Reconstruction 3D de sténoses par modélisation markovienne à partir de plus de deux images d'angiographie rotative par rayons X

- Dans cette contribution, nous proposons une méthode de reconstruction tridimensionnelle (3D) locale de sténoses à partir de plus de deux images ou projections extraites d'une séquence d'images d'angiographie rotative par rayons X. Cette méthode utilise une modélisation markovienne dont l'énergie comprend un terme décrivant l'a priori sur la structure vasculaire à reconstruire ainsi qu'un terme d'ajustement aux projections. Cette modélisation est une généralisation de celle introduite dans [1]. En effet, l'énergie d'ajustement est modifiée afin de prendre en compte un nombre de projections supérieur à deux. Cette généralisation augmente le nombre de contraintes ce qui diminue le nombre de minima globaux de l'énergie markovienne. Les simulations réalisées dans ce travail montre que cela améliore sensiblement la qualité de la reconstruction dans le cas de présence de sténoses de formes complexes

Spatio-temporal data fusion in cerebral angiography

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 153-167).This thesis provides a framework for generating the previously unobtained high resolution time sequences of 3D images that show the dynamics of cerebral blood flow. These sequences allow image feedback during medical procedures that can facilitate the detection and observation of stenosis, aneurysms, and clots. The 3D time series is constructed by fusing together a single static 3D image with one or more time sequence of 2D projections. The fusion process utilizes a variational approach that constrains the volumes to have both smoothly varying regions separated by edges and sparse regions of non-zero support. Results are presented on both clinical and simulated phantom data sets. The 3D time series results are visualized using the following tools: time series of intensity slices, synthetic X-rays from an arbitrary view, time series of isosurfaces, and 3D surfaces that show arrival times of contrast using color. This thesis also details the different steps needed to prepare the two classes of data. In addition to the spatio-temporal data fusion algorithm, three new algorithms are presented: a single pass groupwise registration algorithm for registering the time series, a 2D-3D registration algorithm for registering the time series with respect to the 3D volume, and a modified adaptive version of the Cusum algorithm used for determining arrival times of contrast within the 2D time sequences.by Andrew David Copeland.Ph.D

Reconstruction 3D de vaisseaux à partir d'un faible nombre de projections à l'aide de contours déformables

Un contour actif, évoluant dans un processus stochastique, est proposé pour la reconstruction en tomographie d'images binaires. Une fonction de coût, formée d'un terme d'attachement aux données tomographiques et d'une fonction de régularisation, prenant en compte les artefacts inhérents à la reconstruction, est minimisée pour trouver la solution MAP optimale, dans un cadre Bayesien. La méthode, appliquée à la reconstruction des vaisseaux sanguins, est stable. Les résultats obtenus sur des simulations bruitées et sur des acquisitions sur fantômes sont prometteurs

Automatic Spatiotemporal Analysis of Cardiac Image Series

RÉSUMÉ À ce jour, les maladies cardiovasculaires demeurent au premier rang des principales causes de décès en Amérique du Nord. Chez l’adulte et au sein de populations de plus en plus jeunes, la soi-disant épidémie d’obésité entraînée par certaines habitudes de vie tels que la mauvaise alimentation, le manque d’exercice et le tabagisme est lourde de conséquences pour les personnes affectées, mais aussi sur le système de santé. La principale cause de morbidité et de mortalité chez ces patients est l’athérosclérose, une accumulation de plaque à l’intérieur des vaisseaux sanguins à hautes pressions telles que les artères coronaires. Les lésions athérosclérotiques peuvent entraîner l’ischémie en bloquant la circulation sanguine et/ou en provoquant une thrombose. Cela mène souvent à de graves conséquences telles qu’un infarctus. Outre les problèmes liés à la sténose, les parois artérielles des régions criblées de plaque augmentent la rigidité des parois vasculaires, ce qui peut aggraver la condition du patient. Dans la population pédiatrique, la pathologie cardiovasculaire acquise la plus fréquente est la maladie de Kawasaki. Il s’agit d’une vasculite aigüe pouvant affecter l’intégrité structurale des parois des artères coronaires et mener à la formation d’anévrismes. Dans certains cas, ceux-ci entravent l’hémodynamie artérielle en engendrant une perfusion myocardique insuffisante et en activant la formation de thromboses. Le diagnostic de ces deux maladies coronariennes sont traditionnellement effectués à l’aide d’angiographies par fluoroscopie. Pendant ces examens paracliniques, plusieurs centaines de projections radiographiques sont acquises en séries suite à l’infusion artérielle d’un agent de contraste. Ces images révèlent la lumière des vaisseaux sanguins et la présence de lésions potentiellement pathologiques, s’il y a lieu. Parce que les séries acquises contiennent de l’information très dynamique en termes de mouvement du patient volontaire et involontaire (ex. battements cardiaques, respiration et déplacement d’organes), le clinicien base généralement son interprétation sur une seule image angiographique où des mesures géométriques sont effectuées manuellement ou semi-automatiquement par un technicien en radiologie. Bien que l’angiographie par fluoroscopie soit fréquemment utilisé partout dans le monde et souvent considéré comme l’outil de diagnostic “gold-standard” pour de nombreuses maladies vasculaires, la nature bidimensionnelle de cette modalité d’imagerie est malheureusement très limitante en termes de spécification géométrique des différentes régions pathologiques. En effet, la structure tridimensionnelle des sténoses et des anévrismes ne peut pas être pleinement appréciée en 2D car les caractéristiques observées varient selon la configuration angulaire de l’imageur. De plus, la présence de lésions affectant les artères coronaires peut ne pas refléter la véritable santé du myocarde, car des mécanismes compensatoires naturels (ex. vaisseaux----------ABSTRACT Cardiovascular disease continues to be the leading cause of death in North America. In adult and, alarmingly, ever younger populations, the so-called obesity epidemic largely driven by lifestyle factors that include poor diet, lack of exercise and smoking, incurs enormous stresses on the healthcare system. The primary cause of serious morbidity and mortality for these patients is atherosclerosis, the build up of plaque inside high pressure vessels like the coronary arteries. These lesions can lead to ischemic disease and may progress to precarious blood flow blockage or thrombosis, often with infarction or other severe consequences. Besides the stenosis-related outcomes, the arterial walls of plaque-ridden regions manifest increased stiffness, which may exacerbate negative patient prognosis. In pediatric populations, the most prevalent acquired cardiovascular pathology is Kawasaki disease. This acute vasculitis may affect the structural integrity of coronary artery walls and progress to aneurysmal lesions. These can hinder the blood flow’s hemodynamics, leading to inadequate downstream perfusion, and may activate thrombus formation which may lead to precarious prognosis. Diagnosing these two prominent coronary artery diseases is traditionally performed using fluoroscopic angiography. Several hundred serial x-ray projections are acquired during selective arterial infusion of a radiodense contrast agent, which reveals the vessels’ luminal area and possible pathological lesions. The acquired series contain highly dynamic information on voluntary and involuntary patient movement: respiration, organ displacement and heartbeat, for example. Current clinical analysis is largely limited to a single angiographic image where geometrical measures will be performed manually or semi-automatically by a radiological technician. Although widely used around the world and generally considered the gold-standard diagnosis tool for many vascular diseases, the two-dimensional nature of this imaging modality is limiting in terms of specifying the geometry of various pathological regions. Indeed, the 3D structures of stenotic or aneurysmal lesions may not be fully appreciated in 2D because their observable features are dependent on the angular configuration of the imaging gantry. Furthermore, the presence of lesions in the coronary arteries may not reflect the true health of the myocardium, as natural compensatory mechanisms may obviate the need for further intervention. In light of this, cardiac magnetic resonance perfusion imaging is increasingly gaining attention and clinical implementation, as it offers a direct assessment of myocardial tissue viability following infarction or suspected coronary artery disease. This type of modality is plagued, however, by motion similar to that present in fluoroscopic imaging. This issue predisposes clinicians to laborious manual intervention in order to align anatomical structures in sequential perfusion frames, thus hindering automation o

