proteins have been crystallized using this technique, including the SARS virus Nsp15 endonuclease and the human Toll-like receptor (TLR) 3 extracellular domain (ECD). Single particle analysis can determine protein structures in solution without the need for crystals. 3D structures of several protein complexes had been solved by the single particle method, including IniA from Mycobacterium tuberculosis, Nsp15 and TLR3 ECD. Determining the structures of these proteins is an important step toward understanding pathogenic microbes and our immune system.
20
Hennenfent, Gilles, e Felix J. Herrmann. "Curvelet reconstruction with sparsity-promoting inversion : successes and challenges". European Association of Geoscientists & Engineers, 2007. http://hdl.handle.net/2429/555.
Testo completoAbstract (sommario):
In this overview of the recent Curvelet Reconstruction with Sparsity-promoting Inversion
(CRSI) method, we present our latest 2-D and 3-D interpolation results on both
synthetic and real datasets. We compare these results to interpolated data using other existing
methods. Finally, we discuss the challenges related to sparsity-promoting solvers
for the large-scale problems the industry faces.
21
Sun, Hongyan. "An investigation into the use of scattered photons to improve 2D Position Emission Tomography (PET) functional imaging quality". Hindawi Publishing Corporation, 2012. http://hdl.handle.net/1993/31031.
Testo completoAbstract (sommario):
Positron emission tomography (PET) is a powerful metabolic imaging modality, which is designed to detect two anti-parallel 511 keV photons origniating from a positron-electron annihilation. However, it is possible that one or both of the annihilation photons undergo a Compton scattering in the object. This is more serious for a scanner operated in 3D mode or with large patients, where the scatter fraction can be as high as 40-60%. When one or both photons are scattered, the line of response (LOR) defined by connecting the two relevant detectors no longer passes through the annihilation position. Thus, scattered coincidences degrade image contrast and compromise quantitative accuracy. Various scatter correction methods have been proposed but most of them are based on estimating and subtracting the scatter from the measured data or incorporating it into an iterative reconstruction algorithm.
By accurately measuring the scattered photon energy and taking advantage of the kinematics of Compton scattering, two circular arcs (TCA) in 2D can be identified, which describe the locus of all the possible scattering positions and encompass the point of annihilation. In the limiting case where the scattering angle approaches zero, the TCA approach the LOR for true coincidences. Based on this knowledge, a Generalized Scatter (GS) reconstruction algorithm has been developed in this thesis, which can use both true and scattered coincidences to extract the activity distribution in a consistent way. The annihilation position within the TCA can be further confined by adding a patient outline as a constraint into the GS algorithm. An attenuation correction method for the scattered coincidences was also developed in order to remove the imaging artifacts. A geometrical model that characterizes the different probabilities of the annihilation positions within the TCA was also proposed. This can speed up image convergence and improve reconstructed image quality. Finally, the GS algorithm has been adapted to deal with non-ideal energy resolutions. In summary, an algorithm that implicitly incorporates scattered coincidences into the image reconstruction has been developed. Our results demonstrate that this eliminates the need for scatter correction and can improve system sensitivity and image quality.February 2016
22
Triki-Bchir, Olfa. "Modélisation, reconstruction et animation de personnages virtuels 3D à partir de dessins manuels 2D". Phd thesis, Université René Descartes - Paris V, 2005. http://tel.archives-ouvertes.fr/tel-00273248.
Testo completoAbstract (sommario):
La production de dessins animés 2D, qui suit actuellement un schéma mis en place dans les années 1920, fait intervenir un très nombre de compétences humaines et de métiers différents. Par opposition à ce mode de travail traditionnel, la production de films de synthèse 3D, en exploitant les technologies et outils les plus récents de modélisation et d'animation 3D, s'affranchit pour une bonne part de cette composante artisanale et vient concurrencer l'industrie du dessin animé tradtionnel en termes de délais et de coûts de fabrication.Les défis à relever par l'industrie du dessin animé 2D se formulent donc en termes de:
1. Réutilisation des contenus selon le paradigme Create once, render many,
2. Facilité d'échange et de transmission des contenus, ce qui nécessite de disposer d'un unique format de représentation,
3. Production efficace et économique des contenus, requérant une animation automatisée par ordinateur.
Dans ce contexte compétitif, ce travail de thèse, réalisé dans le cadre du projet industriel TOON financé par la société Quadraxis avec le support de l' Agence Nationale de Valorisation de la Recherche (Oséo-ANVAR), a pour objectif de contribuer au développement d'une plate-forme de reconstruction, déformation et animation de modèles 3D pour les dessins animés 2D.
Un état de l'art des méthodes et outils contribuant à la reconstruction de modèles 3D et à leur animation est présenté et discuté au regard des contraintes spécifiques des règles de création des dessins animés 2D et de la chaîne de fabrication traditionnelle. Ayant identifié les verrous technologiques à lever, nos contributions ont porté sur :
* l'élaboration d'une méthode de reconstruction de personnages virtuels 3D à partir de dessins 2D,
* la mise au point d'une procédure de reconstruction surfacique par NURBS dotée d'une capacité de déformation interactive 2D/3D,
* la conception d'un module de modélisation 3D pour surfaces maillées, compatible avec le standard d'animation MPEG-4/AFX.
Les développements réalisés, intégrés dans un prototype de la plate-forme TOON, montrent un gain en temps de 20% sur l'ensemble de la chaîne de production tout en garantissant une complète interopérabilité des applications via le standard MPEG-4.
23
Da, Costa Luis Eduardo. "Reconstruction de modèles 3D à partir d'information 2D partielle : application au cas d'une plante". Mémoire, École de technologie supérieure, 2007. http://espace.etsmtl.ca/573/1/DA_COSTA_Luis_Eduardo.pdf.
Testo completoAbstract (sommario):
Une méthode pour générer des modèles informatiques fidèles de plantes naturelles est proposée dans ce travail; cette méthode prend comme entrée des photographies 2D prises du champ.
Le formalisme choisi comme base pour la représentation de plantes s'appelle «Systèmes de Lindenmayer» (LSystems), qui sont des systèmes grammaticaux contrôlés par une condition initale et une (ou plusieurs) règle(s) de réécriture Générer un modèle informatique d'une plante est l'équivalent à résoudre le problème inverse pour un sous-type de ce formalisme, appelé «LSystems à crochets»; ce travail utilise un algorithme évolutif pour résoudre ce problème inverse.
Une description détaillée de l'algorithme, ainsi que la justification du design choisi, sont présentées; un ensemble d'expériences démontre que l'algorithme explore de manière satisfaisante l'espace de solutions candidates, et que les approximations qu'il propose sont adéquates dans la majorité des cas. Ses limitations et faiblesses sont aussi rapportées et ensuite discutées.
24
Horna, Sébastien. "Reconstruction géométrique et topologique de complexes architecturaux 3D à partir de plans numériques 2D". Poitiers, 2008. http://theses.edel.univ-poitiers.fr/theses/2008/Horna-Sebastien/2008-Horna-Sebastien-These.pdf.
