WorldWideScience

Sample records for acoustic-radiation-force-driven shear wave

  1. Focusing of Shear Shock Waves

    Science.gov (United States)

    Giammarinaro, Bruno; Espíndola, David; Coulouvrat, François; Pinton, Gianmarco

    2018-01-01

    Focusing is a ubiquitous way to transform waves. Recently, a new type of shock wave has been observed experimentally with high-frame-rate ultrasound: shear shock waves in soft solids. These strongly nonlinear waves are characterized by a high Mach number, because the shear wave velocity is much slower, by 3 orders of magnitude, than the longitudinal wave velocity. Furthermore, these waves have a unique cubic nonlinearity which generates only odd harmonics. Unlike longitudinal waves for which only compressional shocks are possible, shear waves exhibit cubic nonlinearities which can generate positive and negative shocks. Here we present the experimental observation of shear shock wave focusing, generated by the vertical motion of a solid cylinder section embedded in a soft gelatin-graphite phantom to induce linearly vertically polarized motion. Raw ultrasound data from high-frame-rate (7692 images per second) acquisitions in combination with algorithms that are tuned to detect small displacements (approximately 1 μ m ) are used to generate quantitative movies of gel motion. The features of shear shock wave focusing are analyzed by comparing experimental observations with numerical simulations of a retarded-time elastodynamic equation with cubic nonlinearities and empirical attenuation laws for soft solids.

  2. Continuous wave laser for wind shear detection

    Science.gov (United States)

    Nelson, Loren

    1991-01-01

    Details of the design and development of a continuous-wave heterodyne carbon dioxide laser which has wind shear detection capabilities are given in viewgraph form. The goal of the development was to investigate the lower cost CW (rather than pulsed) lidar option for look-ahead wind shear detection from aircraft. The device has potential utility for ground based wind shear detection at secondary airports where the high cost of a Terminal Doppler Weather Radar system is not justifiable.

  3. Seismic shear waves as Foucault pendulum

    Science.gov (United States)

    Snieder, Roel; Sens-Schönfelder, Christoph; Ruigrok, Elmer; Shiomi, Katsuhiko

    2016-03-01

    Earth's rotation causes splitting of normal modes. Wave fronts and rays are, however, not affected by Earth's rotation, as we show theoretically and with observations made with USArray. We derive that the Coriolis force causes a small transverse component for P waves and a small longitudinal component for S waves. More importantly, Earth's rotation leads to a slow rotation of the transverse polarization of S waves; during the propagation of S waves the particle motion behaves just like a Foucault pendulum. The polarization plane of shear waves counteracts Earth's rotation and rotates clockwise in the Northern Hemisphere. The rotation rate is independent of the wave frequency and is purely geometric, like the Berry phase. Using the polarization of ScS and ScS2 waves, we show that the Foucault-like rotation of the S wave polarization can be observed. This can affect the determination of source mechanisms and the interpretation of observed SKS splitting.

  4. Estimation of seabed shear-wave velocity profiles using shear-wave source data.

    Science.gov (United States)

    Dong, Hefeng; Nguyen, Thanh-Duong; Duffaut, Kenneth

    2013-07-01

    This paper estimates seabed shear-wave velocity profiles and their uncertainties using interface-wave dispersion curves extracted from data generated by a shear-wave source. The shear-wave source generated a seismic signature over a frequency range between 2 and 60 Hz and was polarized in both in-line and cross-line orientations. Low-frequency Scholte- and Love-waves were recorded. Dispersion curves of the Scholte- and Love-waves for the fundamental mode and higher-order modes are extracted by three time-frequency analysis methods. Both the vertically and horizontally polarized shear-wave velocity profiles in the sediment are estimated by the Scholte- and Love-wave dispersion curves, respectively. A Bayesian approach is utilized for the inversion. Differential evolution, a global search algorithm is applied to estimate the most-probable shear-velocity models. Marginal posterior probability profiles are computed by Metropolis-Hastings sampling. The estimated vertically and horizontally polarized shear-wave velocity profiles fit well with the core and in situ measurements.

  5. Nongeometrically converted shear waves in marine streamer data

    NARCIS (Netherlands)

    Drijkoningen, G.G.; El Allouche, N.; Thorbecke, J.W.; Bada, G.

    2012-01-01

    Under certain circumstances, marine streamer data contain nongeometrical shear body wave arrivals that can be used for imaging. These shear waves are generated via an evanescent compressional wave in the water and convert to propagating shear waves at the water bottom. They are called

  6. Propagation of waves in shear flows

    CERN Document Server

    Fabrikant, A L

    1998-01-01

    The state of the art in a theory of oscillatory and wave phenomena in hydrodynamical flows is presented in this book. A unified approach is used for waves of different physical origins. A characteristic feature of this approach is that hydrodynamical phenomena are considered in terms of physics; that is, the complement of the conventionally employed formal mathematical approach. Some physical concepts such as wave energy and momentum in a moving fluid are analysed, taking into account induced mean flow. The physical mechanisms responsible for hydrodynamic instability of shear flows are conside

  7. Shear Shock Waves Observed in the Brain

    Science.gov (United States)

    Espíndola, David; Lee, Stephen; Pinton, Gianmarco

    2017-10-01

    The internal deformation of the brain is far more complex than the rigid motion of the skull. An ultrasound imaging technique that we have developed has a combination of penetration, frame-rate, and motion-detection accuracy required to directly observe the formation and evolution of shear shock waves in the brain. Experiments at low impacts on the traumatic-brain-injury scale demonstrate that they are spontaneously generated and propagate within the porcine brain. Compared to the initially smooth impact, the acceleration at the shock front is amplified up to a factor of 8.5. This highly localized increase in acceleration suggests that shear shock waves are a previously unappreciated mechanism that could play a significant role in traumatic brain injury.

  8. Horizontal Shear Wave Imaging of Large Optics

    Energy Technology Data Exchange (ETDEWEB)

    Quarry, M J

    2007-09-05

    When complete the National Ignition Facility (NIF) will be the world's largest and most energetic laser and will be capable of achieving for the first time fusion ignition in the laboratory. Detecting optics features within the laser beamlines and sizing them at diameters of 0.1 mm to 10 mm allows timely decisions concerning refurbishment and will help with the routine operation of the system. Horizontally polarized shear waves at 10 MHz were shown to accurately detect, locate, and size features created by laser operations from 0.5 mm to 8 mm by placing sensors at the edge of the optic. The shear wave technique utilizes highly directed beams. The outer edge of an optic can be covered with shear wave transducers on four sides. Each transducer sends a pulse into the optic and any damage reflects the pulse back to the transmitter. The transducers are multiplexed, and the collected time waveforms are enveloped and replicated across the width of the element. Multiplying the data sets from four directions produces a map of reflected amplitude to the fourth power, which images the surface of the optic. Surface area can be measured directly from the image, and maximum depth was shown to be correlated to maximum amplitude of the reflected waveform.

  9. Shear waves in inhomogeneous, compressible fluids in a gravity field.

    Science.gov (United States)

    Godin, Oleg A

    2014-03-01

    While elastic solids support compressional and shear waves, waves in ideal compressible fluids are usually thought of as compressional waves. Here, a class of acoustic-gravity waves is studied in which the dilatation is identically zero, and the pressure and density remain constant in each fluid particle. These shear waves are described by an exact analytic solution of linearized hydrodynamics equations in inhomogeneous, quiescent, inviscid, compressible fluids with piecewise continuous parameters in a uniform gravity field. It is demonstrated that the shear acoustic-gravity waves also can be supported by moving fluids as well as quiescent, viscous fluids with and without thermal conductivity. Excitation of a shear-wave normal mode by a point source and the normal mode distortion in realistic environmental models are considered. The shear acoustic-gravity waves are likely to play a significant role in coupling wave processes in the ocean and atmosphere.

  10. A unifying fractional wave equation for compressional and shear waves.

    Science.gov (United States)

    Holm, Sverre; Sinkus, Ralph

    2010-01-01

    This study has been motivated by the observed difference in the range of the power-law attenuation exponent for compressional and shear waves. Usually compressional attenuation increases with frequency to a power between 1 and 2, while shear wave attenuation often is described with powers less than 1. Another motivation is the apparent lack of partial differential equations with desirable properties such as causality that describe such wave propagation. Starting with a constitutive equation which is a generalized Hooke's law with a loss term containing a fractional derivative, one can derive a causal fractional wave equation previously given by Caputo [Geophys J. R. Astron. Soc. 13, 529-539 (1967)] and Wismer [J. Acoust. Soc. Am. 120, 3493-3502 (2006)]. In the low omegatau (low-frequency) case, this equation has an attenuation with a power-law in the range from 1 to 2. This is consistent with, e.g., attenuation in tissue. In the often neglected high omegatau (high-frequency) case, it describes attenuation with a power-law between 0 and 1, consistent with what is observed in, e.g., dynamic elastography. Thus a unifying wave equation derived properly from constitutive equations can describe both cases.

  11. Shear wave elastography with a new reliability indicator

    Directory of Open Access Journals (Sweden)

    Christoph F. Dietrich

    2016-09-01

    Full Text Available Non-invasive methods for liver stiffness assessment have been introduced over recent years. Of these, two main methods for estimating liver fibrosis using ultrasound elastography have become established in clinical practice: shear wave elastography and quasi-static or strain elastography. Shear waves are waves with a motion perpendicular (lateral to the direction of the generating force. Shear waves travel relatively slowly (between 1 and 10 m/s. The stiffness of the liver tissue can be assessed based on shear wave velocity (the stiffness increases with the speed. The European Federation of Societies for Ultrasound in Medicine and Biology has published Guidelines and Recommendations that describe these technologies and provide recommendations for their clinical use. Most of the data available to date has been published using the Fibroscan (Echosens, France, point shear wave speed measurement using an acoustic radiation force impulse (Siemens, Germany and 2D shear wave elastography using the Aixplorer (SuperSonic Imagine, France. More recently, also other manufacturers have introduced shear wave elastography technology into the market. A comparison of data obtained using different techniques for shear wave propagation and velocity measurement is of key interest for future studies, recommendations and guidelines. Here, we present a recently introduced shear wave elastography technology from Hitachi and discuss its reproducibility and comparability to the already established technologies.

  12. Shear wavelength estimation based on inverse filtering and multiple-point shear wave generation

    Science.gov (United States)

    Kitazaki, Tomoaki; Kondo, Kengo; Yamakawa, Makoto; Shiina, Tsuyoshi

    2016-07-01

    Elastography provides important diagnostic information because tissue elasticity is related to pathological conditions. For example, in a mammary gland, higher grade malignancies yield harder tumors. Estimating shear wave speed enables the quantification of tissue elasticity imaging using time-of-flight. However, time-of-flight measurement is based on an assumption about the propagation direction of a shear wave which is highly affected by reflection and refraction, and thus might cause an artifact. An alternative elasticity estimation approach based on shear wavelength was proposed and applied to passive configurations. To determine the elasticity of tissue more quickly and more accurately, we proposed a new method for shear wave elasticity imaging that combines the shear wavelength approach and inverse filtering with multiple shear wave sources induced by acoustic radiation force (ARF). The feasibility of the proposed method was verified using an elasticity phantom with a hard inclusion.

  13. Selective excitation of tropical atmospheric waves in wave-CISK: The effect of vertical wind shear

    Science.gov (United States)

    Zhang, Minghua; Geller, Marvin A.

    1994-01-01

    The growth of waves and the generation of potential energy in wave-CISK require unstable waves to tilt with height oppositely to their direction of propagation. This makes the structures and instability properties of these waves very sensitive to the presence of vertical shear in the basic flow. Equatorial Kelvin and Rossby-gravity waves have opposite phase tilt with height to what they have in the stratosphere, and their growth is selectively favored by basic flows with westward vertical shear and eastward vertical shear, respectively. Similar calculations are also made for gravity waves and Rossby waves. It is shown that eastward vertical shear of the basic flow promotes CISK for westward propagating Rossby-gravity, Rossby, and gravity waves and suppresses CISK for eastward propagating Kelvin and gravity waves, while westward shear of the basic flow has the reverse effects.

  14. P1138Cardiac shear wave velocity in healthy individuals.

    Science.gov (United States)

    Strachinaru, M; Geleijnse, M L; Bosch, J G; De Jong, N; Van Der Steen, Afw; Van Dalen, B M; Vos, H J

    2016-12-01

    The closure of the valves generates shear waves in the heart walls. The propagation velocity of shear waves relates to stiffness. This could potentially be used to estimate the stiffness of the myocardium, with huge potential implications in pathologies characterized by a deterioration of the diastolic properties of the left ventricle. In an earlier phantom study we already validated shear wave tracking with a clinical ultrasound system in cardiac mode. In this study we aimed to measure the shear waves velocity in normal individuals. 12 healthy volunteers, mean age=37±10, 33% females, were investigated using a clinical scanner (Philips iE33), equipped with a S5-1 probe, using a clinical tissue Doppler (TDI) application. ECG and phonocardiogram (PCG) were synchronously recorded. We achieved a TDI frame rate of >500Hz by carefully tuning normal system settings. Data were processed offline in Philips Qlab 8 to extract tissue velocity along a virtual M-mode line in the basal third of the interventricular septum, in parasternal long axis view. This tissue velocity showed a propagating wave pattern after closure of the valves. The slope of the wave front velocity in a space-time panel was measured to obtain the shear wave propagation velocity. The velocity of the shear waves induced by the closure of the mitral valve (1st heart sound) and aortic valve (2nd heart sound) was averaged over 4 heartbeats for every subject. Shear waves were visible after each closure of the heart valves, synchronous to the heart sounds. The figure shows one heart cycle of a subject, with the mean velocity along a virtual M-mode line in the upper panel, synchronous to the ECG signal (green line) and phonocardiogram (yellow line) in the lower panel. The slope of the shear waves is marked with dotted lines and the onset of the heart sounds with white lines. In our healthy volunteer group the mean velocity of the shear wave induced by mitral valve closure was 4.8±0.7m/s, standard error of 0.14 m

  15. Ultrasound shear wave simulation based on nonlinear wave propagation and Wigner-Ville Distribution analysis

    Science.gov (United States)

    Bidari, Pooya Sobhe; Alirezaie, Javad; Tavakkoli, Jahan

    2017-03-01

    This paper presents a method for modeling and simulation of shear wave generation from a nonlinear Acoustic Radiation Force Impulse (ARFI) that is considered as a distributed force applied at the focal region of a HIFU transducer radiating in nonlinear regime. The shear wave propagation is simulated by solving the Navier's equation from the distributed nonlinear ARFI as the source of the shear wave. Then, the Wigner-Ville Distribution (WVD) as a time-frequency analysis method is used to detect the shear wave at different local points in the region of interest. The WVD results in an estimation of the shear wave time of arrival, its mean frequency and local attenuation which can be utilized to estimate medium's shear modulus and shear viscosity using the Voigt model.

  16. Optimized shear wave generation using hybrid beamforming methods.

    Science.gov (United States)

    Nabavizadeh, Alireza; Greenleaf, James F; Fatemi, Mostafa; Urban, Matthew W

    2014-01-01

    Elasticity imaging is a medical imaging modality that measures tissue elasticity as an aid in the diagnosis of certain diseases. Shear wave-based methods have been developed to perform elasticity measurements in soft tissue. These methods often use the radiation force mechanism of focused ultrasound to induce shear waves in soft tissue such as liver, kidney, breast, thyroid and skeletal muscle. The efficiency of the ultrasound beam in producing broadband extended shear waves in soft tissue is very important to the widespread use of this modality. Hybrid beamforming combines two types of focusing, conventional spherical focusing and axicon focusing, to produce a beam for generating a shear wave that has increased depth-of-field (DOF) so that measurements can be made with a shear wave with a consistent wave front. Spherical focusing is used in many applications to achieve high lateral resolution, but has low DOF. Axicon focusing, with a cone-shaped transducer, can provide good lateral resolution with large DOF. We describe our linear aperture design and beam optimization performed using angular spectrum simulations. We performed a large parametric simulation study in which we varied the focal depth for the spherical focusing portion of the aperture, the numbers of elements devoted to the spherical and axicon focusing portions of the aperture and the opening angle used for axicon focusing. The hybrid beamforming method was experimentally tested in two phantoms, and shear wave speed measurement accuracy and DOF for each hybrid beam were evaluated. We compared our results with those for shear waves generated using only spherical focusing. The results of this study indicate that hybrid beamforming is capable of producing a beam with increased DOF over which accurate shear wave speed measurements can be made for different-size apertures and at different focal depths. Copyright © 2014 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All

  17. Shear wave anisotropy beneath the Tibetan Plateau

    Science.gov (United States)

    McNamara, Daniel E.; Owens, Thomas J.; Silver, Paul G.; Wu, Frances T.

    1994-07-01

    Eleven broadband digital seismic stations were deployed across the central Tibetan Plateau in the first extensive passive-source experiment attempted within the Tibetan Plateau. One year of recording resulted in 186 event-station pairs which we analyze to determine the characteristics of shear wave splitting in the upper mantle beneath the array. Measurements of the fast polarization direction (phi) and delay time (delta-t) for SKS and direct S arrivals reveal systematic variations along the north-south oriented array. In the north central region of the plateau, very large delay times are observed at three stations, the largest of which is BUDO with delta-t = 2.4 s. However, at TUNL, which is off the northern edge of the plateau and 110 km from BUDO, and at sites in the south central plateau, delta-t decreases by nearly a factor of 3. We also observe a systematic rotation of phi from about 45 deg (NE) to 90 deg (E-W) from south to north along the array. A previously identified zone of inefficient Sn propagation correlates well with our region of large delta-t observations. The large delay times suggest that a relatively high number of anisotropic crystals are preferentially alligned within the mantle-lid, beneath the north central portion of the Tibetan Plateau. In most cases, fast polarization directions appear to be parallel to surface geologic features suggesting as much as 200 km of the upper mantle has been involved in the collisional deformation that has produced the Tibetan Plateau.

  18. Maximum likelihood estimation of shear wave speed in transient elastography.

    Science.gov (United States)

    Audière, Stéphane; Angelini, Elsa D; Sandrin, Laurent; Charbit, Maurice

    2014-06-01

    Ultrasonic transient elastography (TE), enables to assess, under active mechanical constraints, the elasticity of the liver, which correlates with hepatic fibrosis stages. This technique is routinely used in clinical practice to assess noninvasively liver stiffness. The Fibroscan system used in this work generates a shear wave via an impulse stress applied on the surface of the skin and records a temporal series of radio-frequency (RF) lines using a single-element ultrasound probe. A shear wave propagation map (SWPM) is generated as a 2-D map of the displacements along depth and time, derived from the correlations of the sequential 1-D RF lines, assuming that the direction of propagation (DOP) of the shear wave coincides with the ultrasound beam axis (UBA). Under the assumption of pure elastic tissue, elasticity is proportional to the shear wave speed. This paper introduces a novel approach to the processing of the SWPM, deriving the maximum likelihood estimate of the shear wave speed when comparing the observed displacements and the estimates provided by the Green's functions. A simple parametric model is used to interface Green's theoretical values of noisy measures provided by the SWPM, taking into account depth-varying attenuation and time-delay. The proposed method was evaluated on numerical simulations using a finite element method simulator and on physical phantoms. Evaluation on this test database reported very high agreements of shear wave speed measures when DOP and UBA coincide.