Digital ocular fundus imaging: a review

Ocular fundus imaging plays a key role in monitoring the health status of the human eye. Currently, a large number of imaging modalities allow the assessment and/or quantification of ocular changes from a healthy status. This review focuses on the main digital fundus imaging modality, color fundus photography, with a brief overview of complementary techniques, such as fluorescein angiography. While focusing on two-dimensional color fundus photography, the authors address the evolution from nondigital to digital imaging and its impact on diagnosis. They also compare several studies performed along the transitional path of this technology. Retinal image processing and analysis, automated disease detection and identification of the stage of diabetic retinopathy (DR) are addressed as well. The authors emphasize the problems of image segmentation, focusing on the major landmark structures of the ocular fundus: the vascular network, optic disk and the fovea. Several proposed approaches for the automatic detection of signs of disease onset and progression, such as microaneurysms, are surveyed. A thorough comparison is conducted among different studies with regard to the number of eyes/subjects, imaging modality, fundus camera used, field of view and image resolution to identify the large variation in characteristics from one study to another. Similarly, the main features of the proposed classifications and algorithms for the automatic detection of DR are compared, thereby addressing computer-aided diagnosis and computer-aided detection for use in screening programs.Fundação para a Ciência e TecnologiaFEDErPrograma COMPET

Numerical Simulation of Nanoparticle Transportation and Deposition in Pulmonary Vasculature

Nanoparticle holds significant promise as the next generation of drug carrier that can realize targeted therapy with minimal toxicity. To improve the delivery efficiency of nanoparticles, it is important to study their transport and deposition in blood flow. Many factors, like particle size, vessel geometry and blood flow rate, have significant influence on the particle transport, thus on the deposition fraction and distribution.In this thesis, computational fluid dynamics (CFD) simulations of blood flow and drug particle deposition were conducted in four models representing the human lung vasculature: artificial artery geometry, artificial vein geometry, original geometry and over-smoothed original geometry. Flow conditions used included both steady-state inlet flow and pulsatile inlet flow. Parabolic flow pattern and lumped mathematic model were used for inlet and outlet boundary conditions respectively. Blood flow was treated as laminar and Newtonian. Particle trajectories were calculated in each of these models by solving the integrated force balance on the particle, and adding a stochastic Brownian term at each step. A receptor-ligand model was integrated to simulate the particle binding probability. The results indicate the following: (i) Pulsatile flow can accelerate the particle binding activity and improve the particle deposition fraction on bifurcation areas; (ii) Unlike drug delivery in lung respiratory system, particle diffusion is very weak in blood flow, no clear relationship between the particle size and deposition area was found in our four-generation lung vascular model; and (iii) Surface imperfections have the dominant effect on particle deposition fraction over a wide range of particle sizes. Ideal artificial geometry is not sufficient to predict drug deposition, and an accurate image based geometry is required

3D reconstruction of coronary arteries from angiographic sequences for interventional assistance

Introduction -- Review of literature -- Research hypothesis and objectives -- Methodology -- Results and discussion -- Conclusion and future perspectives