Testo completoAbstract (sommario):
L’intérieur des bâtiments est souvent modélisé en 3D pour diverses applications de modélisation ou de simulation. Par exemple, plusieurs méthodes permettent d’étudier l’éclairage, les transferts de chaleur, la propagation d’ondes. Ces applications nécessitent dans la plupart des cas une représentation volumique de l’environnement avec des relations d’adjacence et d’incidence entre les éléments. Malheureusement, les données correspondant au bâtiment sont en général seulement disponibles en 2D et les besoins des applications 3D varient d’une utilisation à l’autre. Pour résoudre ce problème, nous proposons une description formelle d’un ensemble de contraintes de cohérence dédiées à la modélisation d’intérieur de bâtiments. Dans cette thèse nous montrons comment cette représentation est utilisée pour : (i) reconstruire un modèle 3D à partir de plans d’architecte numériques 2D ; (ii) détecter automatiquement les incohérences géométriques, topologiques et sémantiques ; (iii) développer des opérations automatiques et semi-automatiques pour corriger les plans 2D. Toutes les contraintes de cohérence sont définies en 2D et 3D et reposent sur le modèle topologique des cartes généralisées. Ces opérations sont utilisées pour éditer les scènes 2D et 3D afin d’affiner ou de modifier les modèles. Enfin, nous expliquons comment ce modèle est utilisé pour une application de visualisation par lancé de rayonsVirtual architectural (indoor) scenes are often modelled in 3D for various types of simulation systems. For instance, some authors propose methods dedicated to lighting, heat transfer, acoustic or radio wave propagation simulations. These methods rely in most cases on a volumetric representation of the environment, with adjacency and incidence relationships. Unfortunately, many buildings data are only given by 2D plans and the 3D needs varies from one application to another. To solve these problems, we propose a formal representation of consistency constraints dedicated to building interiors and associated with a topological model. We show that such a representation can be used for : (i) reconstructing a 3D model from 2D architectural plans ; (ii) detecting automatically geometrical, topological and semantical inconsistencies ; (iii) designing automatic and semi-automatic operations to correct and enrich a 2D plan. All our constraints are homogeneously defined in 2D and 3D, implemented with generalized maps and used in modeling operations. We explain how this model can be successfully used with various ray-tracing methods
25
Triki, Bchir Olfa. "Modélisation, reconstruction et animation de personnages virtuels 3D à partir de dessins manuels 2D". Paris 5, 2005. http://www.theses.fr/2005PA05S015.
Testo completoAbstract (sommario):
La production de dessins animés 2D qui suit actuellement un schéma mis en place dans les années 1920 fait intervenir un très grand nombre de compétences humaines. Par opposition à ce mode de travail traditionnel, la production de films 3D, en exploitant les technologies et outils les plus récents de modélisation et d'animation 3D, s'affranchit en bonne partie de cette composante artisanale et vient concurrencer l'industrie du dessin animé 2D en termes de temps et coûts de fabrication. Les enjeux à relever par l'industrie du dessin animé 2D se posent donc en termes de : 1. Réutilisation des contenus selon le célèbre paradigme du “Create once, render many”, 2. Facilité d'échange et transmission des contenus ce qui nécessite de disposer d'un unique format de représentation, 3. Production efficace et économique des contenus requérant alors une animation automatisée par ordinateur. Dans ce contexte compétitif, cette thèse, réalisée dans le cadre du projet industriel TOON financé par la société Quadraxis avec le support de l'Agence Nationale pour la Valorisation de la Recherche (ANVAR), a pour objectif de contribuer au développement d'une plate-forme de reconstruction, déformation et animation de modèles 3D pour les dessins animés 2D. Un état de l'art des méthodes et outils contribuant à la reconstruction de modèles 3D et à leur animation est présenté et discuté au regard des contraintes spécifiques des règles de création des dessins animés 2D et de la chaîne de fabrication 2D. Ayant identifié les verrous technologiques à lever, nos contributions ont porté sur : – L'élaboration d'une de reconstruction des personnages virtuels 3D àpartir de dessins 2D, – La mise au point d'une méthode de modélisation 3D par surfaces maillées, compatible avec le standard MPEG-4/AFX, Les développements réalisés, intégrés dans un premier prototype de la plate-forme TOON, montrent un gain en temps de 20% dans la chaîne de production et une complète interopérabilité des applications via le standard MPEG-4.
26
Da, Costa Luis Eduardo. "Reconstruction de modèles 3D à partir d'information 2D partielle : application au cas d'une plante /". Thèse, Montréal : École de technologie supérieure, 2007. http://proquest.umi.com/pqdweb?did=1397920901&sid=3&Fmt=2&clientId=46962&RQT=309&VName=PQD.
Testo completoAbstract (sommario):
Thèse (Ph.D.) -- École de technologie supérieure, Montréal, 2007."Thèse présentée à l'École de technologie supérieure comme exigence partielle à l'obtention du doctorat en génie". CaQQUQ Bibliogr. : f. [173]-179. Également disponible en version électronique. CaQMUQET
27
Dasgupta, Sankarshan. "3D Face Reconstruction From Front And Profile Image". University of Dayton / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1626689472561706.
Testo completo
28
Schramm, Florian. "Contributions à l'asservissement visuel : la commande 2D étendue". Paris 6, 2006. http://www.theses.fr/2006PA066409.
Testo completoAbstract (sommario):
Les manipulateurs doivent de plus en plus interagir avec leur environnement. Par conséquent, L’asservissement visuel s'intéresse à exploiter des informations visuelles pour la commande des manipulateurs. Dans ce cadre, nous avons choisi d'étudier un vecteur de primitives particuliers, basé sur les coordonnées 2D étendues (2Dé). Nous démontrons la stabilité asymptotique pour le système bouclé, un travail original pour la classe d'asservissements visuel étudiés et caractérisés par un traitement d'image simple, car qui ne requière pas de pose de caméra. De suite, la visibilité de la cible est étudiée. En effet, il faut restreindre les déplacements du manipulateur afin que la caméra embarquée sur l'effecteur garde l'objet à l'intérieur du champ visuel. Cette exigence est atteinte par une planification de chemin de points images, basée sur les coordonnées 2Dé. Les deux algorithmes originaux planifient un déplacement garantissant la visibilité et ne requièrent pas de calibrage. Les résultats ont été validés sur site d'essaiVisual servoing aims for actuated manipulators to interact with their environment by exploiting visual cues. Within this framework, this thesis studies the closed loop behaviour for a choosen feature vector, namely composed by the extended 2D coordinates of a cloud of image points. Amongst other, global asymptotic stability can be shown in the nominal case, and local asymptotic stability in the case of calibration errors. The selected features do not require any 3D reconstruction of camera pose nor orientation, which allows for a simple image treatment. Secondly, the visibility problem is treated. Indeed, moving the manipulator with a camera mounted on its end-effector in an arbitrary way may cause the target to leave the field of view and, in turn, the servoing to fail. Hence, trajectories are planned in extended 2D coordinates along which the target remains visible. Two different algorithms are proposed, which guaranties visibility by closed form solutions invariant to calibration errors. All theoretical results have been validated by experiments
29
Zhou, Dianle. "Using 3D morphable models for 3D photo-realistic personalized avatars and 2D face recognition". Thesis, Evry, Institut national des télécommunications, 2011. http://www.theses.fr/2011TELE0017/document.
