Integrated backscatter (IB) from the heart wall is gaining attention as a quantitative tissue characterization method and the cyclic variation (CV) in IB during a cardiac cycle offers potential for the evaluation of myocardial contractility. Since there is large motion in the heart wall owing to the heartbeat, in the conventional method, the position of the region of interest (ROI) for calculating the IB is manually assigned in each frame during one cardiac cycle. Moreover, the change in the size of the ROI during contraction and relaxation of the myocardium is not considered. In this study, the phased tracking method was applied to multiple points in the heart wall for automatic tracking of the position and size of the ROI and, then, IB in the same site of the heart wall was measured in each frame by improving temporal resolution and spatial resolution in the axial direction. As a result, cyclic variations, which differed site by site, were found. Furthermore, the rate of change in thickness was estimated by using the interference cycle obtained by applying the discrete Fourier transform (DFT) to IB signals. According to the results, the rate of change in thickness estimated using the interference cycle of IB was in good agreement with that estimated by the phased tracking method. These results indicate the possibility of estimating the rate of change in thickness using the IB signal. #
One of the valuable methods of cardiac valve diagnosis can be performed by auscultation. We proposed a signal processing and extensive characterization method based on wavelet analysis to investigate important characteristics of heart sounds of normal and pathologic systolic murmur human subjects. Timescale maps yielded by wavelet transform calculation were solved using magnitude thresholding operation and centre of gravity to restrict temporal and frequency-related of valvular activities. From our experimental results, temporal and frequencyrelated parameters of S 1 , S 2 , and their components could be characterized precisely. Application of our method was adequate to characterize the heart sounds objectively, clearly, systematically, and comprehensively. The method was considered valuable to explain mechanisms of cardiac valves functions. We expected that the method would be helpful for clinical diagnosis as well as developing of heart sound modelling and educational purpose. Next topic of our study was addressed for classification of the heart sounds.
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