Download or read book Formation de Voies en mission Et en R ception Pour L am lioration de L imagerie Ultrasonore written by Matthieu Toulemonde and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nowadays, ultrasound imaging is a common diagnostic tool thanks to its non-invasive behavior and relatively cheap equipment. Classic medical echographic imaging is based on the linear response of the biological tissue. However harmonic imaging, based on the harmonic frequencies generated by the nonlinear properties of the tissue, is more and more used for clinical application. The quantification of nonlinearity is based on the evaluation of the nonlinearity parameter which strongly influences the harmonics generation. The nonlinearity parameter estimation using an echographic approach would bring new modalities for imaging and diagnosis. However the echographic method for nonlinearity estimation is limited by two factors: the presence of speckles in the image and the focalization used during transmission, which concentrates the energy at one particular depth. The objectives of this thesis work are developing novel approaches to reduce the speckle noise using original smoothing techniques and improving the nonlinearity parameter estimation in echo mode using new transmission-reception strategies. Firstly, new speckle noise reduction approaches were investigated. The Thomson's multitaper approach was proposed, consisting in using several different orthogonal apodizations during beamforming. This method was combined to a coherent plane-wave compounding transmission-reception strategy improving the spatial resolution and the contrast while improving the frame rate. In a second time, the nonlinearity parameter was estimated using a comparative method. The second-harmonic pressure field of a reference area was compared to the pressure field of an area where the nonlinearity parameter is unknown. However in echo-mode, the pressure field of the medium is unknown. It is assumed in this thesis work that the local pressure can be derived from envelope image local amplitude if the speckle noise is smoothed. The nonlinearity parameter estimation has been improved using plane-wave transmission and orthogonal apodizations compared to the use of a single focalization transmission.

Download or read book Advanced beamforming techniques in ultrasound imaging and the associated inverse problems written by Teodora Szasz and published by . This book was released on 2016 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ultrasound (US) allows non-invasive and ultra-high frame rate imaging procedures at reduced costs. Cardiac, abdominal, fetal, and breast imaging are some of the applications where it is extensively used as diagnostic tool. In a classical US scanning process, short acoustic pulses are transmitted through the region-of-interest of the human body. The backscattered echo signals are then beamformed for creating radiofrequency(RF) lines. Beamforming (BF) plays a key role in US image formation, influencing the resolution and the contrast of final image. The objective of this thesis is to model BF as an inverse problem, relating the raw channel data to the signals to be recovered. The proposed BF framework improves the contrast and the spatial resolution of the US images, compared with the existing BF methods. To begin with, we investigated the existing BF methods in medical US imaging. We briefly review the most common BF techniques, starting with the standard delay-and-sum BF method and emerging to the most known adaptive BF techniques, such as minimum variance BF. Afterwards, we investigated the use of sparse priors in creating original two-dimensional beamforming methods for ultrasound imaging. The proposed approaches detect the strong reflectors from the scanned medium based on the well-known Bayesian Information Criteria used in statistical modeling. Furthermore, we propose a new way of addressing the BF in US imaging, by formulating it as a linear inverse problem relating the reflected echoes to the signal to be recovered. Our approach offers flexibility in the choice of statistical assumptions on the signal to be beamformed and it is robust to a reduced number of pulse emissions. At the end of this research, we investigated the use of the non-Gaussianity properties of the RF signals in the BF process, by assuming alpha-stable statistics of US images.

Download or read book Am lioration de la r solution en imagerie ultrasonore written by Renaud Morin and published by . This book was released on 2013 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: L'imagerie ultrasonore est une modalité d'imagerie médicale couramment utilisée pour l'établissement de diagnostics de thérapie ou de suivi divers (croissance du fœtus, détection de certains cancers, assistance à la réalisation d'actes thérapeutiques). Si cette modalité dispose de nombreux avantages comme son innocuité, sa facilité d'utilisation et son faible coût, elle souffre cependant d'une résolution spatiale limitée quand on la compare à d'autres modalités comme l'imagerie par résonance magnétique. L'amélioration de la résolution des images ultrasonores est un défi de taille et de très nombreux travaux ont depuis longtemps exploré des approches instrumentales portant sur l'optimisation du dispositif d'acquisition. L'imagerie échographique haute résolution permet ainsi d'atteindre cet objectif à l'aide de sondes particulières mais se trouve aujourd'hui confrontée à des limitations d'ordre physique et technologique. L'objet de cette thèse est d'adopter une stratégie de post-traitement afin de contourner ces contraintes inhérentes aux approches instrumentales. Dans ce contexte, nous présentons deux approches pour l'amélioration de la résolution des images ultrasonores, selon que les données disponibles prennent la forme d'une séquence d'images ou d'une image unique. Dans le premier cas, l'adaptation d'une technique d'estimation du mouvement originellement proposée pour l'élastographie nous permet d'établir un cadre de reconstruction haute résolution efficace dédié à la modalité qui nous intéresse. Cette approche est évaluée à l'aide d'une simulation réaliste d'images ultrasonores avant d'être appliquée à des données in vivo. Nous proposons ensuite, dans le cadre du traitement d'une seule image, deux méthodes de déconvolution rapide pour l'amélioration de la résolution. Ces approches prennent en compte, suivant leur disponibilité, certaines informations a priori sur les conditions d'acquisition comme la réponse impulsionnelle spatiale du système. Les résultats sont caractérisés dans un premier temps à l'aide de données synthétiques et sont ensuite validés sur des images in vivo