  19. Deep Shear Wave Velocity of Southern Bangkok and Vicinity

    Science.gov (United States)

    Wongpanit, T.; Hayashi, K.; Pananont, P.

    2017-09-01

    Bangkok is located on the soft marine clay in the Lower Chao Phraya Basin which can amplify seismic wave and can affect the shaking of buildings during an earthquake. Deep shear wave velocity of the sediment in the basin are useful for study the effect of the soft sediment on the seismic wave and can be used for earthquake engineering design and ground shaking estimation, especially for a deep basin. This study aims to measure deep shear wave velocity and create 2D shear wave velocity profile down to a bedrock in the southern Bangkok by the Microtremor measurements with 2 seismographs using Spatial Autocorrelation (2-SPAC) technique. The data was collected during a day time on linear array geometry with offsets varying between 5-2,000 m. Low frequency of natural tremor (0.2-0.6 Hz) was detected at many sites, however, very deep shear wave data at many sites are ambiguous due to man-made vibration noises in the city. The results show that shear wave velocity of the sediment in the southern Bangkok is between 100-2,000 ms-1 and indicate that the bedrock depth is about 600-800 m, except at Bang Krachao where bedrock depth is unclear.

  20. Shear-Wave Elastography: Basic Physics and Musculoskeletal Applications.

    Science.gov (United States)

    Taljanovic, Mihra S; Gimber, Lana H; Becker, Giles W; Latt, L Daniel; Klauser, Andrea S; Melville, David M; Gao, Liang; Witte, Russell S

    2017-01-01

    In the past 2 decades, sonoelastography has been progressively used as a tool to help evaluate soft-tissue elasticity and add to information obtained with conventional gray-scale and Doppler ultrasonographic techniques. Recently introduced on clinical scanners, shear-wave elastography (SWE) is considered to be more objective, quantitative, and reproducible than compression sonoelastography with increasing applications to the musculoskeletal system. SWE uses an acoustic radiation force pulse sequence to generate shear waves, which propagate perpendicular to the ultrasound beam, causing transient displacements. The distribution of shear-wave velocities at each pixel is directly related to the shear modulus, an absolute measure of the tissue's elastic properties. Shear-wave images are automatically coregistered with standard B-mode images to provide quantitative color elastograms with anatomic specificity. Shear waves propagate faster through stiffer contracted tissue, as well as along the long axis of tendon and muscle. SWE has a promising role in determining the severity of disease and treatment follow-up of various musculoskeletal tissues including tendons, muscles, nerves, and ligaments. This article describes the basic ultrasound physics of SWE and its applications in the evaluation of various traumatic and pathologic conditions of the musculoskeletal system. ©RSNA, 2017.

  1. Cardiac Shear Wave Velocity Detection in the Porcine Heart.

    Science.gov (United States)

    Vos, Hendrik J; van Dalen, Bas M; Heinonen, Ilkka; Bosch, Johan G; Sorop, Oana; Duncker, Dirk J; van der Steen, Antonius F W; de Jong, Nico

    2017-04-01

    Cardiac muscle stiffness can potentially be estimated non-invasively with shear wave elastography. Shear waves are present on the septal wall after mitral and aortic valve closure, thus providing an opportunity to assess stiffness in early systole and early diastole. We report on the shear wave recordings of 22 minipigs with high-frame-rate echocardiography. The waves were captured with 4000 frames/s using a programmable commercial ultrasound machine. The wave pattern was extracted from the data through a local tissue velocity estimator based on one-lag autocorrelation. The wave propagation velocity was determined with a normalized Radon transform, resulting in median wave propagation velocities of 2.2 m/s after mitral valve closure and 4.2 m/s after aortic valve closure. Overall the velocities ranged between 0.8 and 6.3 m/s in a 95% confidence interval. By dispersion analysis we found that the propagation velocity only mildly increased with shear wave frequency. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  2. Shear-coupled PL waves observed at the Kerguelen Isles

    Science.gov (United States)

    Pettersen, O.; Maupin, V.

    2003-04-01

    S-waves generated by earthquakes in Indonesia and recorded at the seismological broadband station PAF on the Kerguelen Isles are usually followed by particularly large, long and monochromatic wavetrains. These wavetrains are not observed, or are not as prominent, for events at comparable epicentral distances in other source regions. They have a clear dominant period of about 20 seconds and last usually for more than 100s. They show slight normal dispersion, and have a prograde elliptical motion in the vertical propagation plane with largest amplitude on the radial component. These characteristics suggest that the observed waves are shear-coupled PL-waves, i.e., a phase which propagates partly as a mantle S-wave and partly as P-waves trapped in the crust. The P-wave portion of the propagation may occur close to the source, close to the receiver, or at both ends of the wavepath, over a significant portion of the epicentral distance. Observations at Kerguelen of strong shear-coupled PL waves from Indonesian earthquakes suggest a special crust and upper mantle structure in the region between the Kerguelen hotspot and the South-East Indian Ridge, 1000 km away. This includes the region where a special upper mantle anisotropic structure has been detected from surface wave polarisation anomalies. We analyse which implications the strong shear-coupled PL waves may have on the structure between the hotspot and the ridge.

  3. Measurement and modeling of bed shear stress under solitary waves

    Digital Repository Service at National Institute of Oceanography (India)

    Jayakumar, S.; Guard, P.A.; Baldock, T.E.

    by earlier researchers. Keywords: tsunami; bed shear stress; shear plate; friction factors; convolution integrals; solitary wave; 1 School of Civil Engineering, The University of Queensland, Brisbane, QLD... 4072, Australia, Email: j.seelam@uqconnect.edu.au; Scientist, Ocean Engineering, National Institute of Oceanography (CSIR), Dona Paula, Goa 403 004, India, Email: jay@nio.org 2 BMT-WBM Pty Ltd., Brisbane, Australia, Email:paul.guard@bmtwbm.com.au 3...

  4. Novel Method for Vessel Cross-Sectional Shear Wave Imaging.

    Science.gov (United States)

    He, Qiong; Li, Guo-Yang; Lee, Fu-Feng; Zhang, Qihao; Cao, Yanping; Luo, Jianwen

    2017-07-01

    Many studies have investigated the applications of shear wave imaging (SWI) to vascular elastography, mainly on the longitudinal section of vessels. It is important to investigate SWI in the arterial cross section when evaluating anisotropy of the vessel wall or complete plaque composition. Here, we proposed a novel method based on the coordinate transformation and directional filter in the polar coordinate system to achieve vessel cross-sectional shear wave imaging. In particular, ultrasound radiofrequency data were transformed from the Cartesian to the polar coordinate system; the radial displacements were then estimated directly. Directional filtering was performed along the circumferential direction to filter out the reflected waves. The feasibility of the proposed vessel cross-sectional shear wave imaging method was investigated through phantom experiments and ex vivo and in vivo studies. Our results indicated that the dispersion relation of the shear wave (i.e., the guided circumferential wave) within the vessel can be measured via the present method, and the elastic modulus of the vessel can be determined. Copyright © 2017 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  5. Seismic shear waves as Foucault pendulum

    NARCIS (Netherlands)

    Snieder, Roel; Sens-Schönfelder, C.; Ruigrok, E.; Shiomi, K.

    2016-01-01

    Earth's rotation causes splitting of normal modes. Wave fronts and rays are, however, not affected by Earth's rotation, as we show theoretically and with observations made with USArray. We derive that the Coriolis force causes a small transverse component for P waves and a small longitudinal

  6. Shear wave elastography using phase sensitive optical coherence tomography

    Science.gov (United States)

    Song, Shaozhen; Huang, Zhihong; Nguyen, Thu-Mai; Wong, Emily Y.; Arnal, Bastien; O'Donnell, Matthew; Wang, Ruikang K.

    2014-03-01

    Optical coherence tomography (OCT) provides high spatial resolution and sensitivity that are ideal for imaging the cornea and lens. Quantifying the biomechanical properties of these tissues could add clinically valuable information. Thus, we propose a dynamic elastography method combining OCT detection and a mechanical actuator to map the shear modulus of soft tissues. We used a piezoelectric actuator driven in the kHz range and we used phase-sensitive OCT (PhS-OCT) to track the resulting shear waves at an equivalent frame rate of 47 kHz. We mapped the shear wave speed of anesthetized mice cornea using monochromatic excitations. We found a significant difference between a group of knock-out (3.92 +/- 0.35 m/s, N=4) and wild-type mice (5.04 +/- 0.51 m/s, N=3). These preliminary results demonstrate the feasibility of using PhS-OCT to perform in vivo shear wave elastography of the cornea. We then implemented a shear pulse compression approach on ex vivo human cornea. For that purpose, frequency- modulated excitations were used and the resulting displacement field was digitally compressed in a short broadband pulse with a 7 dB gain in signal-to-noise ratio (SNR).

  7. Shear waves in a fluid saturated elastic plate

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    MS received 25 February 2002. Abstract. In the present context, we consider the propagation of shear waves in the transverse isotropic fluid saturated porous plate. The frequency spectrum for SH-modes in the plate has been studied. It is observed that the frequency of the propagation is damped due to the two-phase ...

  8. Shear wave splitting in the Isparta Angle, southwestern Turkey ...

    Indian Academy of Sciences (India)

    and Priestley K 2001 Shear wave anisotropy in the upper mantle beneath the Aegean related to internal defor- mation; J. Geophys. Res. 106 30,737–30,753. McClusky S, Balassanian S, Barka A, Demir C, Ergintav S,. Georgiev I, Gurkan O, Hamburger M, Hurst K, Kahle H,. Kastens K, Kekelidze G, King R, Kotzev V, Lenk O,.

  9. Ion waves driven by shear flow in a relativistic degenerate ...

    Indian Academy of Sciences (India)

    2015-11-27

    Home; Journals; Pramana – Journal of Physics; Volume 86; Issue 5. Ion waves driven by shear flow in a relativistic degenerate ... Proceedings of the International Workshop/Conference on Computational Condensed Matter Physics and Materials Science (IWCCMP-2015). Posted on November 27, 2015. Guest Editors: ...

  10. Shear wave arrival time estimates correlate with local speckle pattern.

    Science.gov (United States)

    Mcaleavey, Stephen A; Osapoetra, Laurentius O; Langdon, Jonathan

    2015-12-01

    We present simulation and phantom studies demonstrating a strong correlation between errors in shear wave arrival time estimates and the lateral position of the local speckle pattern in targets with fully developed speckle. We hypothesize that the observed arrival time variations are largely due to the underlying speckle pattern, and call the effect speckle bias. Arrival time estimation is a key step in quantitative shear wave elastography, performed by tracking tissue motion via cross-correlation of RF ultrasound echoes or similar methods. Variations in scatterer strength and interference of echoes from scatterers within the tracking beam result in an echo that does not necessarily describe the average motion within the beam, but one favoring areas of constructive interference and strong scattering. A swept-receive image, formed by fixing the transmit beam and sweeping the receive aperture over the region of interest, is used to estimate the local speckle pattern. Metrics for the lateral position of the speckle are found to correlate strongly (r > 0.7) with the estimated shear wave arrival times both in simulations and in phantoms. Lateral weighting of the swept-receive pattern improved the correlation between arrival time estimates and speckle position. The simulations indicate that high RF echo correlation does not equate to an accurate shear wave arrival time estimate-a high correlation coefficient indicates that motion is being tracked with high precision, but the location tracked is uncertain within the tracking beam width. The presence of a strong on-axis speckle is seen to imply high RF correlation and low bias. The converse does not appear to be true-highly correlated RF echoes can still produce biased arrival time estimates. The shear wave arrival time bias is relatively stable with variations in shear wave amplitude and sign (-20 μm to 20 μm simulated) compared with the variation with different speckle realizations obtained along a given tracking

  11. Vortical and internal wave shear and strain

    OpenAIRE

    Pinkel, R.

    2014-01-01

    Depth-time records of isopycnal vertical strain have been collected from intensive CTD profiling programs on the research platform (R/P) Floating Instrument Platform (FLIP). The associated vertical wavenumber frequency spectrum of strain, when viewed in an isopycnal-following frame, displays a clear spectral gap at low vertical wavenumber, separating the quasigeostrophic (vortical) strain field and the superinertial internal wave continuum. This gap enables both model and linear-filter-based ...

  12. Turbulence closure: turbulence, waves and the wave-turbulence transition – Part 1: Vanishing mean shear

    Directory of Open Access Journals (Sweden)

    H. Z. Baumert

    2009-03-01

    Full Text Available This paper extends a turbulence closure-like model for stably stratified flows into a new dynamic domain in which turbulence is generated by internal gravity waves rather than mean shear. The model turbulent kinetic energy (TKE, K balance, its first equation, incorporates a term for the energy transfer from internal waves to turbulence. This energy source is in addition to the traditional shear production. The second variable of the new two-equation model is the turbulent enstrophy (Ω. Compared to the traditional shear-only case, the Ω-equation is modified to account for the effect of the waves on the turbulence time and space scales. This modification is based on the assumption of a non-zero constant flux Richardson number in the limit of vanishing mean shear when turbulence is produced exclusively by internal waves. This paper is part 1 of a continuing theoretical development. It accounts for mean shear- and internal wave-driven mixing only in the two limits of mean shear and no waves and waves but no mean shear, respectively.

    The new model reproduces the wave-turbulence transition analyzed by D'Asaro and Lien (2000b. At small energy density E of the internal wave field, the turbulent dissipation rate (ε scales like ε~E2. This is what is observed in the deep sea. With increasing E, after the wave-turbulence transition has been passed, the scaling changes to ε~E1. This is observed, for example, in the highly energetic tidal flow near a sill in Knight Inlet. The new model further exhibits a turbulent length scale proportional to the Ozmidov scale, as observed in the ocean, and predicts the ratio between the turbulent Thorpe and Ozmidov length scales well within the range observed in the ocean.

  13. Probe Oscillation Shear Elastography (PROSE): A High Frame-Rate Method for Two-Dimensional Ultrasound Shear Wave Elastography.

    Science.gov (United States)

    Mellema, Daniel C; Song, Pengfei; Kinnick, Randall R; Urban, Matthew W; Greenleaf, James F; Manduca, Armando; Chen, Shigao

    2016-09-01

    Ultrasound shear wave elastography (SWE) utilizes the propagation of induced shear waves to characterize the shear modulus of soft tissue. Many methods rely on an acoustic radiation force (ARF) "push beam" to generate shear waves. However, specialized hardware is required to generate the push beams, and the thermal stress that is placed upon the ultrasound system, transducer, and tissue by the push beams currently limits the frame-rate to about 1 Hz. These constraints have limited the implementation of ARF to high-end clinical systems. This paper presents Probe Oscillation Shear Elastography (PROSE) as an alternative method to measure tissue elasticity. PROSE generates shear waves using a harmonic mechanical vibration of an ultrasound transducer, while simultaneously detecting motion with the same transducer under pulse-echo mode. Motion of the transducer during detection produces a "strain-like" compression artifact that is coupled with the observed shear waves. A novel symmetric sampling scheme is proposed such that pulse-echo detection events are acquired when the ultrasound transducer returns to the same physical position, allowing the shear waves to be decoupled from the compression artifact. Full field-of-view (FOV) two-dimensional (2D) shear wave speed images were obtained by applying a local frequency estimation (LFE) technique, capable of generating a 2D map from a single frame of shear wave motion. The shear wave imaging frame rate of PROSE is comparable to the vibration frequency, which can be an order of magnitude higher than ARF based techniques. PROSE was able to produce smooth and accurate shear wave images from three homogeneous phantoms with different moduli, with an effective frame rate of 300 Hz. An inclusion phantom study showed that increased vibration frequencies improved the accuracy of inclusion imaging, and allowed targets as small as 6.5 mm to be resolved with good contrast (contrast-to-noise ratio ≥ 19 dB) between the target and

  14. Shear Wave Measurements for Evaluation of Tendon Diseases.

    Science.gov (United States)

    Yeh, Chia-Lun; Kuo, Po-Ling; Gennisson, Jean-Luc; Brum, Javier; Tanter, Mickael; Li, Pai-Chi

    2016-11-01

    This paper investigated the feasibility of using supersonic shear wave measurements to quantitatively differentiate normal and damaged tendons based on their mechanical properties. Five freshly harvested porcine tendons excised from pig legs were used. Tendon damage was induced by incubating the tendons with a 1% w/v collagenase solution. Values of shear modulus were derived both by a time-of-flight (TOF) approach and a transverse isotropic plate model (TI-model). The results show that as the preload applied to the tendon increased from 0 to 3 N, the mean shear modulus derived based on the TOF approach, the TI-model, and Young's modulus estimated from mechanical testing increased from 14.6 to 89.9 kPa, 53.9 to 348 kPa, and from 1.45 to 10.36 MPa, respectively, in untreated tendons, and from 8.4 to 67 kPa, 28 to 258 kPa, and from 0.93 to 7.2 MPa in collagenase-treated tendons. Both the TOF approach and the TI-model correlated well with the changes in Young's modulus. Although there is bias on the estimation of shear modulus using the TOF approach, it still provides statistical significance to differentiate normal and damaged tendons. Our data indicate that supersonic shear wave imaging is a valuable imaging technique to assess tendon stiffness dynamics and characterize normal and collagenase-damaged tendons.

  15. Nonlinear reflection of shock shear waves in soft elastic media.

    Science.gov (United States)

    Pinton, Gianmarco; Coulouvrat, François; Gennisson, Jean-Luc; Tanter, Mickaël

    2010-02-01

    For fluids, the theoretical investigation of shock wave reflection has a good agreement with experiments when the incident shock Mach number is large. But when it is small, theory predicts that Mach reflections are physically unrealistic, which contradicts experimental evidence. This von Neumann paradox is investigated for shear shock waves in soft elastic solids with theory and simulations. The nonlinear elastic wave equation is approximated by a paraxial wave equation with a cubic nonlinear term. This equation is solved numerically with finite differences and the Godunov scheme. Three reflection regimes are observed. Theory is developed for shock propagation by applying the Rankine-Hugoniot relations and entropic constraints. A characteristic parameter relating diffraction and non-linearity is introduced and its theoretical values are shown to match numerical observations. The numerical solution is then applied to von Neumann reflection, where curved reflected and Mach shocks are observed. Finally, the case of weak von Neumann reflection, where there is no reflected shock, is examined. The smooth but non-monotonic transition between these three reflection regimes, from linear Snell-Descartes to perfect grazing case, provides a solution to the acoustical von Neumann paradox for the shear wave equation. This transition is similar to the quadratic non-linearity in fluids.

