Doppler angle estimation of pulsatile flows using AR modeling
Journal
Ultrasonic Imaging
Journal Volume
24
Journal Issue
2
Pages
65-80
Date Issued
2002
Author(s)
Yeh, C.-K.
Abstract
In quantitative ultrasonic flow measurements, the beam-to-flow angle (i.e., Doppler angle) is an important parameter. An autoregressive (AR) spectral analysis technique in combination with the Doppler spectrum broadening effect was previously proposed to estimate the Doppler angle. Since only a limited number of flow samples are used, real-time two-dimensional Doppler angle estimation is possible. The method was validated for laminar flows with constant velocities. In clinical applications, the flow pulsation needs to be considered. For pulsatile flows, the flow velocity is time-varying and the accuracy of Doppler angle estimation may be affected. In this paper, the AR method using only a limited number of flow samples was applied to Doppler angle estimation of pulsatile flows. The flow samples were properly selected to derive the AR coefficients and then more samples were extrapolated based on the AR model. The proposed method was verified by both simulations and in vitro experiments. A wide range of Doppler angles (from 30° to 78°) and different flow rates were considered. The experimental data for the Doppler angle showed that the AR method using eight flow samples had an average estimation error of 3.50° compared to an average error of 7.08° for the Fast Fourier Transform (FFT) method using 64 flow samples. Results indicated that the AR method not only provided accurate Doppler angle estimates, but also outperformed the conventional FFT method in pulsatile flows. This is because the short data acquisition time is less affected by the temporal velocity changes. It is concluded that real-time two-dimensional estimation of the Doppler angle is possible using the AR method in the presence of pulsatile flows. In addition, Doppler angle estimation with turbulent flows is also discussed. Results show that both the AR and FFT methods are not adequate due to the spectral broadening effects from the turbulence.
Subjects
Autoregressive model; Doppler angle estimation; Doppler bandwidth; Pulsatile flow; Turbulent flow
Other Subjects
Data acquisition; Fast Fourier transforms; Flow velocity; Laminar flow; Spectrum analysis; Turbulent flow; Ultrasonic applications; Auto regressive models; Clinical application; Constant velocities; Doppler; Doppler angle estimation; Spectral analysis techniques; Spectral broadening effects; Ultrasonic flow measurements; Pulsatile flow; article; blood flow velocity; Doppler echography; flow measurement; laminar flow; model; pulsatile flow; quantitative analysis; real time echography; sampling; turbulent flow; ultrasound; biological model; Doppler flowmetry; human; methodology; Blood Flow Velocity; Humans; Models, Cardiovascular; Pulsatile Flow; Ultrasonography, Doppler
Type
journal article