Measurement of Viscoelastic Properties of Polyacrylamide-Based Tissue-Mimicking Phantoms for Ultrasound Elastography Applications
05 Apr 2010-IEEE Transactions on Instrumentation and Measurement (IEEE)-Vol. 59, Iss: 5, pp 1224-1232
TL;DR: Polyacrylamide gel based tissue-mimicking phantoms have been developed to experimentally study the role of viscoelastic properties inPhantoms and indicate that stiffer samples exhibit large variations in the storage modulus when the precompression levels are altered.
Abstract: Many ailments and/or malfunctions of the body have been observed to change the viscous behavior and elastic properties of biological soft tissues. The technique of elastography has evolved to image such properties. The clinical evidence gathered during studies involving elastography to identify cancerous lesions is very promising. However, the quantification of the resolution and specificity of elastography is best achieved under a controlled study using tissue-mimicking phantoms. One challenge is to reproduce viscoelastic behavior in phantoms as observed in biological tissues. In this paper, polyacrylamide gel based tissue-mimicking phantoms have been developed to experimentally study the role of viscoelastic properties in a controlled manner. To measure the Young's modulus, the phantoms were subjected to linear loading, and the stress-strain relationship is deduced therefrom. It is seen that the phantoms show hysteresis behavior. The viscoelastic properties of these phantoms were measured by subjecting the samples to cyclic loading. Normal forces during this process of loading were also measured as a measure of sample elasticity. To emulate the normal and pathological lesions, samples were prepared with varying concentration of monomer and studied. Three models, namely, Maxwell, Kelvin-Voigt (KV), and Kelvin-Voigt fractional derivative (KVFD), were chosen to fit the experimental data. Of these, the KVFD model was found to be best fitting for the experimental data obtained. Results indicate that stiffer samples exhibit large variations in the storage modulus when the precompression levels are altered.
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TL;DR: In this paper, a microviscosity parameter τη is introduced to estimate the increase of microvocosity with increase in the crosslinker, as well as initiator concentrations at the same monomer concentration.
Abstract: Estimation of micropolarity and microfluidity at the water-polymer interface is important in understanding the physicochemical behavior of polymeric gels in the context of their wide biomedical applications. In this work, fluorescence studies of 8-Anilino-1-naphthalene-sulphonate (ANS) were used to introduce a new microviscosity parameter. Z and ET(30) solvent polarity scales were found to work well in resolving the polarity differences in various polyacrylamide gel compositions. A microviscosity parameter τη is an easy-to-estimate parameter that was used to follow the changes in microviscosity with changes in polymer composition. The microviscosity parameter could efficiently estimate the increase of microviscosity with increase in the crosslinker, as well as initiator concentrations at the same monomer concentration.
5 citations
01 May 2019
TL;DR: An amplitude modulated (AM) excitation signal for ARF impulse imaging has been investigated to improve the spatial resolution and would be useful in achieving a larger displacement and further detecting distance using a lower excitation intensity density for safety consideration.
Abstract: Mechanical properties are intrinsic characteristics of biological tissue, which can provide information related to physiological and pathological information. Acoustic radiation force (ARF) is generated by a change of energy density due to the nonlinear ultrasound propagation. Based on ARF excitation, ultrasonic elastography methods had been proved to be able to provide information related to the mechanical properties of tissues. The detection of tissue displacements plays an important role in elastography methods. An amplitude modulation method for ARF impulse (ARFI) excitation has been proposed to increase displacement responses and can further enlarge the difference in displacement responses of media with different stiffness. Two different amplitude-modulated ARF waveforms are employed and compared with traditional ARF waveforms. To understand how these different waveforms may affect displacement responses, the relationship between the ARF and displacement responses has been derived. In the case of different waveforms but with the same impulse and the applying time, the larger the peak-to-peak amplitude of ARF, the greater the displacement response. The influences of the amplitude as well as the applying time of ARF on displacement responses are studied by simulations. Furthermore, a 3.5-MHz focused transducer is excited by different signals in phantom experiments to validate the feasibility of this proposed method. The results demonstrate that displacement responses produced by these amplitude-modulated ARF waveforms can be increased with lower or comparable temperature variation for safety consideration, compared with that of traditional ARF waveforms. Moreover, the displacement sensitivity to distinguish media with different Young’s modulus can be improved.
