Diffraction and Dispersion Effects on the Estimation of Ultrasound Attenuation and Velocity in Biological Tissues
TL;DR: The various methods of estimating the attenuation and velocity of ultrasound in biological media are described and the effect of velocity dispersion on the measurement of velocity in tissues is discussed as well.
Abstract: In this paper, the various methods of estimating the attenuation and velocity of ultrasound in biological media are described. Special attention is paid to the influence of the transducer used in the measurement, i.e., the diffraction effect. This influence is investigated in a systematic way using realistic three-dimensional computer simulation techniques. The results of the analysis are given as universal sets of curves. These curves can be used by the interested reader to estimate the influence of the diffraction effect on the measurements for his own experimental conditions. Methods of preventing the systematic errors caused by the diffraction effect are discussed. For the sake of completeness, the effect of velocity dispersion on the measurement of velocity in tissues is discussed as well.
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TL;DR: In this article, B-mode echograms were simulated by employing the impulse response method in transmission and reception using a discrete scatterer tissue model, with and without attenuation.
208 citations
TL;DR: The effects of spatial, fixed and adaptive, filtering, as well as, of grey scale encoding on the detection of lesions are analytically described and illustrated with representative images.
179 citations
Cites background from "Diffraction and Dispersion Effects ..."
...…in the frequency domain, for the influence of beam diffraction (cf., Thijssen et al., 1981; Cloostermans and Thijssen, 1983; Fink and Cardoso, 1984; Verhoef et al., 1985; Romijn et al., 1989, 1991; Oosterveld et al., 1991; Huisman and Thijssen, 1996) and, in addition, for the employed depth…...
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...It can be concluded that prior to UTC, the rf-signals have to be corrected, in the frequency domain, for the influence of beam diffraction (cf., Thijssen et al., 1981; Cloostermans and Thijssen, 1983; Fink and Cardoso, 1984; Verhoef et al., 1985; Romijn et al., 1989, 1991; Oosterveld et al., 1991; Huisman and Thijssen, 1996) and, in addition, for the employed depth dependent amplification TGC....
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...…that the received echographic spectra, calculated from the rf-data, are highly depth dependent and, therefore, influence the estimates of the frequency dependence of the attenuation- and backscattering-coefficients (see also Fink and Cardoso, 1984; Robinson et al., 1984; Verhoef et al., 1985)....
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..., 1981; Cloostermans and Thijssen, 1983) that the received echographic spectra, calculated from the rf-data, are highly depth dependent and, therefore, influence the estimates of the frequency dependence of the attenuation- and backscattering-coefficients (see also Fink and Cardoso, 1984; Robinson et al., 1984; Verhoef et al., 1985)....
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TL;DR: The overall goal of this research was to characterize the velocity dispersion of human cancellous bone based on a spectral analysis of ultrasound transmitted through the bone specimens, and to demonstrate that the diffraction effect is negligible in the useful frequency bandwidth, and that the ultrasonic parameters reflect intrinsic acoustic properties of bone tissue.
Abstract: Measurement of ultrasonic attenuation and velocity in cancellous bone are being applied to aid diagnosis of women with high fracture risk due to osteoporosis. However, velocity dispersion in cancellous bone has received little attention up to now. The overall goal of this research was to characterize the velocity dispersion of human cancellous bone based on a spectral analysis of ultrasound transmitted through the bone specimens. We have followed a systematic approach, beginning with the investigation of a test material, moving on to the investigation of bone specimens. Particular attention is given to diffraction effect, a potential source of artifacts. Parametric images of phase velocity (measured at the center frequency of the pulse spectrum), slope of attenuation coefficient (dB/cm/MHz) and velocity dispersion were obtained by scanning 15 bone specimens. We have demonstrated that the diffraction effect is negligible in the useful frequency bandwidth, and that the ultrasonic parameters reflect intrinsic acoustic properties of bone tissue. The measured attenuation showed approximately linear behavior over the frequency range 200 to 600 kHz. Velocity dispersion of cancellous bone in the frequency range 200 to 600 kHz was unexpectedly found to be either negative or positive and not correlated with the slope of attenuation coefficient. There was a highly significant correlation between the slope of attenuation coefficient and phase velocity at the center frequency of the spectrum. This behavior contrasts with other biological or nonbiological materials where the local form of the Kramers-Kronig relationship provides accurate prediction of velocity dispersion from the experimental frequency dependent-attenuation for unbounded waves.
