Effect of wavelet denoising on time-frequency and time-scale analysis of quadrature embolic Doppler signals

Early and accurate detection of emboli is important for monitoring of preventive therapy in stroke-prone patients. One of the problems in detection of emboli is the identification of an embolic signal caused by very small emboli. The amplitude of the embolic signal may be so small that advanced processing methods are required to distinguish these signals from Doppler signals arising from red blood cells. Time-frequency and time-scale analysis have been widely used in analysis and detection of embolic signals. In this study we use wavelet denoising to improve analysis and detection of embolic signals. Results demonstrate that considerable improvements can be achieved by wavelet denoising.