Design and Characterization of a Tissue-Mimicking Phantom for Ultrasonic Elastography
18 Jun 2010-pp 1-4
TL;DR: It is indicated that Young's modulus of the polyacrylamide gel based tissue-mimicking phantom is similar to that of human soft tissue, which ranged from several kilopascal to a few tens ofkilopascal.
Abstract: Tissue-mimicking phantoms are essential for the investigation of ultrasonic elastography. A modified polyacrylamide gel based tissue-mimicking phantom is developed in this paper. It shows greater stability than phantom based on physical gel, such as gelatin and agar. The elastic and echographic properties of this phantom are determined by the concentration of acrylamide and graphite powder respectively. Both indentation testing and transient elastography are used to characterize the elastic properties of this phantom. The results are almost consistent with each other. Our work indicate that Young's modulus of the polyacrylamide gel based tissue-mimicking phantom is similar to that of human soft tissue, which ranged from several kilopascal to a few tens of kilopascal.
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TL;DR: It is demonstrated in tissue-mimicking phantoms that using ultrasound insonification causes deformations of ULC microgel particles, and increasing the degree of microgel cross-linking reduces the magnitude of the deformation and increases the optimal concentration required to achieve the largest amount of deformation.
Abstract: Poly(N-isopropylacrylamide) (pNIPAm) microgels (microgels) are colloidal particles that have been used extensively for biomedical applications. Typically, these particles are synthesized in the presence of an exogenous cross-linker, such as N,N′-methylenebis(acrylamide) (BIS); however, recent studies have demonstrated that pNIPAm microgels can be synthesized in the absence of an exogenous cross-linker, resulting in the formation of ultralow cross-linked (ULC) particles, which are highly deformable. Microgel deformability has been linked in certain cases to enhanced bioactivity when ULC microgels are used for the creation of biomimetic particles. We hypothesized that ultrasound stimulation of microgels would enhance particle deformation and that the degree of enhancement would negatively correlate with the degree of particle cross-linking. Here, we demonstrate in tissue-mimicking phantoms that using ultrasound insonification causes deformations of ULC microgel particles. Furthermore, the amount of deformat...
30 citations
TL;DR: A model to predict the elastic modulus of a soft tissue-mimicking phantom based on two very easily controllable parameters: gelatin concentration and refrigeration duration is proposed.
Abstract: The use of mechanically representative phantoms is important for experimental validation in ultrasound (US) imaging, elastography, and image registration. This article proposes a model to predict the elastic modulus of a soft tissue-mimicking phantom based on two very easily controllable parameters: gelatin concentration and refrigeration duration. The model has been validated on small- and large-scale phantoms; it provides a good prediction of the elastic modulus in both cases (error < 16.2%). The tissue-mimicking phantom is made following a low-cost and simple fabrication procedure using commercial household gelatin with psyllium hydrophilic mucilloid fiber to obtain echogenicity. A large range of elastic properties was obtained (15–100kPa) by adjusting the gelatin concentration between 5% and 20% (g/mL) and the refrigeration time of the sample between 2 and 168 h, allowing to mimic normal and pathological human soft tissues. The phantom’s acoustic properties (velocity, attenuation, and acoustic impedance) are also assessed using the American Institute of Ultrasound in Medicine (AIUM) standard.
17 citations
Cites background from "Design and Characterization of a Ti..."
...Recipes allowing the control of elasticity parameters have been documented in the literature for agarose [14]–[20], polyvinyl alcohol (PVA) [2], [21], [22], and polyacrylamide gel [23], [24] phantoms....
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...Moreover, the recipes that allow the tuning of the elastic modulus use either more complex manufacturing processes [21]–[24] (requiring hardware or ingredient difficult to access) and...
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25 Apr 2017
TL;DR: Kokkuv et al. as discussed by the authors used a coupled IPMC (ionic polymer-metal composite) sensor-actuator to control an inverted pendulum using an ionic polymermetal composite actuator.
Abstract: . . . . . . . . . . . . . . . . . . . . . . 145 KOKKUVÕTE. . . . . . . . . . . . . . . . . . . . . . . 149 APPENDIX A: Control of an inverted pendulum using an ionic polymermetal composite actuator . . . . . . . . . . . . . . . . . . 153 APPENDIX B: Feedback control of a coupled IPMC (ionic polymer-metal composite) sensor-actuator . . . . . . . . . . . . . . . . . 161 APPENDIX C: An integrated electroactive polymer sensor–actuator: design, model-based control, and performance characterization . . . . 171 APPENDIX D: Low cost anatomically realistic renal biopsy phantoms for interventional radiology trainees . . . . . . . . . . . . . . . 189 CURRICULUM VITAE . . . . . . . . . . . . . . . . . . . 199 ELULOOKIRJELDUS . . . . . . . . . . . . . . . . . . . . 200
9 citations
Cites background from "Design and Characterization of a Ti..."
...Unfortunately they are much more complex to manufacture than gelatin gels [271, 272, 273]....
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TL;DR: The s2D-SWI system represents a new choice for the quantitative mapping of tissue elasticity, and has great potential for implementation in commercial ultrasound scanners.
7 citations
TL;DR: Golay-coded excitation imaging was successfully demonstrated on freshly harvested pig coronary arteries and a weighted averaging method that compressed the coded pulse was proposed to decrease the range sidelobe level (RSLL).