Download or read book Conception d un imageur ultrasonore dans l air pour la mesure des ondes basses fr quences en surface du corps humain written by Nathan Jeger-Madiot and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: L'objectif des travaux présentés dans cette thèse est le développement d'un système d'imagerie ultrasonore fonctionnant dans l'air pour la mesure sans contact des mouvements vibratoires en surface du corps humain. L'étude des vibrations en surface de la peau ouvre plusieurs champs d'application. L'observation de la vitesse d'une onde de surface sur la peau à partir du film de propagation permet de caractériser l'élasticité de la couche superficielle ainsi que ses hétérogénéités. A partir de cette analyse, il est possible de détecter des objets cachés sur ou sous la peau, dans un objectif de sécurité. Une seconde application est l'observation des vibrations de surface engendrées par le battement cardiaque, la respiration et l'onde de pouls. La réalisation d'un premier dispositif monovoie a permis la mesure locale de vibrations de l'ordre de la dizaine de microns. A partir de ces premiers travaux, nous avons construit un imageur ultrasonore 2D dans l'air à haute cadence d'imagerie. Il est constitué d'un réseau carré de 256 microphones et de 12 émetteurs. La principale nouveauté de notre approche repose sur l'imagerie d'une surface spéculaire. En effet, la rugosité de la peau est négligeable comparée aux longueurs d'onde de travail, de l'ordre du centimètre pour limiter l'atténuation dans l'air. Pour répondre à cette contrainte, l'imagerie est réalisée à partir de la formation de voies émission/réception par synthèse d'ouverture en utilisant une émission séquentielle d'ondes sphériques. Après caractérisation du système, nous avons imagé la propagation d'une onde de surface sur un fantôme mimant le corps humain et l'interférence de cette onde avec un objet étranger. Une seconde version de l'imageur 2D, constituée de 36 émetteurs, a permis la mesure de la déformation du thorax lors du battement cardiaque ainsi que la propagation de l'onde de pouls au niveau de la carotide.

Download or read book Formation directe de champs de d placement en imagerie ultrasonore written by Pierre Gueth and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dans le domaine de l'imagerie médicale ultrasonore, la connaissance du déplacement du milieu imagé est une donnée clinique très importante dans de nombreux examens, parmi lesquels nous pouvons citer les examens Doppler ou les examens d'élastographie. Dans la littérature, les deux principales familles de méthodes permettant d'estimer le déplacement sont les méthodes de mise en correspondance de blocs et les méthodes Doppler. Les méthodes de mise en correspondance de blocs estiment le déplacement en comparant des vignettes prises dans les images ultrasonores avant et après déplacement. Elles dépendent donc de la méthode utilisée pour former les images. Les méthodes Doppler mesurent quant à elles le déplacement suivant une direction particulière, ce qui limite leur gamme d'utilisation à l'estimation de champs de déplacements simple. Dans cette thèse, nous avons proposé un formalisme, ainsi que trois méthodes, permettant d'estimer le déplacement 2D directement à partir de ces signaux bruts. Cette approche permet de s'affranchir de la dépendance envers la méthode de formation d'images, tout en permettant l'estimation de champs complexes. Nous avons mis en évidence le concept de vecteur normal, liant le déplacement réel de milieu aux décalages temporels de long des signaux bruts. Le formalisme général est appliqué à plusieurs séquences ultrasonores: la première méthode d'estimation utilise des signaux acquis à l'aide d'éléments uniques de la sonde; la deuxième est basée sur l'utilisation d'ondes planes et la troisième méthode s'appuie sur une séquence utilisant des faisceaux focalisés. Les méthodes d'estimation directe du mouvement ont été validées en simulation et expérimentalement, et leurs performances ont été comparées à une méthode de référence: la mise en correspondance de blocs. Les méthodes proposées améliorent significativement la précision de l'estimation du champ de déplacement par rapport à la méthode standard, en atteignant une précision de 1.5μm dans la direction transverse et une précision de 2.5μm dans la direction axiale pour une fréquence de travail de 5MHz. Nous avons également développé une méthode de formation d'images améliorant la résolution spatiale. Cette méthode utilise les spectres de signaux RF acquis avec des ondes planes pour former le spectre de l'image ultrasonore. Elle fournit les images utilisées par la méthode d'estimation du mouvement de référence.

