1,776 research outputs found

    Assessment of coronary artery stenosis using myocardial contrast echocardiography.

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    The theoretical advantage of perfusion data over wall motion data for diagnosing coronary artery stenosis relates to the temporal sequence of these phenomena in the ischaemic cascade. Myocardial perfusion evaluation could thus provide earlier information than wall motion assessment, with important clinical consequences. This thesis examines myocardial perfusion assessment using ultrasound and micro-bubble contrast in stable coronary artery stenosis. The first set of experiments were undertaken to establish both a means of infusing Optison (GE Healthcare, UK), and of displaying static frame contrast signal using Power Contrast Imaging (Acuson Sequoia, Siemens Medical Solutions, Mountain View, CA, USA.). Three Optison concentrations, five infusion rates, and five trigger intervals were evaluated. This revealed an appropriate concentration and infusion rate for Optison and identified an ideal trigger interval of one in four cardiac cycles. The second part of this study evaluated Power Contrast Imaging with Optison infusion in stable single or double vessel coronary artery stenosis. Perfusion assessment during Adenosine vasodilator stress was compared with standard wall motion assessment during Dobutamine stress, coronary angiography being the diagnostic standard. Among twenty-eight subjects and eighty-four coronary territories, Power Contrast Imaging had low sensitivity but equivalent specificity compared to wall motion assessment. The third component of this research evaluated micro-bubble preserving real time Coherent Contrast Imaging (Acuson Sequoia , Siemens Medical Solutions) alongside Optison infusion in stable single or double vessel coronary stenosis. Thirty-eight subjects and one hundred and fourteen coronary arteries were evaluated. Each subject underwent Dobutamine stress, during which standard wall motion, contrast wall motion, and contrast perfusion imaging were all assessed, the diagnostic standard being coronary angiography. This demonstrated that contrast wall motion evaluation is accurate and that combined contrast wall motion and perfusion imaging is at least equivalent to standard wall motion imaging alone for detecting underlying coronary stenosis

    Computer integrated system: medical imaging & visualization

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    The intent of this book’s conception is to present research work using a user centered design approach. Due to space constraints, the story of the journey, included in this book is relatively brief. However we believe that it manages to adequately represent the story of the journey, from its humble beginnings in 2008 to the point where it visualizes future trends amongst both researchers and practitioners across the Computer Science and Medical disciplines. This book aims not only to present a representative sampling of real-world collaboration between said disciplines but also to provide insights into the different aspects related to the use of real-world Computer Assisted Medical applications. Readers and potential clients should find the information particularly useful in analyzing the benefits of collaboration between these two fields, the products in and of their institutions. The work discussed here is a compilation of the work of several PhD students under my supervision, who have since graduated and produced several publications either in journals or proceedings of conferences. As their work has been published, this book will be more focused on the research methodology based on medical technology used in their research. The research work presented in this book partially encompasses the work under the MOA for collaborative Research and Development in the field of Computer Assisted Surgery and Diagnostics pertaining to Thoracic and Cardiovascular Diseases between UPM, UKM and IJN, spanning five years beginning from 15 Feb 2013

    Echocardiography

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    The book "Echocardiography - New Techniques" brings worldwide contributions from highly acclaimed clinical and imaging science investigators, and representatives from academic medical centers. Each chapter is designed and written to be accessible to those with a basic knowledge of echocardiography. Additionally, the chapters are meant to be stimulating and educational to the experts and investigators in the field of echocardiography. This book is aimed primarily at cardiology fellows on their basic echocardiography rotation, fellows in general internal medicine, radiology and emergency medicine, and experts in the arena of echocardiography. Over the last few decades, the rate of technological advancements has developed dramatically, resulting in new techniques and improved echocardiographic imaging. The authors of this book focused on presenting the most advanced techniques useful in today's research and in daily clinical practice. These advanced techniques are utilized in the detection of different cardiac pathologies in patients, in contributing to their clinical decision, as well as follow-up and outcome predictions. In addition to the advanced techniques covered, this book expounds upon several special pathologies with respect to the functions of echocardiography

    Aerospace medicine and biology: A continuing bibliography with indexes, supplement 218, April 1981