Testo completoAbstract (sommario):
[Non communiqué]In the past decade, 3D statistical face model (3D Morphable Model) has received much attention by both the commercial and public sectors. It can be used for face modeling for photo-realistic personalized 3D avatars and for the application 2D face recognition technique in biometrics. This thesis describes how to achieve an automatic 3D face reconstruction system that could be helpful for building photo-realistic personalized 3D avatars and for 2D face recognition with pose variability. The first systems we propose Combined Active Shape Model for 2D frontal facial landmark location and its application in 2D frontal face recognition in degraded condition. The second proposal is 3D Active Shape Model (3D-ASM) algorithm which is presented to automatically locate facial landmarks from different views. The third contribution is to use biometric data (2D images and 3D scan ground truth) for quantitatively evaluating the 3D face reconstruction. Finally, we address the issue of automatic 2D face recognition across pose using 3D Morphable Model
30
Dasgupta, Sumantra. "Reconstruction of 3D rigid body motion in a virtual environment from a 2D image sequence". Thesis, [College Station, Tex. : Texas A&M University, 2004. http://hdl.handle.net/1969.1/469.
Testo completoAbstract (sommario):
Thesis (M.S.)--Texas A&M University, 2003."Major Subject: Electrical Engineering" Title from author supplied metadata (record created on Jul. 18, 2005.) Vita. Abstract. Includes bibliographical references.
31
Chighvinadze, Tamar. "A spectroscopic Compton scattering reconstruction algorithm for 2D cross-sectional view of breast CT geometry". Journal of X-Ray Science and Technology, IOS press, 2014. http://hdl.handle.net/1993/23846.
Testo completoAbstract (sommario):
X-ray imaging exams are widely used procedures in medical diagnosis. Whenever an x-ray imaging procedure is performed, it is accompanied by scattered radiation. Scatter is a significant contributor to the degradation of image quality in breast CT. This work uses our understanding of the physics of Compton scattering to overcome the reduction in image quality that typically results from scattered radiation. By measuring the energy of the scattered photons at various locations about the object, an electron density (ρe) image of the object can be obtained.
This work investigates a system modeled using a 2D cross-sectional view of a breast CT geometry. The ρe images can be obtained using filtered backprojection over isogonic curves. If the detector has ideal energy and spatial resolution, a single projection will enable a high quality image to be reconstructed. However, these ideal characteristics cannot be achieved in practice and as the detector size and energy resolution diverge from the ideal, the image quality degrades. To compensate for the realistic detector specifications a multi-projection Compton scatter tomography (MPCST) approach was introduced. In this approach an x-ray source and an array of energy sensitive photon counting detectors located just outside the edge of the incident fan-beam, rotate around the object while acquiring scattering data. The ρe image quality is affected by the size of the detector, the energy resolution of the detector and the number of projections. These parameters, their tradeoffs and the methods for the image quality improvement were investigated.
The work has shown that increasing the energy and spatial resolution of the detector improves the spatial resolution of the reconstructed ρe image. These changes in the size and energy resolution result in an increase in the noise. Thus optimizing the image quality becomes a tradeoff between blurring and noise. We established that a suitable balance is achieved with a 500 eV energy resolution and 2×2 mm2 detector. We have also established that using a multi-projection approach can offset the increase in the noise.
32
Bui, Cao Vu. "Modélisation d'environnements intérieurs par reconstruction 3D en temps réel et extraction de plans architecturaux 2D". Thesis, Troyes, 2018. http://www.theses.fr/2018TROY0032.
Testo completoAbstract (sommario):
Nous explorons le problème de la reconstruction complète d’un environnement intérieur en utilisant des données mixtes issues de la caméra RGB-D (couleur plus profondeur) de faible coût et de la centrale inertielle. Le processus de numérisation est réalisé en temps réel, en déplacement avec 6 degrés de liberté du système de numérisation. Nous nous concentrons sur les systèmes mobiles avec des contraintes informatiques, tels que les smartphones ou les tablettes. Les problèmes problématiques présentent un ensemble de défis fondamentaux : l'estimation du positionnement et de la trajectoire du périphérique lorsqu'il se déplace pendant l'acquisition de l'environnement et l'utilisation de structures de données légères pour stocker la représentation de la scène reconstruite. Le système doit être optimisé et efficace pour la mémoire, de sorte qu'il puisse fonctionner en temps réel, à bord de l'équipement mobile. Nous proposons également une nouvelle méthode de reconstruction de la surface, nommé Dodécaèdre Mapping, une solution de triangulation discrète pour la surface complète de l'environnement intérieur. L’algorithme tente d'approximer le maillage surfacique en déformant et en collant la surface affinée du dodécaèdre sur le nuage de points numérisé. Le dernier module de cette mission de recherche consiste à développer des outils de l'extraction automatique / semi-automatique de plans architecturaux 2D à partir de la reconstruction 3D de la scène scannée. Ce processus d'extraction est possible à partir du nuage de points 3D ou du maillage en définissant un plan de coupeScene reconstruction is the process of building an accurate geometric model of one's environment from We explore the problem of complete scene reconstruction in indoor environments using mixed - data from the low-cost RGB-D camera and the inertial unit. The scanning process is realized in real-time, on the move with 6DoF of the numerizing system. We focus on computationally-constrained mobile systems, such as smartphone or tablet devices. Problematic issues present a set of fundamental challenges - estimating the state and trajectory of the device as it moves while scanning environment and utilizing lightweight data structures to hold the representation of the reconstructed scene. The system needs to be computationally and memory-efficient, so that it can run in real time, on-board the mobile device. The point-cloud resulted in the above module, which is non-structured and noisy cause of the quality of the low-cost sensor, needed a new method for the surface reconstruction. Our Dodecahedron Mapping is presented like a triangulation solution for the completed indoor environment scanning. After filtering and smoothing the point cloud, the algorithm tries to approximating the surface mesh by deforming and pasting the dodecahedron surface to the scanned point cloud. And the last stage of this research mission is to developing tools for the automatic extraction of 2D architectural plans from the 3D scanned building scene. This extracting process is also possible from the 3D point cloud or mesh by defining a section plane
33
Ould, Mohamed Moctar Salem. "Méthodes analytiques de reconstruction 2D de régions d’intérêt à partir de projections incomplètes mais suffisantes". Saint-Etienne, 2009. http://www.theses.fr/2009STET4017.