Download or read book Model of image formation and 2D velocity estimation with a high frequency swept scan ultrasound imaging system written by Yang Liu Li and published by . This book was released on 2009 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: In swept-scan ultrasonic imaging system, the single-element transducer continuously moves during emission and reception. It realizes high-frequency (20-50MHz) real-time ultrasound imaging with high spatial resolution. To realize both real-time flow mapping and high-frequency imaging, it is necessary to consider estimating the blood flow 2D velocity with the data of a single image, acquired with a swept-scan transducer. We propose a model of image formation for an ultrasonic broad-band, high frequency, swept-scan transducer system. In a second part, we develop two velocity estimators based firstly on the time-frequency analysis of the “Chirplet signal” in the space-frequency domain and secondly on the 2D Fourier spatial frequency (2DFT) of the system’s PSF. Time-frequency analysis of the “Chirplet signal” is realized with Wigner-Ville Distribution (WVD). The “Chirplet signal” Sf0(u) is the lateral spatial signal chirp signal filtered with the aperture. The analysis of Chirplet’s WVD shows that the centre frequency is directly related to target’s axial velocity, and the compression of the axial bandwidth of WVD depends on target’s lateral relative velocity. 2D Fourier Transform (2DFT) of the system’s PSF shows clearly that the lateral centre frequency is directly related to target’s axial velocity, and the compression of the lateral bandwidth of the system’s 2DFT depends on target’s lateral relative velocity. Simulations of various situations corresponding to real system parameters show the validity of both models. Parabolic flow profiles are also investigated. Mean and standard deviation of the mean error are presented and show a good agreement.

Download or read book Bases physiques de l imagerie ultrasonore written by André Syrota and published by . This book was released on 1992 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book UTILISATION DU RETOURNEMENT TEMPOREL POUR LA CORRECTION DES ABERRATIONS EN IMAGERIE MEDICALE written by CHRISTIAN.. DORME and published by . This book was released on 1995 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: LES FLUCTUATIONS DE LA VITESSE DU SON DANS LES TISSUS BIOLOGIQUES DEGRADENT LA FOCALISATION DU FAISCEAU ULTRASONORE EMIS PAR LES ECHOGRAPHES CONVENTIONNELS. LE RETOURNEMENT TEMPOREL DE CHAMPS ULTRASONORES EST UNE SOLUTION OPTIMALE DE FOCALISATION SUR UNE CIBLE REFLECTRICE PONCTUELLE EN MILIEU INHOMOGENE. AINSI, UN MIROIR A RETOURNEMENT TEMPOREL REEMET L'ECHO RECU EN PROVENANCE DE LA CIBLE DANS UNE CHRONOLOGIE INVERSE. CECI PERMET DE REFOCALISER PRECISEMENT LE CHAMP DE PRESSION ACOUSTIQUE SUR LE REFLECTEUR. EN FAIT, LA PROCEDURE DE RETOURNEMENT TEMPOREL REALISE AUTOMATIQUEMENT UN PROCESSUS DE FILTRE ADAPTE. LA CONNAISSANCE DE LA SIGNATURE DE LA CIBLE, C'EST A DIRE DE LA FONCTION DE GREEN DU REFLECTEUR, EST ALORS SUFFISANTE POUR GENERER UN FAISCEAU ACOUSTIQUE PARFAITEMENT FOCALISE SUR LA POSITION DE LA CIBLE. LA FONCTION DE GREEN DU REFLECTEUR SERT EGALEMENT A LA FOCALISATION EN RECEPTION. DANS CE CAS, LES LIGNES A RETARDS CLASSIQUES SONT REMPLACEES PAR DES CONVOLUTIONS ENTRE LA FONCTION DE GREEN ENREGISTREE ET L'ECHO RECU PAR LE RESEAU DE TRANSDUCTEURS. CETTE TECHNIQUE CONSERVE LES AVANTAGES DU FILTRE ADAPTE EN MODE RECEPTION. TOUTEFOIS, IMAGER UNE ZONE D'INTERET MEDICAL REQUIERT NON SEULEMENT DE FOCALISER SUR LE POINT BRILLANT DE LA ZONE, MAIS AUSSI EN CHAQUE POINT ELEMENTAIRE DE LA ZONE. C'EST POURQUOI LA CONNAISSANCE DE CHAQUE FONCTION DE GREEN CORRESPONDANT A CHAQUE POINT EST FONDAMENTALE, MAIS N'EST PAS DISPONIBLE EXPERIMENTALEMENT. UN NOUVEL ALGORITHME PERMET DE SYNTHETISER NUMERIQUEMENT LES FONCTIONS DE GREEN DE POINTS VOISINS DU POINT REFLECTEUR. L'EMISSION DE CHAQUE FONCTION DE GREEN SYNTHETISEE FOCALISE EN CHAQUE POINT DU VOISINAGE DU REFLECTEUR. CE PROCEDE ORIGINAL DE FORMATION DE VOIES EN MILIEU INHOMOGENE PEUT ETRE COUPLE A UNE PROCEDURE DE FOCALISATION EN EMISSION-RECEPTION. LA REUNION DE CES DEUX NOUVELLES TECHNIQUES PERMET D'OBTENIR DE BONNES IMAGES B-SCANS DU VOISINAGE D'UN REFLECTEUR PONCTUEL A TRAVERS UN MILIEU INHOMOGENE