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    This bibliography lists 161 reports, articles, and other documents introduced into the NASA scientific and technical information system in March 1981

    Early myocardial infarction detection over multi-view echocardiography

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    Myocardial infarction (MI) is the leading cause of mortality in the world. Its early diagnosis can mitigate the extent of myocardial damage by facilitating early therapeutic interventions. The regional wall motion abnormality (RWMA) of the ischemic myocardial segments is the earliest change to set in that can be captured by echocardiography. However, assessing the motion only from a single echocardiography view may lead to missing the diagnosis of MI as the RWMA may not be visible on that specific view. Therefore, in this study, we propose to fuse apical 4-chamber (A4C) and apical 2-chamber (A2C) views in which a total of 12 myocardial segments can be analyzed for MI detection. The proposed method first estimates the motion of the left ventricle wall by Active Polynomials (APs), which extract and track the endocardial boundary to compute myocardial segment displacements. The features are extracted from the displacements, which are concatenated and fed into the classifiers to detect MI. The main contributions of this study are (1) creation of a new benchmark dataset by including both A4C and A2C views in a total of 260 echocardiography recordings, which is publicly shared with the research community, (2) improving the performance of the prior work of threshold-based APs by a machine learning based approach, and (3) a pioneer MI detection approach via multi-view echocardiography by fusing the information of A4C and A2C views. The proposed method achieves 90.91% sensitivity and 86.36% precision for MI detection over multi-view echocardiography. The software implementation is shared at https://github.com/degerliaysen/MultiEchoAI.Peer reviewe

    The stress radionuclide assessment of diastolic function

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    Background Many patients are referred from primary care with suspected heart failure and are found to have preserved systolic function. These patients may be labelled as having normal ejection fraction or diastolic heart failure, the diagnosis of which is both controversial and difficult. Previous work has identified a large proportion of these patients to have an alternative, pre- existing diagnosis. This thesis prospectively assesses the prevalence of undiagnosed ischaemic heart disease and respiratory disease in this patient group and assess diastolic function using multiple methods. The central hypothesis being tested was that first third fractional filling, a radionuclide ventriculogram (RNVG) parameter previously used to assess diastolic function at rest, would identify diastolic dysfunction more accurately under stress conditions. Methods Patients were recruited from an open access echocardiography service. Echocardiography, including tissue Doppler assessment, was carried out independently by 2 experienced observers. Confounding diagnoses including coronary artery disease and respiratory disease were actively sought by myocardial perfusion imaging and spirometry. N-terminal proBNP was measured. List mode radionuclide ventriculography was performed at rest supine and during upright bicycle exercise with simultaneous measurement of VO2 max. Validation of the reliability and reproducibility of first third fractional filling, peak filling rate, time to peak filling and other radionuclide parameters of systolic and diastolic function was undertaken. This demonstrated that it was possible to measure both first third fractional filling and peak filling rate with the short acquisition times necessary for assessment during stress. Time to peak filling was poorly reproducible under these conditions. A normal range for first third fractional filling at rest and during exercise was established. Due to a strong inverse relationship between heart rate and first third fractional filling, a continuous reference range was constructed using an exponential model. This unique approach enables the calculation of the lower limit of normal at any heart rate. A more conventional mean ± 2 standard deviations was used for the other RNVG parameters. Results Eighty three patients were recruited and completed an extensive multi-modality assessment of systolic and diastolic function. As with previous work in this field, the patients were predominantly female (82%) and elderly (mean age 66.7). Mild left ventricular systolic dysfunction as determined by RNVG was missed by echocardiography in one third of patients. Systolic dysfunction more significant than this was not observed. N-terminal proBNP was elevated in 21 of 82 patients where it was available with no significant difference in left ventricular ejection fraction between those with normal and elevated levels. Myocardial perfusion scanning was normal in 46 of 83 patients and showed significant ischaemia in 20 of 83. Spirometry was normal in 58 of 82 patients, with mild airflow obstruction in 20 patients and moderate obstruction in 4. In only one patient were no alternative diagnoses present. There was poor correlation between indices of diastolic function at rest including first third fractional filling, echocardiographic parameters and NT-proBNP. The assessment of diastolic function using stress radionuclide ventriculography did not improve the correlation between measured indices. On stress, however, low first third fractional filling predicted exercise intolerance as an inability to reach anaerobic threshold. Conclusions Alternative diagnoses to diastolic dysfunction are present almost universally in patients with suspected normal ejection fraction heart failure. This is true even where these diagnoses are not previously established. This thesis underlines the need to fully assess this patient group to allow appropriate targeting of therapy. It is also clear that echocardiography alone is potentially misleading and it is suggested that it is better placed within a tiered assessment process. The assessment of diastolic function using stress radionuclide ventriculography, although an appealing concept, does not improve diagnostic accuracy within this patient group. The marked heterogeneity of this patient group is likely to have played a role in this and it may be of interest to reassess stress radionuclide ventriculography in a more acute heart failure population