  16. Histoscanning and shear wave ultrasound elastography for prostate cancer diagnosis

    Directory of Open Access Journals (Sweden)

    A. V. Amosov

    2016-01-01

    Full Text Available Introduction. The shear wave ultrasound elastography is a recently developed ultrasound-based method in the clinical practice, which allows the qualitative visual and quantitative measurements of tissue stiffness. In the 2010 this technology of the shear wave was called Shear Wave Elastograhpy. Due to the front of the shear waves the qualitative and quantitative assessment of the tissue stiffness is possible.Objective is to examine the efficacy of the shear wave ultrasound elastography in the evaluation of the prevalence of the oncological disease in patients with the prostate cancer and to compare the obtained results with the routine method X-ray diagnostics.Materials and methods. From the april 2015 in the I.M. Sechenov First Moscow State Medical University Urology Clinic there were conducted 314 shear wave ultrasound elastography examinations of the prostate. The ultrasound system Aixplorer® by SuperSonic Imagine was used. This system provides information provided by B-mode and shear wave ultrasound elastography mode. The transrectal echograms were made in 6 dimensions, so called Q-boxes (3 demensions in the every lobe on the segments from the base to the apex, according to the biopsy zone. The unit of measurement was the mean value in the kilopaskals (kPa. All the patients were randomized into 3 groups. There were 146 men with the possible prostate cancer in the first group (prospective study, 120 men with the certain diagnosis of the prostate cancer in the second group (retrospective study and 48 healthy men in the third group (control study. In all the patients of the first and the second groups the routine complete examination, including the prostate specific antigen (PSA level examination, digital rectal examination (DRE, doppler transrectal ultrasonography (TRUS, histoscanning and ultrasound shear wave elastography (SWE, was conducted. In the 229 patients of the first and the second groups the prostatectomy with the

  17. Spatial Statistics of Deep-Water Ambient Noise; Dispersion Relations for Sound Waves and Shear Waves

    Science.gov (United States)

    2015-09-30

    Propeller noise from a light aircraft for low-frequency measurements of the speed of sound in a marine sediment,” J. Comp. Acoust., 10 (4), 445-464...Dispersion Relations for Sound Waves and Shear Waves Michael J. Buckingham Marine Physical Laboratory, Scripps Institution of Oceanography University...propagation in saturated, unconsolidated marine sediments. New focus is on: 1) the dispersion associated with a frequency power law attenuation; 2) wave

  18. Surface waves on currents with arbitrary vertical shear

    Science.gov (United States)

    Smeltzer, Benjamin K.; Ellingsen, Simen Å.

    2017-04-01

    We study dispersion properties of linear surface gravity waves propagating in an arbitrary direction atop a current profile of depth-varying magnitude using a piecewise linear approximation and develop a robust numerical framework for practical calculation. The method has been much used in the past for the case of waves propagating along the same axis as the background current, and we herein extend and apply it to problems with an arbitrary angle between the wave propagation and current directions. Being valid for all wavelengths without loss of accuracy, the scheme is particularly well suited to solve problems involving a broad range of wave vectors, such as ship waves and Cauchy-Poisson initial value problems. We examine the group and phase velocities over different wavelength regimes and current profiles, highlighting characteristics due to the depth-variable vorticity. We show an example application to ship waves on an arbitrary current profile and demonstrate qualitative differences in the wake patterns between concave down and concave up profiles when compared to a constant shear profile with equal depth-averaged vorticity. We also discuss the nature of additional solutions to the dispersion relation when using the piecewise-linear model. These are vorticity waves, drifting vortical structures which are artifacts of the piecewise model. They are absent for a smooth profile and are spurious in the present context.

  19. Shear wave induced resonance elastography of spherical masses with polarized torsional waves.

    Science.gov (United States)

    Henni, Anis Hadj; Schmitt, Cédric; Trop, Isabelle; Cloutier, Guy

    2012-03-26

    Shear Wave Induced Resonance (SWIR) is a technique for dynamic ultrasound elastography of confined mechanical inclusions. It was developed for breast tumor imaging and tissue characterization. This method relies on the polarization of torsional shear waves modeled with the Helmholtz equation in spherical coordinates. To validate modeling, an in vitro set-up was used to measure and image the first three eigenfrequencies and eigenmodes of a soft sphere. A preliminary in vivo SWIR measurement on a breast fibroadenoma is also reported. Results revealed the potential of SWIR elastography to detect and mechanically characterize breast lesions for early cancer detection.

  20. Forward and inverse viscoelastic wave scattering by irregular inclusions for shear wave elastography.

    Science.gov (United States)

    Bernard, Simon; Cloutier, Guy

    2017-10-01

    Inversion methods in shear wave elastography use simplifying assumptions to recover the mechanical properties of soft tissues. Consequently, these methods suffer from artifacts when applied to media containing strong stiffness contrasts, and do not provide a map of the viscosity. In this work, the shear wave field recorded inside and around an inclusion was used to estimate the viscoelastic properties of the inclusion and surrounding medium, based on an inverse problem approach assuming local homogeneity of both media. An efficient semi-analytical method was developed to model the scattering of an elastic wave by an irregular inclusion, based on a decomposition of the field by Bessel functions and on a decomposition of the boundaries as Fourier series. This model was validated against finite element modeling. Shear waves were experimentally induced by acoustic radiation force in soft tissue phantoms containing stiff and soft inclusions, and the displacement field was imaged at a high frame rate using plane wave imaging. A nonlinear least-squares algorithm compared the model to the experimental data and adjusted the geometrical and mechanical parameters. The estimated shear storage and loss moduli were in good agreement with reference measurements, as well as the estimated inclusion shape. This approach provides an accurate estimation of geometry and viscoelastic properties for a single inclusion in a homogeneous background in the context of radiation force elastography.

  1. Hammering Yucca Flat, Part Two: Shear-Wave Velocity

    Science.gov (United States)

    Finlay, T. S.; Abbott, R. E.; Knox, H. A.; Tang, D. G.; James, S. R.; Haney, M. M.; Hampshire, J. B., II

    2015-12-01

    In preparation for the next phase of the Source Physics Experiment (SPE), we conducted an active-source seismic survey of Yucca Flat, Nevada, on the Nevada National Security Site. Results from this survey will be used to inform the geologic models associated with the SPE project. For this study, we used a novel 13,000 kilogram weight-drop seismic source to interrogate an 18-km North-South transect of Yucca Flat. Source points were spaced every 200 meters and were recorded by 350 to 380 3-component 2-Hz geophones with variable spacings of 10, 20, and 100 meters. We utilized the Refraction-Microtremor (ReMi) technique to create multiple 1D dispersion curves, which were then inverted for shear-wave velocity profiles using the Dix inversion method (Tsai and Haney, 2015). Each of these 1D velocity models was subsequently stitched together to create a 2D profile over the survey area. The dispersion results indicate a general decrease in surface-wave phase velocity to the south. This result is supported by slower shear-wave velocity sediments and increasing basin depth towards the survey's southern extent. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  2. The Shear Wave Velocity on Elastography Correlates with the Clinical Symptoms and Histopathological Features of Keloids

    OpenAIRE

    Aya, Rino; Yamawaki, Satoko; Yoshikawa, Katsuhiro; Katayama, Yasuhiro; Enoshiri, Tatsuki; Naitoh, Motoko; Suzuki, Shigehiko

    2015-01-01

    Background: Keloids present as red, painful lesions causing serious functional and cosmetic problems; however, there is no consensus regarding tools for objectively evaluating keloids. To demonstrate the utility of shear wave elastography in keloids, we investigated the correlations between clinical symptoms, ultrasound shear wave velocity, and histopathological findings. Methods: Three patients with keloids containing both red hypertrophic and mature areas were evaluated using the shear wave...

  3. Delensing gravitational wave standard sirens with shear and flexion maps

    Science.gov (United States)

    Shapiro, C.; Bacon, D. J.; Hendry, M.; Hoyle, B.

    2010-05-01

    Supermassive black hole binary (SMBHB) systems are standard sirens - the gravitational wave analogue of standard candles - and if discovered by gravitational wave detectors, they could be used as precise distance indicators. Unfortunately, gravitational lensing will randomly magnify SMBHB signals, seriously degrading any distance measurements. Using a weak lensing map of the SMBHB line of sight, we can estimate its magnification and thereby remove some uncertainty in its distance, a procedure we call `delensing'. We find that delensing is significantly improved when galaxy shears are combined with flexion measurements, which reduce small-scale noise in reconstructed magnification maps. Under a Gaussian approximation, we estimate that delensing with a 2D mosaic image from an Extremely Large Telescope could reduce distance errors by about 25-30 per cent for an SMBHB at z = 2. Including an additional wide shear map from a space survey telescope could reduce distance errors by nearly a factor of 2. Such improvement would make SMBHBs considerably more valuable as cosmological distance probes or as a fully independent check on existing probes.

  4. Shallow shear-wave reflection seismics in the tsunami struck Krueng Aceh River Basin, Sumatra

    National Research Council Canada - National Science Library

    Polom, U; Arsyad, I; Kümpel, H.-J

    2008-01-01

    ...), Hanover, high resolution shallow shear-wave reflection seismics was applied in the Indonesian province Nanggroe Aceh Darussalam, North Sumatra in cooperation with the Government of Indonesia, local...

  5. DISCRETE DEFORMATION WAVE DYNAMICS IN SHEAR ZONES: PHYSICAL MODELLING RESULTS

    Directory of Open Access Journals (Sweden)

    S. A. Bornyakov

    2016-01-01

    Full Text Available Observations of earthquake migration along active fault zones [Richter, 1958; Mogi, 1968] and related theoretical concepts [Elsasser, 1969] have laid the foundation for studying the problem of slow deformation waves in the lithosphere. Despite the fact that this problem has been under study for several decades and discussed in numerous publications, convincing evidence for the existence of deformation waves is still lacking. One of the causes is that comprehensive field studies to register such waves by special tools and equipment, which require sufficient organizational and technical resources, have not been conducted yet.The authors attempted at finding a solution to this problem by physical simulation of a major shear zone in an elastic-viscous-plastic model of the lithosphere. The experiment setup is shown in Figure 1 (A. The model material and boundary conditions were specified in accordance with the similarity criteria (described in detail in [Sherman, 1984; Sherman et al., 1991; Bornyakov et al., 2014]. The montmorillonite clay-and-water paste was placed evenly on two stamps of the installation and subject to deformation as the active stamp (1 moved relative to the passive stamp (2 at a constant speed. The upper model surface was covered with fine sand in order to get high-contrast photos. Photos of an emerging shear zone were taken every second by a Basler acA2000-50gm digital camera. Figure 1 (B shows an optical image of a fragment of the shear zone. The photos were processed by the digital image correlation method described in [Sutton et al., 2009]. This method estimates the distribution of components of displacement vectors and strain tensors on the model surface and their evolution over time [Panteleev et al., 2014, 2015].Strain fields and displacements recorded in the optical images of the model surface were estimated in a rectangular box (220.00×72.17 mm shown by a dot-and-dash line in Fig. 1, A. To ensure a sufficient level of

  6. Current status of musculoskeletal application of shear wave elastography

    Directory of Open Access Journals (Sweden)

    JeongAh Ryu

    2017-07-01

    Full Text Available Ultrasonography (US is a very powerful diagnostic modality for the musculoskeletal system due to the ability to perform real-time dynamic high-resolution examinations with the Doppler technique. In addition to acquiring morphologic data, we can now obtain biomechanical information by quantifying the elasticity of the musculoskeletal structures with US elastography. The earlier diagnosis of degeneration and the ability to perform follow-up evaluations of healing and the effects of treatment are possible. US elastography enables a transition from US-based inspection to US-based palpation in order to diagnose the characteristics of tissue. Shear wave elastography is considered the most suitable type of US elastography for the musculoskeletal system. It is widely used for tendons, ligaments, and muscles. It is important to understand practice guidelines in order to enhance reproducibility. Incorporating viscoelasticity and overcoming inconsistencies among manufacturers are future tasks for improving the capabilities of US elastography.

  7. Current status of musculoskeletal application of shear wave elastography

    Energy Technology Data Exchange (ETDEWEB)

    Ryu, Jeong Ah [Dept. of Radiology, Hanyang University Guri Hospital, Hanyang University School of Medicine, Guri (Korea, Republic of); Jeong, Woo Kyoung [Dept. of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of)

    2017-07-15

    Ultrasonography (US) is a very powerful diagnostic modality for the musculoskeletal system due to the ability to perform real-time dynamic high-resolution examinations with the Doppler technique. In addition to acquiring morphologic data, we can now obtain biomechanical information by quantifying the elasticity of the musculoskeletal structures with US elastography. The earlier diagnosis of degeneration and the ability to perform follow-up evaluations of healing and the effects of treatment are possible. US elastography enables a transition from US-based inspection to US-based palpation in order to diagnose the characteristics of tissue. Shear wave elastography is considered the most suitable type of US elastography for the musculoskeletal system. It is widely used for tendons, ligaments, and muscles. It is important to understand practice guidelines in order to enhance reproducibility. Incorporating viscoelasticity and overcoming inconsistencies among manufacturers are future tasks for improving the capabilities of US elastography.

  8. Shear-driven dynamo waves at high magnetic Reynolds number.

    Science.gov (United States)

    Tobias, S M; Cattaneo, F

    2013-05-23

    Astrophysical magnetic fields often display remarkable organization, despite being generated by dynamo action driven by turbulent flows at high conductivity. An example is the eleven-year solar cycle, which shows spatial coherence over the entire solar surface. The difficulty in understanding the emergence of this large-scale organization is that whereas at low conductivity (measured by the magnetic Reynolds number, Rm) dynamo fields are well organized, at high Rm their structure is dominated by rapidly varying small-scale fluctuations. This arises because the smallest scales have the highest rate of strain, and can amplify magnetic field most efficiently. Therefore most of the effort to find flows whose large-scale dynamo properties persist at high Rm has been frustrated. Here we report high-resolution simulations of a dynamo that can generate organized fields at high Rm; indeed, the generation mechanism, which involves the interaction between helical flows and shear, only becomes effective at large Rm. The shear does not enhance generation at large scales, as is commonly thought; instead it reduces generation at small scales. The solution consists of propagating dynamo waves, whose existence was postulated more than 60 years ago and which have since been used to model the solar cycle.

  9. Analysis shear wave velocity structure obtained from surface wave methods in Bornova, Izmir

    Energy Technology Data Exchange (ETDEWEB)

    Pamuk, Eren, E-mail: eren.pamuk@deu.edu.tr; Akgün, Mustafa, E-mail: mustafa.akgun@deu.edu.tr [Department of Geophysical Engineering, Dokuz Eylul University, Izmir (Turkey); Özdağ, Özkan Cevdet, E-mail: cevdet.ozdag@deu.edu.tr [Dokuz Eylul University Rectorate, Izmir (Turkey)

    2016-04-18

    Properties of the soil from the bedrock is necessary to describe accurately and reliably for the reduction of earthquake damage. Because seismic waves change their amplitude and frequency content owing to acoustic impedance difference between soil and bedrock. Firstly, shear wave velocity and depth information of layers on bedrock is needed to detect this changing. Shear wave velocity can be obtained using inversion of Rayleigh wave dispersion curves obtained from surface wave methods (MASW- the Multichannel Analysis of Surface Waves, ReMi-Refraction Microtremor, SPAC-Spatial Autocorrelation). While research depth is limeted in active source study, a passive source methods are utilized for deep depth which is not reached using active source methods. ReMi method is used to determine layer thickness and velocity up to 100 m using seismic refraction measurement systems.The research carried out up to desired depth depending on radius using SPAC which is utilized easily in conditions that district using of seismic studies in the city. Vs profiles which are required to calculate deformations in under static and dynamic loads can be obtained with high resolution using combining rayleigh wave dispersion curve obtained from active and passive source methods. In the this study, Surface waves data were collected using the measurements of MASW, ReMi and SPAC at the İzmir Bornova region. Dispersion curves obtained from surface wave methods were combined in wide frequency band and Vs-depth profiles were obtained using inversion. Reliability of the resulting soil profiles were provided by comparison with theoretical transfer function obtained from soil paremeters and observed soil transfer function from Nakamura technique and by examination of fitting between these functions. Vs values are changed between 200-830 m/s and engineering bedrock (Vs>760 m/s) depth is approximately 150 m.

  10. Modelling the impulse diffraction field of shear waves in transverse isotropic viscoelastic medium

    Science.gov (United States)

    Chatelin, Simon; Gennisson, Jean-Luc; Bernal, Miguel; Tanter, Mickael; Pernot, Mathieu

    2015-05-01

    The generation of shear waves from an ultrasound focused beam has been developed as a major concept for remote palpation using shear wave elastography (SWE). For muscular diagnostic applications, characteristics of the shear wave profile will strongly depend on characteristics of the transducer as well as the orientation of muscular fibers and the tissue viscoelastic properties. The numerical simulation of shear waves generated from a specific probe in an anisotropic viscoelastic medium is a key issue for further developments of SWE in fibrous soft tissues. In this study we propose a complete numerical tool allowing 3D simulation of a shear wave front in anisotropic viscoelastic media. From the description of an ultrasonic transducer, the shear wave source is simulated by using Field’s II software and shear wave propagation described by using the Green’s formalism. Finally, the comparison between simulations and experiments are successively performed for both shear wave velocity and dispersion profile in a transverse isotropic hydrogel phantom, in vivo forearm muscle and in vivo biceps brachii.

  11. Spectral analysis of surface waves method to assess shear wave velocity within centrifuge models

    Science.gov (United States)

    Murillo, Carol Andrea; Thorel, Luc; Caicedo, Bernardo

    2009-06-01

    The method of the spectral analysis of surface waves (SASW) is tested out on reduced scale centrifuge models, with a specific device, called the mini Falling Weight, developed for this purpose. Tests are performed on layered materials made of a mixture of sand and clay. The shear wave velocity VS determined within the models using the SASW is compared with the laboratory measurements carried out using the bender element test. The results show that the SASW technique applied to centrifuge testing is a relevant method to characterize VS near the surface.

  12. Shear-wave elastography for breast masses: local shear wave speed (m/sec) versus Young modulus (kPa)

    Energy Technology Data Exchange (ETDEWEB)

    Youk, Ji Hyun; Son, Eun Ju; Park, Ah Young; Kim, Jeong Ah [Dept. of Radiology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul (Korea, Republic of)

    2014-03-15

    To evaluate and compare the performance of shear-wave elastography (SWE) for breast masses using the local shear wave speed (m/sec) vs. Young modulus (kPa). A total of 130 breast lesions in 123 women who underwent SWE before ultrasound- guided core needle biopsy or surgical excision were included. With the region-of-interest placed over the stiffest areas of the lesion on SWE, the quantitative mean, maximum, and standard deviation (SD) of the elasticity values were measured in kPa and m/sec for each lesion. The SD was also measured with the region-of-interest including the whole breast lesion (wSD). The area under the receiver operating characteristic curve (AUC), sensitivity, and specificity of each elasticity value measured in kPa and m/sec were compared. Of the 130 lesions, 49 (37.7%) were malignant and 81 (62.3%) were benign. The AUCs for the mean, maximum, and SD of the elasticity values using kPa and m/sec did not differ significantly: mean, 0.974 vs. 0.974; maximum, 0.960 vs. 0.976; SD, 0.916 vs. 0.916. However, the AUC for wSD showed a significant difference: 0.964 (kPa) vs. 0.960 (m/sec) (P=0.036). There was no significant difference in the sensitivity and specificity of the mean, maximum, and wSD of the elasticity values. However, the specificity of the SD was significantly different between the two different measurements: 95.1% (kPa) vs. 87.7% (m/sec) (P=0.031). The quantitative elasticity values measured in kPa and m/sec on SWE showed good diagnostic performance. The specificity of the SD and AUC of the wSD measured in kPa were significantly higher than those measured in m/sec.

