Fundamental Mechanical Limitations on the Visualization of Elasticity Contrast in Elastography

Ponnekanti, H.; Ophir, Jonathan; Huang, Yijun; Céspedes, I.

doi:10.1007/978-1-4419-8772-3_27

Cited by 21 publications

(40 citation statements)

References 7 publications

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Section: Methodssupporting

confidence: 85%

“…Each of these phantoms was subjected to an axial compressive strain of 1%. Note that similar studies for the case of firmly bonded inclusion have been reported previously in Ponnekanti et al (1995) and Kallel et al (1996).To study the effect of the degree of bonding, seven phantoms with loosely bonded inclusion were generated, each with a different coefficient of friction. The values for the coefficient of friction ranged from 0.01 to 1.…”

mentioning

confidence: 69%

“…Ponnekanti et al (1995) described this relationship in terms of contrast transfer efficiency (CTE), defined as the ratio of estimated modulus contrast from elastogram (as inverse of strain contrast) to actual modulus contrast. Later, Kallel et al (1996) reported an analytic study (2D) on the fundamental limitations on the CTE in elastography.…”

Section: Nih Public Accessmentioning

confidence: 99%

“…This relationship justifies the use of an inverse strain image as a first approximation for a modulus image under certain conditions. Prior literature reports have investigated the relationship between the strain contrast and the modulus contrast (Ponnekanti et al 1995;Kallel et al 1996;Bilgen and Insana 1998). Ponnekanti et al (1995) described this relationship in terms of contrast transfer efficiency (CTE), defined as the ratio of estimated modulus contrast from elastogram (as inverse of strain contrast) to actual modulus contrast.…”

mentioning

confidence: 99%

“…Prior literature reports have investigated the relationship between the strain contrast and the modulus contrast (Ponnekanti et al 1995;Kallel et al 1996;Bilgen and Insana 1998). Ponnekanti et al (1995) described this relationship in terms of contrast transfer efficiency (CTE), defined as the ratio of estimated modulus contrast from elastogram (as inverse of strain contrast) to actual modulus contrast. Later, Kallel et al (1996) reported an analytic study (2D) on the fundamental limitations on the CTE in elastography.…”

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confidence: 99%

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Effect of Lesion Boundary Conditions on Axial Strain Elastograms: A Parametric Study

Thitaikumar

Ophir²

2007

Ultrasound in Medicine & Biology

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Ultrasound elastograsphy produces strain images of compliant tissues under quasi-static compression. When a material is compressed, there are several parameters that affect the stressdistribution, and hence the strain distribution in the material. The state of bonding of an inclusion to the background material is a critical parameter. Heretofore in the field of elastography, the inclusion was considered to be firmly bonded to the background material and analytical solutions were derived for the elasticity problem involving simple geometries like circular inclusion (for 2D) and spherical inclusion (3D). Under these conditions, simple analytical expressions relating the strain contrast to the modulus contrast were derived. However, it is known that the state of bonding of some tumors to their surrounding tissues depends on the type of the lesion. For example, benign lesions of the breast are known to be loosely bonded to the surrounding tissue, while malignant breast lesions are firmly bonded. In this study we perform a parametric study using Finite Element Modeling (FEM) to investigate the validity of the analytical expression relating the strain contrast to the modulus contrast, when the state of bonding at the inclusion/background interface spans a large dynamic range. The results suggest that estimated modulus contrast using the analytical expression is sensitive to the region of interest within the inclusion that is considered in the computation of the strain contrast. By considering the inclusion region lying along the axis of lateral symmetry instead of whole region of the inclusion, the estimated modulus contrast (obtained using the analytical expression present in the literature) can be computed to within a systematic error of 10% of the actual modulus contrast. Additional estimation errors are expected to accrue in experimental and in-vivo conditions. KeywordsBonding; Contrast Transfer Efficiency; Elastography; Modulus Contrast; Strain Contrast; Ultrasound INTODUCTIONElastography is a technique that produces images (elastograms) that map the strain experienced by tissue elements subjected to a quasi-static compression (Ophir et al. 1991). Ultrasound elastography typically produces high resolution axial strain elastograms due to high sampling Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. (Srinivasan et al. 2004). This relationship justifies the use of an inverse strain image as a first approximation for a modulus image under certain conditions. NIH Public AccessPrior literature reports have investigated the relationship between the strain contrast and th...