164 citations
TL;DR: The mutual correlations between the estimated parameters were used to preselect parameters contributing independent information, and which can subsequently be used in a discriminant analysis to differentiate between the various diseased conditions.
Abstract: A study was performed to find and test quantitative methods of analysing echographic signals for the differentiation of diffuse liver diseases. An on-line data acquisition system was used to acquire radiofrequency (RF) echo signals from volunteers and patients. Several methods to estimate the frequency-dependent attenuation coefficient were evaluated, in which a correction for the frequency and depth-dependent diffraction and focusing effects caused by the sound beam was applied. Using the estimated value of the attenuation coefficient the RF signals themselves were corrected to remove the depth dependencies caused by the sound beam and by the frequency-dependent attenuation. After this preprocessing the envelope of the corrected RF signals was calculated and B-mode images were reconstructed. The texture was analysed in the axial direction by first- and second-order statistical methods. The accuracy and precision of the attenuation methods were assessed by using computer simulated RF signals and RF data obtained from a tissue-mimicking phantom. The phantom measurements were also used to test the performance of the methods to correct for the depth dependencies.
130 citations
TL;DR: Copolymer-in-oil phantoms are shown to be stable over time and attractive materials for elastography, and their mechanical and acoustic properties mimic those of most soft tissues.
Abstract: Phantoms that mimic mechanical and acoustic properties of soft biological tissues are essential to elasticity imaging investigation and to elastography device characterization. Several materials including agar/gelatin, polyvinyl alcohol and polyacrylamide gels have been used successfully in the past to produce tissue phantoms, as reported in the literature. However, it is difficult to find a phantom material with a wide range of stiffness, good stability over time and high resistance to rupture. We aim at developing and testing a new copolymer-in-oil phantom material for elastography. The phantom is composed of a mixture of copolymer, mineral oil and additives for acoustic scattering. The mechanical properties of phantoms were evaluated with a mechanical test instrument and an ultrasound-based elastography technique. The acoustic properties were investigated using a through-transmission water-substituting method. We showed that copolymer-in-oil phantoms are stable over time. Their mechanical and acoustic properties mimic those of most soft tissues: the Young's modulus ranges from 2.2-150 kPa, the attenuation coefficient from 0.4-4.0 dB.cm(-1) and the ultrasound speed from 1420-1464 m/s. Their density is equal to 0.90 +/- 0.04 g/cm3. The results suggest that copolymer-in-oil phantoms are attractive materials for elastography.
105 citations
References
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TL;DR: An analytic model is described for application in ultrasonic tissue characterization that treats spectra derived from received echo signals and relates them to physical tissue properties and has proven useful in interpreting data from various types of tissues.
Abstract: An analytic model is described for application in ultrasonic tissue characterization. The model is applicable to clinical broadband pulse echo systems. It treats spectra derived from received echo signals and relates them to physical tissue properties. The model can be applied to deterministic tissue structures (e.g., retinal detachments, larger blood vessels, and surface layers of the kidney) and to stochastic tissue structures (e.g., various tumors). The beam patterns included in the model are those generated by focused transducers typically used in high-resolution clinical ultrasound. Appropriate calibration procedures are also treated; these are needed for interpretation of absolute spectral parameters. The results obtained with the analytic model have been used to design a digital processing system and the associated techniques which are now being applied during examinations of the eye and abdominal organs. The results have proven useful in interpreting data from various types of tissues. To illustrate the application of these results, representative clinical data, obtained from the digital system, are presented for two types of tissue architectures. The first case is a detached retina representing a deterministic structure characterized by well-defined thickness and reflection coefficients. The second case is asteroid hyalosis and represents a stochastic entity in which the positions of small scattering particles are best described in statistical terms, and characterization is accompanied by means of normalized power spectra.
