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

Iryna V Sheina ,Olexander B Kiselov ,E A Barannik

doi:10.26565/2312-4334-2020-4-01

Iryna V Sheina , Olexander B Kiselov + Show 1 more

Open Access

https://doi.org/10.26565/2312-4334-2020-4-01

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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.

Highlights

We investigated the influence of dynamic change in the steering angle at transmitting and receiving the wave beams on the spectral characteristics of the sensitivity function of the probing system and the spectrum of the ultrasonic Doppler response in the case, when the Doppler response signals were averaged over the period of the change in the steering angle
Even at a constant velocity of the ultrasound scatterers V, the measured speed V cos constantly increases or decreases, depending on whether the angle decreases or increases. This situation is physically equivalent to the accelerated movement of ultrasound scatterers, what leads to broadening of the Doppler signal spectrum, as shown in [52]
It is still relevant to study the influence of the factor of dynamic changes in the parameters and geometry of probing ultrasonic fields on the spectra of Doppler signals and, on the estimates of the parameters of the biological objects motion

Summary

Introduction

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. As a result of the introduction of multilinear data processing into ultrasound diagnostic systems, it became possible to visualize in-vivo blood flows using the synthetic aperture method, which, in comparison with the conventional Doppler techniques, allowed to improve spectral estimates [31], to determine the velocity vector [32], and to increase the sensitivity to slow velocity flows [33].

Results

Conclusion