  13. Shear-wave elastography for breast masses: local shear wave speed (m/sec) versus Young modulus (kPa).

    Science.gov (United States)

    Youk, Ji Hyun; Son, Eun Ju; Park, Ah Young; Kim, Jeong-Ah

    2014-01-01

    To evaluate and compare the performance of shear-wave elastography (SWE) for breast masses using the local shear wave speed (m/sec) vs. Young modulus (kPa). A total of 130 breast lesions in 123 women who underwent SWE before ultrasound- guided core needle biopsy or surgical excision were included. With the region-of-interest placed over the stiffest areas of the lesion on SWE, the quantitative mean, maximum, and standard deviation (SD) of the elasticity values were measured in kPa and m/sec for each lesion. The SD was also measured with the region-of-interest including the whole breast lesion (wSD). The area under the receiver operating characteristic curve (AUC), sensitivity, and specificity of each elasticity value measured in kPa and m/sec were compared. Of the 130 lesions, 49 (37.7%) were malignant and 81 (62.3%) were benign. The AUCs for the mean, maximum, and SD of the elasticity values using kPa and m/sec did not differ significantly: mean, 0.974 vs. 0.974; maximum, 0.960 vs. 0.976; SD, 0.916 vs. 0.916. However, the AUC for wSD showed a significant difference: 0.964 (kPa) vs. 0.960 (m/sec) (P=0.036). There was no significant difference in the sensitivity and specificity of the mean, maximum, and wSD of the elasticity values. However, the specificity of the SD was significantly different between the two different measurements: 95.1% (kPa) vs. 87.7% (m/sec) (P=0.031). The quantitative elasticity values measured in kPa and m/sec on SWE showed good diagnostic performance. The specificity of the SD and AUC of the wSD measured in kPa were significantly higher than those measured in m/sec.

  14. Estimation of viscoelastic parameters in Prony series from shear wave propagation

    Science.gov (United States)

    Jung, Jae-Wook; Hong, Jung-Wuk; Lee, Hyoung-Ki; Choi, Kiwan

    2016-06-01

    When acquiring accurate ultrasonic images, we must precisely estimate the mechanical properties of the soft tissue. This study investigates and estimates the viscoelastic properties of the tissue by analyzing shear waves generated through an acoustic radiation force. The shear waves are sourced from a localized pushing force acting for a certain duration, and the generated waves travel horizontally. The wave velocities depend on the mechanical properties of the tissue such as the shear modulus and viscoelastic properties; therefore, we can inversely calculate the properties of the tissue through parametric studies.

  15. Estimation of viscoelastic parameters in Prony series from shear wave propagation

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Jae-Wook; Hong, Jung-Wuk, E-mail: j.hong@kaist.ac.kr, E-mail: jwhong@alum.mit.edu [Department of Civil and Environmental Engineering, KAIST, 291 Deahak-ro, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Lee, Hyoung-Ki; Choi, Kiwan [Health and Medical Equipment, Samsung Electronics, 1003 Daechi-dong, Gangnam-gu, Seoul 135-280 (Korea, Republic of)

    2016-06-21

    When acquiring accurate ultrasonic images, we must precisely estimate the mechanical properties of the soft tissue. This study investigates and estimates the viscoelastic properties of the tissue by analyzing shear waves generated through an acoustic radiation force. The shear waves are sourced from a localized pushing force acting for a certain duration, and the generated waves travel horizontally. The wave velocities depend on the mechanical properties of the tissue such as the shear modulus and viscoelastic properties; therefore, we can inversely calculate the properties of the tissue through parametric studies.

  16. Compressibility and shock wave interaction effects on free shear layers

    Science.gov (United States)

    Samimy, M.; Erwin, D. E.; Elliott, G. S.

    1989-01-01

    Two compressible free shear layers with convective Mach numbers of .51 and .86 were studied as baseline configurations to investigate the effects of compressibility on the turbulence characteristics. These shear layers were then disturbed by the placement of an obstruction in the shear layer in an attempt to enhance the shear layer growth rate. These models produced a curved shock in the supersonic side of the shear layer. The results indicate a significant reduction in turbulence levels with increased compressibility. However, there are not any significant changes due to the bow shock interaction with the shear layer.

  17. Measurement of sound speed vs. depth in South Pole ice: pressure waves and shear waves

    Energy Technology Data Exchange (ETDEWEB)

    IceCube Collaboration; Klein, Spencer

    2009-06-04

    We have measured the speed of both pressure waves and shear waves as a function of depth between 80 and 500 m depth in South Pole ice with better than 1% precision. The measurements were made using the South Pole Acoustic Test Setup (SPATS), an array of transmitters and sensors deployed in the ice at the South Pole in order to measure the acoustic properties relevant to acoustic detection of astrophysical neutrinos. The transmitters and sensors use piezoceramics operating at {approx}5-25 kHz. Between 200 m and 500 m depth, the measured profile is consistent with zero variation of the sound speed with depth, resulting in zero refraction, for both pressure and shear waves. We also performed a complementary study featuring an explosive signal propagating vertically from 50 to 2250 m depth, from which we determined a value for the pressure wave speed consistent with that determined for shallower depths, higher frequencies, and horizontal propagation with the SPATS sensors. The sound speed profile presented here can be used to achieve good acoustic source position and emission time reconstruction in general, and neutrino direction and energy reconstruction in particular. The reconstructed quantities could also help separate neutrino signals from background.

  18. 3-D FDTD simulation of shear waves for evaluation of complex modulus imaging.

    Science.gov (United States)

    Orescanin, Marko; Wang, Yue; Insana, Michael

    2011-02-01

    The Navier equation describing shear wave propagation in 3-D viscoelastic media is solved numerically with a finite differences time domain (FDTD) method. Solutions are formed in terms of transverse scatterer velocity waves and then verified via comparison to measured wave fields in heterogeneous hydrogel phantoms. The numerical algorithm is used as a tool to study the effects on complex shear modulus estimation from wave propagation in heterogeneous viscoelastic media. We used an algebraic Helmholtz inversion (AHI) technique to solve for the complex shear modulus from simulated and experimental velocity data acquired in 2-D and 3-D. Although 3-D velocity estimates are required in general, there are object geometries for which 2-D inversions provide accurate estimations of the material properties. Through simulations and experiments, we explored artifacts generated in elastic and dynamic-viscous shear modulus images related to the shear wavelength and average viscosity.

  19. Measurement and modelling of bed shear induced by solitary waves

    Digital Repository Service at National Institute of Oceanography (India)

    JayaKumar, S.

    generated in the laboratory and the corresponding shear stresses were measured using a Shear Plate apparatus. A physical model was set up in the laboratory that represented the deep horizontal ocean floor, inclined continental slope and the shallow...

  20. A comparative study of strain and shear-wave elastography in an elasticity phantom.

    Science.gov (United States)

    Carlsen, Jonathan F; Pedersen, Malene R; Ewertsen, Caroline; Săftoiu, Adrian; Lönn, Lars; Rafaelsen, Søren R; Nielsen, Michael B

    2015-03-01

    OBJECTIVE. The purpose of this study was to assess the diagnostic accuracy of strain and shear-wave elastography for determining targets of varying stiffness in a phantom. The effect of target diameter on elastographic assessments and the effect of depth on shear-wave velocity were also investigated. MATERIALS AND METHODS. We examined 20 targets of varying diameters (2.5-16.7 mm) and stiffnesses (8, 14, 45, and 80 kPa) with a 4-9-MHz linear-array transducer. Targets were evaluated 10 times with three different methods-shear-wave elastography, strain ratio, and strain histogram analysis-yielding 600 evaluations. AUCs were calculated for data divided between different stiffnesses. A 1.5-6-MHz curved-array transducer was used to assess the effect of depth (3.5 vs 6 cm) on shear-wave elastography in 80 scans. Mixed model analysis was performed to assess the effect of target diameter and depth. RESULTS. Strain ratio and strain histogram AUCs were higher than the shear-wave velocity AUC (p < 0.001) in data divided as 80 versus 45, 14, and 8 kPa. In data divided as 80 and 45 versus 14 and 8 kPa, the methods were equal (p = 0.959 and p = 1.000, respectively). Strain ratios were superior (p = 0.030), whereas strain histograms were not significantly better (p = 0.083) than shear-wave elastography in data divided as 80, 45, and 14 versus 8 kPa. Target diameter had an effect on all three methods (p = 0.001). Depth had an effect on shear-wave velocity (p = 0.001). CONCLUSION. The ability to discern different target stiffnesses varies between shear-wave and strain elastography. Target diameter affected all methods. Shear-wave elastography is affected by target depth.

  1. Coupling of an acoustic wave to shear motion due to viscous heating

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Bin; Goree, J. [Department of Physics and Astronomy, The University of Iowa, Iowa City, Iowa 52242 (United States)

    2016-07-15

    Viscous heating due to shear motion in a plasma can result in the excitation of a longitudinal acoustic wave, if the shear motion is modulated in time. The coupling mechanism is a thermal effect: time-dependent shear motion causes viscous heating, which leads to a rarefaction that can couple into a longitudinal wave, such as an acoustic wave. This coupling mechanism is demonstrated in an electrostatic three-dimensional (3D) simulation of a dusty plasma, in which a localized shear flow is initiated as a pulse, resulting in a delayed outward propagation of a longitudinal acoustic wave. This coupling effect can be profound in plasmas that exhibit localized viscous heating, such as the dusty plasma we simulated using parameters typical of the PK-4 experiment. We expect that a similar phenomenon can occur with other kinds of plasma waves.

  2. The formation of Laurentia: Evidence from shear wave splitting

    Science.gov (United States)

    Liddell, Mitch V.; Bastow, Ian; Darbyshire, Fiona; Gilligan, Amy; Pugh, Stephen

    2017-12-01

    The northern Hudson Bay region in Canada comprises several Archean cratonic nuclei, assembled by a number of Paleoproterozoic orogenies including the Trans-Hudson Orogen (THO) and the Rinkian-Nagssugtoqidian Orogen. Recent debate has focused on the extent to which these orogens have modern analogues such as the Himalayan-Karakoram-Tibet Orogen. Further, the structure of the lithospheric mantle beneath the Hudson Strait and southern Baffin Island is potentially indicative of Paleoproterozoic underthrusting of the Superior plate beneath the Churchill collage. Also in question is whether the Laurentian cratonic root is stratified, with a fast, depleted, Archean core underlain by a slower, younger, thermally-accreted layer. Plate-scale process that create structures such as these are expected to manifest as measurable fossil seismic anisotropic fabrics. We investigate these problems via shear wave splitting, and present the most comprehensive study to date of mantle seismic anisotropy in northern Laurentia. Strong evidence is presented for multiple layers of anisotropy beneath Archean zones, consistent with the episodic development model of stratified cratonic keels. We also show that southern Baffin Island is underlain by dipping anisotropic fabric, where underthrusting of the Superior plate beneath the Churchill has previously been interpreted. This provides direct evidence of subduction-related deformation at 1.8 Ga, implying that the THO developed with modern plate-tectonic style interactions.

  3. [Assessment of plantar fasciitis using shear wave elastography].

    Science.gov (United States)

    Zhang, Lining; Wan, Wenbo; Zhang, Lihai; Xiao, Hongyu; Luo, Yukun; Fei, Xiang; Zheng, Zhixin; Tang, Peifu

    2014-02-01

    To assess the stiffness and thickness of the plantar fascia using shear wave elastography (SWE) in healthy volunteers of different ages and in patients with plantar fasciitis. The bilateral feet of 30 healthy volunteers and 23 patients with plantar fasciitis were examined with SWE. The plantar fascia thickness and elasticity modulus value were measured at the insertion of the calcaneus and at 1 cm from the insertion. The elderly volunteers had a significantly greater plantar fascia thickness measured using conventional ultrasound (P=0.005) and a significantly lower elasticity modulus value than the young volunteers (P=0.000). The patients with fasciitis had a significantly greater plantar fascia thickness (P=0.001) and a lower elasticity modulus value than the elderly volunteers (P=0.000). The elasticity modulus value was significantly lower at the calcaneus insertion than at 1 cm from the insertion in patients with fasciitis (P=0.000) but showed no significantly difference between the two points in the elderly or young volunteers (P=0.172, P=0.126). SWE allows quantitative assessment of the stiffness of the plantar fascia, which decreases with aging and in patients with plantar fasciitis.

  4. Shear wave elastography findings of de Quervain tenosynovitis.

    Science.gov (United States)

    Turkay, Rustu; Inci, Ercan; Aydeniz, Banu; Vural, Meltem

    2017-10-01

    Our aim was to evaluate the feasibility of using shear wave elastography (SWE) to assess first extensor compartment tendons rigidity and its alterations with tenosynovitis. We performed B-mode ultrasound and SWE to total number of 80 participants. All participants were evaluated clinically to call the diagnosis of de Quervain tenosynovitis or to rule out the diagnosis. We composed 2 groups. Group 1 included 40 healthy volunteers (33 females and 7 male participants with ages ranging from 24 to 60 years, median age was 37.5 years) and group 2 had 40 de Quervain patients (32 females and 8 male patients with ages ranging from 25 to 51 years, median age was 34 years). SWE measurements were repeated 3 times and arithmetic average was used for the final SWE value. The median SWE value of healthy group (group 1) was 72kPa and the de Quervain patient group (group 2) was 29kPa. Two groups demonstrated statistically significant difference (p<0.001). The ROC curve analysis was performed and the SWE value of 40.5kPA was calculated as a cut-off value for the diagnosis of de Quervain tenosynovitis with 95% specificity and 85% sensitivity. SWE modality can provide useful data regarding de Quervain tenosynovitis. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Shear Wave Generation and Modeling Ground Motion From a Source Physics Experiment (SPE) Underground Explosion

    Science.gov (United States)

    Pitarka, Arben; Mellors, Robert; Rodgers, Arthur; Vorobiev, Oleg; Ezzedine, Souheil; Matzel, Eric; Ford, Sean; Walter, Bill; Antoun, Tarabay; Wagoner, Jeffery; Pasyanos, Mike; Petersson, Anders; Sjogreen, Bjorn

    2014-05-01

    We investigate the excitation and propagation of far-field (epicentral distance larger than 20 m) seismic waves by analyzing and modeling ground motion from an underground chemical explosion recorded during the Source Physics Experiment (SPE), Nevada. The far-field recorded ground motion is characterized by complex features, such as large azimuthal variations in P- and S-wave amplitudes, as well as substantial energy on the tangential component of motion. Shear wave energy is also observed on the tangential component of the near-field motion (epicentral distance smaller than 20 m) suggesting that shear waves were generated at or very near the source. These features become more pronounced as the waves propagate away from the source. We address the shear wave generation during the explosion by modeling ground motion waveforms recorded in the frequency range 0.01-20 Hz, at distances of up to 1 km. We used a physics based approach that combines hydrodynamic modeling of the source with anelastic modeling of wave propagation in order to separate the contributions from the source and near-source wave scattering on shear motion generation. We found that wave propagation scattering caused by the near-source geological environment, including surface topography, contributes to enhancement of shear waves generated from the explosion source. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-06NA25946/ NST11-NCNS-TM-EXP-PD15.

  6. Contactless Remote Induction of Shear Waves in Soft Tissues Using a Transcranial Magnetic Stimulation Device

    CERN Document Server

    Grasland-Mongrain, Pol; Tang, An; Catheline, Stefan; Cloutier, Guy

    2016-01-01

    This study presents the first observation of shear wave induced remotely within soft tissues. It was performed through the combination of a transcranial magnetic stimulation device and a permanent magnet. A physical model based on Maxwell and Navier equations was developed. Experiments were performed on a cryogel phantom and a chicken breast sample. Using an ultrafast ultrasound scanner, shear waves of respective amplitude of 5 and 0.5 micrometers were observed. Experimental and numerical results were in good agreement. This study constitutes the framework of an alternative shear wave elastography method.

  7. Rescaled Local Interaction Simulation Approach for Shear Wave Propagation Modelling in Magnetic Resonance Elastography

    Science.gov (United States)

    Packo, P.; Staszewski, W. J.; Uhl, T.

    2016-01-01

    Properties of soft biological tissues are increasingly used in medical diagnosis to detect various abnormalities, for example, in liver fibrosis or breast tumors. It is well known that mechanical stiffness of human organs can be obtained from organ responses to shear stress waves through Magnetic Resonance Elastography. The Local Interaction Simulation Approach is proposed for effective modelling of shear wave propagation in soft tissues. The results are validated using experimental data from Magnetic Resonance Elastography. These results show the potential of the method for shear wave propagation modelling in soft tissues. The major advantage of the proposed approach is a significant reduction of computational effort. PMID:26884808

  8. Rescaled Local Interaction Simulation Approach for Shear Wave Propagation Modelling in Magnetic Resonance Elastography

    Directory of Open Access Journals (Sweden)

    Z. Hashemiyan

    2016-01-01

    Full Text Available Properties of soft biological tissues are increasingly used in medical diagnosis to detect various abnormalities, for example, in liver fibrosis or breast tumors. It is well known that mechanical stiffness of human organs can be obtained from organ responses to shear stress waves through Magnetic Resonance Elastography. The Local Interaction Simulation Approach is proposed for effective modelling of shear wave propagation in soft tissues. The results are validated using experimental data from Magnetic Resonance Elastography. These results show the potential of the method for shear wave propagation modelling in soft tissues. The major advantage of the proposed approach is a significant reduction of computational effort.

  9. Ultrasonic Shear Wave Elasticity Imaging (SWEI) Sequencing and Data Processing Using a Verasonics Research Scanner.

    Science.gov (United States)

    Deng, Yufeng; Rouze, Ned C; Palmeri, Mark L; Nightingale, Kathryn R

    2016-10-03

    Ultrasound elasticity imaging has been developed over the last decade to estimate tissue stiffness. Shear wave elasticity imaging (SWEI) quantifies tissue stiffness by measuring the speed of propagating shear waves following acoustic radiation force excitation. This work presents the sequencing and data processing protocols of SWEI using a Verasonics system. The selection of the sequence parameters in a Verasonics programming script is discussed in detail. The data processing pipeline to calculate group shear wave speed (SWS), including tissue motion estimation, data filtering, and SWS estimation is demonstrated. In addition, the procedures for calibration of beam position, scanner timing, and transducer face heating are provided to avoid SWS measurement bias and transducer damage.