Testo completoAbstract (sommario):
La tomographie médicale en 2D, vise à reconstruire une coupe du corps humain à partir de ses projections (mesures prises depuis l’extérieur de la coupe). La méthode standard de rétroprojection filtrée (FBP= Filtered Backprojection, en anglais), permet de reconstruire un objet si et seulement si on dispose de toutes ses projections. Si pour des raisons physiques les projections sont incomplètes (taille de l’objet trop grande par rapport au détecteur, balayage limité de la source. . . ), la méthode de rétroprojection des dérivées des projections (DBP = Differentiated Backprojection, en anglais) ainsi que la méthode du fanbeam virtuel, permettent de reconstruire une région d’intérêt (ROI) de l’objet si les projections incomplètes sont suffisantes. Chacune de ces deux méthodes a ses contraintes et ses limites. Cette thèse concerne l’amélioration et le développement de la méthode du fanbeam virtuel. Nous y présenterons des résultats originaux (nouvelles formules explicites de reconstruction) qui étendent le domaine d’application de la méthode du fanbeam virtuel. Nous montrons comment cette méthode peut être combinée avec la FBP pour reconstruire certaines ROI ne pouvant pas être reconstruites par les méthodes existantes. Des simulations numériques sont également montréesMedical tomography in 2D consists of reconstructing a section of the human body from its projections (measurements taken from outside the section). The standard method of Filtered Backprojection (FBP) is able to reconstruct an object if and only if all of its projections are available. If, for some physical reasons (small detectors, low X-ray dose, limited scanning , etc. ) projections are incomplete, the Differentiated Backprojection (DBP) and the Virtual Fanbeam methods are available to reconstruct some region of interest (ROI) of the object provided the incomplete projections are sufficient. Both of these methods have their constraints and limitations. This thesis deals with the improvement and development of the method of virtual fanbeam. Original results, including new explicit reconstruction formulas, that extend the scope of the method of virtual fanbeam are presented. It is also shown how to combine this method with FBP to reconstruct some ROI that can not be reconstructed by existing methods. Illustrative numerical simulations are also presented
34
Jia, Hongjun. "A study of the missing data problems in 3D structure reconstruction and 2D face recognition". Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1235750224.
Testo completo
35
Günther, Thomas. "Inversion methods and resolution analysis for the 2D/3D reconstruction of resistivity structures from DC measurements". Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2009. http://nbn-resolving.de/urn:nbn:de:swb:105-4152277.
Testo completoAbstract (sommario):
The presented thesis deals with the multi-dimensional reconstruction of the earth's conductivity distribution based on DC resistivity data. This task represents a nonlinear and ill-posed minimization problem with many degrees of freedom. In this work, techniques for regularization and controlling of this problem are depicted and classified. Particularly, it is concentrated on explicit regularization types, which impose constraints onto the model. The system of equations as resulting from the application of the Gauss-Newton minimization can be solved efficiently. Furthermore, it is shown how the regularization strength can be controlled. The method of non-linear resolution analysis plays a central role in the thesis. It represents a powerful tool to estimate the quality of inversion results. Furthermore, the derived resolution measures provide the basis for the optimization of experimental design concerning information content and efficiency. Methods of error estimation, forward modeling and the calculation of the Jacobian matrix for DC resistivity data are developed. Procedures for appropriate parameterization and inversion control are pointed out by studies of synthetic models. Different inversion and regularization methods are examined in detail. A linearized study is used to compare different data sets considering their efficiency. Moreover, a triplegrid-technique for the incorporation of topography into three-dimensional inversion is presented. Finally the inversion methods are applied to field data. The depicted optimization strategies are realized in practice, which increases the economic relevance of threedimensional data acquisition. The structure of the subsurface is imaged in detail for several applications in the fields of cavity detection, archaeology and the investigation of ground falls. The resolution analysis is successfully established to appraise the obtained results.
36
Ehsani, Ali Reza 1963. "A hardware reconstruction system for real-time magnetic resonance imaging via 2D FFT or filtered backprojection". Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/290683.
Testo completoAbstract (sommario):
A "real-time" hardware reconstruction system for Magnetic Resonance Imaging (MRI) has been designed, constructed, and demonstrated. Here, "real-time" corresponds to frame rates of 30 or more per second (i.e., video rate). The system is capable of reconstructing images via either the 2D FFT algorithm or the filtered backprojection algorithm. The 2D FFT hardware reconstructs 256 x 256 images from complex-valued data (on a rectilinear grid) at a rate of 30 frames/sec while the filtered backprojection hardware is capable of reconstructing 64 x 64 images from complex-valued data (on a polar grid) at a rate of 37 frames/sec. Real-time MRI may be achieved by interfacing the reconstruction system to MR scanners with ultra-fast acquisition capabilities, such as echo-planar imaging (EPI) for rectilinear data or spiral-scan for polar data. The reconstruction system consists of a number of circuit boards plugged into the bus of a personal computer (PC). The circuit boards are configured by the PC, and thereafter, communicate with each other through ribbon cables independent of the PC operation. Three of the circuit boards are common in both reconstruction methods. They are an analog-to-digital convertor board (ADC), an interface memory board (IM), and a display processor board (DP). In the 2D FFT method a fourth circuit board referred to as the Fourier processor board (FP) is utilized. In the filtered backprojection method two additional circuit boards, a projection filter board (PF) and a backprojection board (BP) are used. The basic theory of the two reconstruction methods as well as design and implementation of the digital-electronic hardware are described in this dissertation. Real-time reconstructed images by both methods are presented to demonstrate the capabilities of the digital-electronic system.
37
Noé, Estelle. "3D layered articulated object from a single 2D drawing". Thesis, KTH, Medieteknik och interaktionsdesign, MID, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-216943.
Testo completoAbstract (sommario):
Modeling articulated objects made of rigid layered parts used to populate 3D scenes in video games or movie production is a complex and time-consuming task for digital artists. This work proposes a sketch-based approach to efficiently model 3D layered articulated objects, such as animals with rigid shells and armors, in annotating a single 2D photo manually, and eventually fabricate it from automatically computed 2D patterns. In considering symmetrical objects seen under a 3/4 view, and an- notating salient features such as extremities of the rigid articulated parts as a mix of circular and Bézier curve, this approach is able to retrieve depth information, hidden parts, and rotation-articulated structure. The resulting shape consists of a set of quadrangulated polygons that may be flattened in 2D. Details such as ears, tails, and legs were further models using dedicated annotations. The accuracy of the reconstruction has been validated on synthetic cylindrical examples, and its ro- bustness in reconstructing a 3D model of armor, armadillo, and shrimp. The latter was finally fabricated using paper.Att modellera artikulerade objekt gjorda av styva delar lagda i lager som används till att fylla 3D-scener i datorspel och filmskapande är en komplex och tidsödande uppgift för digitala konstnärer. Den här undersökningen föreslår ett skiss-baserat tillvägagångssätt att effektivt modellera artikulerade 3D-objekt lagda i lager, såsom djur med styva skal och rustning, i att annotera ett 2D-foto manuellt, och eventuellt skapa det från automatiskt beräknade 2D-mönster. Hänsyn är tagen till symmetriska objekt sedda under en 3/4 vy, och annotera framträdande egenskapersåsom extremiteter av de styva artikulerade delarna som en blandning avcirkulära och Bézier-kurvor, kan det här tillvägagångssättet hämta information om djup, gömda delar och rotations-artikulerade strukturer. Den slutliga formen består av ett set av fyrsidiga polygoner som kan bli tillplattade i 2D. Detaljer såsom öron, svansar och ben där framtida modeller använder dedikerade annotationer. Noggrannheten av rekonstruktionen har blivit validerad på syntetiska cylindriska exempeloch dess robusthet i att rekonstruera en 3D-modell av en rustning, ett bältdjur och en räka. Den senare skapades slutligen med hjälp av papper.
