The Application Research Of Speckle Tracking In Echocardiography Processing And Analysis

Ultrasonic imaging is widely used in the clinic diagnosis for its advantages of being non-invasive, no-pain, real-time and convenient. Now, more than 25% medical imaging studies is related with ultrasonic imaging. In competition with other imaging modalities, ultrasound has an inherent character - speckle. We can consider that ultrasound image consists of lots of speckle pattern. Speckle, limiting the quality of conventional images, but it provides excellent markers for accurate motion tracking. Speckle tracking is a variety of ultrasound techniques used for tracking tissue motion by tracking the movement of speckle pattern produced by the backscattering of the ultrasound itself.This paper is divided into two sections. First is the theoretic research of speckle tracking, a B-mode based speckle tracking technique is implemented. In the next section, the application research of speckle tracking in echocardiography processing and analysis is studied. Assessment of left ventricle torsion and tracking of myocardial region-of-interest in real-time MCE are solved by speckle tracking separately.Current speckle tracking algorithms have been divided into two main groups: optical flow algorithms and block-matching algorithms. Comparing the two methods, the author concluded that block matching is better for its simple principle and high efficiency. In order to satisfy the requirement for robustness and real-time of speckle tracking technique in clinical application, a speckle tracking technique based on block matching is implemented, using sum of absolute difference as matching criteria and diamond search as search algorithm. Then simulation of ultrasound images is presented for verification of the speckle tracking method.Left ventricular (LV) torsion is a sensitive indicator of LV performance. It is well established that LV torsion is more sensitive to changes in both regional and global LV function than LV ejection fraction. Therefore, assessment of LV torsion represents an interesting approach for quantifying LV function. However, so far, magnetic resonance imaging (MRI) tagging has been the only clinically available and noninvasive method but implementation has therefore been limited by complexity and cost. In this study, on the basis of myocardial ROI tracking through ultrasound image sequences, LV torsionwas estimated by speckle tracking technique clinically applicable.Real-time Myocardial Contrast Echocardiography (RT-MCE) is a new method for assessing myocardium microcirculation and is starting to be introduced into clinical practice. Quantitative analysis of RT-MCE is the focus now; time-intensity curve is the most popular way. In this case, as the heart moves, a fixed ROI position does not represent the same structure along cardiac cycle. Therefore, for accurate quantification, regions must be repositioned along the sequence. This problem was solved also by speckle tracking. Clinicians evaluated that automatic alignment by speckle tracking might increase the accuracy of quantification, which can drive a widespread clinical acceptance of this technique.