Les diagnostics cliniques des maladies cardio-vasculaires sont principalement effectués à l’aide d’échographies Doppler-couleur malgré ses restrictions : mesures de vélocité dépendantes de l’angle ainsi qu’une fréquence d’images plus faible à cause de focalisation traditionnelle. Deux études, utilisant des approches différentes, adressent ces restrictions en utilisant l’imagerie à onde-plane, post-traitée avec des méthodes de délai et sommation et d’autocorrélation. L’objectif de la présente étude est de ré-implémenté ces méthodes pour analyser certains paramètres qui affecte la précision des estimations de la vélocité du flux sanguin en utilisant le Doppler vectoriel 2D. À l’aide d’expériences in vitro sur des flux paraboliques stationnaires effectuées avec un système Verasonics, l’impact de quatre paramètres sur la précision de la cartographie a été évalué : le nombre d’inclinaisons par orientation, la longueur d’ensemble pour les images à orientation unique, le nombre de cycles par pulsation, ainsi que l’angle de l’orientation pour différents flux. Les valeurs optimales sont de 7 inclinaisons par orientation, une orientation de ±15° avec 6 cycles par pulsation. La précision de la reconstruction est comparable à l’échographie Doppler conventionnelle, tout en ayant une fréquence d’image 10 à 20 fois supérieure, permettant une meilleure caractérisation des transitions rapides qui requiert une résolution temporelle élevée. / Clinical diagnosis of cardiovascular disease is dominated by colour-Doppler ultrasound despite its limitations: angle-dependent velocity measurements and low frame-rate from conventional focusing. Two studies, varying in their approach, address these limitations using plane-wave imaging, post-processed with the delay-and-sum and autocorrelation methods. The aim of this study is to re-implement these methods, investigating some parameters which affect blood velocity estimation accuracy using 2D vector-Doppler. Through in vitro experimentation on stationary parabolic flow, using a Verasonics system, four parameters were tested on mapping accuracy: number of tilts per orientation, ensemble length for single titled images, cycles per transmit pulse, and orientation angle at various flow-rates. The optimal estimates were found for 7 compounded tilts per image, oriented at ±15° with 6 cycles per pulse. Reconstruction accuracies were comparable to conventional Doppler; however, maintaining frame-rates more than 10 to 20 times faster, allowing better characterization of fast transient events requiring higher temporal resolution.

Devido à variação na qualidade e ao ruído nas imagens médicas, a aplicação de técnicas tradicionais de segmentação é geralmente ineficiente. Nesse sentido, apresenta-se um novo algoritmo a partir de duas técnicas: o modelo de contornos deformáveis por fluxo do vetor gradiente (GVF deformable contours) e a técnica de espaço de escalas utilizando o processo de difusão. Assim, foi realizada uma revisão bibliográfica dos modelos que trabalham com os contornos deformáveis, os quais foram classificados em modelos paramétricos e geométricos. Entre os modelos paramétricos foi escolhido o modelo de contornos deformáveis por fluxo do vetor gradiente (GVF). Esta aproximação oferece precisão na representação de estruturas biológicas não observada em outros modelos. Desta forma, o algoritmo apresentado mapeia as bordas (edge map) e aperfeiçoa a condução da deformação utilizando uma técnica baseada em operações recursivas. Com este cálculo apoiado no comportamento de espaço de escalas, obtem-se a localização e correção de sub-regiões do edge map que perturbam a deformação. Por outro lado, é incorporada uma nova característica que permite ao algoritmo realizar atividades de classificação. O algoritmo consegue determinar a presença ou ausência de um objeto de interesse utilizando um valor mínimo de deformação. O algoritmo é validado através do tratamento de imagens sintéticas e médicas comparando os resultados com os obtidos no modelo tradicional de contornos deformáveis GVF. / Due to the variation of the quality and noise in medical images, the classic image segmentation techniques are usually ineffective. In this work, we present a new algorithm that is composed of two techniques: the gradient vector flow deformable contours (GVF) and the scale-space technique using a diffusion process. A bibliographical revision of the models that work with deformable contours was accomplished, they were classified in parametric and geometric models. Among the parametric models the gradient vector flow deformable contours (GVF) was chosen. This approach offers precision in the representation of biological structures where other models does not. Thus, the algorithm improves the edge map to guide the deformation using recursive operations. With this estimation based on the behavior of the scale-space techniques it is realized, the localization and correction of sub-areas of the edge map that disturb the deformation. On the other hand, it was incorporated a new characteristic that allows the algorithm to accomplish classification activities. That is, the algorithm determines the presence or absence of a target object using a minimal deformation area. Our method was validated on both, simulated images and medical images making a comparison with the traditional GVF deformable contours.

