The scattering of ultrasound by cylinders: Implications for diffraction tomography

Robinson, B.S.

doi:10.1121/1.394081

Cited by 36 publications

(18 citation statements)

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“…Several approaches, including ray propagation algorithms [1], diffraction tomography [2], and inverse scattering methods [3] have been developed to reconstruct quantitative images of speed of sound and acoustic attenuation.…”

Section: Motivationmentioning

confidence: 99%

Two approaches for tomographic density imaging using inverse scattering

Lavarello

Oelze

2008

2008 IEEE Ultrasonics Symposium

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Most acoustic tomography methods neglect density variations in order to obtain speed of sound and attenuation profiles. However, density may provide additional sources of image contrast. In this work, two approaches for density imaging using inverse scattering were explored through simulations in order to evaluate the feasibility of density imaging. The first method consisted of inverting the wave equation by solving for a single functional that depended on both speed of sound and density variations. Density profiles were separated by combining reconstructions at two frequencies (DF-DBIM approach). The second method consisted of solving for two functionals simultaneously: one that depended only on compressibility and one that depended only on density variations. A T-matrix approach was used to relate these functionals to the scattered data. The DF-DBIM approach allowed separation of density and speed of sound profiles at low termination tolerance values and less than an order of magnitude between the largest and smallest frequencies used. However, the convergence of DF-DBIM was compromised even when moderate (around 2%) termination tolerances were used. The T-matrix approach converged when multiple frequency data was used, but required a ka product smaller than one at the lowest frequency. The DF-DBIM requires a very high SNR to obtain reliable quantitative density reconstructions, while the T-matrix approach requires excessively large bandwidths when imaging large targets. These limitations will serve as reference points for further algorithmic improvements required for practical implementation of density imaging on ultrasound tomographic systems. I. MOTIVATIONUltrasonic computerized tomography (UCT) is an imaging modality used to reconstruct quantitative images of acoustic properties. Several approaches, including ray propagation algorithms [1], diffraction tomography [2], and inverse scattering methods [3] have been developed to reconstruct quantitative images of speed of sound and acoustic attenuation.However, experimental evidence is available in the literature suggesting that relative density changes in tissues may be comparable in magnitude to relative sound speed changes [4]. The effects of variable density in the reconstruction of sound speed were observed to result in overshoots of sound speed estimates at the edges of objects where density underwent abrupt changes [5]. Even further, density may also provide additional sources of image contrast.The number of UCT studies that consider variable density is limited. Variable density UCT was introduced in the context of single scattering formulations [6], [7]. However, the fact that these works are based on linearized scattering theory limits their applicability. Two classes of variable density inverse scattering algorithms have been identified, which consist of inverting the wave equation by 1) solving for a single functional that depended on both speed of sound and density variations, and using multiple frequency data to isolate density information [8], [9...

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Section: Motivationmentioning

confidence: 99%

Two approaches for tomographic density imaging using inverse scattering

Lavarello

Oelze

2008

2008 IEEE Ultrasonics Symposium

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“…We will use a relatively simple wave equation to describe the propagation and scattering of ultrasonic pulses in soft tissue. Recent studies [22], [36] have indicated that at the diagnostic intensities used in commercial pulse-echo systems the scattering is caused primarily by spatial variations in bulk modulus, and a linear wave equation involving only longitudinal disturbances is appropriate. Under these circumstances the acoustic pressure P ( 7 , t ) describing the sum of incident and scattered fields P, ( 7 , t ) + P, (r, t ) satisfies the following partial differential equation [2]:…”

Section: Formulat~on Of T H E Scattering Modelmentioning

confidence: 99%

“…It is incapable of describing frequency-dependent attenuation in soft tissue. Such attenuation can be introduced in a phenomenological manner, for example, by generalizing the phase speed to a complex variable [36] in which the imaginary part is related to the attenuation coefficient, or by adding a damping term such as -2 A (7) ( aP ( t 1 / a t ) to the left side of ( l ) . We choose the latter approach here, which has basically the same effect in the sense that the term introduces a complex dispersion relation for the wave It will be useful to rewrite (1) with the attenuation term in the following form in the ( 7 , 1 ) domain: with where c. is the constant phase speed in water.…”

Section: Formulat~on Of T H E Scattering Modelmentioning

confidence: 99%

Computational Methods for Simulating Ultrasonic Scattering in Soft Tissue

Finette

1987

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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The direct scattering problem of pulsed ultrasound in spatially inhomogeneous dispersive tissue is investigated with emphasis on computer simulation techniques. The motivation for this is that model images synthesized from known system and tissue parameters may be useful in designing and testing algorithms for ultrasonic tissue characterization. In this context the scattering process is fundamental to forming sonograms commonly used for medical diagnosis, and simulation of the scattered field is the most computationally demanding step in forming realistic models of sonograms. Some potential problems and trade-offs associated with the implementation of large-scale simulations are discussed, including constraints on the choice of spatial and temporal sampling increments, spatial aliasing, numerical dispersion, and wrap-around error.An example of transient scattering is presented using a spectral approach applied to an integral formulation for the scattered field.

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“…The potential for the use of ultrasound computed diffraction tomography in medicine has been recognized since its initial development in the early 1980s (Devaney, 1982, 1983, 1985; Devaney and Beylkin, 1984; Harris, 1987; Robinson and Greenleaf, 1986). Yet, despite successful implementation in other areas of acoustics, numerous factors have limited widespread medical use.…”

Section: Introductionmentioning

confidence: 99%

A computerized tomography system for transcranial ultrasound imaging

Tang

Clement

2015

Proceedings of Meetings on Acoustics

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Hardware for tomographic imaging presents both challenge and opportunity for simplification when compared with traditional pulse-echo imaging systems. Specifically, point diffraction tomography does not require simultaneous powering of elements, in theory allowing just a single transmit channel and a single receive channel to be coupled with a switching or multiplexing network. In our ongoing work on transcranial imaging, we have developed a 512-channel system designed to transmit and/or receive a high voltage signal from/to arbitrary elements of an imaging array. The overall design follows a hierarchy of modules including a software interface, microcontroller, pulse generator, pulse amplifier, high-voltage power converter, switching mother board, switching daughter board, receiver amplifier, analog-to-digital converter, peak detector, memory, and USB communication. Two pulse amplifiers are included, each capable of producing up to 400Vpp via power MOSFETS. Switching is based around mechanical relays that allow passage of 200V, while still achieving switching times of under 2ms, with an operating frequency ranging from below 100kHz to 10MHz. The system is demonstrated through ex vivo human skulls using 1MHz transducers. The overall system design is applicable to planned human studies in transcranial image acquisition, and may have additional tomographic applications for other materials necessitating a high signal output.

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The scattering of ultrasound by cylinders: Implications for diffraction tomography

Cited by 36 publications

References 0 publications

Two approaches for tomographic density imaging using inverse scattering

Two approaches for tomographic density imaging using inverse scattering

Computational Methods for Simulating Ultrasonic Scattering in Soft Tissue

A computerized tomography system for transcranial ultrasound imaging

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