  10. Ultrasonic Shear Wave Elasticity Imaging Sequencing and Data Processing Using a Verasonics Research Scanner.

    Science.gov (United States)

    Deng, Yufeng; Rouze, Ned C; Palmeri, Mark L; Nightingale, Kathryn R

    2017-01-01

    Ultrasound elasticity imaging has been developed over the last decade to estimate tissue stiffness. Shear wave elasticity imaging (SWEI) quantifies tissue stiffness by measuring the speed of propagating shear waves following acoustic radiation force excitation. This paper presents the sequencing and data processing protocols of SWEI using a Verasonics system. The selection of the sequence parameters in a Verasonics programming script is discussed in detail. The data processing pipeline to calculate group shear wave speed (SWS), including tissue motion estimation, data filtering, and SWS estimation, is demonstrated. In addition, the procedures for calibration of beam position, scanner timing, and transducer face heating are provided to avoid SWS measurement bias and transducer damage.

  11. Upper Mantle Shear Wave Structure Beneath North America From Multi-mode Surface Wave Tomography

    Science.gov (United States)

    Yoshizawa, K.; Ekström, G.

    2008-12-01

    The upper mantle structure beneath the North American continent has been investigated from measurements of multi-mode phase speeds of Love and Rayleigh waves. To estimate fundamental-mode and higher-mode phase speeds of surface waves from a single seismogram at regional distances, we have employed a method of nonlinear waveform fitting based on a direct model-parameter search using the neighbourhood algorithm (Yoshizawa & Kennett, 2002). The method of the waveform analysis has been fully automated by employing empirical quantitative measures for evaluating the accuracy/reliability of estimated multi-mode phase dispersion curves, and thus it is helpful in processing the dramatically increasing numbers of seismic data from the latest regional networks such as USArray. As a first step toward modeling the regional anisotropic shear-wave velocity structure of the North American upper mantle with extended vertical resolution, we have applied the method to long-period three-component records of seismic stations in North America, which mostly comprise the GSN and US regional networks as well as the permanent and transportable USArray stations distributed by the IRIS DMC. Preliminary multi-mode phase-speed models show large-scale patterns of isotropic heterogeneity, such as a strong velocity contrast between the western and central/eastern United States, which are consistent with the recent global and regional models (e.g., Marone, et al. 2007; Nettles & Dziewonski, 2008). We will also discuss radial anisotropy of shear wave speed beneath North America from multi-mode dispersion measurements of Love and Rayleigh waves.

  12. On the internal gravity waves in the stratified ocean with shear flows

    CERN Document Server

    Bulatov, Vitaly V

    2013-01-01

    In this paper, we consider a fundamental problem of describing the dynamics of internal gravity waves in the stratified ocean with shear flows. We develop an asymptotic representation of the wave fields in terms of the Green's functions. We explore the far field of the internal gravity waves generated by disturbing sources, and propose asymptotic algorithms for calculating its dynamics.

  13. Two-dimensional shear-wave elastography on conventional ultrasound scanners with time-aligned sequential tracking (TAST) and comb-push ultrasound shear elastography (CUSE).

    Science.gov (United States)

    Song, Pengfei; Macdonald, Michael; Behler, Russell; Lanning, Justin; Wang, Michael; Urban, Matthew; Manduca, Armando; Zhao, Heng; Callstrom, Matthew; Alizad, Azra; Greenleaf, James; Chen, Shigao

    2015-02-01

    Two-dimensional shear-wave elastography presents 2-D quantitative shear elasticity maps of tissue, which are clinically useful for both focal lesion detection and diffuse disease diagnosis. Realization of 2-D shear-wave elastography on conventional ultrasound scanners, however, is challenging because of the low tracking pulse-repetition-frequency (PRF) of these systems. Although some clinical and research platforms support software beamforming and plane-wave imaging with high PRF, the majority of current clinical ultrasound systems do not have the software beamforming capability, which presents a critical challenge for translating the 2-D shear-wave elastography technique from laboratory to clinical scanners. To address this challenge, this paper presents a time-aligned sequential tracking (TAST) method for shear-wave tracking on conventional ultrasound scanners. TAST takes advantage of the parallel beamforming capability of conventional systems and realizes high-PRF shear-wave tracking by sequentially firing tracking vectors and aligning shear wave data in the temporal direction. The comb-push ultrasound shear elastography (CUSE) technique was used to simultaneously produce multiple shear wave sources within the field-of-view (FOV) to enhance shear wave SNR and facilitate robust reconstructions of 2-D elasticity maps. TAST and CUSE were realized on a conventional ultrasound scanner. A phantom study showed that the shear-wave speed measurements from the conventional ultrasound scanner were in good agreement with the values measured from other 2-D shear wave imaging technologies. An inclusion phantom study showed that the conventional ultrasound scanner had comparable performance to a state-of-the-art shear-wave imaging system in terms of bias and precision in measuring different sized inclusions. Finally, in vivo case analysis of a breast with a malignant mass, and a liver from a healthy subject demonstrated the feasibility of using the conventional ultrasound

  14. Crust and upper mantle shear wave structure of Northeast Algeria from Rayleigh wave dispersion analysis

    Science.gov (United States)

    Radi, Zohir; Yelles-Chaouche, Abdelkrim; Corchete, Victor; Guettouche, Salim

    2017-09-01

    We resolve the crust and upper mantle structure beneath Northeast Algeria at depths of 0-400 km, using inversion of fundamental mode Rayleigh wave. Our data set consists of 490 earthquakes recorded between 2007 and 2014 by five permanent broadband seismic stations in the study area. Applying a combination of different filtering technics and inversion method shear wave velocities structure were determined as functions of depth. The resolved changes in Vs at 50 km depth are in perfect agreement with crustal thickness estimates, which reflect the study area's orogenic setting, partly overlying the collision zone between the African and Eurasian plates. The inferred Moho discontinuity depths are close to those estimated for other convergent areas. In addition, there is good agreement between our results and variations in orientations of regional seismic anisotropy. At depths of 80-180 km, negative Vs anomalies at station CBBR suggest the existence of a failed subduction slab.

  15. A comparative study of strain and shear-wave elastography in an elasticity phantom

    DEFF Research Database (Denmark)

    Carlsen, Jonathan F.; Pedersen, Malene R; Ewertsen, Caroline

    2015-01-01

    OBJECTIVE. The purpose of this study was to assess the diagnostic accuracy of strain and shear-wave elastography for determining targets of varying stiffness in a phantom. The effect of target diameter on elastographic assessments and the effect of depth on shear-wave velocity were also...... investigated. MATERIALS AND METHODS. We examined 20 targets of varying diameters (2.5-16.7 mm) and stiffnesses (8, 14, 45, and 80 kPa) with a 4-9-MHz linear-array transducer. Targets were evaluated 10 times with three different methods-shear-wave elastography, strain ratio, and strain histogram analysis....... RESULTS. Strain ratio and strain histogram AUCs were higher than the shear-wave velocity AUC (p Strain ratios were superior (p = 0...

  16. Multi-Channel Optical Coherence Elastography Using Relative and Absolute Shear-Wave Time of Flight

    DEFF Research Database (Denmark)

    Elyas, Eli; Grimwood, Alex; Erler, Janine Terra

    2017-01-01

    propagating in a three-dimensional (3D) medium. A needle, embedded in the gel, was excited to vibrate along its long axis and the displacement as a function of time and distance from the needle associated with the resulting shear waves was detected using four M-mode images acquired simultaneously using...... of this technique should ply the field of cellular biology with valuable information with regard to elastic properties of cells and their environment. This paper evaluates the potential to develop such a tool by modifying a commercial optical coherence tomography (OCT) device to measure the speed of shear waves...... a commercial four-channel swept-source OCT system. Shear-wave time of arrival (TOA) was detected by tracking the axial OCT-speckle motion using cross-correlation methods. Shear-wave speed was then calculated from inter-channel differences of TOA for a single burst (the relative TOA method) and compared...

  17. Mantle Shear-Wave Velocity Structure beneath the Hawaiian Hot Spot

    National Research Council Canada - National Science Library

    Cecily J. Wolfe; Sean C. Solomon; Gabi Laske; John A. Collins; Robert S. Detrick; John A. Orcutt; David Bercovici; Erik H. Hauri

    2009-01-01

    .... Three-dimensional images of shear-wave velocity beneath the Hawaiian Islands, obtained from a network of sea-floor and land seismometers, show an upper-mantle low-velocity anomaly that is elongated...

  18. Measurement of Elastic Properties of Tissue by Shear Wave Propagation Generated by Acoustic Radiation Force

    Science.gov (United States)

    Tabaru, Marie; Azuma, Takashi; Hashiba, Kunio

    2010-07-01

    Acoustic radiation force (ARF) imaging has been developed as a novel elastography technology to diagnose hepatic disease and breast cancer. The accuracy of shear wave speed estimation, which is one of the applications of ARF elastography, is studied. The Young's moduli of pig liver and foie gras samples estimated from the shear wave speed were compared with those measured the static Young's modulus measurement. The difference in the two methods was 8%. Distance attenuation characteristics of the shear wave were also studied using finite element method (FEM) analysis. We found that the differences in the axial and lateral beam widths in pressure and ARF are 16 and 9% at F-number=0.9. We studied the relationship between two branch points in distance attenuation characteristics and the shape of ARF. We found that the maximum measurable length to estimate shear wave speed for one ARF excitation was 8 mm.

  19. Diffusing Wave Spectroscopy Used to Study the Influence of Shear on Aggregation

    NARCIS (Netherlands)

    Ruis, H.G.M.; Venema, P.; Linden, van der E.

    2008-01-01

    In this study, diffusing wave spectroscopy (DWS) is used to investigate the effect of shear on a food-related aggregating emulsion. The principle of the method is validated using a nonaggregating, nearly monodisperse latex suspension. In general, with increasing shear rate the diffusive motion of

  20. Computer-aided tumor diagnosis using shear wave breast elastography.

    Science.gov (United States)

    Moon, Woo Kyung; Huang, Yao-Sian; Lee, Yan-Wei; Chang, Shao-Chien; Lo, Chung-Ming; Yang, Min-Chun; Bae, Min Sun; Lee, Su Hyun; Chang, Jung Min; Huang, Chiun-Sheng; Lin, Yi-Ting; Chang, Ruey-Feng

    2017-07-01

    The shear wave elastography (SWE) uses the acoustic radiation force to measure the stiffness of tissues and is less operator dependent in data acquisition compared to strain elastography. However, the reproducibility of the result is still interpreter dependent. The purpose of this study is to develop a computer-aided diagnosis (CAD) method to differentiate benign from malignant breast tumors using SWE images. After applying the level set method to automatically segment the tumor contour and hue-saturation-value color transformation, SWE features including average tissue elasticity, sectional stiffness ratio, and normalized minimum distance for grouped stiffer pixels are calculated. Finally, the performance of CAD based on SWE features are compared with those based on B-mode ultrasound (morphologic and textural) features, and a combination of both feature sets to differentiate benign from malignant tumors. In this study, we use 109 biopsy-proved breast tumors composed of 57 benign and 52 malignant cases. The experimental results show that the sensitivity, specificity, accuracy and the area under the receiver operating characteristic ROC curve (Az value) of CAD are 86.5%, 93.0%, 89.9%, and 0.905 for SWE features whereas they are 86.5%, 80.7%, 83.5% and 0.893 for B-mode features and 90.4%, 94.7%, 92.3% and 0.961 for the combined features. The Az value of combined feature set is significantly higher compared to the B-mode and SWE feature sets (p=0.0296 and p=0.0204, respectively). Our results suggest that the CAD based on SWE features has the potential to improve the performance of classifying breast tumors with US. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Monitoring polymer properties using shear horizontal surface acoustic waves.

    Science.gov (United States)

    Gallimore, Dana Y; Millard, Paul J; Pereira da Cunha, Mauricio

    2009-10-01

    Real-time, nondestructive methods for monitoring polymer film properties are increasingly important in the development and fabrication of modern polymer-containing products. Online testing of industrial polymer films during preparation and conditioning is required to minimize material and energy consumption, improve the product quality, increase the production rate, and reduce the number of product rejects. It is well-known that shear horizontal surface acoustic wave (SH-SAW) propagation is sensitive to mass changes as well as to the mechanical properties of attached materials. In this work, the SH-SAW was used to monitor polymer property changes primarily dictated by variations in the viscoelasticity. The viscoelastic properties of a negative photoresist film were monitored throughout the ultraviolet (UV) light-induced polymer cross-linking process using SH-SAW delay line devices. Changes in the polymer film mass and viscoelasticity caused by UV exposure produced variations in the phase velocity and attenuation of the SH-SAW propagating in the structure. Based on measured polymer-coated delay line scattering transmission responses (S(21)) and the measured polymer layer thickness and density, the viscoelastic constants c(44) and eta(44) were extracted. The polymer thickness was found to decrease 0.6% during UV curing, while variations in the polymer density were determined to be insignificant. Changes of 6% in c(44) and 22% in eta(44) during the cross-linking process were observed, showing the sensitivity of the SH-SAW phase velocity and attenuation to changes in the polymer film viscoelasticity. These results indicate the potential for SH-SAW devices as online monitoring sensors for polymer film processing.

  2. Shear wave elastography and parathyroid adenoma: A new tool for diagnosing parathyroid adenomas.

    Science.gov (United States)

    Azizi, Ghobad; Piper, Kelé; Keller, James M; Mayo, Michelle L; Puett, David; Earp, Karly M; Malchoff, Carl D

    2016-09-01

    This study prospectively determines the shear wave elastography characteristics of parathyroid adenomas using virtual touch imaging quantification, a non-invasive ultrasound based shear wave elastography method. This prospective study examined 57 consecutive patients with biochemically proven primary hyperparathyroidism and solitary parathyroid adenoma identified by ultrasound and confirmed by at least one of the following: surgical resection, positive Technetium-99m Sestamibi Scintigraphy (MIBI) scan, or fine needle aspiration biopsy with positive PTH washout (performed only in MIBI negative patients). Vascularity and shear wave elastography were performed for all patients. Parathyroid adenoma stiffness was measured as shear wave velocity in meters per second. The median (range) pre-surgical value for PTH and calcium were 58pg/mL (19, 427) and 10.8mg/dL (9.5, 12.1), respectively. 37 patients had positive MIBI scan. 20 patients had negative MIBI scan but diagnosis was confirmed with positive PTH washout. 42 patients underwent parathyroidectomy, and an adenoma was confirmed in all. The median (range) shear wave velocity for all parathyroid adenomas enrolled in this study was 2.02m/s (1.53, 2.50). The median (range) shear wave velocity for thyroid tissue was 2.77m/s (1.89, 3.70). The shear wave velocity of the adenomas was independent of adenoma size, serum parathyroid hormone concentration, or plasma parathyroid hormone concentration. Tissue elasticity of parathyroid adenoma is significantly lower than thyroid tissue. B-mode features and distinct vascularity pattern are helpful tools in diagnosing parathyroid adenoma with ultrasound. Shear wave elastography may provide valuable information in diagnosing parathyroid adenoma. Copyright © 2016 The Author(s). Published by Elsevier Ireland Ltd.. All rights reserved.

  3. Two-dimensional Shear Wave Elastography on Conventional Ultrasound Scanners with Time Aligned Sequential Tracking (TAST) and Comb-push Ultrasound Shear Elastography (CUSE)

    Science.gov (United States)

    Song, Pengfei; Macdonald, Michael C.; Behler, Russell H.; Lanning, Justin D.; Wang, Michael H.; Urban, Matthew W.; Manduca, Armando; Zhao, Heng; Callstrom, Matthew R.; Alizad, Azra; Greenleaf, James F.; Chen, Shigao

    2014-01-01

    Two-dimensional (2D) shear wave elastography presents 2D quantitative shear elasticity maps of tissue, which are clinically useful for both focal lesion detection and diffuse disease diagnosis. Realization of 2D shear wave elastography on conventional ultrasound scanners, however, is challenging due to the low tracking pulse-repetition-frequency (PRF) of these systems. While some clinical and research platforms support software beamforming and plane wave imaging with high PRF, the majority of current clinical ultrasound systems do not have the software beamforming capability, which presents a critical challenge for translating the 2D shear wave elastography technique from laboratory to clinical scanners. To address this challenge, this paper presents a Time Aligned Sequential Tracking (TAST) method for shear wave tracking on conventional ultrasound scanners. TAST takes advantage of the parallel beamforming capability of conventional systems and realizes high PRF shear wave tracking by sequentially firing tracking vectors and aligning shear wave data in the temporal direction. The Comb-push Ultrasound Shear Elastography (CUSE) technique was used to simultaneously produce multiple shear wave sources within the field-of-view (FOV) to enhance shear wave signal-to-noise-ratio (SNR) and facilitate robust reconstructions of 2D elasticity maps. TAST and CUSE were realized on a conventional ultrasound scanner (the General Electric LOGIQ E9). A phantom study showed that the shear wave speed measurements from the LOGIQ E9 were in good agreement to the values measured from other 2D shear wave imaging technologies. An inclusion phantom study showed that the LOGIQ E9 had comparable performance to the Aixplorer (Supersonic Imagine) in terms of bias and precision in measuring different sized inclusions. Finally, in vivo case analysis of a breast with a malignant mass, and a liver from a healthy subject demonstrated the feasibility of using the LOGIQ E9 for in vivo 2D shear wave

  4. Stability of an external gravity wave in a stratified basic flow with lateral shear

    OpenAIRE

    Tomizuka, Akira

    2005-01-01

    The author investigates the stability of an external gravity wave progressing horizontally in an inviscid and incompressible stratified basic flow with lateral shear. (1) In the model which basic flow has a Helmholtz velocity profile, there exist no neutral solutions contrary to internal gravity waves. Perturbations are always unstable independent of the coefficient of vertical wave mode m or the wave number k_y. (2) In the model which basic flow is composed of unbounded layers with the centr...

  5. Shear-wave velocity of slope sediments near Hudson Canyon from analysis of ambient noise

    Science.gov (United States)

    Miller, N. C.; Ten Brink, U. S.; Collins, J. A.; McGuire, J. J.; Flores, C. H.

    2014-12-01

    We present new ambient noise data that help constrain the shear strength of marine sediments on the continental slope north of Hudson Canyon on the U.S. Atlantic margin. Sediment shear strength is a key parameter in models of potentially tsunamigenic, submarine slope failures, but shear strength is difficult to measure in situ and is expected to evolve in time with changes in pore pressure. The ambient noise data were recorded by 11 short-period, ocean-bottom seismometers and hydrophones deployed in a ~1 by 1.5 km array for ~6 months on the continental slope. These high frequency (~0.1 - 50 Hz), narrow-aperture data are expected to record noise propagating as interface waves and/or resonating in the upper ~500 m of sediment. Propagation of interface waves is controlled by the shear-wave velocity of the sediment, which we measure by calculating lag-times in cross-correlations of waveforms recorded by pairs of receivers. These measurements of shear-wave velocity will be used to constrain shear strength. The data also appear to record wind-generated noise resonating in layered sediment. We expect this resonance to also be sensitive to shear-wave velocity, and spectral analysis and modeling of harmonics may provide a second constraint on sediment shear strength. Both the correlogram- and spectral-based measurements can be made using hour- to day-long segments of data, enabling us to constrain temporal evolution of shear-wave velocity and potential forcing mechanisms (e.g., tidal and storm loading and submarine groundwater discharge) through the ~6 month deployment.