Le but de ces travaux est de proposer une contribution au recalage d'images TDM-TEP dans les régions thoraciques et abdominales. Notre méthodologie est fondée sur l'introduction de contraintes anatomiques au recalage non linéaire appliqué sur les intensités. Cette introduction est faite d'une manière explicite, en divisant la procédure en une phase d'initialisation recalant les structures segmentées dans les deux images, et une deuxième phase de recalage à niveaux de gris, raffinant l'étape précédente de l'algorithme. Les transformations sont modélisées dans les deux étapes à partir de Free Form Deformations (FFD). La segmentation est réalisée selon une procédure hiérarchique de reconnaissance de formes. La mesure fournie par le protocole d'évaluation que nous avons développé indique une erreur inférieure à 1cm pour les structures les plus significatives (poumons, foie, reins, coeur), sauf pour le stomach (erreur d'1.5cm).

Title from PDF of title page. / Document formatted into pages; contains 76 pages. / Thesis (M.S.E.E.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: The use of digitized information is rapidly gaining acceptance in bio-medical applications. Video compression plays an important role in the archiving and transmission of different digital diagnostic modalities. The present scheme of video compression for low bit-rate networks is not suitable for medical video sequences. The instability is the result of block artifacts resulting from the block based DCT coefficient quantization. The possibility of applying deformable motion estimation techniques to make the video compression standard (H.263) more adaptable for bio-medial applications was studied in detail. The study on the network characteristics and the behavior of various congestion control mechanisms was used to analyze the complete characteristics of existing low bit rate video compression algorithms. The study was conducted in three phases. The first phase involved the implementation and study of the present H.263 compression standard and its limitations. / ABSTRACT: The second phase dealt with the analysis of an external force for active contours which was used to obtain estimates for deformable objects. The external force, which is termed Gradient Vector Flow (GVF), was computed as a diffusion of the gradient vectors associated with a gray-level or binary edge map derived from the image. The mathematical aspect of a multi-scale framework based on a medial representation for the segmentation and shape characterization of anatomical objects in medical imagery was derived in detail. The medial representations were based on a hierarchical representation of linked figural models such as protrusions, indentations, neighboring figures and included figures--which represented solid regions and their boundaries. The third phase dealt with the vital parameters for effective video streaming over the internet in the bottleneck bandwidth, which gives the upper limit for the speed of data delivery from one end point to the other in a network. / ABSTRACT: If a codec attempts to send data beyond this limit, all packets above the limit will be lost. On the other hand, sending under this limit will clearly result in suboptimal video quality. During this phase the packet-drop-rate (PDR) performance of TCP(1/2) was investigated in conjunction with a few representative TCP-friendly congestion control protocols (CCP). The CCPs were TCP(1/256), SQRT(1/256) and TFRC (256), with and without self clocking. The CCPs were studied when subjected to an abrupt reduction in the available bandwidth. Additionally, the investigation studied the effect on the drop rates of TCP-Compatible algorithms by changing the queuing scheme from Random Early Detection (RED) to DropTail. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

Les diagnostics cliniques des maladies cardio-vasculaires sont principalement effectués à l’aide d’échographies Doppler-couleur malgré ses restrictions : mesures de vélocité dépendantes de l’angle ainsi qu’une fréquence d’images plus faible à cause de focalisation traditionnelle. Deux études, utilisant des approches différentes, adressent ces restrictions en utilisant l’imagerie à onde-plane, post-traitée avec des méthodes de délai et sommation et d’autocorrélation. L’objectif de la présente étude est de ré-implémenté ces méthodes pour analyser certains paramètres qui affecte la précision des estimations de la vélocité du flux sanguin en utilisant le Doppler vectoriel 2D. À l’aide d’expériences in vitro sur des flux paraboliques stationnaires effectuées avec un