38
Rekik, Wafa. "Fusion de données temporelles, ou 2D+t, et spatiales, ou 3D, pour la reconstruction de scènes 3D+t et traitement d'images sphériques : applications à la biologie cellulaire". Paris 6, 2007. http://www.theses.fr/2007PA066655.
Testo completoAbstract (sommario):
Dans certaines applications en vision, nous disposons de données volumiques (3D) et des séquences planaires (2D+t). Les données 3D définissent la géométrie en trois dimensions de la scène observée. Elles comportent donc des informations purement spatiales. Les séquences 2D+t sont porteuses d'informations temporelles et partiellement spatiales puisqu'elles décrivent en deux dimensions la dynamique des objets en mouvement. La fusion de ces données permet de restituer une séquence volumique (3D+t) de la scène filmée. Ces travaux s'articulent en deux volets. Le premier volet concerne une étude méthodologique de la reconstruction 3D+t par compensation du mouvent. Nous proposons deux familles d'approches : avec ou sans modèle a priori sur les structures observées dans les données. Le modèle a priori étudiée concernent des objets de géométrie sphérique. Le second volet décrit le traitement d'image multi-dimensionnels (2D, 3D, 2D+t, 3D+t) toujours dans le contexte de forme sphérique. Nous proposons alors diverses applications comme le suivi temporel sur les séquences 2D+t, la visualisation, la segmentation des données 2D ou 3D,. . . Une application possible est donnée en imagerie biologique dans le cadre de la simulation de parois cellulaires, contexte dans lequel nous observons dans diverses modalités des objets sphéroïdes.
39
Garnero, Line. "Reconstruction d'images tomographiques à partir d'un ensemble limite de projections". Paris 11, 1987. http://www.theses.fr/1987PA112012.
Testo completoAbstract (sommario):
Nous proposons dans cette thèse deux méthodes de reconstitution d'images tomographiques à partir d'un nombre limité de projections couvrant un angle de vue limité. Ces circonstances se rencontrent aussi bien en Imagerie Médicale, que dans d'autres domaines comme la microscopie électronique. Ces méthodes utilisent des informations a priori sur l'objet afin de retrouver les données manquantes. Nous avons appliqué une de ces méthodes aussi bien à reconstructions bidimensionnelles, que directement tridimensionnelles, et nous l'avons aussi utilisée dans deux cas concrets relevant du domaine des contrôles non destructifs et de la microimagerie plasma laser. Nous présentons aussi une étude des artéfacts paraissant sur les images tomographiques de Médecine Nucléaire à la suite de mauvaises conditions d'acquisition.
40
Durix, Bastien. "Squelettes pour la reconstruction 3D : de l'estimation de la projection du squelette dans une image 2D à la triangulation du squelette en 3D". Phd thesis, Toulouse, INPT, 2017. http://oatao.univ-toulouse.fr/19589/1/durix.pdf.
Testo completoAbstract (sommario):
La reconstruction 3D consiste à acquérir des images d’un objet, et à s’en servir pour en estimer un modèle 3D. Dans ce manuscrit, nous développons une méthode de reconstruction basée sur la modélisation par squelette. Cette méthode a l’avantage de renvoyer un modèle 3D qui est un objet virtuel complet (i.e. fermé) et aisément éditable, grâce à la structure du squelette. Enfin, l’objet acquis n’a pas besoin d’être texturé, et entre 3 et 5 images sont suffisantes pour la reconstruction. Dans une première partie, nous étudions les aspects 2D de l’étude. En effet, l’estimation d’un squelette 3D nécessite d’étudier la formation de la silhouette de l’objet à partir de son squelette, et donc les propriétés de sa projection perspective, appelée squelette perspectif. Cette étude est suivie par notre première contribution : un algorithme d’estimation de la projection perspective d’un squelette 3D curviligne, constitué d’un ensemble de courbes. Cet algorithme a toutefois tendance, comme beaucoup d’algorithmes estimant un squelette, à générer des branches peu informatives, notamment sur une image rastérisée. Notre seconde contribution est donc un algorithme d’estimation de squelette 2D, capable de prendre en compte la discrétisation du contour de la forme 2D, et d’éviter ces branches peu informatives. Cet algorithme, d’abord conçu pour estimer un squelette classique, est ensuite généralisé à l’estimation d’un squelette perspectif. Dans une seconde partie, nous estimons le squelette 3D d’un objet à partir de ses projections. Tout d’abord, nous supposons que le squelette de l’objet 3D à reconstruire est curviligne. Ainsi, chaque squelette perspectif estimé correspond à la projection du squelette 3D de l’objet, sous différents points de vue. La topologie du squelette étant affectée par la projection, nous proposons notre troisième contribution, l’estimation de la topologie du squelette 3D à partir de l’ensemble de ses projections. Une fois celle-ci estimée, la projection d’une branche 3D du squelette est identifiée sur chaque image, i.e. sur chacun des squelettes perspectifs. Avec cette identification, nous pouvons trianguler les branches du squelette 3D, ce qui constitue notre quatrième contribution : nous sommes donc en mesure d’estimer un squelette curviligne associé à un ensemble d’images d’un objet. Toutefois, les squelettes 3D ne sont pas tous constitués d’un ensemble de courbes : certains d’entre eux possèdent aussi des parties surfaciques. Notre dernière contribution, pour reconstruire des squelettes 3D surfaciques, est une nouvelle approche pour l’estimation d’un squelette 3D à partir d’images : son principe est de faire grandir le squelette 3D, sous les contraintes données par les images de l’objet.
41
Delestre, Barbara. "Reconstruction 3D de particules dans un écoulement par imagerie interférométrique". Electronic Thesis or Diss., Normandie, 2022. http://www.theses.fr/2022NORMR116.