  6. The Influence of the Shear on the Gravitational Waves in the Early Anisotropic Universe

    CERN Document Server

    Song, Yoogeun

    2016-01-01

    We study the singularity of the congruences for both timelike and null geodesic curves using the expansion of the early anisotropic Bianchi type I Universe. In this paper, we concentrate on the influence of the shear of the timelike and null geodesic congruences in the early Universe. Under some natural conditions, we derive the Raychaudhuri type equation for the expansion and the shear-related equations. Recently, scientists working on the LIGO (Laser Interferometer Gravitational-Wave Observatory) have shown many possibilities to observing the anisotropy of the primordial gravitational wave background radiation. We deduce the evolution equation for the shear that may be responsible for those observational results.

  7. Convectively generated stratospheric gravity waves - The role of mean wind shear

    Science.gov (United States)

    Holton, J. R.; Durran, D.

    1993-01-01

    A two-dimensional numerical simulation of mid-latitude squall lines is used to study the properties of storm-induced stratospheric gravity waves. Owing to the tendency for convective cells to form at the forward edge of a squall line, and then propagate toward the rear, the simulated storms preferentially generate gravity waves that propagate toward the rear of the storm. This anisotropy in gravity wave generation leads to a net vertical transfer of momentum into the stratosphere. Cases with and without stratospheric mean wind shear are compared. In the latter case Doppler shifting of the waves to lower frequencies leads to wave breaking and enhanced wave - mean-flow interaction.

  8. Shear wave elastography in medullary thyroid carcinoma diagnostics

    Directory of Open Access Journals (Sweden)

    Katarzyna Dobruch-Sobczak

    2015-12-01

    Full Text Available Shear wave elastography (SWE is a modern method for the assessment of tissue stiffness. There has been a growing interest in the use of this technique for characterizing thyroid focal lesions, including preoperative diagnostics. Aim: The aim of the study was to assess the clinical usefulness of SWE in medullary thyroid carcinoma (MTC diagnostics. Materials and methods: A total of 169 focal lesions were identifi ed in the study group (139 patients, including 6 MTCs in 4 patients (mean age: 45 years. B-mode ultrasound and SWE were performed using Aixplorer (SuperSonic, Aix-en-Provence, with a 4–15 MHz linear probe. The ultrasound was performed to assess the echogenicity and echostructure of the lesions, their margin, the halo sign, the height/width ratio (H/W ratio, the presence of calcifi cations and the vascularization pattern. This was followed by an analysis of maximum and mean Young’s (E modulus values for MTC (EmaxLR, EmeanLR and the surrounding thyroid tissues (EmaxSR, EmeanSR, as well as mean E-values (EmeanLRz for 2 mm region of interest in the stiffest zone of the lesion. The lesions were subject to pathological and/or cytological evaluation. Results: The B-mode assessment showed that all MTCs were hypoechogenic, with no halo sign, and they contained micro- and/ or macrocalcifi cations. Ill-defi ned lesion margin were found in 4 out of 6 cancers; 4 out of 6 cancers had a H/W ratio > 1. Heterogeneous echostructure and type III vascularity were found in 5 out of 6 lesions. In the SWE, the mean value of EmaxLR for all of the MTCs was 89.5 kPa and (the mean value of EmaxSR for all surrounding tissues was 39.7 kPa Mean values of EmeanLR and EmeanSR were 34.7 kPa and 24.4 kPa, respectively. The mean value of EmeanLRz was 49.2 kPa. Conclusions: SWE showed MTCs as stiffer lesions compared to the surrounding tissues. The lesions were qualifi ed for fi ne needle aspiration biopsy based on B-mode assessment. However, the diagnostic algorithm

  9. Determination of Shear Properties in the Upper Seafloor Using Seismo-acoustic Interface Waves

    Energy Technology Data Exchange (ETDEWEB)

    Frivik, Svein Arne

    1998-12-31

    This thesis develops methods for recording and analysis of seismo-acoustic interface waves for determination of shear wave velocity as a function of depth and includes this in standard refraction seismic surveying. It investigates different techniques for estimation of dispersion characteristics of the interface waves and demonstrates that multi sensor spectral estimation techniques improve the dispersion estimates. The dispersion estimate of the fundamental interface wave mode is used as input to an object function for a model based linearized inversion. The inversion scheme provides an estimate of the shear wave velocity as a function of depth. Three field surveys were performed. Data were acquired with a standard bottom deployed refraction seismic hydrophone array containing 24 or 48 receivers, with a receiver spacing of 2.5 m. Explosive charges were used as sources. The recording time was increased from 0.5 to 8 s, compared to standard refraction seismic surveys. Shear wave velocity and shear modulus estimates were obtained from all the sites. At one of the sites, geotechnically obtained shear wave parameters were available, and a comparison between the two techniques were performed. the result of the comparison is promising and shows the potential of the technique. Although the result of applying the processing scheme to all three data sets is promising, it appears that survey parameters, like source-array spacing, receiver spacing and type of source might have been optimized for better performance. Based on this limitation, a new processing scheme and a new array configuration is proposed for surveys which integrates the recording and processing of both compressional waves and shear waves. 89 refs., 65 refs., 19 tabs.

  10. A Guided Wave Sensor Enabling Simultaneous Wavenumber-Frequency Analysis for Both Lamb and Shear-Horizontal Waves.

    Science.gov (United States)

    Ren, Baiyang; Cho, Hwanjeong; Lissenden, Cliff J

    2017-03-01

    Guided waves in plate-like structures have been widely investigated for structural health monitoring. Lamb waves and shear horizontal (SH) waves, two commonly used types of waves in plates, provide different benefits for the detection of various types of defects and material degradation. However, there are few sensors that can detect both Lamb and SH waves and also resolve their modal content, namely the wavenumber-frequency spectrum. A sensor that can detect both waves is desirable to take full advantage of both types of waves in order to improve sensitivity to different discontinuity geometries. We demonstrate that polyvinylidene difluoride (PVDF) film provides the basis for a multi-element array sensor that detects both Lamb and SH waves and also measures their modal content, i.e., the wavenumber-frequency spectrum.

  11. Prediction of shear wave velocity using empirical correlations and artificial intelligence methods

    Science.gov (United States)

    Maleki, Shahoo; Moradzadeh, Ali; Riabi, Reza Ghavami; Gholami, Raoof; Sadeghzadeh, Farhad

    2014-06-01

    Good understanding of mechanical properties of rock formations is essential during the development and production phases of a hydrocarbon reservoir. Conventionally, these properties are estimated from the petrophysical logs with compression and shear sonic data being the main input to the correlations. This is while in many cases the shear sonic data are not acquired during well logging, which may be for cost saving purposes. In this case, shear wave velocity is estimated using available empirical correlations or artificial intelligent methods proposed during the last few decades. In this paper, petrophysical logs corresponding to a well drilled in southern part of Iran were used to estimate the shear wave velocity using empirical correlations as well as two robust artificial intelligence methods knows as Support Vector Regression (SVR) and Back-Propagation Neural Network (BPNN). Although the results obtained by SVR seem to be reliable, the estimated values are not very precise and considering the importance of shear sonic data as the input into different models, this study suggests acquiring shear sonic data during well logging. It is important to note that the benefits of having reliable shear sonic data for estimation of rock formation mechanical properties will compensate the possible additional costs for acquiring a shear log.

  12. Prediction of shear wave velocity using empirical correlations and artificial intelligence methods

    Directory of Open Access Journals (Sweden)

    Shahoo Maleki

    2014-06-01

    Full Text Available Good understanding of mechanical properties of rock formations is essential during the development and production phases of a hydrocarbon reservoir. Conventionally, these properties are estimated from the petrophysical logs with compression and shear sonic data being the main input to the correlations. This is while in many cases the shear sonic data are not acquired during well logging, which may be for cost saving purposes. In this case, shear wave velocity is estimated using available empirical correlations or artificial intelligent methods proposed during the last few decades. In this paper, petrophysical logs corresponding to a well drilled in southern part of Iran were used to estimate the shear wave velocity using empirical correlations as well as two robust artificial intelligence methods knows as Support Vector Regression (SVR and Back-Propagation Neural Network (BPNN. Although the results obtained by SVR seem to be reliable, the estimated values are not very precise and considering the importance of shear sonic data as the input into different models, this study suggests acquiring shear sonic data during well logging. It is important to note that the benefits of having reliable shear sonic data for estimation of rock formation mechanical properties will compensate the possible additional costs for acquiring a shear log.

  13. Effects of Underground Cavities on the Frequency Spectrum of Seismic Shear Waves

    OpenAIRE

    Lancioni, G.; Bernetti, R.; Quagliarini, E.; Tonti, L.

    2014-01-01

    A numerical method is proposed to study the scattering of seismic shear waves induced by the presence of underground cavities in homogeneous soils. The method is based on the superposition of two solutions: the solution of the free-wave propagation problem in a uniform half-space, easily determined analytically, and the solution of the wave scattering problem due to the cave presence, evaluated numerically by means of an ad hoc code implemented by using the ANSYS Parametric ...

  14. Spatial bandwidth enlargement and field enhancement of shear horizontal waves in finite graded piezoelectric layered media

    KAUST Repository

    Xu, Yanlong

    2015-09-01

    Shear horizontal (SH) wave propagation in finite graded piezoelectric layered media is investigated by transfer matrix method. Different from the previous studies on SH wave propagation in completely periodic layered media, calculations on band structure and transmission in this paper show that the graded layered media possess very large band gaps. Harmonic wave simulation by finite element method (FEM) confirms that the reason of bandwidth enlargement is that waves within the band gap ranges are spatially enhanced and stopped by the corresponding graded units. The study suggests that the graded structure possesses the property of manipulating elastic waves spatially, which shows potential applications in strengthening energy trapping and harvesting. © 2015.

  15. Effect of gas on shear wave velocity of sandy soils densified with explosives

    Directory of Open Access Journals (Sweden)

    Carlos Alberto Vega-Posada

    2017-01-01

    Full Text Available Context: Shear wave velocity tests (Vs are commonly used to estimate the increase in resistance of explosive densified soils. In some historical cases, Vs tests performed after the soil improvement process do not show a significant increase in soil resistance, even though the soil surface sits more than 0.50 m. It is believed that this response is due to the presence of gas on the soil mass. Method: This paper presents the results of monotonic triaxial tests performed on samples of dense gaseous sandy soils to evaluate the effect of occluded gas on the response to the shear wave velocity in densified sands with explosives. For sand sampling, it was collected from a loose sand deposit located in South Carolina, USA. These samples were densified in-situ with explosives, and consolidated to the in-situ effective stress conditions, which are considered representative in the conditions of effort at the moment of the densification with explosives. Results: Triaxial tests were performed under global non-drained conditions. The results of these tests show that gas causes the shear wave velocity values obtained for the gaseous sands to approximate the shear wave velocity values obtained in the saturated samples tested under drained conditions. In addition, behavior tends to be more pronounced as the soil is denser. Conclusions: These response may offer some insights as to why the shear wave velocity does not increase significantly in densified soils with explosives, even though the density increases considerably.

  16. Shear wave splitting observations and implications on stress regimes in the Los Angeles basin, California

    Science.gov (United States)

    Li, Yong-Gang

    1996-06-01

    A systematic analysis of three-component seismograms recorded at 15 stations from earthquakes occurring at depths of 5 to 18 km beneath the Los Angeles basin and adjacent areas during the period between 1988 and 1994 shows 20 to 160 ms shear wave splitting. Shallow events exhibit little splitting, while deeper events show progressively greater splitting with depth. The preferred polarization direction of the fast shear wave is nearly N-S, consistent with the direction of the regional maximum horizontal compressive stress but independent of the azimuth between the event and station. We interpret that the shear wave splitting is caused by fluid-filled crustal microcracks and macrofractures aligned in the N-S direction. The shear wave splitting observations of 2.8 to 7.8 ms/km can be explained in terms of an anisotropic crust containing vertical cracks with the apparent crack density of 0.023-0.08. On a regional basis, the crack density may vary from station to station, but we find that the apparent crack density in the strike-slip region of the Newport-Inglewood fault and the Whittier fault is higher than in the reverse-thrusting Santa Monica Mountains and Palos Verdes Hills. No systematic change of shear wave splitting in the Los Angeles basin is found in this study.

  17. Lower hybrid waves instability in a velocity–sheared inhomogenous ...

    African Journals Online (AJOL)

    An electrostatic linear kinetic analysis of velocity-sheared inhomogeneous charged dust streaming parallel to a magnetic field in plasma is presented. Excited mode and the growth rates are derived in the lower hybrid-like mode regime, with collisional effects included. In the case where the drift velocity u is very small the ...

  18. Ultrasound Shear Wave Simulation of Breast Tumor Using Nonlinear Tissue Elasticity

    OpenAIRE

    Dae Woo Park

    2016-01-01

    Shear wave elasticity imaging (SWEI) can assess the elasticity of tissues, but the shear modulus estimated in SWEI is often less sensitive to a subtle change of the stiffness that produces only small mechanical contrast to the background tissues. Because most soft tissues exhibit mechanical nonlinearity that differs in tissue types, mechanical contrast can be enhanced if the tissues are compressed. In this study, a finite element- (FE-) based simulation was performed for a breast tissue model...

  19. Effect of Calcifications on Breast Ultrasound Shear Wave Elastography: An Investigational Study

    OpenAIRE

    Adriana Gregory; Mohammad Mehrmohammadi; Max Denis; Mahdi Bayat; Stan, Daniela L.; Mostafa Fatemi; Azra Alizad

    2015-01-01

    Purpose To investigate the effects of macrocalcifications and clustered microcalcifications associated with benign breast masses on shear wave elastography (SWE). Methods SuperSonic Imagine (SSI) and comb-push ultrasound shear elastography (CUSE) were performed on three sets of phantoms to investigate how calcifications of different sizes and distributions influence measured elasticity. To demonstrate the effect in vivo, three female patients with benign breast masses associated with mammogra...

  20. Shear wave sonoelastography of skeletal muscle: basic principles, biomechanical concepts, clinical applications, and future perspectives.

    Science.gov (United States)

    Creze, Maud; Nordez, Antoine; Soubeyrand, Marc; Rocher, Laurence; Maître, Xavier; Bellin, Marie-France

    2017-12-09

    Imaging plays an important role in the diagnosis and therapeutic response evaluation of muscular diseases. However, one important limitation is its incapacity to assess the in vivo biomechanical properties of the muscles. The emerging shear wave sonoelastography technique offers a quantifiable spatial representation of the viscoelastic characteristics of skeletal muscle. Elastography is a non-invasive tool used to analyze the physiologic and biomechanical properties of muscles in healthy and pathologic conditions. However, radiologists need to familiarize themselves with the muscular biomechanical concepts and technical challenges of shear wave elastography. This review introduces the basic principles of muscle shear wave elastography, analyzes the factors that can influence measurements and provides an overview of its potential clinical applications in the field of muscular diseases.

  1. Shear Wave Velocity for Evaluation of State of Cohesionless Soils with Fines

    Science.gov (United States)

    Lipiński, Mirosław J.; Wdowska, Małgorzata K.; Jaroń, Łukasz

    2017-10-01

    The paper concerns evaluation of cohesionless soils containing fines. In clean sands, state of soil is usually quantified by relative density DR with use of field techniques like static or dynamic probes. However, in cohesionless soils containing considerable amount of fines, relative density alone, which is based solely on void ratio values, is not representative. This results from the fact that in case of cohesionless soil there is no unique intrinsic compressibility line, like it is in case of cohesive soils. Thus state of soil depends not only on void ratio but also state of stress. For this reason it is necessary to look for an alternative means to quantify state of soils with fines. The paper concerns possibility of evaluation of state of soil containing various amount of fines on the basis of shear wave velocity measurement. The idea rests on the fact that void ratio and state of stress are the major factors which contribute to a state of soil and shear wave velocity as well. When measured shear wave velocities are normalised with respect to stresses the resulting values might be strictly correlated to void ratio. To validate this approach, an experimental test programme (based on series of sophisticated triaxial tests) was carried out on four kinds of sandy material containing various amount of fines up to 60%. The experimental data made possible to establish basic correlation between soil states and shear wave velocity for each kind of soil. Normalized shear wave velocity was compared with void ratio and state parameter as well. The obtained results revealed that determination of void ratio on the basis of shear wave velocity in a certain range of fines can be much more adequate than for clean sands. However, if the fines content exceeds certain value, the obtained correlation is no longer as good.

  2. Multi-source and multi-directional shear wave generation with intersecting steered ultrasound push beams.

    Science.gov (United States)

    Nabavizadeh, Alireza; Song, Pengfei; Chen, Shigao; Greenleaf, James F; Urban, Matthew W

    2015-04-01

    Elasticity imaging is becoming established as a means of assisting in diagnosis of certain diseases. Shear wave-based methods have been developed to perform elasticity measurements in soft tissue. Comb-push ultrasound shear elastography (CUSE) is one of these methods that apply acoustic radiation force to induce the shear wave in soft tissues. CUSE uses multiple ultrasound beams that are transmitted simultaneously to induce multiple shear wave sources into the tissue, with improved shear wave SNR and increased shear wave imaging frame rate. We propose a novel method that uses steered push beams (SPB) that can be applied for beam formation for shear wave generation. In CUSE beamforming, either unfocused or focused beams are used to create the propagating shear waves. In SPB methods we use unfocused beams that are steered at specific angles. The interaction of these steered beams causes shear waves to be generated in more of a random nature than in CUSE. The beams are typically steered over a range of 3 to 7° and can either be steered to the left (-θ) or right (+θ).We performed simulations of 100 configurations using Field II and found the best configurations based on spatial distribution of peaks in the resulting intensity field. The best candidates were ones with a higher number of the intensity peaks distributed over all depths in the simulated beamformed results. Then these optimal configurations were applied on a homogeneous phantom and two different phantoms with inclusions. In one of the inhomogeneous phantoms we studied two spherical inclusions with 10 and 20 mm diameters, and in the other phantom we studied cylindrical inclusions with diameters ranging from 2.53 to 16.67 mm. We compared these results with those obtained using conventional CUSE with unfocused and focused beams. The mean and standard deviation of the resulting shear wave speeds were used to evaluate the accuracy of the reconstructions by examining bias with nominal values for the phantoms

  3. Wave excitation by nonlinear coupling among shear Alfvén waves in a mirror-confined plasma

    Energy Technology Data Exchange (ETDEWEB)

    Ikezoe, R., E-mail: ikezoe@prc.tsukuba.ac.jp; Ichimura, M.; Okada, T.; Hirata, M.; Yokoyama, T.; Iwamoto, Y.; Sumida, S.; Jang, S.; Takeyama, K.; Yoshikawa, M.; Kohagura, J.; Shima, Y.; Wang, X. [Plasma Research Center, University of Tsukuba, Tsukuba 305-8577 (Japan)

    2015-09-15

    A shear Alfvén wave at slightly below the ion-cyclotron frequency overcomes the ion-cyclotron damping and grows because of the strong anisotropy of the ion temperature in the magnetic mirror configuration, and is called the Alfvén ion-cyclotron (AIC) wave. Density fluctuations caused by the AIC waves and the ion-cyclotron range of frequencies (ICRF) waves used for ion heating have been detected using a reflectometer in a wide radial region of the GAMMA 10 tandem mirror plasma. Various wave-wave couplings are clearly observed in the density fluctuations in the interior of the plasma, but these couplings are not so clear in the magnetic fluctuations at the plasma edge when measured using a pick-up coil. A radial dependence of the nonlinearity is found, particularly in waves with the difference frequencies of the AIC waves; bispectral analysis shows that such wave-wave coupling is significant near the core, but is not so evident at the periphery. In contrast, nonlinear coupling with the low-frequency background turbulence is quite distinct at the periphery. Nonlinear coupling associated with the AIC waves may play a significant role in the beta- and anisotropy-limits of a mirror-confined plasma through decay of the ICRF heating power and degradation of the plasma confinement by nonlinearly generated waves.