système Verasonics, l’impact de quatre paramètres sur la précision de la cartographie a été évalué : le nombre d’inclinaisons par orientation, la longueur d’ensemble pour les images à orientation unique, le nombre de cycles par pulsation, ainsi que l’angle de l’orientation pour différents flux. Les valeurs optimales sont de 7 inclinaisons par orientation, une orientation de ±15° avec 6 cycles par pulsation. La précision de la reconstruction est comparable à l’échographie Doppler conventionnelle, tout en ayant une fréquence d’image 10 à 20 fois supérieure, permettant une meilleure caractérisation des transitions rapides qui requiert une résolution temporelle élevée. / Clinical diagnosis of cardiovascular disease is dominated by colour-Doppler ultrasound despite its limitations: angle-dependent velocity measurements and low frame-rate from conventional focusing. Two studies, varying in their approach, address these limitations using plane-wave imaging, post-processed with the delay-and-sum and autocorrelation methods. The aim of this study is to re-implement these methods, investigating some parameters which affect blood velocity estimation accuracy using 2D vector-Doppler. Through in vitro experimentation on stationary parabolic flow, using a Verasonics system, four parameters were tested on mapping accuracy: number of tilts per orientation, ensemble length for single titled images, cycles per transmit pulse, and orientation angle at various flow-rates. The optimal estimates were found for 7 compounded tilts per image, oriented at ±15° with 6 cycles per pulse. Reconstruction accuracies were comparable to conventional Doppler; however, maintaining frame-rates more than 10 to 20 times faster, allowing better characterization of fast transient events requiring higher temporal resolution.

Devido à variação na qualidade e ao ruído nas imagens médicas, a aplicação de técnicas tradicionais de segmentação é geralmente ineficiente. Nesse sentido, apresenta-se um novo algoritmo a partir de duas técnicas: o modelo de contornos deformáveis por fluxo do vetor gradiente (GVF deformable contours) e a técnica de espaço de escalas utilizando o processo de difusão. Assim, foi realizada uma revisão bibliográfica dos modelos que trabalham com os contornos deformáveis, os quais foram classificados em modelos paramétricos e geométricos. Entre os modelos paramétricos foi escolhido o modelo de contornos deformáveis por fluxo do vetor gradiente (GVF). Esta aproximação oferece precisão na representação de estruturas biológicas não observada em outros modelos. Desta forma, o algoritmo apresentado mapeia as bordas (edge map) e aperfeiçoa a condução da deformação utilizando uma técnica baseada em operações recursivas. Com este cálculo apoiado no comportamento de espaço de escalas, obtem-se a localização e correção de sub-regiões do edge map que perturbam a deformação. Por outro lado, é incorporada uma nova característica que permite ao algoritmo realizar atividades de classificação. O algoritmo consegue determinar a presença ou ausência de um objeto de interesse utilizando um valor mínimo de deformação. O algoritmo é validado através do tratamento de imagens sintéticas e médicas comparando os resultados com os obtidos no modelo tradicional de contornos deformáveis GVF. / Due to the variation of the quality and noise in medical images, the classic image segmentation techniques are usually ineffective. In this work, we present a new algorithm that is composed of two techniques: the gradient vector flow deformable contours (GVF) and the scale-space technique using a diffusion process. A bibliographical revision of the models that work with deformable contours was accomplished, they were classified in parametric and geometric models. Among the parametric models the gradient vector flow deformable contours (GVF) was chosen. This approach offers precision in the representation of biological structures where other models does not. Thus, the algorithm improves the edge map to guide the deformation using recursive operations. With this estimation based on the behavior of the scale-space techniques it is realized, the localization and correction of sub-areas of the edge map that disturb the deformation. On the other hand, it was incorporated a new characteristic that allows the algorithm to accomplish classification activities. That is, the algorithm determines the presence or absence of a target object using a minimal deformation area. Our method was validated on both, simulated images and medical images making a comparison with the traditional GVF deformable contours.

