Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 1990
Statistical properties of the ultrasound speckle in B-scan images have been analyzed for years. I... more Statistical properties of the ultrasound speckle in B-scan images have been analyzed for years. In many cases the properties may differ from the Rayleigh statistics which are assumed at most of the time. The differences can be applied to examine the isonated tissue structures. In this paper we demonstrate the existence of non-Rayleigh statistics under phantom experiments and computer simulations.
1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118), 1997
Gaseous contrast agents can be used to enhance conventional Doppler measurements and to create ne... more Gaseous contrast agents can be used to enhance conventional Doppler measurements and to create new harmonic Doppler modalities. The effect of bubble destruction on both conventional and harmonic Doppler spectra was studied using an in vitro, pulsatile flow system. Similar spectrograms were observed for low levels of insonification (below 0.62 MPa) in both conventional and harmonic Doppler measurements of the
Proceedings of IEEE Ultrasonics Symposium ULTSYM-94, 1994
Describes a numerical model that can produce Doppler signals for nonaxial, pulsatile flow. The mo... more Describes a numerical model that can produce Doppler signals for nonaxial, pulsatile flow. The model consists of two main units. The first unit models the physics of blood now and provides output variables that describe the flow. It is built upon the Fluid Dynamic Analysis Package, an existing software tool for studying and visualizing fluid flow. The second unit models the acoustic field of the transducer and accounts for the beam focusing effect. With blood treated as a cloud of moving point-like scatterers of ultrasound, these two units provide information about the path and acoustic response of the individual scatterers. Thus, both hemodynamic and acoustic factors are accounted for. Finally, the principle of superposition is applied to compute the total backscattered signal, which is then gated or sampled to produce the Doppler signal. To validate the model Doppler signals from flow near a stenosis were simulated, and their spectra presented
A prototype water-tank-based analog/digital pulsed imaging system was built to study the feasibil... more A prototype water-tank-based analog/digital pulsed imaging system was built to study the feasibility of tumor differentiation using color flow Doppler under low-flow and weak scattering conditions. Images of the whole breast instead of one section were obtained. Data from 20 slices per patient were taken. Since attenuation increases with depth, the recorded ultrasound images were characterized by low signal-to-noise (S/N)
… in Medicine and Biology Society, 1990., …, Jan 1, 1990
ABSTRACT The application of a modified Wigner Distribution (WD) to Doppler ultrasound is studied.... more ABSTRACT The application of a modified Wigner Distribution (WD) to Doppler ultrasound is studied. The modified WD is a nonstationary spectral estimator that does not have the cross-terms effect of the original WD. The new technique gives much better resolution and much ...
… and Modeling, 1990., Fifth ASSP Workshop …, Jan 1, 1990
1 .Introduction For the spectral analysis of nonstationary signal, the Short-Time Fourier Transfo... more 1 .Introduction For the spectral analysis of nonstationary signal, the Short-Time Fourier Transform (STFT) or spectrogram is known to be smeared in time and frequency. A long window length is required for good frequency resolution but results in poor time resolution. A short ...
Doppler blood flow signals is usually obtained using the spectrogram, which requires signal stati... more Doppler blood flow signals is usually obtained using the spectrogram, which requires signal stationarity and is known to produce large estimation variance. This paper examines three alternative, nonstationary spectral estimators: the Choi-Williams distribution (CWD), the ...
Two types of errors resulting from the numerical evaluation of a transducer's spatial impuls... more Two types of errors resulting from the numerical evaluation of a transducer's spatial impulse response function have been identified, One is geometric and is due to the mismatch between the emulated piston surface (approximated using many small planar elements) and the true surface. The other error is algebraic and is due to the inexact formulation of the response of the
Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 1990
Statistical properties of the ultrasound speckle in B-scan images have been analyzed for years. I... more Statistical properties of the ultrasound speckle in B-scan images have been analyzed for years. In many cases the properties may differ from the Rayleigh statistics which are assumed at most of the time. The differences can be applied to examine the isonated tissue structures. In this paper we demonstrate the existence of non-Rayleigh statistics under phantom experiments and computer simulations.
1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118), 1997
Gaseous contrast agents can be used to enhance conventional Doppler measurements and to create ne... more Gaseous contrast agents can be used to enhance conventional Doppler measurements and to create new harmonic Doppler modalities. The effect of bubble destruction on both conventional and harmonic Doppler spectra was studied using an in vitro, pulsatile flow system. Similar spectrograms were observed for low levels of insonification (below 0.62 MPa) in both conventional and harmonic Doppler measurements of the
Proceedings of IEEE Ultrasonics Symposium ULTSYM-94, 1994
Describes a numerical model that can produce Doppler signals for nonaxial, pulsatile flow. The mo... more Describes a numerical model that can produce Doppler signals for nonaxial, pulsatile flow. The model consists of two main units. The first unit models the physics of blood now and provides output variables that describe the flow. It is built upon the Fluid Dynamic Analysis Package, an existing software tool for studying and visualizing fluid flow. The second unit models the acoustic field of the transducer and accounts for the beam focusing effect. With blood treated as a cloud of moving point-like scatterers of ultrasound, these two units provide information about the path and acoustic response of the individual scatterers. Thus, both hemodynamic and acoustic factors are accounted for. Finally, the principle of superposition is applied to compute the total backscattered signal, which is then gated or sampled to produce the Doppler signal. To validate the model Doppler signals from flow near a stenosis were simulated, and their spectra presented
A prototype water-tank-based analog/digital pulsed imaging system was built to study the feasibil... more A prototype water-tank-based analog/digital pulsed imaging system was built to study the feasibility of tumor differentiation using color flow Doppler under low-flow and weak scattering conditions. Images of the whole breast instead of one section were obtained. Data from 20 slices per patient were taken. Since attenuation increases with depth, the recorded ultrasound images were characterized by low signal-to-noise (S/N)
… in Medicine and Biology Society, 1990., …, Jan 1, 1990
ABSTRACT The application of a modified Wigner Distribution (WD) to Doppler ultrasound is studied.... more ABSTRACT The application of a modified Wigner Distribution (WD) to Doppler ultrasound is studied. The modified WD is a nonstationary spectral estimator that does not have the cross-terms effect of the original WD. The new technique gives much better resolution and much ...
… and Modeling, 1990., Fifth ASSP Workshop …, Jan 1, 1990
1 .Introduction For the spectral analysis of nonstationary signal, the Short-Time Fourier Transfo... more 1 .Introduction For the spectral analysis of nonstationary signal, the Short-Time Fourier Transform (STFT) or spectrogram is known to be smeared in time and frequency. A long window length is required for good frequency resolution but results in poor time resolution. A short ...
Doppler blood flow signals is usually obtained using the spectrogram, which requires signal stati... more Doppler blood flow signals is usually obtained using the spectrogram, which requires signal stationarity and is known to produce large estimation variance. This paper examines three alternative, nonstationary spectral estimators: the Choi-Williams distribution (CWD), the ...
Two types of errors resulting from the numerical evaluation of a transducer's spatial impuls... more Two types of errors resulting from the numerical evaluation of a transducer's spatial impulse response function have been identified, One is geometric and is due to the mismatch between the emulated piston surface (approximated using many small planar elements) and the true surface. The other error is algebraic and is due to the inexact formulation of the response of the
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