"Speckle" in Continuous Wave Doppler Ultrasound Spectra: A Simulation Study

The statistical properties of continuous wave (CW) Doppler ultrasound signals are investigated. First, the analysis of some Doppler data obtained from a human carotiadr tery is reported. Based on the chi-square test, it was found that for each of seven recorded cardiac cycles, the amplitude histogram of a stationary signal segment of a duration of 10 ms around peak systole satisfies the Gaussian hypothesis. Second, it is shown that the Doppler signal, wihs i cehv idently a band-limited Gaussian noise, can be synthesized on a computer using a sinusoidal model. The statistical behavior of the synthesized signals in both the time and the frequency domains, are shown to be in close agreement with the Doppler signals observed over a IO-ms interval around peak systole. This work has led to an understanding of the structure of the conventional grey-scale Doppler spectrogram, particularly its granular structure, which has been likened to the speckle seen in ultrasound B-mode images. Finally, some potential applications of the simulation model are discussed.