  4. Turbulence generation by mountain wave breaking in flows with directional wind shear

    Science.gov (United States)

    Vittoria Guarino, Maria; Teixeira, Miguel A. C.

    2016-04-01

    In this study, wave breaking, and the potential for the generation of turbulence in the atmosphere, is investigated using high-resolution numerical simulations of idealized atmospheric flows with directional wind shear over a three-dimensional isolated mountain. These simulations, which use the WRF-ARW model, differ in degree of flow non-linearity and directional wind shear intensity, quantified through the dimensionless mountain height and the Richardson number of the incoming flow. The aim is to predict wave breaking occurrence based on large-scale variables. The simulation results have been used to produce a regime diagram representing a description of wave breaking behavior in parameter space. By selecting flow overturning occurrence as a discriminating factor, it was possible to split the regime diagram in two sub-regions representing: a non-wave breaking regime and a wave breaking regime. The regime diagram shows that in the presence of directional shear wave breaking may occur over lower mountains that in a constant-wind case. When mountain waves break, the associated convective instability can lead to turbulence generation (known as Clear Air Turbulence or CAT in a non-cloudy atmosphere), thus, regions within the simulation domain where wave breaking and potential development of CAT are expected have been identified. The extent of these regions is variable and increases with the background shear intensity. In contrast with constant-wind flows, where wave breaking occurs in the stream-wise direction aligned with the mountain, for the helical wind profiles considered in this study as prototypes of flows with directional wind shear, flow overturning regions have a more three-dimensional geometry. The analysis of the model outputs, supported by theoretical arguments, suggest the existence of a link between wave breaking and the relative orientation of the incoming wind vector and the horizontal velocity perturbation vector. In particular, in a wave breaking

  5. Shear Wave Elastographic Alterations in the Kidney After Extracorporeal Shock Wave Lithotripsy.

    Science.gov (United States)

    Turkay, Rustu; Inci, Ercan; Bas, Derya; Atar, Arda

    2017-10-13

    Extracorporeal shock wave lithotripsy (ESWL) is a method used frequently for the treatment of renal stone disease. Although its safety is proven, there are still concerns about its unwanted effects on kidneys. In this prospective study, we aimed to evaluate renal tissue alterations with shear wave elastography (SWE) after ESWL. We also studied the correlation between SWE and resistive index (RI) changes. The study included 59 patients who underwent ESWL treatment for renal stone disease. We performed SWE and color Doppler ultrasonography to calculate SWE and RI values before, 1 hour after, and 1 week after lithotripsy treatment. A binary comparison was performed by the Bonferroni test. The correlation between SWE and RI values was evaluated by a Pearson correlation analysis. The patients included 26 women (44.1%) and 33 men (55.9%). Their ages ranged from 20 to 65 years (mean ± SD, 45.0 ± 1.1 years). Stone diameters ranged from 7 to 19 mm (mean, 13.0 ± 0.5 mm). There was a significant difference in SWE values before and 1 hour after lithotripsy treatment (P = .001; P  .99; P > .05). Resistive index values increased significantly 1 hour after lithotripsy treatment and returned to prelithotripsy values 1 week after treatment. In the correlation analysis, SWE and RI values were not correlated. Measurements of alterations in SWE values after ESWL can provide useful information about renal tissue injury. © 2017 by the American Institute of Ultrasound in Medicine.

  6. Excitation of instability waves in a two-dimensional shear layer by sound

    Science.gov (United States)

    Tam, C. K. W.

    1978-01-01

    The excitation of instability waves in a plane compressible shear layer by sound waves is studied. The problem is formulated mathematically as an inhomogeneous boundary-value problem. A general solution for abitrary incident sound wave is found by first constructing the Green's function of the problem. Numerical values of the coupling constants between incident sound waves and excited instability waves for a range of flow Mach number are calculated. The effect of the angle of incidence in the case of a beam of acoustic waves is analyzed. It is found that for moderate subsonic Mach numbers a narrow beam aiming at an angle between 50 to 80 deg to the flow direction is most effective in exciting instability waves.

  7. Shear-horizontal surface waves on piezoelectric ceramics with depolarized surface layer.

    Science.gov (United States)

    Kielczynski, P J; Pajewski, W; Szalewski, M

    1989-01-01

    Theoretical analysis and numerical results describing the propagation of SH (shear-horizontal) surface waves on piezoelectric ceramics with a depolarized surface layer are described. SH surface waves propagating in piezoelectric ceramics with a depolarized surface layer are shown to be a mixture of the Bleustein-Gulyaev surface wave, electrical potential, and the Love surface-wave mechanical displacement. Depolarization of the surface layer in piezoelectric ceramics produces strong dispersion and a multimode structure of the SH surface wave. The penetration depth of the SH surface waves propagating on an electrically free surface of a piezoelectric ceramic with a depolarized surface layer can be significantly smaller than that of the Bleustein-Gulyaev surface waves propagating on a free piezoelectric half-space. It is concluded that piezoelectric ceramics with a depolarized surface layer can be used in hybrid piezoelectric semiconductor convolvers of reduced size.

  8. Second-harmonic generation in shear wave beams with different polarizations

    Energy Technology Data Exchange (ETDEWEB)

    Spratt, Kyle S., E-mail: sprattkyle@gmail.com; Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.; Hamilton, Mark F. [Applied Research Laboratories, The University of Texas at Austin, P. O. Box 8029, Austin, Texas 78713–8029, US (United States)

    2015-10-28

    A coupled pair of nonlinear parabolic equations was derived by Zabolotskaya [1] that model the transverse components of the particle motion in a collimated shear wave beam propagating in an isotropic elastic solid. Like the KZK equation, the parabolic equation for shear wave beams accounts consistently for the leading order effects of diffraction, viscosity and nonlinearity. The nonlinearity includes a cubic nonlinear term that is equivalent to that present in plane shear waves, as well as a quadratic nonlinear term that is unique to diffracting beams. The work by Wochner et al. [2] considered shear wave beams with translational polarizations (linear, circular and elliptical), wherein second-order nonlinear effects vanish and the leading order nonlinear effect is third-harmonic generation by the cubic nonlinearity. The purpose of the current work is to investigate the quadratic nonlinear term present in the parabolic equation for shear wave beams by considering second-harmonic generation in Gaussian beams as a second-order nonlinear effect using standard perturbation theory. In order for second-order nonlinear effects to be present, a broader class of source polarizations must be considered that includes not only the familiar translational polarizations, but also polarizations accounting for stretching, shearing and rotation of the source plane. It is found that the polarization of the second harmonic generated by the quadratic nonlinearity is not necessarily the same as the polarization of the source-frequency beam, and we are able to derive a general analytic solution for second-harmonic generation from a Gaussian source condition that gives explicitly the relationship between the polarization of the source-frequency beam and the polarization of the second harmonic.

  9. The instability of counter-propagating kernel gravity waves in a constant shear flow

    CERN Document Server

    Umurhan, O M; Harnik, N; Lott, F

    2007-01-01

    The mechanism describing the recently developed notion of kernel gravity waves (KGWs) is reviewed and such structures are employed to interpret the unstable dynamics of an example stratified plane parallel shear flow. This flow has constant vertical shear, is infinite in the vertical extent, and characterized by two density jumps of equal magnitude each decreasing successively with height, in which the jumps are located symmetrically away from the midplane of the system. We find that for a suitably defined bulk-Richardson number there exists a band of horizontal wavenumbers which exhibits normal-mode instability. The instability mechanism closely parallels the mechanism responsible for the instability seen in the problem of counter-propagating Rossby waves. In this problem the instability arises out of the interaction of counter-propagating gravity waves. We argue that the instability meets the Hayashi-Young criterion for wave instability. We also argue that the instability is the simplest one that can arise ...

  10. 2D instabilities of surface gravity waves on a linear shear current

    Science.gov (United States)

    Francius, Marc; Kharif, Christian

    2016-04-01

    Periodic 2D surface water waves propagating steadily on a rotational current have been studied by many authors (see [1] and references therein). Although the recent important theoretical developments have confirmed that periodic waves can exist over flows with arbitrary vorticity, their stability and their nonlinear evolution have not been much studied extensively so far. In fact, even in the rather simple case of uniform vorticity (linear shear), few papers have been published on the effect of a vertical shear current on the side-band instability of a uniform wave train over finite depth. In most of these studies [2-5], asymptotic expansions and multiple scales method have been used to obtain envelope evolution equations, which allow eventually to formulate a condition of (linear) instability to long modulational perturbations. It is noted here that this instability is often referred in the literature as the Benjamin-Feir or modulational instability. In the present study, we consider the linear stability of finite amplitude two-dimensional, periodic water waves propagating steadily on the free surface of a fluid with constant vorticity and finite depth. First, the steadily propagating surface waves are computed with steepness up to very close to the highest, using a Fourier series expansions and a collocation method, which constitutes a simple extension of Fenton's method [6] to the cases with a linear shear current. Then, the linear stability of these permanent waves to infinitesimal 2D perturbations is developed from the fully nonlinear equations in the framework of normal modes analysis. This linear stability analysis is an extension of [7] to the case of waves in the presence of a linear shear current and permits the determination of the dominant instability as a function of depth and vorticity for a given steepness. The numerical results are used to assess the accuracy of the vor-NLS equation derived in [5] for the characteristics of modulational

  11. Drift wave shear damping annulment due to parametric coupling and magnetic field variation

    Energy Technology Data Exchange (ETDEWEB)

    Davydova, T.A. [Inst. for Nuclear Research, Ukrainian Academy of Sciences, Kiev (Ukraine); Jovanovic, D.; Vranjes, J. [Inst. of Physics, Belgrade (Yugoslavia); Weiland, J. [Inst. for Electromagnetic Field Theory, Chalmers Univ. of Technology and EURATOM-NFR Association, Gothenburg (Sweden)

    1993-12-31

    Nonlinear suppression of the drift wave shear damping by the simultaneous action of a strong standing pump wave and of the magnetic field variation along the magnetic field line is studied using a version of the Hasegawa-Mima equation. The threshold for the parametric destabilization is calculated as a function of the plasma parameters. Destabilization occurs due to the elimination of the energy convection towards the dissipative layer, by both the linear toroidal coupling and nonlinear parametric coupling.

  12. Drift wave shear damping annulment due to parametric coupling and magnetic field variation

    Science.gov (United States)

    Davydova, T. A.; Jovanović, D.; Vranješ, J.; Weiland, J.

    1993-11-01

    Nonlinear suppression of the drift wave shear damping by the simultaneous action of a strong standing pump wave, and of the magnetic field variation along the magnetic field line is studied using a version of the Hasegawa-Mima equation. The threshold for the parametric destabilization is calculated as a function of the plasma parameters. Destabilization occurs due to the elimination of the energy convection towards the dissipative layer, by both the linear toroidal coupling and nonlinear parametric coupling.

  13. Reliable protocol for shear wave elastography of lower limb muscles at rest and during passive stretching.

    Science.gov (United States)

    Dubois, Guillaume; Kheireddine, Walid; Vergari, Claudio; Bonneau, Dominique; Thoreux, Patricia; Rouch, Philippe; Tanter, Mickael; Gennisson, Jean-Luc; Skalli, Wafa

    2015-09-01

    Development of shear wave elastography gave access to non-invasive muscle stiffness assessment in vivo. The aim of the present study was to define a measurement protocol to be used in clinical routine for quantifying the shear modulus of lower limb muscles. Four positions were defined to evaluate shear modulus in 10 healthy subjects: parallel to the fibers, in the anterior and posterior aspects of the lower limb, at rest and during passive stretching. Reliability was first evaluated on two muscles by three operators; these measurements were repeated six times. Then, measurement reliability was compared in 11 muscles by two operators; these measurements were repeated three times. Reproducibility of shear modulus was 0.48 kPa and repeatability was 0.41 kPa, with all muscles pooled. Position did not significantly influence reliability. Shear wave elastography appeared to be an appropriate and reliable tool to evaluate the shear modulus of lower limb muscles with the proposed protocol. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  14. Added value of Virtual Touch IQ shear wave elastography in the ultrasound assessment of breast lesions

    Energy Technology Data Exchange (ETDEWEB)

    Ianculescu, Victor; Ciolovan, Laura Maria [Radiology Department, Gustave Roussy, Villejuif (France); Dunant, Ariane [Department of Statistics, Gustave Roussy, Villejuif (France); Vielh, Philippe [Department of Biopathology, Gustave Roussy, Villejuif (France); Mazouni, Chafika [Department of Surgery, Gustave Roussy, Villejuif (France); Delaloge, Suzette [Department of Oncology, Gustave Roussy, Villejuif (France); Dromain, Clarisse [Radiology Department, Gustave Roussy, Villejuif (France); Blidaru, Alexandru [Department of Surgery, Bucharest Institute of Oncology, Bucharest (Romania); Balleyguier, Corinne, E-mail: corinne.balleyguier@gustaveroussy.fr [Radiology Department, Gustave Roussy, Villejuif (France); UMR 8081, IR4M, Paris-Sud University, 91405 Orsay (France)

    2014-05-15

    Purpose: To determine the diagnostic performance of Acoustic Radiation Force Impulse (ARFI) Virtual Touch IQ shear wave elastography in the discrimination of benign and malignant breast lesions. Materials and methods: Conventional B-mode and elasticity imaging were used to evaluate 110 breast lesions. Elastographic assessment of breast tissue abnormalities was done using a shear wave based technique, Virtual Touch IQ (VTIQ), implemented on a Siemens Acuson S3000 ultrasound machine. Tissue mechanical properties were interpreted as two-dimensional qualitative and quantitative colour maps displaying relative shear wave velocity. Wave speed measurements in m/s were possible at operator defined regions of interest. The pathologic diagnosis was established on samples obtained by ultrasound guided core biopsy or fine needle aspiration. Results: BIRADS based B-mode evaluation of the 48 benign and 62 malignant lesions achieved 92% sensitivity and 62.5% specificity. Subsequently performed VTIQ elastography relying on visual interpretation of the colour overlay displaying relative shear wave velocities managed similar standalone diagnostic performance with 92% sensitivity and 64.6% specificity. Lesion and surrounding tissue shear wave speed values were calculated and a significant difference was found between the benign and malignant populations (Mann–Whitney U test, p < 0.0001). By selecting a lesion cut-off value of 3.31 m/s we achieved 80.4% sensitivity and 73% specificity. Applying this threshold only to BIRADS 4a masses, we reached overall levels of 92% sensitivity and 72.9% specificity. Conclusion: VTIQ qualitative and quantitative elastography has the potential to further characterise B-mode detected breast lesions, increasing specificity and reducing the number of unnecessary biopsies.

  15. Development of a low frequency shear horizontal piezoelectric transducer for the generation of plane SH waves

    Science.gov (United States)

    Boivin, Guillaume; Viens, Martin; Belanger, Pierre

    2016-02-01

    The shear horizontal guided wave fundamental mode (SH0) has the particularity of being the only non-dispersive plate guided wave mode. This characteristic makes this ultrasonic guided wave mode very attractive in non-destructive testing, facilitating signal processing for long range inspections. It is, however, difficult to generate only a single guided wave mode when using piezoelectric transduction. This work aims to develop a piezoelectric transducer capable of generating a virtually pure plane zeroth order shear horizontal wave. The chosen material was the PZT-5H for its dominant d15 piezoelectric constant, which makes it a perfect candidate for SH-wave generation. The transducer dimensions were optimised using an analytical model based on the Huygens' principle of superposition and the dipole pattern of a shear point source. A 3D multiphysics finite element model was then used to validate the analytical model results. Experimental validation was finally conducted with a laser Doppler vibrometer (LDV) system. Excellent agreement between the analytical model, finite element model and experimental validation was seen.

  16. Single-sided Marchenko focusing of compressional and shear waves

    NARCIS (Netherlands)

    Wapenaar, C.P.A.

    2014-01-01

    In time-reversal acoustics, waves recorded at the boundary of a strongly scattering medium are sent back into the medium to focus at the original source position. This requires that the medium can be accessed from all sides. We discuss a focusing method for media that can be accessed from one side

  17. Shear wave velocity structure of the Bushveld Complex, South Africa

    CSIR Research Space (South Africa)

    Kgaswane, EM

    2012-07-01

    Full Text Available The structure of the crust in the environs of the Bushveld Complex has been investigated by jointly inverting high-frequency teleseismic receiver functions and 2–60 s period Rayleigh wave group velocities for 16 broadband seismic stations located...

  18. Ion waves driven by shear flow in a relativistic degenerate ...

    Indian Academy of Sciences (India)

    Abstract. We investigate the existence and propagation of low-frequency (in comparison to ion cyclotron frequency) electrostatic ion waves in highly dense inhomogeneous astrophysical mag- netoplasma comprising relativistic degenerate electrons and non-degenerate ions. The dispersion equation is obtained by Fourier ...

  19. Estimation of near-surface shear-wave velocities and quality factors using multichannel analysis of surface-wave methods

    Science.gov (United States)

    Xia, Jianghai

    2014-04-01

    This overview article gives a picture of multichannel analysis of high-frequency surface (Rayleigh and Love) waves developed mainly by research scientists at the Kansas Geological Survey, the University of Kansas and China University of Geosciences (Wuhan) during the last eighteen years by discussing dispersion imaging techniques, inversion systems, and real-world examples. Shear (S)-wave velocities of near-surface materials can be derived from inverting the dispersive phase velocities of high-frequency surface waves. Multichannel analysis of surface waves—MASW used phase information of high-frequency Rayleigh waves recorded on vertical component geophones to determine near-surface S-wave velocities. The differences between MASW results and direct borehole measurements are approximately 15% or less and random. Studies show that inversion with higher modes and the fundamental mode simultaneously can increase model resolution and an investigation depth. Multichannel analysis of Love waves—MALW used phase information of high-frequency Love waves recorded on horizontal (perpendicular to the direction of wave propagation) component geophones to determine S-wave velocities of shallow materials. Because of independence of compressional (P)-wave velocity, the MALW method has some attractive advantages, such as 1) Love-wave dispersion curves are simpler than Rayleigh wave's; 2) dispersion images of Love-wave energy have a higher signal to noise ratio and more focused than those generated from Rayleigh waves; and 3) inversion of Love-wave dispersion curves is less dependent on initial models and more stable than Rayleigh waves.

