Excitation and propagation of surface waves on a viscoelastic half-space with application to medical diagnosis

Royston, Thomas J.; Mansy, Hansen A.; Sandler, Richard H.

doi:10.1121/1.428219

Cited by 70 publications

(49 citation statements)

References 19 publications

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“…15, a simplified analytical solution was derived for Rayleigh wave propagation on the surface of an isotropic homogeneous viscoelastic half-space caused by normal force excitation over a circular region of radius "a" on the surface of amplitude per unit area P in with harmonic time dependence e jxt as depicted in Fig. 2.…”

Section: Surface Wave Propagation On a Half-space Due To A Surfamentioning

confidence: 99%

“…In previous studies of the first author of the present article 15,16 there has been an emphasis on understanding the surface wave field created in a material like biological tissue by canonical vibratory sources. In Ref.…”

Section: Introductionmentioning

confidence: 99%

“…In Ref. 15, a new analytical solution was derived for the problem of surface wave generation on a linear viscoelastic half-space caused by a finite rigid circular disk located on the surface and oscillating normal to it. While the motivation of the work was to better understand surface wave propagation in biological tissue, the solution approach taken was an incremental advancement of theoretical work reported in seminal articles in the geophysics literature.…”

Section: Introductionmentioning

confidence: 99%

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Estimating material viscoelastic properties based on surface wave measurements: A comparison of techniques and modeling assumptions

Royston

Dai

Chaunsali

et al. 2011

The Journal of the Acoustical Society of America

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Previous studies of the first author and others have focused on low audible frequency (<1 kHz) shear and surface wave motion in and on a viscoelastic material comprised of or representative of soft biological tissue. A specific case considered has been surface (Rayleigh) wave motion caused by a circular disk located on the surface and oscillating normal to it. Different approaches to identifying the type and coefficients of a viscoelastic model of the material based on these measurements have been proposed. One approach has been to optimize coefficients in an assumed viscoelastic model type to match measurements of the frequency-dependent Rayleigh wave speed. Another approach has been to optimize coefficients in an assumed viscoelastic model type to match the complex-valued frequency response function (FRF) between the excitation location and points at known radial distances from it. In the present article, the relative merits of these approaches are explored theoretically, computationally, and experimentally. It is concluded that matching the complex-valued FRF may provide a better estimate of the viscoelastic model type and parameter values; though, as the studies herein show, there are inherent limitations to identifying viscoelastic properties based on surface wave measurements.

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Section: Surface Wave Propagation On a Half-space Due To A Surfamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Estimating material viscoelastic properties based on surface wave measurements: A comparison of techniques and modeling assumptions

Royston

Dai

Chaunsali

et al. 2011

The Journal of the Acoustical Society of America

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“…Given the significant difference in values for 1 and 1 in soft biological tissue (typically six orders of magnitude), shear wave lengths are substantially shorter than compression (longitudinal) wavelengths. For example, at a driving frequency of 500 Hz, the compression wavelength is ϳ3 m and the shear wavelength is ϳ9.5 mm, assuming typical soft-tissue values of 1 ϭ 2.6 GPa, 2 ϭ 0, 1 ϭ 2.5 kPa, 2 ϭ 15 Pa-s, ϭ 1100 kg/m 3 (16,17). Isotropic material models can be applied to MRE measurements to obtain localized estimates of elastic moduli and attenuation parameters (19 -22).…”

Section: Theorymentioning

confidence: 99%

Microscopic magnetic resonance elastography (μMRE)

