A Characterization of Wavefront Distortion for Analysis of Ultrasound Diffraction Measurements Made Through an Inhomogeneous Medium

Waag, Robert C.; Astheimer, Jeffrey P.; Swartout, G.W.

doi:10.1109/t-su.1985.31567

Cited by 8 publications

(8 citation statements)

References 6 publications

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“…͑2͒ has been used on many occasions as a starting point for developing scattering models for random media variability; it has been used for scattering of electromagnetic waves from atmospheric turbulence ͑Chernov, 1960; Tatarski, 1961;Morse and Ingard, 1968;Ishimaru, 1978͒, scattering of ultrasonic waves from different tissues in the field of medical ultrasound ͑Waag, 1984; Waag et al, 1985, and it has also been used previously for scattering of high-frequency sound from temperature microstructure in the ocean ͑Munk and Garrett, 1973;Goodman and Kemp, 1981;Goodman, 1990͒. In addition, it has been used as a starting point for a number of acoustic scattering models for weakly scattering zooplankton ͑McGehee et Stanton et al, 1998;Chu and Ye, 1999;Lavery et al, 2002͒.…”

Section: ͑4͒mentioning

confidence: 99%

“…For wave front curvature effects to be unimportant ͑Good-man, 1990; Waag et al, 1985͒, there must be many characteristic length scales of the media variability encompassed within the first Fresnel radius, R F . For a point transmitter and receiver, the first Fresnel radius refers to the locus of points for which the phase difference that arises from the path length difference between this locus of points and the center of the volume V is equal to /2.…”

Section: ͑4͒mentioning

confidence: 99%

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High-frequency acoustic scattering from turbulent oceanic microstructure: The importance of density fluctuations

Lavery

Schmitt

Stanton

2003

The Journal of the Acoustical Society of America

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Acoustic scattering techniques provide a unique and powerful tool to remotely investigate the physical properties of the ocean interior over large spatial and temporal scales. With high-frequency acoustic scattering it is possible to probe physical processes that occur at the microstructure scale, spanning submillimeter to centimeter scale processes. An acoustic scattering model for turbulent oceanic microstructure is presented in which the current theory, which only accounts for fluctuations in the sound speed, has been extended to include fluctuations in the density as well. The inclusion of density fluctuations results in an expression for the scattering cross section per unit volume, v , that is explicitly dependent on the scattering angle. By relating the variability in the density and sound speed to random fluctuations in oceanic temperature and salinity, v has been expressed in terms of the temperature and salinity wave number spectra, and the temperature-salinity co-spectrum. A Batchelor spectrum for temperature and salinity, which depends on parameters such as the dissipation rates of turbulent kinetic energy and temperature variance, has been used to evaluate v . Two models for the temperature-salinity co-spectrum have also been used. The predictions indicate that fluctuations in the density could be as important in determining backscattering as fluctuations in the sound speed. Using data obtained in the ocean with a high resolution vertical microstructure profiler, it is predicted that scattering from oceanic microstructure can be as strong as scattering from zooplankton.

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Section: ͑4͒mentioning

confidence: 99%

Section: ͑4͒mentioning

confidence: 99%

High-frequency acoustic scattering from turbulent oceanic microstructure: The importance of density fluctuations

Lavery

Schmitt

Stanton

2003

The Journal of the Acoustical Society of America

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“…The following analysis closely follows the theoretical work done by Waag for phase aberration, 18 and is therefore subject to the same constraints. Namely, in order to properly apply his geometric ray/perturbation theory formalism, it must be assumed that the scale of the distorting inhomogeneities, or aberrators, are larger than the insonifying wavelength.…”

Section: Theorymentioning

confidence: 99%

“…In particular, Waag et al developed a theoretical scattering model which incorporates the effects of phase aberration, and relates the physical characteristics of inhomogeneities to aberration quantifiers. 18 O'Donnell looked at the effects of phase aberration upon backscatter measurement, 19 and Smith, Trahey et al investigated the properties of B-mode speckle in the presence of phase aberration. 13,14 Recent work has focused primarily upon compensating for errors due to phase aberration through the incorporation of appropriate time delays in array transducer processing.…”

Section: Introductionmentioning

confidence: 99%

“…[20][21][22][23] Varghese et al, however, recently investigated the implications of phase aberration for elastographic imaging. 24 In this work we extend the basic model published by Waag et al 18 to include amplitude aberration due to variations in inhomogeneity attenuation with respect to the background, and investigate the effects of both aberration types ͑amplitude and phase͒ upon scatterer size estimation. In particular, aberration quantification is briefly discussed before inclusion in the general expression for Fourier-transformed rf-data segments.…”

Section: Introductionmentioning

confidence: 99%

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Errors in ultrasonic scatterer size estimates due to phase and amplitude aberration

Gerig

Zagzebski

2004

The Journal of the Acoustical Society of America

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Current ultrasonic scatterer size estimation methods assume that acoustic propagation is free of distortion due to large-scale variations in medium attenuation and sound speed. However, it has been demonstrated that under certain conditions in medical applications, medium inhomogeneities can cause significant field aberrations that lead to B-mode image artifacts. These same aberrations may be responsible for errors in size estimates and parametric images of scatterer size. This work derives theoretical expressions for the error in backscatter coefficient and size estimates as a function of statistical parameters that quantify phase and amplitude aberration, assuming a Gaussian spatial autocorrelation function. Results exhibit agreement with simulations for the limited region of parameter space considered. For large values of aberration decorrelation lengths relative to aberration standard deviations, phase aberration errors appear to be minimal, while amplitude aberration errors remain significant. Implications of the results for accurate backscatter and size estimation are discussed. In particular, backscatter filters are suggested as a method for error correction. Limitations of the theory are also addressed. The approach, approximations, and assumptions used in the derivation are most appropriate when the aberrating structures are relatively large, and the region containing the inhomogeneities is offset from the insonifying transducer.

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Wavefront distortion in ultrasonic imaging

Waag

Smith

Sumino

Images of the Twenty-First Century. Proceedings of the Annual International Engineering in Medicine and Biology Society

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The influence of wavefront distortion in ultrasonic imaging is examined using a model which represents the received signal as a convolution of the scattering source and the system beam pattern. Assuming the beam pattern can be factored into the product of axial and lateral functions, a sinusoidal and a Gaussianly distributed time jitter are employed to show the effect of wavefront distortion on the correlation of the signal across the system aperture. The results illustrate how time jitter couples into beam width to degrade resolution.

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A Characterization of Wavefront Distortion for Analysis of Ultrasound Diffraction Measurements Made Through an Inhomogeneous Medium

Cited by 8 publications

References 6 publications

High-frequency acoustic scattering from turbulent oceanic microstructure: The importance of density fluctuations

High-frequency acoustic scattering from turbulent oceanic microstructure: The importance of density fluctuations

Errors in ultrasonic scatterer size estimates due to phase and amplitude aberration

Wavefront distortion in ultrasonic imaging

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