4 citations
TL;DR: This work implements a mechanism on top of Marathon and Chronos Mesos frameworks to vary the resources assigned to an application dynamically according to its progress and considering a specific Quality of Service (QoS).
4 citations
TL;DR: The main outcome of the inverse approach is a validation of the results of forward characterization for a broad frequency range and under critical temperature conditions adopting a simple experimental arrangement and a barely complex numerical procedure.
Abstract: The design for the reliability of automotive electronics involving viscoelastic materials requires accurate knowledge of material properties under critical frequency and temperature conditions. Both forward and inverse approaches for the dynamic characterization of a soft silicone-based thermal interface material used in electronic control units are presented and discussed. The classic forward characterization implying dynamic mechanical analysis and the principle of time–temperature superposition is applied in a first step. The identified material model under critical temperature conditions is restrained to a narrow frequency range and a validation for higher frequencies is needed. The proposed inverse method presented in the second part minimizes the residue between the measured and numerical transfer functions of single-lap joint specimens at chosen control frequency ranges located at the resonances of the structure. The specimens are excited by an electrodynamic shaker situated in an environmental chamber allowing measurements under different temperature conditions. The main outcome of the inverse approach is a validation of the results of forward characterization for a broad frequency range and under critical temperature conditions adopting a simple experimental arrangement and a barely complex numerical procedure.
4 citations
Cites background or methods from "Measurement of Viscoelastic Propert..."
...Although this method has been successfully applied for the characterization of many thermorheologically simple polymers [2], [7], [8], it may not be applicable in some cases including block copolymers or polymeric blends [9], polymers with long chain branching [10], or in case any crystallization or partial melting [11] occurs in the temperature range concerned....
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...the possibility of measuring the dynamic properties of very soft materials in shear or torsion modes [7]....
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TL;DR: The PAM-BCs represent a new, solid ultrasonic membrane which is suitable for diagnosing disease in superficial vessels which is possible to acquire high resolution intravascular ultrasound images to assess superficial vessels in humans and the superficial vasculature in rats and miniature pigs using various brands of ultrasound instruments.
Abstract: Superficial thrombophlebitis is one of the most significant complications of superficial vein thrombosis. Rapid imaging and mapping with high resolution is particularly important for accurate diagnosis so as to carry out treatment as soon as possible. Ultrasound imaging technology has been used extensively because of the low-cost, minimal invasiveness, and convenient application in clinical practice. And the ultrasonic couplant is an essential component in ultrasound examination. However, when imaging superficial structures, traditional liquid ultrasonic couplants often produce inadequate results. In this study, we investigate whether a hydrogel membrane can be used to improve the imaging of superficial vessels. To this end, we generated a polyacrylamide-bacterial nanocellulose hydrogel membrane (PAM-BC) that efficiently forms at 60 °C in only 10 min by redox polymerization. With PAM-BC-2.5, it was possible to acquire high resolution intravascular ultrasound images to assess superficial vessels in humans and the superficial vasculature in rats and miniature pigs using various brands of ultrasound instruments. The PAM-BCs represent a new, solid ultrasonic membrane which is suitable for diagnosing disease in superficial vessels.
3 citations
References
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Book•
01 Jan 1961
TL;DR: In this article, the authors describe the nature of Viscoelastic behavior of polymeric systems and approximate relations among the linear Viscoels and approximate interrelations among the Viscelastic Functions.