Die vorliegende Arbeit befasst sich mit Algorithmen aus dem Bereich der Bildsegmentierung sowie der Datensynthese für das so genannte Hologrammdruck-Prinzip. Angelehnt an ein anatomisch motiviertes Forschungsprojekt werden aktive Konturen zur halbautomatischen Segmentierung digitalisierter histologischer Schnitte herangezogen. Die besondere Herausforderung liegt dabei in der Entwicklung von verschiedenen Ansätzen, die der Anpassung des Verfahrens für sehr große Bilder dienen, welche in diesem Kontext eine Größe von einigen hundert Megapixel erreichen können. Unter dem Aspekt der größtmöglichen Effizienz, jedoch mit der Beschränkung auf die Verwendung von Consumer-Hardware, werden Ideen vorgestellt, welche eine auf aktiven Konturen basierende Segmentierung bei derartigen Bildgrößen erstmals ermöglichen sowie zur Beschleunigung und Reduktion des Speicheraufwandes beitragen. Darüber hinaus wurde das Verfahren um ein intuitives Werkzeug erweitert, das eine interaktive lokale Korrektur der finalen Kontur gestattet und damit die Praxistauglichkeit der Methode maßgeblich erhöht. Der zweite Teil der Arbeit beschäftigt sich mit einem Druckprinzip für die Herstellung von Hologrammen, basierend auf virtuellen Abbildungsgegenständen. Der Hologrammdruck, der namentlich an die Arbeitsweise eines Tintenstrahldruckers erinnern soll, benötigt dazu spezielle diskrete Bilddaten, die als Elementarhologramme bezeichnet werden. Diese tragen die visuelle Information verschiedener Blickrichtungen durch einen festen geometrischen Ort auf der Hologrammebene. Ein vollständiges, aus vielen Elementarhologrammen zusammengesetztes Hologramm erzeugt dabei ein erhebliches Datenvolumen, das parameterabhängig schnell im Terabyte-Bereich liegen kann. Zwei unabhängige Algorithmen zur Erzeugung geeignet aufbereiteter Daten unter intensiver Ausnutzung von Standard-Graphikhardware werden präsentiert, hinsichtlich ihrer Berechnungs- sowie Speicherkomplexität verglichen und unter Berücksichtigung von Qualitätsaspekten bewertet.

Ces travaux de thèse portent sur le développement de nouvelles modalités d’imagerie cardiovasculaire basé sur l’utilisation de l'imagerie ultrarapide 2D et 3D. Les modalités d’imagerie développées dans cette thèse appartiennent au domaine de de l’élastographie par onde de cisaillement et de l'imagerie Doppler des flux sanguins.Dans un premier temps, la technique de l’élastographie par onde de cisaillement du myocarde a été développée pour les applications cliniques. Une approche d'imagerie non-linéaire a été utilisée pour améliorer l’estimation de vitesse des ondes de cisaillement (ou la rigidité des tissus cardiaques) de manière non invasive et localisée. La validation de cette nouvelle approche de « l’imagerie par sommation cohérente harmonique ultrarapide » a été réalisée in vitro et la faisabilité in vivo a été testée chez l’humain. Dans un second temps, nous avons utilisé cette technique sur des patients lors de deux essais cliniques, chacun ciblant une population différente (adultes et enfants). Nous avons étudié la possibilité d’évaluer quantitativement la rigidité des tissus cardiaques par élastographie chez des volontaires sains, ainsi que chez des malades souffrant de cardiomyopathie hypertrophique. Les résultats ont montré que l’élastographie pourrait devenir un outil d'imagerie pertinent et robuste pour évaluer la rigidité du muscle cardiaque en pratique clinique. Par ailleurs, nous avons également développé une nouvelle approche appelée « imagerie de tenseur élastique 3-D » pour mesurer quantitativement les propriétés élastiques des tissus anisotropes comme le myocarde. Ces techniques ont été testées in vitro sur des modèles de de gels isotropes transverses. La faisabilité in vivo de l’élastographie par onde cisaillement à trois-dimensions a été également évaluée sur un muscle squelettique humain.D'autre part, nous avons développé une toute nouvelle modalité d’imagerie ultrasonore des flux coronariens basée sur l’imagerie Doppler ultrarapide. Cette technique nous a permis d'imager la circulation coronarienne avec une sensibilité élevée, grâce notamment au développement d’un nouveau filtre adaptatif permettant de