Use of Image Processing Techniques for the Analysis of Echocardiographic Images

Echocardiography is a medical imaging modality that uses ultrasound in order to obtain cross sectional views of the heart. The basic problem in the use of echocardiography is the ability to obtain a reliable set of physical parameters related to cardiac status, so that assessment of heart disease can be performed automatically. This work overviews different image processing techniques used in the analysis of two dimensional echocardiographic images. After reviewing how the echocardiographic image formation process works, an outline of the general processing steps from image acquisition to automatic detection of important features is presented. Special emphasis on cardiac image segmentation is presented. In particular, a relaxation algorithm for image segmentation is discussed. Also, echocardiographic image segmentation using temporal analysis and a new algorithm for boundary detection is described. Measurements of left ventricular area, wall thickness, and ejection fraction is also presented. Shape analysis is introduced as a tool for echocardiographic image analysis. A high level description of the left ventricular boundaries using curvature is proposed. Curvature analysis attempts to identify stable landmarks during the beating process, muscles. Tracking these landmarks aids in the detection of abnormal heart contractions. Finally the use of expert systems is proposed in the analysis of echocardiographic images

Early diagnosis of cardiovascular diseases in workers: role of standard and advanced echocardiography

Cardiovascular disease (CVD) still remains the main cause of morbidity and mortality and consequently early diagnosis is of paramount importance. Working conditions can be regarded as an additional risk factor for CVD. Since different aspects of the job may affect vascular health differently, it is important to consider occupation from multiple perspectives to better assess occupational impacts on health. Standard echocardiography has several targets in the cardiac population, as the assessment of myocardial performance, valvular and/or congenital heart disease, and hemodynamics. Three-dimensional echocardiography gained attention recently as a viable clinical tool in assessing left ventricular (LV) and right ventricular (RV), volume, and shape. Two-dimensional (2DSTE) and, more recently, three-dimensional speckle tracking echocardiography (3DSTE) have also emerged as methods for detection of global and regional myocardial dysfunction in various cardiovascular diseases, and applied to the diagnosis of subtle LV and RV dysfunction. Although these novel echocardiographic imaging modalities have advanced our understanding of LV and RV mechanics, overlapping patterns often show challenges that limit their clinical utility. This review will describe the current state of standard and advanced echocardiography in early detection (secondary prevention) of CVD and address future directions for this potentially important diagnostic strategy

The monophasic action potential as an index of myocardial ischaemia: Studies incorporating myocardial perfusion scintigraphy

Malignant ventricular arrhythmias continue to be the major cause of death in relation to myocardial ischaemia. The basic electrophysiological alterations that accompany the onset of myocardial ischaemia have been extensively studied in in vitro preparations and animal studies. However, studies of myocardial ischaemia in man are limited by the difficulty in recording basic electrophysiological changes in the beating heart. Furthermore, such studies require production of controlled ischaemia and the ability to detect and verify such ischaemia during the electrophysiological study. This thesis has developed this technically complex approach. The advent of the monophasic action potential (MAP) recording technique using pressure contact electrodes has allowed the study of myocardial cellular repolarization characteristics in human hearts during cardiac catheterisation. Also, advances in myocardial perfusion imaging techniques with the development of newer 99m technetium isonitrile analogues have made possible, the use of myocardial perfusion scintigraphy to document myocardial perfusion characteristics during interventions in the cardiac catheterisation laboratory. This thesis is based on a series of studies that have examined the use of MAPs to document typical early electrophysiological changes of myocardial ischaemia during experimental myocardial ischaemia and its use in combination with technetium 99m hexakis-2-methoxy-2-methylpropyl-isonitrile (99mTc- MIBI) myocardial perfusion scintigraphy to study myocardial ischaemia in patients during cardiac catheterisation. An initial study in intact porcine hearts during transient coronary occlusion examined the ability of action potentials recorded by the MAP technique to register early changes of myocardial ischaemia from the ventricular endocardium. A second study in 26 patients undergoing cardiac catheterisation used endocardial recordings of the MAP during atrial pacing to angina threshold. Ischaemic areas of myocardium were identified by injection of 99m Tc-MIBI at peak pacing stress. Recordings from the ischaemic endocardial regions showed a significantly greater shortening of action potential duration corrected for heart rate changes compared with the non-ischaemic areas. Sensitivity and specificity of various changes in MAP duration per unit change in heart rate for the detection of myocardial ischaemic were derived. The third study used endocardial recordings of the MAP as a measure of myocardial ischaemia during dypiridamole myocardial perfusion imaging in patients with coronary artery disease.Finally, the combination of MAP recordings and 99m Tc-MIBI perfusion scintigraphy was employed to study regional and potential arrhythmogenic effects of beta adrenoceptor stimulation in potentially ischaemic versus normal areas of human myocardium. MAPs were recorded simultaneously from the right and left ventricular endocardium in 14 patients (28 recording sites) during infusion of dobutamine. Perfusion at the recording site was assessed by the injection of 99m Tc-MIBI at peak doses of dobutamine. Action potential duration during dobutamine was compared to that during atrial pacing to identical pacing rates in the absence of dobutamine. In 21 recordings from normally perfused recordings, dobutamine produced a variable effect on the action potential duration over and above that produced by atrial pacing alone to identical pacing rates either lengthening or shortening the action potential duration. In the ischaemic zones, dobutamine invariably shortened the action potential duration. The data provide a possible mechanistic basis for the beneficial effects of beta adrenergic blockade in ischaemic heart disease. A unique series of studies combining basic electrophysiological studies with a radionuclide imaging technique is presented. Validation and application of the two techniques to evaluate regional myocardial ischaemia and arrhythmogenic potential in the human heart are addressed

Echocardiography

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

Contrast-enhanced ultrasound: clinical applications in patients with atherosclerosis

Contrast-enhanced ultrasound (CEUS) is increasingly being used to evaluate patients with known or suspected atherosclerosis. The administration of a microbubble contrast agent in conjunction with ultrasound results in an improved image quality and provides information that cannot be assessed with standard B-mode ultrasound. CEUS is a high-resolution, noninvasive imaging modality, which is safe and may benefit patients with coronary, carotid, or aortic atherosclerosis. CEUS allows a reliable assessment of endocardial borders, left ventricular function, intracardiac thrombus and myocardial perfusion. CEUS results in an improved detection of carotid atherosclerosis, and allows assessment of high-risk plaque characteristics including intraplaque vascularization, and ulceration. CEUS provides real-time bedside information in patients with a suspected or known abdominal aortic aneurysm or aortic dissection. The absence of ionizing radiation and safety of the contrast agent allow repetitive imaging which is particularly useful in the follow-up of patients after endovascular aneurysm repair. New developments in CEUS-based molecular imaging will improve the understanding of the pathophysiology of atherosclerosis and may in the future allow to image and directly treat cardiovascular diseases (theragnostic CEUS). Familiarity with the strengths and limitations of CEUS may have a major impact on the management of patients with atherosclerosis