Download or read book Biomedical Images and Computers written by J. Sklansky and published by Springer. This book was released on 2014-03-12 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt: The technology of automatic pattern recognition and digital image processing, after over two decades of basic research, is now appearing in important applications in biology and medicine as weIl as industrial, military and aerospace systems. In response to a suggestion from Mr. Norman Caplan, ·the Program Director for Automation, Bioengineering and Sensing at the United States National Science Foundation, the authors of this book organized the first Uni ted States-France Seminar on Biomedical Image Processing. The seminar met at the Hotel Beau Site, St. Pierre de Chartreuse, France on May 27-31, 1980. This book contains most of the papers presented at this seminar, as weIl as two papers (by Bisconte et al. and by Ploem ~ al.) discussed at the seminar but not appearing on the program. We view the subject matter of this seminar as a confluence amon~ three broad scientific and engineering disciplines: 1) biology and medicine, 2) imaging and optics, and 3) computer science and computer engineering. The seminar had three objectives: 1) to discuss the state of the art of biomedical image processing with emphasis on four themes: microscopic image analysis, radiological image analysis, tomography, and image processing technology; 2) to place values on directions for future research so as to give guidance to agencies supporting such research; and 3) to explore and encourage various areas of cooperative research between French and Uni ted States scientists within the field of Biomedical Image Processing.

Download or read book Critical Care Nursing written by Linda Diann Urden and published by Saunders. This book was released on 2010 with total page 1242 pages. Available in PDF, EPUB and Kindle. Book excerpt: Focusing on critical care nursing, this full-color text provides an examination of the important aspects of critical care nursing. It is organized in ten units around alterations in body systems.

Download or read book Cambridge Handbook of Engineering Education Research written by Aditya Johri and published by Cambridge University Press. This book was released on 2014-02-10 with total page 1124 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Cambridge Handbook of Engineering Education Research is the critical reference source for the growing field of engineering education research, featuring the work of world luminaries writing to define and inform this emerging field. The Handbook draws extensively on contemporary research in the learning sciences, examining how technology affects learners and learning environments, and the role of social context in learning. Since a landmark issue of the Journal of Engineering Education (2005), in which senior scholars argued for a stronger theoretical and empirically driven agenda, engineering education has quickly emerged as a research-driven field increasing in both theoretical and empirical work drawing on many social science disciplines, disciplinary engineering knowledge, and computing. The Handbook is based on the research agenda from a series of interdisciplinary colloquia funded by the US National Science Foundation and published in the Journal of Engineering Education in October 2006.

Download or read book Engineering written by Unesco and published by UNESCO. This book was released on 2010-01-01 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report reviews engineering's importance to human, economic, social and cultural development and in addressing the UN Millennium Development Goals. Engineering tends to be viewed as a national issue, but engineering knowledge, companies, conferences and journals, all demonstrate that it is as international as science. The report reviews the role of engineering in development, and covers issues including poverty reduction, sustainable development, climate change mitigation and adaptation. It presents the various fields of engineering around the world and is intended to identify issues and challenges facing engineering, promote better understanding of engineering and its role, and highlight ways of making engineering more attractive to young people, especially women.--Publisher's description.