    An improved classification approach for echocardiograms embedding temporal information

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    Cardiovascular disease is an umbrella term for all diseases of the heart. At present, computer-aided echocardiogram diagnosis is becoming increasingly beneficial. For echocardiography, different cardiac views can be acquired depending on the location and angulations of the ultrasound transducer. Hence, the automatic echocardiogram view classification is the first step for echocardiogram diagnosis, especially for computer-aided system and even for automatic diagnosis in the future. In addition, heart views classification makes it possible to label images especially for large-scale echo videos, provide a facility for database management and collection. This thesis presents a framework for automatic cardiac viewpoints classification of echocardiogram video data. In this research, we aim to overcome the challenges facing this investigation while analyzing, recognizing and classifying echocardiogram videos from 3D (2D spatial and 1D temporal) space. Specifically, we extend 2D KAZE approach into 3D space for feature detection and propose a histogram of acceleration as feature descriptor. Subsequently, feature encoding follows before the application of SVM to classify echo videos. In addition, comparison with the state of the art methodologies also takes place, including 2D SIFT, 3D SIFT, and optical flow technique to extract temporal information sustained in the video images. As a result, the performance of 2D KAZE, 2D KAZE with Optical Flow, 3D KAZE, Optical Flow, 2D SIFT and 3D SIFT delivers accuracy rate of 89.4%, 84.3%, 87.9%, 79.4%, 83.8% and 73.8% respectively for the eight view classes of echo videos

    Automated Analysis of 3D Stress Echocardiography

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    __Abstract__ The human circulatory system consists of the heart, blood, arteries, veins and capillaries. The heart is the muscular organ which pumps the blood through the human body (Fig. 1.1,1.2). Deoxygenated blood flows through the right atrium into the right ventricle, which pumps the blood into the pulmonary arteries. The blood is carried to the lungs, where it passes through a capillary network that enables the release of carbon dioxide and the uptake of oxygen. Oxygenated blood then returns to the heart via the pulmonary veins and flows from the left atrium into the left ventricle. The left ventricle then pumps the blood through the aorta, the major artery which supplies blood to the rest of the body [Drake et a!., 2005; Guyton and Halt 1996]. Therefore, it is vital that the cardiovascular system remains healthy. Disease of the cardiovascular system, if untreated, ultimately leads to the failure of other organs and death

    Novel applications of transoesophageal echocardiography

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    Medical image segmentation and analysis using statistical shape modelling and inter-landmark relationships

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    The study of anatomical morphology is of great importance to medical imaging, with applications varying from clinical diagnosis to computer-aided surgery. To this end, automated tools are required for accurate extraction of the anatomical boundaries from the image data and detailed interpretation of morphological information. This thesis introduces a novel approach to shape-based analysis of medical images based on Inter- Landmark Descriptors (ILDs). Unlike point coordinates that describe absolute position, these shape variables represent relative configuration of landmarks in the shape. The proposed work is motivated by the inherent difficulties of methods based on landmark coordinates in challenging applications. Through explicit invariance to pose parameters and decomposition of the global shape constraints, this work permits anatomical shape analysis that is resistant to image inhomogeneities and geometrical inconsistencies. Several algorithms are presented to tackle specific image segmentation and analysis problems, including automatic initialisation, optimal feature point search, outlier handling and dynamic abnormality localisation. Detailed validation results are provided based on various cardiovascular magnetic resonance datasets, showing increased robustness and accuracy.Open acces
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