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Section: Methodssupporting

confidence: 85%

mentioning

confidence: 69%

Section: Nih Public Accessmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Effect of Lesion Boundary Conditions on Axial Strain Elastograms: A Parametric Study

Thitaikumar

Ophir²

2007

Ultrasound in Medicine & Biology

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Comparison of quantitative shear wave MR‐elastography with mechanical compression tests

Hamhaber

Grieshaber

Nagel

et al. 2002

Magnetic Resonance in Med

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The mechanical properties of in vivo soft tissue are generally determined by palpation, ultrasound measurements (US), and magnetic resonance elastography (MRE). While it has been shown that US and MRE are capable of quantitatively measuring soft tissue elasticity, there is still some uncertainty about the reliability of quantitative MRE measurements. Mechanical properties of tissues such as Young's modulus, shear modulus, and bulk modulus are of special interest in tissue characterization. By palpation, the stiffness of the tissue, in particular its resistance to pressure and shear forces, is inspected by the physician's hand. Often, cancerous tissue can be detected since it appears as a hard lesion which is a result of increased stromal density (1). Within the last 10 years various ultrasound (US) and MR methods to quantitatively determine the elasticity of soft tissue have been established. Noninvasive US techniques that measure the elastic properties of soft tissue have been described by Ophir et al. (1) (5) showed that in many cases breast lesions cause changes of the elastic modulus as assessed by US measurements. MR elastography is a more recently proposed technique to measure tissue elastic moduli noninvasively. There are two principally different methods of MRE: static or quasi static (11-16) and dynamic (17-26). Static MRE uses two different static compressional states of the investigated material to determine its corresponding distortions. Dynamic MRE is based on the excitation of mechanical waves in soft tissue. In order to evaluate the quantitative precision of dynamic shear wave MRE, we compared quantitative shear wave MRE results with those from mechanical compression tests. MATERIALS AND METHODS Tissue-Mimicking Phantoms and Compression Test SpecimensFor the MRE measurements and compression tests a series of tissue phantoms and compression test specimens were produced. Ideally, the material of the phantoms and the specimens should mimic human soft tissue. Agar-agar gel was used as a test material because it shows mechanical properties similar to human soft tissues. To produce the phantoms, different amounts of agar-agar powder (Agar Agar Kobe I pulv., Roth, Karlsruhe, Germany) were stirred in distilled water and boiled for about 2 min. Then the liquid agar-agar was poured into cylindrical heat-resistant plastic molds having both a diameter and height of about 16 cm and allowed to cool to room temperature. At about 40°C a chemical cross-linking occurs and the agar-agar changes from a fluid to a solid state. As agar-agar gel is a biological material, water diluted formalin was applied to the surface of the phantoms to inhibit the growth of fungi; this allowed for a lifespan of the phantoms of several months. For the compression tests, cylindrical specimens of 4 cm height and 5 cm diameter were cast. To ensure that the corresponding phantoms and specimens had the same elastic properties, they were made from dilutions with identical agar-agar concentrations.The concentration of the agar-agar powder wa...

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Elastography: Imaging the elastic properties of soft tissues with ultrasound

et al. 2002

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Elastography is a method that can ultimately generate several new kinds of images, called elastograms. As such, all the properties of elastograms are different from the familiar properties of sonograms. While sonograms convey information related to the local acoustic backscatter energy from tissue components, elastograms relate to its local strains, Young's moduli or Poisson's ratios. In general, these elasticity parameters are not directly correlated with sonographic parameters, i.e. elastography conveys new information about internal tissue structure and behavior under load that is not otherwise obtainable. In this paper we summarize our work in the field of elastography over the past decade. We present some relevant background material from the field of biomechanics. We then discuss the basic principles and limitations that are involved in the production of elastograms of biological tissues. Results from biological tissues in vitro and in vivo are shown to demonstrate this point. We conclude with some observations regarding the potential of elastography for medical diagnosis.

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Fundamental Mechanical Limitations on the Visualization of Elasticity Contrast in Elastography

Cited by 21 publications

References 7 publications

Effect of Lesion Boundary Conditions on Axial Strain Elastograms: A Parametric Study

Effect of Lesion Boundary Conditions on Axial Strain Elastograms: A Parametric Study

Comparison of quantitative shear wave MR‐elastography with mechanical compression tests

Elastography: Imaging the elastic properties of soft tissues with ultrasound

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