Download or read book Engineering for Sustainable Development written by International Centre for Engineering Education and published by UNESCO Publishing. This book was released on 2021-03-02 with total page 183 pages. Available in PDF, EPUB and Kindle. Book excerpt: The report highlights the crucial role of engineering in achieving each of the 17 SDGs. It shows how equal opportunities for all is key to ensuring an inclusive and gender balanced profession that can better respond to the shortage of engineers for implementing the SDGs. It provides a snapshot of the engineering innovations that are shaping our world, especially emerging technologies such as big data and AI, which are crucial for addressing the pressing challenges facing humankind and the planet. It analyses the transformation of engineering education and capacity-building at the dawn of the Fourth Industrial Revolution that will enable engineers to tackle the challenges ahead. It highlights the global effort needed to address the specific regional disparities, while summarizing the trends of engineering across the different regions of the world.

Download or read book The European Respiratory Journal written by and published by . This book was released on 1993 with total page 688 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Echocardiography in Pediatric and Congenital Heart Disease written by Wyman W. Lai and published by John Wiley & Sons. This book was released on 2012-01-03 with total page 1618 pages. Available in PDF, EPUB and Kindle. Book excerpt: Echocardiography is essential in the practice of pediatric cardiology. A clinical pediatric cardiologist is expected to be adept at the non-invasive diagnosis of congenital heart disease and those who plan to specialize in echocardiography will need to have knowledge of advanced techniques. Echocardiography in Pediatric and Congenital Heart Disease addresses the needs of trainees and practitioners in this field, filling a void caused by the lack of material in this fast-growing area. This new title comprehensively covers the echocardiographic assessment of congenital heart disease, from the fetus to the adult, plus acquired heart disease in children. Topics covered include: ultrasound physics laboratory set-up a protocol for a standard pediatric echocardiogram quantitative methods of echocardiographic evaluation, including assessment of diastolic function in depth coverage of congenital cardiovascular malformations acquired pediatric heart disease topics of special interest, such as 3D echocardiography, transesophageal echocardiography, and fetal echocardiography The approach of this book is a major advancement for educational materials in the field of pediatric cardiology, and greatly enhances the experience for the reader. An accompanying DVD with moving images of the subjects covered in the textbook will further enhance the learning experience.

Download or read book Hypoxic Respiratory Failure in the Newborn written by Shyamala Dakshinamurti and published by CRC Press. This book was released on 2021-10-29 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have all been hypoxic. Fetal tolerance for intrauterine hypoxia arises from evolutionarily conserved physiological mechanisms, the antecedents of which can be learned from diving mammals or species at high altitudes. Understanding fetal hypoxia leads to understanding the huge physiological shifts of neonatal transition and the dangers of perinatal hypoxia. This comprehensive volume of topical review articles by expert authors addresses the origins of hypoxia tolerance, the impact of oxygen on circulatory transition at birth, and the biochemistry of hypoxia in the pulmonary circuit, as well as the classification, diagnosis, and clinical management of hypoxic respiratory failure and persistent pulmonary hypertension in the term neonate. The goal of Hypoxic Respiratory Failure in the Newborn is to connect our understanding of hypoxia from animals in extreme environments, with how the human fetus handles its hypoxic environment; and why the human newborn suddenly cannot. The book will educate health care professionals on how to care for newborns with hypoxic respiratory failure, including the use of up-to-date diagnostic tools and therapies. It also highlights areas of controversy and ongoing research in hypoxic respiratory failure and pulmonary hypertension of the newborn, including challenging case studies. Key Features Explores evolutionary context and comparative physiology of hypoxia tolerance in the fetus and neonate, from basic research to clinical scenarios Provides guidance to trainees, physicians, and allied health professionals engaged in NICU care; pediatricians, cardiologists, pulmonologists, anesthesiologists, neonatologists, and physiologists to effectively manage infants in hypoxic respiratory failure Includes case scenarios emphasizing current diagnostic and therapeutic controversies and algorithmic approaches to decipher difficult clinical cases

Download or read book Phonology for Communication Disorders written by Martin J. Ball and published by Psychology Press. This book was released on 2014-02-25 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt: This textbook describes the approaches to phonology that are most relevant to communication disorders. It examines schools of thought in theoretical phonology, and their relevance to description, explanation and remediation in the clinical context. A recurring theme throughout the book is the distinction between phonological theories that attempt elegant, parsimonious descriptions of phonological data, and those that attempt to provide a psycholinguistic model of speech production and perception. This book introduces all the relevant areas of phonology to the students and practitioners of speech-language pathology and is a companion volume to the authors’ Phonetics for Communication Disorders.