Testo completoAbstract (sommario):
Pour de nombreuses applications industrielles ou environnementales, il est important de mesurer la taille et le volume de particules de formes irrégulières. C'est par exemple le cas dans le cadre du givrage des aéronefs qui se produit durant les vols, où il est nécessaire de mesurer in-situ la teneur en eau et la teneur en glace dans la troposphère afin de détecter et d’éviter les zones à risques. Notre intérêt s’est porté sur l’imagerie interférométrique en défaut de mise au point, une technique optique offrant de nombreux avantages (large champ de mesure, gamme de tailles étudiée étendue [50 μm : quelques millimètres], distance particule/appareil de mesure de plusieurs dizaines de centimètres…). Au cours de ces travaux de thèse, nous avons montré que la reconstruction 3D d'une particule peut se faire à partir d'un ensemble de trois images interférométriques de cette particule (sous trois angles de vue perpendiculaires). Cela peut être fait en utilisant l'algorithme de réduction d'erreur (ER) qui permet d'obtenir la fonction f(x,y) à partir des mesures du module de sa transformée de Fourier 2D |F(u,v)|, en reconstruisant la phase de sa transformée de Fourier 2D. La mise en œuvre de cet algorithme nous a permis de reconstruire la forme de particules irrégulières à partir de leurs images interférométriques. Des démonstrations expérimentales ont été réalisées à l'aide d'un montage spécifique basé sur l'utilisation d’une matrice de micro-miroirs (DMD) qui génère les images interférométriques de particules rugueuses programmables. Les résultats obtenus sont très encourageants. Les volumes obtenus restent assez proches du volume réel de la particule et les formes 3D reconstruites nous donnent une bonne idée de la forme générale de la particule étudiée même dans les cas les plus extrêmes où l'orientation de la particule est quelconque. Enfin, nous avons montré qu'une reconstruction 3D précise d'une particule rugueuse "programmée" peut être effectuée à partir d'un ensemble de 120 images interférométriquesFor many industrial or environmental applications, it is important to measure the size and volume of irregularly shaped particles. This is for example the case in the context of aircraft icing which occurs during flights, where it is necessary to measure in situ the water content and the ice content in the troposphere in order to detect and avoid risk areas. Our interest has been on interferometric out-of-focus imaging, an optical technique offering many advantages (wide measurement field, extended range of sizes studied [50 μm: a few millimeters], distance particle / measuring device several tens of centimeters ...). During this thesis, we showed that the 3D reconstruction of a particle can be done from a set of three interferometric images of this particle (under three perpendicular viewing angles). This can be done using the error reduction (ER) algorithm which allows to obtain the function f(x,y) from the measurements of the modulus of its 2D Fourier transform |F(u,v)| , by reconstructing the phase of its 2D Fourier transform. The implementation of this algorithm allowed us to reconstruct the shape of irregular particles from their interferometric images. Experimental demonstrations were carried out using a specific assembly based on the use of a micro-mirror array (DMD) which generates the interferometric images of programmable rough particles. The results obtained are very encouraging. The volumes obtained remain quite close to the real volume of the particle and the reconstructed 3D shapes give us a good idea of the general shape of the particle studied even in the most extreme cases where the orientation of the particle is arbitrary. Finally, we showed that an accurate 3D reconstruction of a "programmed" rough particle can be performed from a set of 120 interferometric images
42
Ben, Hamadou Achraf. "Contribution à la cartographie 3D des parois internes de la vessie par cystoscopie à vision active". Phd thesis, Institut National Polytechnique de Lorraine - INPL, 2011. http://tel.archives-ouvertes.fr/tel-00628292.
Testo completoAbstract (sommario):
La cystoscopie est actuellement l'examen clinique de référence permettant l'exploration visuelle des parois internes de la vessie. Le cystoscope (instrument utilisé pour cet examen) permet d'acquérir une séquence vidéo des parois épithéliales de la vessie. Cependant, chaque image de la séquence vidéo ne visualise qu'une surface réduite de quelques centimètres carrés de la paroi. Les travaux réalisés dans le cadre de cette thèse ont pour objectif de construire une carte 3D reproduisant d'une manière fidèle les formes et les textures des parois internes de la vessie. Une telle représentation de l'intérieur de la vessie permettrait d'améliorer l'interprétation des données acquises lors d'un examen cystoscopique. Pour atteindre cet objectif, un nouvel algorithme flexible est proposé pour le calibrage de systèmes cystoscopiques à vision active. Cet algorithme fournit les paramètres nécessaires à la reconstruction précise de points 3D sur la portion de surface imagée à chaque instant donné de la séquence vidéo cystoscopique. Ainsi, pour chaque acquisition de la séquence vidéo, un ensemble de quelques points 3D/2D et une image 2D est disponible. L'objectif du deuxième algorithme proposé dans cette thèse est de ramener l'ensemble des données obtenues pour une séquence dans un repère global pour générer un nuage de points 3D et une image panoramique 2D représentant respectivement la forme 3D et la texture de la totalité de la paroi imagée dans la séquence vidéo. Cette méthode de cartographie 3D permet l'estimation simultanée des transformations 3D rigides et 2D perspectives liant respectivement les positions du cystoscope et les images de paires d'acquisitions consécutives. Les résultats obtenus sur des fantômes réalistes de vessie montrent que ces algorithmes permettent de calculer des surfaces 3D reproduisant les formes à retrouver.
43
Kang, Xin, e 康欣. "Feature-based 2D-3D registration and 3D reconstruction from a limited number of images via statistical inference for image-guidedinterventions". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B48079625.
Testo completoAbstract (sommario):
Traditional open interventions have been progressively replaced with minimally invasive techniques.
Most notably, direct visual feedback is transitioned into indirect, image-based feedback,
leading to the wide use of image-guided interventions (IGIs). One essential process of all IGIs is to
align some 3D data with 2D images of patient through a procedure called 3D-2D registration during
interventions to provide better guidance and richer information. When the 3D data is unavailable, a
realistic 3D patient-speci_c model needs to be constructed from a few 2D images.
The dominating methods that use only image intensity have narrow convergence range and are
not robust to foreign objects presented in 2D images but not existed in 3D data. Feature-based
methods partly addressed these problems, but most of them heavily rely on a set of \best" paired
correspondences and requires clean image features. Moreover, the optimization procedures used in
both kinds of methods are not e_cient.
In this dissertation, two topics have been studied and novel algorithms proposed, namely, contour
extraction from X-ray images and feature-based rigid/deformable 3D-2D registration.
Inspired by biological and neuropsychological characteristics of primary visual cortex (V1), a
contour detector is proposed for simultaneously extracting edges and lines in images. The synergy
of V1 neurons is mimicked using phase congruency and tensor voting. Evaluations and comparisons
showed that the proposed method outperformed several commonly used methods and the results are
consistent with human perception. Moreover, the cumbersome \_ne-tuning" of parameter values is
not always necessary in the proposed method.
