Time domain formulation of pulse-Doppler ultrasound and blood velocity estimation by cross correlation.

https://ieeexplore.ieee.org/iel4/5388/14578/00664417.pdf

Ultrasound Imaging

An ultrasound scanner is equipped with one or more fuzzy control units that can perform adaptive system parameter optimization anywhere in the system. In one embodiment, an ultrasound system comprises a plurality of ultrasound image generating subsystems configured to generate an ultrasound image, the plurality of ultrasound image generating subsystems including a transmitter subsystem, a receiver subsystem, and an image processing subsystem; and a fuzzy logic controller communicatively coupled with at least one of the plurality of ultrasound imaging generating subsystems. The fuzzy logic controller is configured to receive, from at least one of the plurality of ultrasound imaging generating subsystems, input data including at least one of pixel image data and data for generating pixel image data; to process the input data using a set of inference rules to produce fuzzy output; and to convert the fuzzy output into numerical values or system states for controlling at least one of the transmit subsystem and the receiver subsystem that generate the pixel image data.

Ultrasound imaging system parameter optimization via fuzzy logic

Recently, real-time blood flow imaging became possible thanks to the development of a velocity estimator based on the phase-shift measurement of the successive echoes obtained from moving blood [ I]. However, this method suffers from the well known limitations of pulse-Doppler instruments. These drawbacks are mainly the conflict between velocity precision and axial resolution requirements, and the velocity limitation due to the aliasing phenomenon. In this paper, a new principle for velocity estimation, based on time domain correlation [21, is shown to overcome these problems. A simplified version of the technique using only I bit signals has been derived. This processing scheme has been optimized through extensive computer simulations. Experiments carried out on recorded in-vivo data, have confirmed the feasibility of measuring velocity profiles accurately, without the high velocity limitation (aliasing). Moreover, the possibility of obtain instantaneous and accurate velocity profiles by processing a limited number of echo response (about IO A-lines) should provide new potential modalities for clinical application of ultrasound.

A New Velocity Estimator for Color Flow Mapping

The operation of a novel ultrasound multigate instrument capable of computing in real-time the fast Fourier transform (FFT) of Doppler signals detected from 64 equally spaced range cells is presented. The new system provides up to 50 velocity profiles per second, which are displayed in such a manner that information about the full spectral content of Doppler signals at all the investigated depths is continuously monitored over a PRF-wide frequency range which can be set arbitrarily between -PRF and +PRF. Experimental results are presented, which demonstrate that the true velocity profile can be accurately detected through the computation of "local" maximum velocities obtained by properly correcting the maximum frequency of each spectrum. There is also a discussion on how the results of multigate analysis are influenced by the sample volume length, a parameter which can be usually set by modifying the duration of the transmitted burst. In particular, it is shown that, in regions close to the vessel walls, the shear rate can be measured with a spatial resolution related to the spacing between subsequent range cells and not to the sample volume length.

Spectral velocity profiles for detailed ultrasound flow analysis

Abstmct-An ultrasound pulse Doppler system is discussed, capable of performing real time spectral analysis of data originating from a number of sample volumes. The use of a surface-acoustic-wave-based ultrafast spectrum analyzer allows for a large amount of Doppler data to be processed in a time equal to a few tens of microseconds for each equivalent channel. Sonograms comparable to those obtained in single gate-fast Fourier transform-based-Doppler systems can thus be simultaneously presented, showing the velocity distribution in different sample volumes as a function of time. Alternately, the instantaneous velocity profile can be mapped as a function of depth, thus allowing for the possibility of bidimensional imaging. A prototype flowmeter capable of processing Doppler data from 32 range cells in real time is described and preliminary results obtained in virro under simulated flow conditions are presented.

G. Maines

Papers

Velocity Profile Reconstruction Using Ultrafast Spectral Analysis of Doppler Ultrasound