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A new test object has been developed with the aim of covering a wide range of Doppler quality assurance requirements, with particular emphasis on color Doppler imaging (both velocity and power modes). The test object consists of a rotating string-loop, which provides the single velocity source required for velocity calibration. The loop geometry provides(More)
This paper describes a new noninvasive ultrasonic method for estimating pulse wave velocity (PWV), an important physical parameter for characterizing the elastic properties of the arterial walls. The method utilizes a relatively new color Doppler modality for measuring tissue motion (tissue Doppler imaging or TDI). In contrast to previously proposed(More)
This paper describes a digital image processor for ultrasonic speckle suppression that was explicitly designed to satisfy the requirements of detail preservation, adequate smoothing and real-time operation. The first two of these requirements were addressed by selecting a nonlinear adaptive algorithm, which uses a measure of local homogeneity to adjust the(More)
Autoregressive (AR) techniques are investigated by developing mean and maximum frequency estimators suitable for use in Doppler color flow mapping systems, where they are most needed. The estimators are based on low-order (for computational efficiency) AR models applied to complex signals whose real and imaginary parts are the in-phase and quadrature(More)
The effect of three physical parameters on the accuracy of estimation of the maximum frequency envelope and pulsatility index (PI) of simulated umbilical artery Doppler waveforms was investigated. The physical parameters were beam-vessel angle, the offset between the beam axis and vessel axis, and the thickness of overlying attenuating material. Waveforms(More)
This paper is concerned with speckle suppression in Discrete Fourier Transform based Doppler signals by means of digital image processing. The Doppler spectrum is treated as a greyscale image, and three different noise smoothing algorithms are applied to it. These are the Double Window Modified Trimmed Mean filter, which is nonlinear, and Lee's and the(More)
Deconvolution can, in principle, enhance the spatial resolution of specular reflectors in medical ultrasonic imaging but, in practice, the resolution improvement offered is offset by the introduction of undesirable artefacts. In this study, several problems related to deconvolution were identified and practical suggestions for minimising artefacts were(More)
A comparison between the Doppler signals from human blood and artificial blood used in a flow phantom is described. The artificial blood used was a suspension of Sephadex particles in a glycerol solution. The Doppler power was measured as a function of Sephadex concentration and found to peak at a concentration of about 40% by volume. The power from blood(More)
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