An extensible feature-based 3D-2D registration framework is proposed by rigorously formulating
the registration as a probability density estimation problem and solving it via a generalized expectation
maximization algorithm. It optimizes the transformation directly and treats correspondences
as nuisance parameters. This is signi_cantly di_erent from almost all feature-based method in the
literature that _rst single out a set of \best" correspondences and then estimate a transformation
associated with it. This property makes the proposed algorithm not rely on paired correspondences
and thus inherently robust to outliers. The framework can be adapted as a point-based method with
the major advantages of 1) independency on paired correspondences, 2) accurate registration using
a single image, and 3) robustness to the initialization and a large amount of outliers. Extended to
a contour-based method, it di_ers from other contour-based methods mainly in that 1) it does not
rely on correspondences and 2) it incorporates gradient information via a statistical model instead of
a weighting function. Tuning into model-based deformable registration and surface reconstruction,
our method solves the problem using the maximum penalized likelihood estimation. Unlike almost
all other methods that handle the registration and deformation separately and optimized them sequentially,
our method optimizes them simultaneously. The framework was evaluated in two example
clinical applications and a simulation study for point-based, contour-based and surface reconstruction,
respectively. Experiments showed its sub-degree and sub-millimeter registration accuracy and
superiority to the state-of-the-art methods.
It is expected that our algorithms, when thoroughly validated, can be used as valuable tools for
image-guided interventions.published_or_final_version
Orthopaedics and Traumatology
Doctoral
Doctor of Philosophy
44
Merabet, Lucas. "Etude d’algorithmes de reconstruction ultrasonore dans le domaine de Fourier pour l’imagerie rapide 2D et 3D en contrôle non- destructif". Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLET060.
Testo completoAbstract (sommario):
Ce travail de thèse s’intéresse à l’imagerie ultrasonore multi-éléments pour le Contrôle Non-Destructif (CND), et vise à accélérer l’imagerie échographique en 2D et 3D. Les méthodes étudiées s’inspirent des algorithmes de reconstruction dans le domaine de Fourier (f-k) en imagerie sismique. La littérature montre que ces méthodes offrent un avantage numérique par rapport à celles dans le domaine temporel basées sur un principe de focalisation en émission/réception. D’autre part, l’essor des traducteurs multi-éléments a permis d’explorer de nouveaux modes d’émission, comme les ondes planes en imagerie médicale ultra-rapide. Dans cette thèse, on se propose de combiner les algorithmes rapides du domaine f-k avec des émissions planes pour calculer des images aussi rapidement que possible. Ces algorithmes sont adaptés pour traiter des configurations d’inspection usuelles en CND. Une analyse des complexités algorithmiques, des temps de calcul et de la qualité des reconstructions est menée en 2D. La comparaison avec la méthode temporelle Plane Wave Imaging (PWI) démontre un avantage certain pour l’imagerie f-k. Ces avantages sont confirmés en 3D où l’on démontre que cette dernière améliore la qualité d’image tout en réduisant le temps de calcul d’un facteur allant jusqu’à 300 par rapport à PWI. Enfin, la méthode f-k est généralisée à l’imagerie multimodale pour la caractérisation de fissures. La théorie est d’abord présentée, puis on montre qu’il est possible d’améliorer la qualité des reconstructions grâce à un fenêtrage des fréquences spatiales de l’image. Ce filtre spectral élimine des artéfacts d’imagerie liés à des échos de géométrie, améliorant ainsi le contraste des imagesThis research work deals with ultrasound imaging with transducer arrays for Non Destructive Testing (NDT), and aims at speeding up the formation of 2D and 3D images. The methods studied in this manuscript are inspired from reconstruction algorithms in the Fourier frequency-wavenumber (f-k) domain introduced in seismic imaging in the 70’s. The literature shows that f-k methods offer a numerical advantage over the more conventional time-domain focusing algorithms. On the other hand, the rise of transducer arrays has allowed for the exploration of new emission modes, such as plane wave emissions in ultra-fast medical imaging. In this thesis, we propose to combine fast f-k algorithms with plane wave emissions to form 2D and 3D images as fast as possible. These algorithms are adapted to deal with realistic NDT inspection configurations. Analyses of algorithmic complexities, computation times, and image qualities are carried out in 2D, and a comparison with the time-domain Plane Wave Imaging (PWI) shows a clear advantage for f-k methods. This is confirmed in 3D, where we show that Fourier domain algorithms improve image quality while reducing computation times by a factor up to 300 compared to PWI. Finally, the f-k methods are generalized to multi-modal imaging to characterize cracks. The theory, which accounts for mode conversions and reflections at the specimen interfaces, is first presented, and we then demonstrate that it is possible to improve the reconstruction quality thanks to spectral windowing in the image frequency-domain. This spectral filter cancels undesired artifacts caused by interface echoes, and improves the image contrast
45
XHELAJ, ANDI. "Downburst Wind Field Reconstruction by means of a 2D Analytical Model and Investigation of the Parameter’s Variability through an Ensemble Approach". Doctoral thesis, Università degli studi di Genova, 2022. https://hdl.handle.net/11567/1097493.
Testo completoAbstract (sommario):
A “downburst” is defined as a diverging wind system that occurs when a strong downdraft induces an outflow of damaging winds on or near the ground. Severe wind damage in many parts of the world are often due to thunderstorm outflows and their knowledge is therefore relevant for structural safety and design wind speed evaluation. Nevertheless, there is not yet a shared model for thunderstorm outflows and their actions on structures. In this paper, an analytical model that simulates the horizontal mean wind velocity originated from a travelling downburst is proposed. The horizontal wind velocity is expressed as the vector summation of three independent components: the stationary radial velocity generated by an impinging jet over a flat surface, the downdraft translating velocity, which corresponds to the parent cloud motion, and the boundary layer background wind field at the surface where the downburst is immersed. A parametric analysis is also developed and coupled with the analytical model aiming to investigate two observed downburst events and extract their main parameters – e.g. downdraft diameter, touch-down position, translating downdraft speed and direction, intensity and decay period - in order to reconstruct the space-time evolution of these events. Due to large computational cost for the reconstruction of a single downburst wind field a novel strategy is implemented to speed up the process. Two metaheuristic optimization algorithms are used, namely the Teaching Learning Based Optimization and the Differential Evolution. The metric to evaluate the algorithm’s efficiency is based on the convergence behaviour of the objective function towards the best solution as the number of iterations increases. The decision variable parameters (e.g. downdraft diameter, touch-down position, translating downdraft speed and direction, iintensity,and decay period and so on) that minimize the objective function are very important in Wind Engineering since their knowledge allows statistical analysis of the intense wind fields that are generated during downburst winds, and therefore allows to better define the actions that these extreme events have on structures. Lastly the proposed model was validated against s strong downburst event that took place in Sânnicolau Mare (Romania) during the summer of 2021. This event was accompanied by hail of 2-3 cm in size and the hail near the surface was driven by the downburst wind. This means that the horizontal velocity of the ice projectile near the surface was less or equal to the horizontal downburst wind velocity. After this strong event, a damage survey was carried out in collaboration between the University of Genoa (Italy) and the University of Bucharest (Romania). The damage survey identified locations of buildings in Sânnicolau Mare that suffered hail damage during the event. The analytical model was used to reproduce the recorded wind speed and direction due to the severe downburst. Using the simulated wind field, the simulated damage “footprint” (i.e., the maximum wind speed that occurred at a given place at any time during the passage of the downburst) was calculated. The simulated footprint was able to matches with a very good extent the areas that suffered from hail damage, and consequently permit to validate the proposed analytical model.
