| Summary: | Coronary heart disease is the most common cause of death in the UK affecting more than one in five men and one in six women. The cause is generally a constriction of the coronary arteries which supply the heart muscle, or myocardium with blood. In around 95% of cases, the constriction is caused by the process of arteriosclerosis which results in the development of a plaque on the vessel wall. Even though these plaques tend to develop quite slowly, they are sometimes liable to sudden rupture, which causes clotting of the blood in the vessel and hence a sudden reduction in the supply of blood to the myocardium. This thesis is concerned with the signal processing techniques which are used in the form of Doppler Tissue Imaging (DTI) and real-time B-Mode imaging to study the motion of cardiac structures. Although these techniques are well suited to this task, improvements in B-mode contrast resolution and DTI velocity resolution are required if image quality and quantitative measurements are to reach a more acceptable level. Results are presented which demonstrate that the accuracy of the velocity estimations made using DTI can be improved with the use of model based signal processing techniques. The use of the fractional Fourier transform is explored in the context of coded excitation, which is a technique to allow improvements in imaging depth and axial resolution and results are shown which show that this technique is able to offer improvements similar to matched filtering. The combined techniques of empirical mode decomposition and the Hilbert spectrum are used to demonstrate a new interpretation of the physical process underlying non-linear acoustic wave propagation and the existing technique of tissue harmonic imaging.
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