Othman

Royston

et al. 2005

Magnetic Resonance in Med

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Magnetic resonance elastography (MRE) was extended to the microscopic scale to image low-frequency acoustic shear waves (typically less than 1 kHz) in soft gels and soft biological tissues with high spatial resolution (34 m ؋ 34 m ؋ 500 m). Microscopic MRE (MRE) was applied to agarose gel phantoms, frog oocytes, and tissue-engineered adipogenic and osteogenic constructs. Analysis of the low-amplitude shear wave pattern in the samples allowed the material stiffness and viscous loss properties (complex shear stiffness) to be identified with high spatial resolution. MRE experiments were conducted at 11.74 T in a 56-mm vertical bore magnet with a 10 mm diameter ؋ 75 mm length cylindrical space available for the elastography imaging system. The acoustic signals were generated at 550 -585 Hz using a piezoelectric transducer and high capacitive loading amplifier. Shear wave motion was applied in synchrony with the MR pulse sequence. Key words: tissue elasticity; elastography; magnetic resonance elastography; magnetic resonance microscopy; tissue engineering; cell mechanobiology A goal of soft-tissue mechanobiology is to understand the mechanisms by which physical forces regulate cell and tissue growth, differentiation, and division. In order to evaluate the effect of applied mechanical stresses on living systems, we must develop a safe and noninvasive method to characterize the elements of the stress-strain tensor at or near the cellular scale. Measurement of shear wave motion in small tissues provides unique spatially-localized information about the tissue's material properties. Such information can reflect the development of pathology and in some cases biomechanical integrity.Many disease states can significantly change a tissue's shear viscoelastic parameters, which in turn can significantly affect shear wave propagation through the tissue.Recently this concept was combined with ultrasound (US) and magnetic resonance imaging (MRI) to provide a noninvasive means of visualizing shear wave motion suitable for use in a clinical setting. In US elastography, the Doppler effect has been used to provide localized information about tissue motion to map shear wave propagation at excitation frequencies from 20 to several hundred Hertz (1-4). Magnetic resonance elastography (MRE) employs a phase contrast (PC) MRI technique to extract a measure of the mechanical vibration in tissue, and to visualize the spatial and temporal patterns of strains associated with the propagation of the shear waves. From these data, a map of the "shear stiffness" throughout the tissue can be reconstructed (5,6). Both approaches are finding wide application for the noninvasive study of nontransparent materials and for the evaluation and diagnosis of developing pathologies.The elastography imaging techniques have received much attention recently in the fields of biology and medicine because they provide quantitative information on the shear elastic moduli of soft tissues (liver, brain, muscle, solid tumors, etc.), which span a large dynamic range (1-20...

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“…Royston et al. [20] obtained an analytical solution to the problem of surface wave generation in a viscoelastic half space due to a normal circular vibrator placed on a surface. They analyzed the change in surface displacement inside tissue as a function of the distance from the vibrator.…”

Section: Techniquesmentioning

confidence: 99%

Comparison of Vibrational Displacements Generated by Different Types of Surface Source in a Soft Tissue

Park¹,

Kwon²,

Jeong³

2012

Journal of the Korean Society for Nondestructive Testing

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The propagation characteristics of a mechanical wave in human soft tissue depend on its elastic properties. Investigation of these propagation characteristics is of paramount importance because it may enable us to diagnose cancer or tumor from the vibration response of the tissue. This paper investigates and compares displacement patterns generated in soft tissue due to several forms of low-frequency vibration sources placed on a surface. Among vibration sources considered are a normal load, tangential load, and antiplane shear load. We derive analytical expressions for displacements in viscoelastic single layers, and calculate displacement patterns in half space and infinite plate type tissue. Also, we simulate the vibration response of a finite-sized tissue using finite element method. The effects of the type of stress, the size and frequency of vibration sources, and medium boundaries on displacement patterns are discussed.

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Excitation and propagation of surface waves on a viscoelastic half-space with application to medical diagnosis

Cited by 70 publications

References 19 publications

Estimating material viscoelastic properties based on surface wave measurements: A comparison of techniques and modeling assumptions

Estimating material viscoelastic properties based on surface wave measurements: A comparison of techniques and modeling assumptions

Microscopic magnetic resonance elastography (μMRE)

Comparison of Vibrational Displacements Generated by Different Types of Surface Source in a Soft Tissue

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