637 citations
"Diffraction and Dispersion Effects ..." refers background in this paper
...[3], a few papers have been devoted to the physical description of it [9], [11], [12]....
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TL;DR: In this article, an approach to compute the near and farfield transient radiation resulting from a specified velocity motion of a piston or array of pistons in a rigid infinite baffle is presented.
Abstract: An approach is presented to compute the near‐ and farfield transient radiation resulting from a specified velocity motion of a piston or array of pistons in a rigid infinite baffle. The approach, which is based on a Green's function development, utilizes a transformation of coordinates to simplify the evaluation of the resultant surface integrals. A simple expression is developed for an impulse response function, which is the time‐dependent velocity potential at a spatial point resulting from an impulse velocity of a piston of any shape. The time‐dependent velocity potential and pressure for any piston velocity motion may then be computed by a convolution of the piston velocity with the appropriate impulse response. The response of an array may be computed using superposition. Several examples illustrating the usefulness of the approach are presented. The farfield time‐dependent radiation from a rectangular piston is discussed for both continuous and pulsed velocity conditions. For a pulsed velocity of time duration T it is shown that the pressure at several of the field points can consist of two separate pulses of the same duration, when T is less than the travel time across the piston.
580 citations
"Diffraction and Dispersion Effects ..." refers methods in this paper
...For that purpose, a realistic three-dimensional simulation study is performed, based on the impulse response method [13], to calculate both the sound field and the backscattered spectra....
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...Calculation ofAcoustic Echo Signal and Spectrograms The acoustic pressure in the space in front of a flat or focused transducer is calculated by means of the so-called impulse response method [13], [17]....
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TL;DR: In this paper, Kramers-Kronig relations linking attenuation and dispersion are presented for a linear acoustic system and approximate, nearly local expressions relating the ultrasonic attenuation at a specific frequency to the local frequency derivative of the phase velocity are derived.
Abstract: Kramers-Kronig relations linking the attenuation and dispersion are presented for a linear acoustic system. These expressions are used as a starting point to derive approximate, nearly local expressions relating the ultrasonic attenuation at a specific frequency to the local frequency derivative of the phase velocity (i.e., dispersion). The validity of these approximate relationships is demonstrated in several acoustic systems exhibiting substantially different physical properties.
459 citations
"Diffraction and Dispersion Effects ..." refers background or methods in this paper
...The same applies to the dispersion of the velocity which is linked to the frequency dependence of the attenuation in tissues [14]....
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...(19) The dispersion is calculated using the attenuation coefficient of the tissue under consideration with the formula [14]...
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TL;DR: In this paper, an acoustic Fabry-Perot interferometer is used for measuring high-frequency acoustic losses in isotropic and anisotropic materials with high Q-factor.
Abstract: An acoustic Fabry-Perot interferometer is used for measuring high-frequency acoustic losses in isotropic and anisotropic materials with high Q-factor. Interferometer samples of the investigated materials were fabricated in the form of cubes. The reduction in interferometer contrast caused by acoustic losses is used for determining the attenuation coefficient. The spectral distribution of the acoustic field in the interferometer is measured by means of an acoustooptic method. The attenuation coefficient is determined from the ratio ImaX/Imin and the additional losses of acoustic energy causing a reduction of the contrast are taken into account. The results obtained in this way are used for a determination of the attenuation coefficient for waves propagating in fused quartz as well as in a-quartz.
272 citations
TL;DR: The use of short-time Fourier analysis is investigated to provide an estimation of the echographic spectral composition as a function of time and it will be shown that the time dependence of the spectral centroid of this representation allows one to deduce easily the frequency-dependent attenuation.
184 citations