Abstract: Intravascular ultrasound (IVUS) imaging employs high imaging frequencies (from 20 to 60 MHz) to visualize microvascular structures by sacrificing the depth of penetration with an increased signal attenuation. To compensate for the reduced echo signal-to-noise ratio, chirp-coded excitations, which require complex system configurations in high-frequency ultrasound imaging, are considered as suitable methods for rotational IVUS. Golay-coded excitations, which only need simple electronics and have no range sidelobe artifacts if the incident locations of the Golay pair are the same, have not been considered for rotational IVUS. In this study, computer simulations and experiments with a custom-made IVUS imaging system running at 30 fps are performed to investigate on the optimal operational conditions of Golay-coded excitations in rotational IVUS imaging. While the code length was not a significant factor affecting the range sidelobe level (RSLL), a change in the imaging frequency from 25 MHz to 66 MHz increased the RSLL from -65 dB to -45 dB with 2048 beamlines. In addition, an increase in the number of beamlines from 64 to 2048 reduced the RSLL from -17 dB to -50 dB in the simulation and from -14 dB dB to -38 dB in the experiment. To further decrease the RSLL, a weighted averaging method that compressed the coded pulse was proposed. The RSLL could be suppressed from -50 dB to -80 dB and from -38 dB to -53 dB in the simulation and experiment, respectively. Golay-coded excitation imaging was also successfully demonstrated on freshly harvested pig coronary arteries.
5 citations
Cites methods from "Design and Characterization of a Ti..."
...After degassing the solution for 30 min, ammonium persulfate and N,N,N’,N’-tetramethylethylenediamine (TEMED) were added to the mixed solution, and the solution was stirred quickly [22]....
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References
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TL;DR: In this paper, the authors used a Berkovich indenter to determine hardness and elastic modulus from indentation load-displacement data, and showed that the curve of the curve is not linear, even in the initial stages of the unloading process.
Abstract: The indentation load-displacement behavior of six materials tested with a Berkovich indenter has been carefully documented to establish an improved method for determining hardness and elastic modulus from indentation load-displacement data. The materials included fused silica, soda–lime glass, and single crystals of aluminum, tungsten, quartz, and sapphire. It is shown that the load–displacement curves during unloading in these materials are not linear, even in the initial stages, thereby suggesting that the flat punch approximation used so often in the analysis of unloading data is not entirely adequate. An analysis technique is presented that accounts for the curvature in the unloading data and provides a physically justifiable procedure for determining the depth which should be used in conjunction with the indenter shape function to establish the contact area at peak load. The hardnesses and elastic moduli of the six materials are computed using the analysis procedure and compared with values determined by independent means to assess the accuracy of the method. The results show that with good technique, moduli can be measured to within 5%.
22,557 citations
TL;DR: Initial results of several phantom and excised animal tissue experiments are reported which demonstrate the ability of this technique to quantitatively image strain and elastic modulus distributions with good resolution, sensitivity and with diminished speckle.
3,636 citations
TL;DR: Liver elasticity measurements were reproducible, operator-independent and well correlated and the intra- and interoperator reproducibility of the technique, as well as its ability to quantify liver fibrosis, were evaluated in 106 patients with chronic hepatitis C.
Abstract: Chronic hepatitis is accompanied by progressive deposit of hepatic fibrosis, which may lead to cirrhosis. Evaluation of liver fibrosis is, thus, of great clinical interest and, up to now, has been assessed with liver biopsy. This work aims to evaluate a new noninvasive device to quantify liver fibrosis: the shear elasticity probe or fibroscan. This device is based on one-dimensional (1-D) transient elastography, a technique that uses both ultrasound (US) (5 MHz) and low-frequency (50 Hz) elastic waves, whose propagation velocity is directly related to elasticity. The intra- and interoperator reproducibility of the technique, as well as its ability to quantify liver fibrosis, were evaluated in 106 patients with chronic hepatitis C. Liver elasticity measurements were reproducible (standardized coefficient of variation: 3%), operator-independent and well correlated (partial correlation coefficient = 0.71, p /= F2) and with cirrhosis ( = F4), respectively. The Fibroscan is a noninvasive, painless, rapid and objective method to quantify liver fibrosis.
2,517 citations
"Design and Characterization of a Ti..." refers background or methods in this paper
...The development of elastographic techniques yields four major approaches: static elastography, dynamic elastography, transient elastography and remote elastography [2]....
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...The elastic property of biological tissue is important because of its well-known correlation with pathology and the clinical value for early diagnosis of many serious diseases such as tumor [1] and hepatic cirrhosis [2]....
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...Transient elastography differs from other ultrasound based elastographic techniques by relying on a low frequency vibrator to generate a mechanical stimulation which leads to a shear wave propagating in the medium and inducing tiny displacements in the region of interest (ROI)[2][3][4], then the echoes are collected by an ultrasound transducer and the resulting displacements are estimated using ultrasonic correlation based algorithms, strain image can be obtained eventually through applying a classical differentiation algorithm to the estimated displacements....
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TL;DR: To evaluate the dynamic range of tissue imaged by elastography, the mechanical behavior of breast and prostate tissue samples subject to compression loading has been investigated and the data show that breast fat tissue has a constant modulus over the strain range tested while the other tissues have a modulus that is dependent on the strain level.
1,698 citations
"Design and Characterization of a Ti..." refers background in this paper
...Indenters have been developed for measuring the modulus value of soft tissue later [9][10]....
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Book•
01 Jan 1980
555 citations
"Design and Characterization of a Ti..." refers background in this paper
...Under the assumptions of a nonviscous, isotropic, soft elastic medium, the Young’s modulus E is expressed as [14]:...
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