Power Spectra of Doppler Response Signals from Biological Objects Using Synthetic Aperture Ultrasound

Abstract

The influence of dynamic change in the steering angle of incident and scattered wave beams on the spectra of the ultrasonic Doppler response is studied on the basis of the previously developed continuum model of ultrasound waves scattering in biological objects for the case, when the Doppler response signals are averaged over the period of changing the steering angle. A general expression is obtained, which combines the resultant spectrum of the power of the ultrasonic Doppler response signal from the region of interest, the spectral characteristics of the ultrasound scatterers movement, and the sensitivity function of the diagnostic synthetic aperture system. It is shown that, as compared to the Doppler response, which is a sequence of discrete values of the response signals from different steering angles, the use of averaging allows to reduce the width of the Doppler spectra without deterioration of their resolution. It is concluded that the achievement of better spatial resolution, when using the synthetic aperture method, is possible without deterioration of the spectral characteristics and, accordingly, of the accuracy of Doppler measurements of diagnostic parameters, which are determined during the ultrasound studies. The results obtained make it possible to optimize different Doppler techniques within the framework of the general synthetic aperture method.