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Title:Doppler-Based Ultrasonic Blood Velocity Estimation
Author(s):Arikan, Toros
Contributor(s):Singer, Andrew C.
Cramér-Rao Lower Bound
Blood Velocity
Signal Processing
Abstract:Blood velocity estimation is a useful clinical tool for assessing the condition of blood vessels and organ functionality. Current methods monitor the shift of position of red blood cells over time to estimate velocity, and generally do not use Doppler shift information. The tracking of these particles based on their shifts in position is a computationally intensive and time-consuming process. The development of Doppler-based methods using short chirps would allow significantly faster calculations because the positions of particulates would not have to be tracked over several pulses. Use of additional information embedded in the received waveform would also allow operation in a noisier environment. We investigate the feasibility of such a system for linear, hyperbolic and superposed hyperbolic chirps. Interrogation of a simulated blood vessel with these chirps, followed by correlation with a filter bank, demonstrates the chirps’ Doppler insensitivity for the given constraints. The true ambiguity functions of the chirps are plotted, and short signal duration is found to be the cause of the small Doppler resolution we obtain. Cramér-Rao lower bounds in Doppler are calculated for the case of a simple delayed and Doppler-shifted chirp, and the results indicate that a Doppler-based approach is feasible. Future research will refine the Cramér-Rao lower bound to incorporate attenuation and other physical effects, which will increase the SNR we need to obtain a given Doppler resolution. We will also focus on modifying the chirps used to interrogate blood vessels to have greater Doppler resolution.
Issue Date:2014-12
Date Available in IDEALS:2015-03-31

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