PSEUDO-WIGNER DISTRIBUTION FOR ANALYSIS OF PULSED DOPPLER ULTRASOUND

Existing pulsed Doppler ultrasound systems apply the spectrogram as a tool for analysis and display of signals scattered from the blood. The spectrogram is a time-frequency representation (TFR) of a signal that maps a one-dimensional signal of time into a two-dimensional function of time and frequency. The analysis of Doppler ultrasound signals req uires application of a two-dimensional TFR rather than one-dimensional spectral representations due to the nonstationary nature of the signa ls scattered from blood. The classical spectrogram is a smoothed Wigne r distribution (SWD) with a specific smoothing function. For this smoo thing function, the smoothing, and hence the resolution in time and fr equency, cannot be controlled independently. The purpose of this study is to examine the application of other SWD's to analysis and display of Doppler ultrasound signals. The present paper concentrates on the p seudo-Wigner distribution (PWD). The PWD and the spectrogram are exami ned and compared as analysis tools for nonstationary Doppler ultrasoun d signals. The performance of these two TFR's as a function of Doppler bandwidth is evaluated and compared for time-varying flow.