COMPARISON OF TIME-FREQUENCY DISTRIBUTION TECHNIQUES FOR ANALYSIS OF SIMULATED DOPPLER ULTRASOUND SIGNALS OF THE FEMORAL-ARTERY

The time-frequency distribution of the Doppler ultrasound blood flow s ignal is normally computed by using the short-time Fourier transform o r autoregressive modeling. These two techniques require stationarity o f the signal during a finite interval. This requirement imposes some l imitations on the distribution estimate. In the present study, three n ew techniques for nonstationary signal analysis (the Choi-Williams dis tribution, a reduced interference distribution, and the Bessel distrib ution) were tested to determine their advantages and limitations for a nalysis of the Doppler blood flow signal of the femoral artery. For th e purpose of comparison, a model simulating the quadrature Doppler sig nal was developed, and the parameters of each technique mere optimized based on the theoretical distribution. Distributions computed using t hese new techniques were assessed and compared with those computed usi ng the short-time Fourier transform and autoregressive modeling. Three indexes, the correlation coefficient, the integrated squared error, a nd the normalized root-mean-squared error of the mean frequency wavefo rm, were used to evaluate the performance of each technique. The resul ts showed that the Bessel distribution performed the best, but the Cho i-Williams distribution and autoregressive modeling are also technique s which can generate good time-frequency distributions of Doppler sign als.