Abstract: The Nature of Viscoelastic Behavior. Illustrations of Viscoelastic Behavior of Polymeric Systems. Exact Interrelations among the Viscoelastic Functions. Approximate Interrelations among the Linear Viscoelastic Functions. Experimental Methods for Viscoelastic Liquids. Experimental Methods for Soft Viscoelastic Solids and Liquids of High Viscosity. Experimental Methods for Hard Viscoelastic Solids. Experimental Methods for Bulk Measurements. Dilute Solutions: Molecular Theory and Comparisons with Experiments. Molecular Theory for Undiluted Amorphous Polymers and Concentrated Solutions Networks and Entanglements. Dependence of Viscoelastic Behavior on Temperature and Pressure. The Transition Zone from Rubberlike to Glasslike Behavior. The Plateau and Terminal Zones in Uncross-Linked Polymers. Cross-Linked Polymers and Composite Systems. The Glassy State. Crystalline Polymers. Concentrated Solutions, Plasticized Polymers, and Gels. Viscoelastic Behavior in Bulk (Volume) Deformation. Applications to Practical Problems. Appendices. Author & Subject Indexes.
12,676 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
"Measurement of Viscoelastic Propert..." refers methods in this paper
...The measurements of these properties were done using external quasi-static [11] or dynamic [17] excitations or using ultrasound-generated radiation force [18], [19]....
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...Ultrasound elastography is a method to identify pathological changes by measuring elastic properties of tissues [11], [16] using ultrasound....
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...As opposed to a procedure involving human intervention, there are several techniques that use phase-sensitive imaging modalities such as ultrasound [11]–[13] and magnetic resonance imaging [14], [15] to image the mechanical properties of soft tissues....
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3,350 citations
06 Nov 2008
TL;DR: A balanced mechanics-materials approach and coverage of the latest developments in biomaterials and electronic materials, the new edition of this popular text is the most thorough and modern book available for upper-level undergraduate courses on the mechanical behavior of materials as discussed by the authors.
Abstract: A balanced mechanics-materials approach and coverage of the latest developments in biomaterials and electronic materials, the new edition of this popular text is the most thorough and modern book available for upper-level undergraduate courses on the mechanical behavior of materials To ensure that the student gains a thorough understanding the authors present the fundamental mechanisms that operate at micro- and nano-meter level across a wide-range of materials, in a way that is mathematically simple and requires no extensive knowledge of materials This integrated approach provides a conceptual presentation that shows how the microstructure of a material controls its mechanical behavior, and this is reinforced through extensive use of micrographs and illustrations New worked examples and exercises help the student test their understanding Further resources for this title, including lecture slides of select illustrations and solutions for exercises, are available online at wwwcambridgeorg/97800521866758
2,905 citations
Book•
15 Jun 1989
TL;DR: In this article, the authors discuss the importance of non-linearity solids and liquids rheology is a difficult subject for rheological research, and present some demonstrations of high extensional viscosity behaviour.
Abstract: 1) What is rheology? historical perspective the importance of non-linearity solids and liquids rheology is a difficult subject components of rheological research. 2) Viscosity practical ranges of variables which affect viscosity the shear-dependent viscosity of non-Newtonian liquids viscometers for measuring shear viscosity. 3) Linear viscoelasticity the meaning and consequences of linearity the Kelvin and Maxwell models the relaxation spectrum oscillatory shear relationships between functions of linear viscoelasticity methods of measurement. 4) Normal stresses the nature and origin of normal stresses typical behaviour of N 1 and N 2 observable consequences of N 1 and N 2 methods of measuring N 1 and N 2 relationships between viscometric functions and linear viscoelastic functions. 5) extensional viscosity importance of extensional flow theoretical considerations experimental methods experimental results some demonstrations of high extensional viscosity behaviour. 6) Rheology of polymeric liquids general behaviour effect of temperature on polymer rheology effect of molecular weight on polymer rheology effect of concentration on the rheology of polymer solutions polymer gels liquid crystal polymers. molecular theories the method of reduced variables empirical relations between rheological functions practical applications. 7) Rheology of suspensions the viscosity of suspensions of solid particles in Newtonian liquids the colloidal contribution to viscosity viscoelastic properties of suspensions suspensions of deformable particles the interaction of suspended particles with polymer molecules also present in the continuous phase computer simulation studies of suspension rheology. 8. Theoretical rheology basic principles of continuum mechanics successful applications of the formulation principles some general constitutive equations constitutive equations for restricted classes of flows simple constitutive equations of the Oldroyd/Maxwell type solution of flow problems.
2,569 citations