Measuring the nonlinear elastic properties of tissue-like phantoms

Erkamp, Ramon; Skovoroda, A.R.; Emelianov, Stanislav; O’Donnell, Matthew

doi:10.1109/tuffc.2004.1295426

Cited by 30 publications

(26 citation statements)

References 28 publications

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“…Specifically, this study demonstrated that the TTS method could measure the complex mechanical behavior of tissue-like samples over the wide range of frequencies ͑i.e., between 1 and 1000 Hz͒ currently employed in MRE, a task that none of the methods that have been proposed for obtaining reliable biomechanical data from soft tissues can accomplish. Indentation methods [27][28][29] have provided reliable estimates of the biomechanical properties of ex vivo tissue samples, but they are not suitable for MRE validation studies because of differences in the measurement conditions. More specifically, indentation methods measure the biomechanical properties of soft tissues under quasistatic conditions, whereas MRE measures the biomechanical properties of soft tissues under dynamic conditions.…”

Section: Iib4 Shear-modulus Estimationmentioning

confidence: 99%

The performance of steady‐state harmonic magnetic resonance elastography when applied to viscoelastic materials

et al. 2010

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Purpose:The clinical efficacy of breast elastography may be limited when the authors employ the assumption that soft tissues exhibit linear, frequency-independent isotropic mechanical properties during the recovery of shear modulus. Thus, the purpose of this research was to evaluate the degradation in performance incurred when linear-elastic MR reconstruction methods are applied to phantoms that are fabricated using viscoelastic materials. Methods: To develop phantoms with frequency-dependent mechanical properties, the authors measured the complex modulus of two groups of cylindrical-shaped gelatin samples over a wide frequency range ͑up to 1 kHz͒ with the established principles of time-temperature superposition ͑TTS͒. In one group of samples, the authors added varying amounts of agar ͑1%-4%͒; in the other group, the authors added varying amounts of sucrose ͑2.5%-20%͒. To study how viscosity affected the performance of the linear-elastic reconstruction method, the authors constructed an elastically heterogeneous MR phantom to simulate the case where small viscoelastic lesions were surrounded by relatively nonviscous breast tissue. The breast phantom contained four linear, viscoelastic spherical inclusions ͑10 mm diameter͒ that were embedded in normal gelatin. The authors imaged the breast phantom with a clinical prototype of a MRE system and recovered the shear-modulus distribution using the overlapping-subzone-linear-elastic image-reconstruction method. The authors compared the recovered shear modulus to that measured using the TTS method. Results: The authors demonstrated that viscoelastic phantoms could be fabricated by including sucrose in the gelation process and that small viscoelastic inclusions were visible in MR elastograms recovered using a linear-elastic MR reconstruction process; however, artifacts that degraded contrast and spatial resolution were more prominent in highly viscoelastic inclusions. The authors also established that the accuracy of the MR elastograms depended on the degree of viscosity that the inclusion exhibited. Conclusions:The results demonstrated that reconstructing shear modulus from other constitutive laws, such as viscosity, should improve both the accuracy and quality of MR elastograms of the breast.

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Section: Iib4 Shear-modulus Estimationmentioning

confidence: 99%

The performance of steady‐state harmonic magnetic resonance elastography when applied to viscoelastic materials

et al. 2010

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“…9 Because of this nonlinearity, contrast between solid masses and background will decrease at higher preloads. [18][19][20][21] Thus, maximum strain contrast between masses and background occurs at near-zero preloads. However, the signal in a cyst either is noise or moves randomly when compressed, independent of the level of precompres- S/N(ε) and C/N(ε) are the strain signal-to-noise and contrast-to-noise ratios, respectively, whereas S/N(ρ) and C/N(ρ) are the correlation coefficient signal-to-noise and contrast-to-noise ratios.…”

Section: Discussionmentioning

confidence: 99%

Diagnosing Cysts With Correlation Coefficient Images From 2-Dimensional Freehand Elastography

Booi

Carson

O’Donnell

et al. 2007

Journal of Ultrasound in Medicine

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Objective. We compared the diagnostic potential of using correlation coefficient images versus elastograms from 2-dimensional (2D) freehand elastography to characterize breast cysts. Methods. In this preliminary study, which was approved by the Institutional Review Board and compliant with the Health Insurance Portability and Accountability Act, we imaged 4 consecutive human subjects (4 cysts, 1 biopsy-verified benign breast parenchyma) with freehand 2D elastography. Data were processed offline with conventional 2D phase-sensitive speckle-tracking algorithms. The correlation coefficient in the cyst and surrounding tissue was calculated, and appearances of the cysts in the correlation coefficient images and elastograms were compared. Results. The correlation coefficient in the cysts was considerably lower (14%-37%) than in the surrounding tissue because of the lack of sufficient speckle in the cysts, as well as the prominence of random noise, reverberations, and clutter, which decorrelated quickly. Thus, the cysts were visible in all correlation coefficient images. In contrast, the elastograms associated with these cysts each had different elastographic patterns. The solid mass in this study did not have the same high decorrelation rate as the cysts, having a correlation coefficient only 2.1% lower than that of surrounding tissue. Conclusions. Correlation coefficient images may produce a more direct, reliable, and consistent method for characterizing cysts than elastograms.

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“…We only include the papers that are most relevant to our interest, i.e., those that deal with the computational aspect of solving an inverse elastic problem with either a deterministic or a stochastic algorithm. For studies on the direct measurement and the development of special imaging modalities such as magnetic resonance elastography, ultrasonic elastography, and optical coherence tomography, we refer to [19], [9], [13], [51], and [34].…”

Section: B Related Workmentioning

confidence: 99%

“…The finite-element formulation of partial differential equations can be derived using a variational method. Assuming an elastic body in static equilibrium without inertia and dynamic vibrations, the principle of virtual work states that the external work equals the internal work (9) where is the body force within an element, is the surface traction, and is the point load. denotes the virtual displacement, denotes the virtual strain, is the number of elements, and is the number of point loads.…”

Section: A Forward Problem Of Linear Elasticitymentioning

confidence: 99%

A constrained genetic approach for computing material property of elastic objects

Zhang

Hall

Goldgof

et al. 2006

IEEE Trans. Evol. Computat.

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Abstract-This paper presents a constrained genetic approach for reconstructing the material properties of elastic objects. The considered reconstruction problem is ill-posed and must be constrained properly so that a unique and stable numerical solution can be obtained. Qualitative prior information is incorporated using a rank-based scheme to constrain the admissible solutions. Experiments show that the proposed approach is robust when presented with noisy data and can reconstruct the elastic property accurately and reliably. In a comparison study with the deterministic Gauss-Newton methods, the constrained genetic approach also shows very consistent performance.Index Terms-Constrained genetic algorithm (CGA), elastic property, finite-element model, inverse problem.

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Measuring the nonlinear elastic properties of tissue-like phantoms

Cited by 30 publications

References 28 publications

The performance of steady‐state harmonic magnetic resonance elastography when applied to viscoelastic materials

The performance of steady‐state harmonic magnetic resonance elastography when applied to viscoelastic materials

Diagnosing Cysts With Correlation Coefficient Images From 2-Dimensional Freehand Elastography

A constrained genetic approach for computing material property of elastic objects

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