supprimer le signal du myocarde en mouvement, basé sur la décomposition en valeurs singulières (SVD). Des expériences à thorax ouvert chez le porc ont permis d'évaluer et de valider notre technique et les résultats ont montré que la circulation coronaire intramurale, peut être évaluée sur des vaisseaux de diamètres allant jusqu’à 100 µm. La faisabilité sur l’homme a été démontrée chez l’enfant en imagerie clinique transthoracique.Enfin, nous avons développé une nouvelle approche d’imagerie des flux sanguins, « l’imagerie ultrarapide 3-D des flux», une nouvelle technique d'imagerie quantitative des flux. Nous avons démontré que cette technique permet d’évaluer le débit volumétrique artériel directement en un seul battement cardiaque, indépendamment de l'utilisateur. Cette technique a été mise en place à l'aide d'une sonde matricielle 2-D et d’un prototype d’échographe ultrarapide 3-D développé au sein du laboratoire. Nous avons évalué et validé notre technique in vitro sur des fantômes artériels, et la faisabilité in vivo a été démontrée sur des artères carotides humaines. / This thesis was focused on the development of novel cardiovascular imaging applications based on 2-D and 3-D ultrafast ultrasound imaging. More specifically, new technical and clinical developments of myocardial shear wave elastography and ultrafast blood flow imaging are presented in this manuscript.At first, myocardial shear wave elastography was developed for transthoracic imaging and improved by a non-linear imaging approach to non-invasively and locally assess shear wave velocity measurements, and consequently tissue stiffness in the context of cardiac imaging. This novel imaging approach (Ultrafast Harmonic Coherent Compounding) was tested and validated in-vitro and the in vivo feasibility was performed in humans for biomechanical evaluation of the cardiac muscle wall, the myocardium. Then, we have translated shear wave elastography to the clinical practice within two clinical trials, each one with a different population (adults and children). In both clinical trials, we have studied the capability of shear wave elastography to assess quantitatively myocardial stiffness in healthy volunteers and in patients suffering from hypertrophic cardiomyopathy. The results in the adult population indicated that shear wave elastography may become an effective imaging tool to assess cardiac muscle stiffness in clinical practice and help the characterization of hypertrophic cardiomyopathy. Likewise, we have also translated Shear Wave Elastography into four-dimensions and we have developed a new approach to map tissue elastic anisotropy in 3-D. 3-D Elastic Tensor Imaging allowed us to estimate quantitatively in a single acquisition the elastic properties of fibrous tissues. This technique was tested and validated in vitro in transverse isotropic models. The in-vivo feasibility of 3D elastic tensor imaging was also assessed in a human skeletal muscle.In parallel, we have developed a novel imaging technique for the non-invasive and non-radiative imaging of coronary circulation using ultrafast Doppler. This approach allowed us to image blood flow of the coronary circulation with high sensitivity. A new adaptive filter based on the singular value decomposition was used to remove the clutter signal of moving tissues. Open-chest swine experiments allowed to evaluate and validate this technique and results have shown that intramural coronary circulation, with diameters up to 100 µm, could be assessed. The in-vivo transthoracic feasibility was also demonstrated in humans in pediatric cardiology.Finally, we have developed a novel imaging modality to map quantitatively the blood flow in 3-D: 3-D ultrafast ultrasound flow imaging. We demonstrated that 3-D ultrafast ultrasound flow imaging can assess non-invasively, user-independently and directly volumetric flow rates in large arteries within a single heartbeat. We have evaluated and validated our technique in vitro in arterial phantoms using a 2-D matrix-array probe and a customized, programmable research 3-D ultrafast ultrasound system, and the in-vivo feasibility was demonstrated in human carotid arteries.

