Research On Speckle Tracking Echocardiography And Its Applications

Ultrasound medicine is a subject combined of medical science, acoustics and electronic information engineering. Ultrasonic imaging is widely used in the diagnosis for its advantage of being non-invasive, no-pain, real-time and convenience. Speckle Tracking Echocardiography, is a promising clinical application of medical ultrasound imaging technology developed in recent years. This technology tracks inherent properties of ultrasound image, selects regions of interest (ROI) inside the myocardial wall, throughout a cardiac cycle, and tracks and records position and movement of speckles or speckle pattern within the area of myocardial tissue on ultrasound images. By calculating the trajectory of speckle in the ROI, the method quantitatively analyzes myocardial tissue motion parameters such as displacement, strain, strain rate, speed and torsion angle of left ventricular (LV); The parameters acquired by speckle tracking, provide a quantitative basis for the clinicians to evaluate global and local myocardial function, and overcomes the angular dependence of myocardial Doppler imaging techniques, So speckle tracking echocardiography is more advantageous.This Thesis consists of two parts. The first half systematically studies and deeply elaborates speckle tracking technology, and proposes and implements a new speckle tracking method—RATracking Method. The RATracking method is been applied in quantitative analysis of echocardiography in the second half, with the realization of the calculation of LV radial strain and torsion angles. And the method is validated by simulated ultrasound sequences. And then, RATracking method is applied in clinical ultrasound sequences to calculate radial strain and torsion angle Preliminary.In order to improve the robustness of the traditional block matching method, and with referencing optical flow field based speckle tracking how to solve the aperture effect of optical flow constraint equation, RATracking applies a spatial smoothing constraint to the traditional block matching method. Additionally, the accumulation of error leads to precision of the traditional block matching not being ideal. In order to avoid error accumulation RATracking method introduces adaptive Kalman filtering technique so as to achieve high precision speckle tracking echocardiography. This method establishes a technical roadmap containing diamond search, SAD matching criteria, spatial smoothness constraints, adaptive Kalman filter to updating reference blocks. This method with high tracking accuracy, good robustness, and computational processing efficiency, can meet the needs of clinical applications.Strain measurement is a non-invasive, new technology of quantitative evaluation of myocardial function and contractility. It is a high sensitivity for the early discovery of myocardial disorders, so it has very important clinical needs in many aspects of cardiovascular disease, such as detection of different causes of coronary heart disease. Strain in different myocardial segments represents local systolic function in myocardial tissue, so strain of myocardial tissue index is a quantitative evaluation of systolic function, unaffected by surrounding myocardial tissue and cardiac overall movement. Using RATracking method, this thesis realizes tracking ROIs on myocardial intima, myocardial epicardial, and achieves the measure of myocardial radial strain on echocardiography.Myocardial torsion is a sensitive indicator of the changes in the overall performance of myocardial tissue function. The rotation of apical part relates to LV systolic, and unwinding at the bottom of heart relates to LV diastolic. Clinical study finds that LV torsion angle, torsional torque and other parameters, positively relate with the contractility of myocardial tissue fibers, and are quite sensitive to local or global LV lesions. So it is a more reliable and earlier indicator than the traditional ejection fraction to reflect LV systolic function, with wide clinical applications. This thesis studies a very important part of the calculation of torsion of LV, which is based on RATracking method and achieves the measurement of torsion angle of LV.