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May 2012

Volume 131, Issue 5, pp. EL355-4232

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Experimental evaluation of time domain models for ultrasound attenuation losses in photoacoustic imaging

H. Roitner, J. Bauer-Marschallinger, T. Berer, and P. Burgholzer

J. Acoust. Soc. Am. Volume 131, Issue 5, pp. 3763-3774 (2012); (12 pages) | Cited 2 times

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Understanding and compensating ultrasound attenuation losses is an important issue in photoacoustic imaging. To contribute to this effort, simulated attenuated time domain waveforms are compared to experimental waveforms. The experimental waveforms are acquired by transmitting broadband ultrasound pulses through distilled water and porcine fat tissue. Three well-known modeling approaches are examined in detail with regard to accuracy and computation time. Furthermore, the influence of attenuation on imaging resolution is addressed. In the present paper, the focus lies on the calculation of attenuated detector signals. The results, however, also provide clues about the quality of image reconstruction.
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43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions
43.20.Hq Velocity and attenuation of acoustic waves
43.20.Bi Mathematical theory of wave propagation
43.35.Wa Biological effects of ultrasound, ultrasonic tomography

Sensitivity of the resonant ultrasound spectroscopy to weak gradients of elastic properties

Hanuš Seiner, Petr Sedlák, Lucie Bodnárová, Alena Kruisová, Michal Landa, Angel de Pablos, and Manuel Belmonte

J. Acoust. Soc. Am. Volume 131, Issue 5, pp. 3775-3785 (2012); (11 pages) | Cited 2 times

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The applicability of resonant ultrasound spectroscopy on materials with weak spatial gradients in elastic coefficients and density is analyzed. It is shown that such gradients do not affect measurably the resonant spectrum but have a significant impact on the modal shapes. A numerical inverse procedure is proposed to explore the possibility of reconstructing the gradients from experimentally obtained modal shapes. This procedure is tested on synthetic data and applied to determine the gradient of the shear modulus in a continuously graded silicon nitride ceramic material. The results are in a good agreement with the gradient calculated for the examined material theoretically as well as with the results of other experimental methods.
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43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
43.40.At Experimental and theoretical studies of vibrating systems

Sound field reconstruction using acousto-optic tomography

Antoni Torras-Rosell, Salvador Barrera-Figueroa, and Finn Jacobsen

J. Acoust. Soc. Am. Volume 131, Issue 5, pp. 3786-3793 (2012); (8 pages) | Cited 1 time

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When sound propagates through a medium, it results in pressure fluctuations that change the instantaneous density of the medium. Under such circumstances, the refractive index that characterizes the propagation of light is not constant, but influenced by the acoustic field. This kind of interaction is known as the acousto-optic effect. The formulation of this physical phenomenon into a mathematical problem can be described in terms of the Radon transform, which makes it possible to reconstruct an arbitrary sound field using tomography. The present work derives the fundamental equations governing the acousto-optic effect in air, and demonstrates that it can be measured with a laser Doppler vibrometer in the audible frequency range. The tomographic reconstruction is tested by means of computer simulations and measurements. The main features observed in the simulations are also recognized in the experimental results. The effectiveness of the tomographic reconstruction is further confirmed with representations of the very same sound field measured with a traditional microphone array.
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43.35.Sx Acoustooptical effects, optoacoustics, acoustical visualization, acoustical microscopy, and acoustical holography

On the Coriolis effect in acoustic waveguides

Henry Wegert, Leonard M. Reindl, Werner Ruile, and Andreas P. Mayer

J. Acoust. Soc. Am. Volume 131, Issue 5, pp. 3794-3801 (2012); (8 pages)

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Rotation of an elastic medium gives rise to a shift of frequency of its acoustic modes, i.e., the time-period vibrations that exist in it. This frequency shift is investigated by applying perturbation theory in the regime of small ratios of the rotation velocity and the frequency of the acoustic mode. In an expansion of the relative frequency shift in powers of this ratio, upper bounds are derived for the first-order and the second-order terms. The derivation of the theoretical upper bounds of the first-order term is presented for linear vibration modes as well as for stable nonlinear vibrations with periodic time dependence that can be represented by a Fourier series.
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43.35.Ty Other physical effects of sound
43.20.Bi Mathematical theory of wave propagation
43.40.At Experimental and theoretical studies of vibrating systems

Non-linear inverse scattering: High resolution quantitative breast tissue tomography

J. Wiskin, D. T. Borup, S. A. Johnson, and M. Berggren

J. Acoust. Soc. Am. Volume 131, Issue 5, pp. 3802-3813 (2012); (12 pages) | Cited 1 time

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Recent published results in inverse scattering generally show the difficulty in dealing with moderate to high contrast inhomogeneities when employing linearized or iteratively linearized algorithms (e.g., distorted Born iterative method). This paper presents a fully nonlinear algorithm utilizing full wave field data, that results in ultrasound computed tomographic images from a laboratory breast scanner, and shows several such unique images from volunteer subjects. The forward problem, data collection process and inverse scattering algorithm used are discussed. A functional that represents the “best fit” between predicted and measured data is minimized, and therefore requires a very fast forward problem solver, Jacobian calculation, and gradient estimation, all of which are described. The data collection device is described. The algorithm and device yield quantitative estimates of human breast tissue in vivo. Several high resolution images, measuring ∼150 by 150 wavelengths, obtained from the 2D inverse scattering algorithms, using data collected from a first prototype, are shown and discussed. The quantitative values are compared with previous published work.
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43.35.Wa Biological effects of ultrasound, ultrasonic tomography
43.60.Lq Acoustic imaging, displays, pattern recognition, feature extraction
43.60.Rw Remote sensing methods, acoustic tomography
43.80.Vj Acoustical medical instrumentation and measurement techniques
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