46
Lopez-Hernandez, Juan. "Imagerie Cardiaque Multimodalités 2D et 3D :application à la Coronarographie/Tomoscintigraphie/TEP-CT". Phd thesis, Institut National Polytechnique de Lorraine - INPL, 2006. http://tel.archives-ouvertes.fr/tel-00118991.
Testo completoAbstract (sommario):
La coronarographie et la tomoscintigraphie (SPECT, de l'anglais "Single Photon Emission ComputedTomography") sont deux techniques d'imagerie utilisées couramment pour diagnostiquer les maladies
cardiovasculaires. La première modalité est constituée de séquences d'images à rayon X visualisant chacune,
dans un même plan, les artères coronaires situées sur la face avant et la face arrière du coeur. Les images à
rayons X fournissent des informations anatomiques liées à l'arbre artériel et mettent en évidence d'éventuels
rétrécissements des artères (sténoses). La modalité SPECT (imagerie nucléaire) fournit une représentation 3D
de la perfusion du volume myocardique. Cette information fonctionnelle permet la visualisation de régions
myocardiques souffrant de défauts d'irrigations. Le but du travail présenté est de superposer, en 3D, les
informations fonctionnelles et anatomiques pour établir un lien visuel entre des lésions artérielles et leurs
conséquences en termes de défauts d'irrigation. Dans la représentation 3D choisie pour faciliter le diagnostic, la
structure d'un arbre artériel schématique, comprenant les sténoses, est placée sur le volume de perfusion. Les
données initiales sont constituées d'une liste de points représentatifs de l'arbre artériel (points d'arrivée et de
départs de segments d'artères, bifurcations, sténoses, etc.) marqués par le coronarographiste dans les images à
rayons X des différentes incidences. Le volume de perfusion est ensuite projeté sous les incidences des images
de coronarographie. Un algorithme de recalage superposant les images à rayons X et les projections SPECT
correspondantes fournit les paramètres des transformations géométriques ramenant les points marqués dans les
images à rayons X dans une position équivalente dans les images SPECT. Un algorithme de reconstruction 3D
permet ensuite de placer les points artériels et les sténoses sur le volume de perfusion et de former un arbre
schématique servant de repère au clinicien. Une base de données formée de 28 patients a été utilisée pour
effectuer 40 superpositions 3D de données anatomo-fonctionnelles. Ces reconstructions ont montré que la
représentation 3D est suffisamment précise pour permettre d'établir visuellement un lien entre sténoses et
défauts de perfusions. Nos algorithmes de superpositions 3D ont ensuite été complétés pour remplacer la
modalité SPECT par les données de l'examen bimodal TEP/CT (Tomographie par Emission de
Positons/Tomodensitométrie). Les données d'un cas clinique trimodal TEP/CT/coronarographie ont été utilisées
pour vérifier l'adéquation de nos algorithmes à la nouvelle modalité d'imagerie.
47
Abbood, Zainab Ali. "Study of the Fly algorithm for 2-D and 3-D image reconstruction". Thesis, Bangor University, 2017. https://research.bangor.ac.uk/portal/en/theses/study-of-the-fly-algorithm-for-2d-and-3d-image-reconstruction(97fc0202-c054-425b-9688-bff5c23d38fe).html.
Testo completoAbstract (sommario):
The aim of this study is to investigate the behaviour and application of an evolutionary algorithm (EA) based on a particular approach of cooperative co-evolution algorithm (CCEA), the Parisian Approach. It evolves and keeps an entire population as an optimal solution to the problem instead of keeping only the best individual in classical EAs. The CCEA we selected is called the “Fly algorithm”. It is named after flies, because the individuals are extremely primitive and correspond to three-dimensional (3-D) points. This algorithm has been relatively overlooked despite showing promising results in real-time robotic and image reconstruction in tomography. Our focus in this study is on two types of applications: medical imaging and digital art. i) In the medical application, we aim to improve quantitative results in 3-D reconstructed volumes in positron emission tomography (PET).We investigate the use of density fields, based on Metaballs and on Gaussian functions respectively, to obtain a realistic output. We also investigate how to exploit individuals’ fitness to modulate their individual footprint in the final reconstructed volume. An individual’s fitness can be seen as a level of confidence in its 3-D position. The resulting volumes are compared with previous work in terms of normalised-cross correlation. In our test cases, data fidelity increases by more than 10% when density fields are used instead of using a naive approach. Our method also provides reconstructions comparable to those obtained using well-established techniques used in medicine (e.g., filtered back-projection (FBP) and ordered subset expectation-maximization (OSEM)). Our algorithm relies heavily on the mutation operator. We propose 4 different fully adaptive mutation operators: basic mutation, adaptive mutation variance, dual mutation and directed mutation. Their impact on the algorithm efficiency is analysed and validated on PET reconstruction. ii) In the digital art application, we present the first application of the Fly algorithm in digital art. This branch of digital art is called “evolutionary art”. The motivation is to evaluate the algorithm with a much more complex structure of flies. They are still defined as simplistic primitives (3-D points) but with colours, sizes and rotations. Different visual effects were investigated, such as mosaic-like images and spray paint rendering. An online survey (including 41 participates) was conducted to validate our approach. Participants compared our results with similar ones generated with open-source software (GIMP). Again, our method shows promising results. In conclusion, our investigations confirm that the Fly algorithm works well with a complex search space. We demonstrate a fast and accurate solution to optimise a set of parameters in both applications. The Fly algorithm can improve reconstructed image quality compared to FBP and OSEM in medical application and to GIMP in digital art application.
48
Jibrini, Hassan. "Reconstruction automatique des bâtiments en modèles polyédriques 3-D à partir de données cadastrales vectorisées 2D et d'un couple d'images aériennes à haute résolution". Paris, ENST, 2002. http://www.theses.fr/2002ENST0010.
Testo completo
49
Wisnet, Andreas [Verfasser], e Christina [Akademischer Betreuer] Scheu. "1D TiO2 nanostructures probed by 2D transmission electron microscopy : while paving the way for their 3D reconstruction / Andreas Wisnet. Betreuer: Christina Scheu". München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2014. http://d-nb.info/106740127X/34.
Testo completo
50
Ehlke, Moritz [Verfasser], Olaf [Akademischer Betreuer] Hellwich, Olaf [Gutachter] Hellwich, Bernhard [Gutachter] Preim e Stefan [Gutachter] Zachow. "3D reconstruction of anatomical structures from 2D X-ray images / Moritz Ehlke ; Gutachter: Olaf Hellwich, Bernhard Preim, Stefan Zachow ; Betreuer: Olaf Hellwich". Berlin : Technische Universität Berlin, 2021. http://d-nb.info/1230468536/34.
Testo completo