Σε αυτή την εργασία παρουσιάζεται μια πλήρως αυτοματοποιημένη μεθοδολογία κατάτμησης για την ανίχνευση των ορίων του αρτηριακού τοιχώματος σε διαμήκεις εικόνες καρωτίδας β-σάρωσης. Συγκεκριμένα υλοποιείται ένας συνδυασμός της μεθοδολογίας του μετασχηματισμού Hough για την ανίχνευση ευθειών με μια μεθοδολογία ενεργών καμπυλών. Η μεθοδολογία του μετασχηματισμού Hough χρησιμοποιείται για τον ορισμό της αρχικής καμπύλης, η οποία στη συνέχεια παραμορφώνεται σύμφωνα με ένα μοντέλο ενεργών καμπυλών βασισμένων σε πεδίο ροής του διανύσματος κλίσης (Gradient Vector Flow - GVF). Το GVF μοντέλο ενεργών καμπυλών βασίζεται στον υπολογισμό του χάρτη ακμών της εικόνας και τον μετέπειτα υπολογισμό του διανυσματικού πεδίου ροής κλίσης, το οποίο με τη σειρά του προκαλεί την παραμόρφωση της αρχικής καμπύλης με σκοπό την εκτίμηση των πραγματικών ορίων του αρτηριακού τοιχώματος. Η προτεινόμενη μεθοδολογία εφαρμόστηκε σε είκοσι (20) εικόνες υγιών περιπτώσεων και δεκαοχτώ (18) εικόνες περιπτώσεων με αθηρωμάτωση για τον υπολογισμό της διαμέτρου του αυλού και την αξιολόγηση της μεθόδου από ποσοτικούς δείκτες ανάλυσης κατά ROC (Receiver Operating Characteristic – ROC). Σύμφωνα με τα αποτελέσματα, δεν παρατηρήθηκαν στατιστικά σημαντικές διαφορές ανάμεσα στις μετρήσεις της διαμέτρου που πραγματοποιήθηκαν από τη διαδικασία της αυτόματης ανίχνευσης και τις αντίστοιχες μετρήσεις που προέκυψαν από την χειροκίνητη ανίχνευση. Οι τιμές της ευαισθησίας, της ειδικότητας και της ακρίβειας στις υγιείς περιπτώσεις ήταν αντίστοιχα 0.97, 0.99 και 0.98 για τις διαστολικές και τις συστολικές εικόνες. Στις παθολογικές περιπτώσεις οι αντίστοιχες τιμές ήταν μεγαλύτερες από 0.89, 0.96 και 0.93. Συμπερασματικά, η προτεινόμενη μεθοδολογία αποτελεί μια ακριβή και αξιόπιστη μέθοδο κατάτμησης εικόνων καρωτίδας και μπορεί να χρησιμοποιηθεί στην κλινική πράξη. / In this thesis, a fully automatic segmentation method based on a combination of a combination of the Hough Transform for the detection of straight lines with active contours is presented, for detecting the carotid artery wall in longitudinal B-mode ultrasound images. A Hough-transform-based methodology is used for the definition of the initial snake, followed by a gradient vector flow (GVF) snake deformation. The GVF snake is based on the calculation of the image edge map and the calculation of the gradient vector flow field which guides its deformation for the estimation of the real arterial wall boundaries. The proposed methodology was applied in twenty and eighteen cases of healthy and atherosclerotic carotid respectively, in order to calculate the lumen diameter and evaluate the method by means of ROC analysis (Receiver Operating Characteristic – ROC). According to the results, there was no significant difference between the automated segmentation and the manual diameter measurements. In healthy cases the sensitivity, specificity and accuracy were 0.97, 0.99 and 0.98, respectively, for both diastolic and systolic phase. In atherosclerotic cases the calculated values of the indices were larger than 0.89, 0.96 and 0.93, respectively. In conclusion, the proposed methodology provides an accurate and reliable way to segment ultrasound images of the carotid wall and can be used in clinical practice.

This master’s thesis is focused on automating the process of differential leukocyte count in peripherial blood using image processing. It deals with the design of the processing of digital images - from scanning and image preprocessing, segmentation nucleus and cytoplasm, feature selection and classifier, including testing on a set of images that were scanned in the context of this work. This work introduces used segmentation methods and classification procedures which separate nucleus and the cytoplasm of leukocytes. A statistical analysis is performed on the basis of these structures. Following adequate statistical parameters, a set of features has been chosen. This data then go through a classification process realized by three artificial neural networks. Overall were classified 5 types of leukocytes: neutropfiles, lymphocytes, monocytes, eosinophiles and basophiles. The sensitivity and specificity of the classification made for 4 out of 5 leukocyte types (neutropfiles, lymphocytes, monocytes, eosinophiles) is higher than 90 %. Sensitivity of classiffication basophiles was evaluated at 75 % and specificity at 67 %. The total ability of classification has been tested on 111 leukocytes and was approximately 91% successful. All algorithms were created in the MATLAB program.