  20. Assessment of biopsy-proven liver fibrosis by 2D-shear wave elastography

    DEFF Research Database (Denmark)

    Herrmann, Eva; de Lédinghen, Victor; Cassinotto, Christophe

    2017-01-01

    BACKGROUND AND AIMS: 2D shear wave elastography (2D-SWE) has proven to be efficient for the evaluation of liver fibrosis in small to moderate size clinical trials. We aimed at running a larger scale meta-analysis of individual data. METHODS: Centers which have worked with Aixplorer ultrasound equ...

  1. Measurements of upper mantle shear wave anisotropy from a permanent network in southern Mexico

    NARCIS (Netherlands)

    van Benthem, S.A.C.; Valenzuela, R.W.; Ponce, G.J.

    2013-01-01

    Upper mantle shear wave anisotropy under stations in southern Mexico was measured using records of SKS phases. Fast polarization directions where the Cocos plate subducts subhorizontally are oriented in the direction of the relative motion between the Cocos and North American plates, and are

  2. A Shear-Wave Seismic System to Look Ahead of a Tunnel Boring Machine

    NARCIS (Netherlands)

    Bharadwaj, Pawan; Drijkoningen, G.G.; Mulder, W.A.; Tscharner, Thomas; Jenneskens, Rob

    2016-01-01

    The Earth’s properties, composition and structure ahead of a tunnel boring machine (TBM) should be mapped for hazard assessment during excavation. We study the use of seismic-exploration techniques for this purpose. We focus on a seismic system for soft soils, where shear waves are better and easier

  3. An integrated shear-wave velocity model for the Groningen gas field, The Netherlands

    NARCIS (Netherlands)

    Kruiver, Pauline P.; van Dedem, Ewoud; Romijn, Remco; de Lange, Ger; Korff, M.; Stafleu, Jan; Gunnink, Jan L.; Rodriguez-Marek, Adrian; Bommer, Julian J.; van Elk, Jan; Doornhof, Dirk

    2017-01-01

    A regional shear-wave velocity (VS) model has been developed for the Groningen gas field in the Netherlands as the basis for seismic microzonation of an area of more than 1000 km2. The VS model, extending to a depth of almost 1 km, is an essential input to the

  4. Reproducibility of shear wave elastography (SWE) in patients with chronic liver disease.

    Science.gov (United States)

    Mancini, Marcello; Salomone Megna, Angelo; Ragucci, Monica; De Luca, Massimo; Marino Marsilia, Giuseppina; Nardone, Gerardo; Coccoli, Pietro; Prinster, Anna; Mannelli, Lorenzo; Vergara, Emilia; Monti, Serena; Liuzzi, Raffaele; Incoronato, Mariarosaria

    2017-01-01

    The presence of significant fibrosis is an indicator for liver disease staging and prognosis. The aim of the study was to determine reproducibility of real-time shear wave elastography using a hepatic biopsy as the reference standard to identify patients with chronic liver disease. Forty patients with chronic liver disease and 12 normal subjects received shear wave elastography performed by skilled operators. Interoperator reproducibility was studied in 29 patients. Fibrosis was evaluated using the Metavir score. The median and range shear wave elastography values in chronic liver disease subjects were 6.15 kPa and 3.14-16.7 kPa and were 4.49 kPa and 2.92-7.32 kPa in normal subjects, respectively. With respect to fibrosis detected by liver biopsy, shear wave elastography did not change significantly between F0 and F1 (p = 0.334), F1 and F2 (p = 0.611), or F3 and F4 (0.327); a significant difference was observed between the F0-F2 and F3-F4 groups (p = 0.002). SWE also correlated with inflammatory activity (Rs = 0.443, p = 0.0023) and ALT levels (Rs = 0.287, p = 0.0804). Age, sex and body mass index did not affect shear wave elastography measurements. Using receiver operator characteristic curves, two threshold values for shear wave elastography were identified: 5.62 kPa for patients with fibrosis (≥F2; sensitivity 80%, specificity 69.4%, and accuracy 77%) and 7.04 kPa for patients with severe fibrosis (≥F3; sensitivity 88.9%, specificity 81%, and accuracy 89%). Overall interobserver agreement was excellent and was analysed using an interclass correlation coefficient (0.94; CI 0.87-0.97).This study shows that shear wave elastography executed by skilled operators can be performed on almost all chronic liver disease patients with high reproducibility. It is not influenced by age, sex or body mass index, identifies severely fibrotic patients and is also related to inflammatory activity.

  5. Reproducibility of shear wave elastography (SWE) in patients with chronic liver disease

    Science.gov (United States)

    Salomone Megna, Angelo; Ragucci, Monica; De Luca, Massimo; Marino Marsilia, Giuseppina; Nardone, Gerardo; Coccoli, Pietro; Prinster, Anna; Mannelli, Lorenzo; Vergara, Emilia; Monti, Serena; Liuzzi, Raffaele; Incoronato, Mariarosaria

    2017-01-01

    The presence of significant fibrosis is an indicator for liver disease staging and prognosis. The aim of the study was to determine reproducibility of real-time shear wave elastography using a hepatic biopsy as the reference standard to identify patients with chronic liver disease. Forty patients with chronic liver disease and 12 normal subjects received shear wave elastography performed by skilled operators. Interoperator reproducibility was studied in 29 patients. Fibrosis was evaluated using the Metavir score. The median and range shear wave elastography values in chronic liver disease subjects were 6.15 kPa and 3.14–16.7 kPa and were 4.49 kPa and 2.92–7.32 kPa in normal subjects, respectively. With respect to fibrosis detected by liver biopsy, shear wave elastography did not change significantly between F0 and F1 (p = 0.334), F1 and F2 (p = 0.611), or F3 and F4 (0.327); a significant difference was observed between the F0-F2 and F3-F4 groups (p = 0.002). SWE also correlated with inflammatory activity (Rs = 0.443, p = 0.0023) and ALT levels (Rs = 0.287, p = 0.0804). Age, sex and body mass index did not affect shear wave elastography measurements. Using receiver operator characteristic curves, two threshold values for shear wave elastography were identified: 5.62 kPa for patients with fibrosis (≥F2; sensitivity 80%, specificity 69.4%, and accuracy 77%) and 7.04 kPa for patients with severe fibrosis (≥F3; sensitivity 88.9%, specificity 81%, and accuracy 89%). Overall interobserver agreement was excellent and was analysed using an interclass correlation coefficient (0.94; CI 0.87–0.97).This study shows that shear wave elastography executed by skilled operators can be performed on almost all chronic liver disease patients with high reproducibility. It is not influenced by age, sex or body mass index, identifies severely fibrotic patients and is also related to inflammatory activity. PMID:29023554

  6. Quantitative shear wave imaging optical coherence tomography for noncontact mechanical characterization of myocardium

    Science.gov (United States)

    Wang, Shang; Lopez, Andrew L.; Morikawa, Yuka; Tao, Ge; Li, Jiasong; Larina, Irina V.; Martin, James F.; Larin, Kirill V.

    2015-03-01

    Optical coherence elastography (OCE) is an emerging low-coherence imaging technique that provides noninvasive assessment of tissue biomechanics with high spatial resolution. Among various OCE methods, the capability of quantitative measurement of tissue elasticity is of great importance for tissue characterization and pathology detection across different samples. Here we report a quantitative OCE technique, termed quantitative shear wave imaging optical coherence tomography (Q-SWI-OCT), which enables noncontact measurement of tissue Young's modulus based on the ultra-fast imaging of the shear wave propagation inside the sample. A focused air-puff device is used to interrogate the tissue with a low-pressure short-duration air stream that stimulates a localized displacement with the scale at micron level. The propagation of this tissue deformation in the form of shear wave is captured by a phase-sensitive OCT system running with the scan of the M-mode imaging over the path of the wave propagation. The temporal characteristics of the shear wave is quantified based on the cross-correlation of the tissue deformation profiles at all the measurement locations, and linear regression is utilized to fit the data plotted in the domain of time delay versus wave propagation distance. The wave group velocity is thus calculated, which results in the quantitative measurement of the Young's modulus. As the feasibility demonstration, experiments are performed on tissuemimicking phantoms with different agar concentrations and the quantified elasticity values with Q-SWI-OCT agree well with the uniaxial compression tests. For functional characterization of myocardium with this OCE technique, we perform our pilot experiments on ex vivo mouse cardiac muscle tissues with two studies, including 1) elasticity difference of cardiac muscle under relaxation and contract conditions and 2) mechanical heterogeneity of the heart introduced by the muscle fiber orientation. Our results suggest the

  7. Approximation of wave action flux velocity in strongly sheared mean flows

    Science.gov (United States)

    Banihashemi, Saeideh; Kirby, James T.; Dong, Zhifei

    2017-08-01

    Spectral wave models based on the wave action equation typically use a theoretical framework based on depth uniform current to account for current effects on waves. In the real world, however, currents often have variations over depth. Several recent studies have made use of a depth-weighted current U˜ due to [Skop, R. A., 1987. Approximate dispersion relation for wave-current interactions. J. Waterway, Port, Coastal, and Ocean Eng. 113, 187-195.] or [Kirby, J. T., Chen, T., 1989. Surface waves on vertically sheared flows: approximate dispersion relations. J. Geophys. Res. 94, 1013-1027.] in order to account for the effect of vertical current shear. Use of the depth-weighted velocity, which is a function of wavenumber (or frequency and direction) has been further simplified in recent applications by only utilizing a weighted current based on the spectral peak wavenumber. These applications do not typically take into account the dependence of U˜ on wave number k, as well as erroneously identifying U˜ as the proper choice for current velocity in the wave action equation. Here, we derive a corrected expression for the current component of the group velocity. We demonstrate its consistency using analytic results for a current with constant vorticity, and numerical results for a measured, strongly-sheared current profile obtained in the Columbia River. The effect of choosing a single value for current velocity based on the peak wave frequency is examined, and we suggest an alternate strategy, involving a Taylor series expansion about the peak frequency, which should significantly extend the range of accuracy of current estimates available to the wave model with minimal additional programming and data transfer.

  8. Quantitative ultrasound mapping of regional variations in shear wave speeds of the aging Achilles tendon.

    Science.gov (United States)

    Slane, Laura Chernak; Martin, Jack; DeWall, Ryan; Thelen, Darryl; Lee, Kenneth

    2017-02-01

    Evaluate the effects of aging on healthy Achilles tendon and aponeurosis shear wave speed (SWS), a quantitative metric which reflects tissue elasticity. Shear wave elastography was used to measure spatial variations in Achilles tendon SWS in healthy young (n = 15, 25 ± 4 years), middle-aged (n = 10, 49 ± 4 years) and older (n = 10, 68 ± 5 years) adults. SWS was separately measured in the free Achilles tendon, soleus aponeurosis and gastrocnemius aponeurosis in resting (R), stretched (dorsiflexed 15° from R) and slack (plantarflexed 15° from R) postures. SWS significantly increased with stretch and varied with age in all tendon regions. Slack free tendon SWS was significantly higher in older adults than young adults (p = 0.025). However, stretched soleus aponeurosis SWS was significantly lower in older adults than young adults (p = 0.01). Stretched gastrocnemius aponeurosis SWS was significantly lower in both middle-aged (p = 0.003) and older (p = 0.001) adults, relative to younger adults. These results suggest that aging alters spatial variations in Achilles tendon elasticity, which could alter deformations within the triceps surae muscle-tendon units, thus affecting injury potential. The observed location- and posture-dependent variations highlight the importance of controlling ankle posture and imaging location when using shear wave approaches clinically to evaluate tendon disorders. • Shear wave elastography shows promise as a clinical quantitative ultrasound-based technique. • Aging induces location-dependent changes in Achilles tendon shear wave speed. • Spatial and postural dependence necessitates careful integration of this approach clinically.

  9. Integration of SH seismic reflection and Love-wave dispersion data for shear wave velocity determination over quick clays

    Science.gov (United States)

    Comina, Cesare; Krawczyk, Charlotte M.; Polom, Ulrich; Socco, Laura Valentina

    2017-09-01

    Quick clay is a water-saturated formation originally formed through flocculation and deposition in a marine to brackish environment. It is subsequently leached to low salinity by freshwater flow. If its strength decreases, then the flocculated structure collapses leading to landslides of varying destructiveness. Leaching can result in a reduction of the undisturbed shear strength of these clays and suggestions exist that a reduction in shear wave velocities is also possible. Integration of SH seismic reflection and Love-wave dispersion data was undertaken, in an area near the Göta River in southwest Sweden, to evaluate the potential of shear wave velocity imaging for detecting quick clays. Seismic reflection processing evidenced several geologically interesting interfaces related to the probable presence of quick clays (locally confirmed by boreholes) and sand-gravelly layers strongly contributing to water circulation within them. Dispersion data were extracted with a Gaussian windowing approach and inverted with a laterally constrained inversion using a priori information from the seismic reflection imaging. The inversion of dispersion curves has evidenced the presence of a low velocity layer (lvl, with a velocity reduction of ca. 30 per cent) probably associable to quick clays. This velocity reduction is enough to produce detectable phase-velocity differences in the field data and to achieve a better velocity resolution if compared to reflection seismic velocity analyses. The proposed approach has the potential of a comprehensive determination of the shear wave velocity distribution in the shallow subsurface. A sensitivity analysis of Love-wave dispersion data is also presented underlining that, despite limited dispersion of the data set and the velocity-reducing effect of quick-clay leaching, the proposed interpretation procedure arises as a valuable approach in quick clay and other lvl identification.

  10. Feasibility of waveform inversion of Rayleigh waves for shallow shear-wave velocity using a genetic algorithm

    Science.gov (United States)

    Zeng, C.; Xia, J.; Miller, R.D.; Tsoflias, G.P.

    2011-01-01

    Conventional surface wave inversion for shallow shear (S)-wave velocity relies on the generation of dispersion curves of Rayleigh waves. This constrains the method to only laterally homogeneous (or very smooth laterally heterogeneous) earth models. Waveform inversion directly fits waveforms on seismograms, hence, does not have such a limitation. Waveforms of Rayleigh waves are highly related to S-wave velocities. By inverting the waveforms of Rayleigh waves on a near-surface seismogram, shallow S-wave velocities can be estimated for earth models with strong lateral heterogeneity. We employ genetic algorithm (GA) to perform waveform inversion of Rayleigh waves for S-wave velocities. The forward problem is solved by finite-difference modeling in the time domain. The model space is updated by generating offspring models using GA. Final solutions can be found through an iterative waveform-fitting scheme. Inversions based on synthetic records show that the S-wave velocities can be recovered successfully with errors no more than 10% for several typical near-surface earth models. For layered earth models, the proposed method can generate one-dimensional S-wave velocity profiles without the knowledge of initial models. For earth models containing lateral heterogeneity in which case conventional dispersion-curve-based inversion methods are challenging, it is feasible to produce high-resolution S-wave velocity sections by GA waveform inversion with appropriate priori information. The synthetic tests indicate that the GA waveform inversion of Rayleigh waves has the great potential for shallow S-wave velocity imaging with the existence of strong lateral heterogeneity. ?? 2011 Elsevier B.V.

  11. Connecting the grain-shearing mechanism of wave propagation in marine sediments to fractional order wave equations.

    Science.gov (United States)

    Pandey, Vikash; Holm, Sverre

    2016-12-01

    The characteristic time-dependent viscosity of the intergranular pore-fluid in Buckingham's grain-shearing (GS) model [Buckingham, J. Acoust. Soc. Am. 108, 2796-2815 (2000)] is identified as the property of rheopecty. The property corresponds to a rare type of a non-Newtonian fluid in rheology which has largely remained unexplored. The material impulse response function from the GS model is found to be similar to the power-law memory kernel which is inherent in the framework of fractional calculus. The compressional wave equation and the shear wave equation derived from the GS model are shown to take the form of the Kelvin-Voigt fractional-derivative wave equation and the fractional diffusion-wave equation, respectively. Therefore, an analogy is drawn between the dispersion relations obtained from the fractional framework and those from the GS model to establish the equivalence of the respective wave equations. Further, a physical interpretation of the characteristic fractional order present in the wave equations is inferred from the GS model. The overall goal is to show that fractional calculus is not just a mathematical framework which can be used to curve-fit the complex behavior of materials. Rather, it can also be derived from real physical processes as illustrated in this work by the example of GS.

  12. Flow under standing waves Part 1. Shear stress distribution, energy flux and steady streaming

    DEFF Research Database (Denmark)

    Gislason, Kjartan; Fredsøe, Jørgen; Deigaard, Rolf

    2009-01-01

    The conditions for energy flux, momentum flux and the resulting streaming velocity are analysed for standing waves formed in front of a fully reflecting wall. The exchange of energy between the outer wave motion and the near bed oscillatory boundary layer is considered, determining the horizontal...... energy flux inside and outside the boundary layer. The momentum balance, the mean shear stress and the resulting time averaged streaming velocities are determined. For a laminar bed boundary layer the analysis of the wave drift gives results similar to the original work of Longuet-Higgins from 1953...

  13. Coupled magnetic and elastic dynamics generated by a shear wave propagating in ferromagnetic heterostructure

    Science.gov (United States)

    Azovtsev, A. V.; Pertsev, N. A.

    2017-11-01

    Using advanced micromagnetic simulations, we describe the coupled elastic and magnetic dynamics induced in ferromagnet/normal metal bilayers by shear waves generated by the attached piezoelectric transducer. Our approach is based on the numerical solution of a system of differential equations, which comprises the Landau-Lifshitz-Gilbert equation and the elastodynamic equation of motion, both allowing for the magnetoelastic coupling between spins and lattice strains. The simulations have been performed for heterostructures involving a Fe81Ga19 layer with the thickness ranging from 100 to 892 nm and a few-micrometer-thick film of a normal metal (Au). We find that the traveling shear wave induces inhomogeneous magnetic dynamics in the ferromagnetic layer, which generally has an intermediate character between coherent magnetization precession and the pure spin wave. Owing to the magnetoelastic feedback, the magnetization precession generates two additional elastic waves (shear and longitudinal), which propagate into the normal metal. Despite such complex elastic dynamics and reflections of elastic waves at the Fe81Ga19|Au interface, periodic magnetization precession with the excitation frequency settles in the steady-state regime. The results obtained for the magnetization dynamics at the Fe81Ga19|Au interface are used to evaluate the spin current pumped into the Au layer and the accompanying charge current caused by the inverse spin Hall effect. The calculations show that the dc component of the charge current is high enough to be detected experimentally even at small strains ˜10-4 generated by the piezoelectric transducer.

  14. Surface shear strains induced by quasi-steady sweeping detonation waves

    Science.gov (United States)

    Hull, Lawrence; Briggs, Matthew; Faulkner, James

    2012-03-01

    Sweeping wave experiments create conditions of greater shear than corresponding onedimensional motion experiments, and are of current interest for material damage characterization. Sweeping waves are also important with regards to the spectrum of applications of explosives driving metals. The intensity of the shear developed in a sweeping wave experiment may be monitored using crossed beams of Photon Doppler Velocimetry (PDV). During the time the material is traversing the volume defined by the crossed beams, the interferometer is measuring the velocity of the same mass element (approximately) from two directions. It is known that PDV measures the velocity component that lies along the beam direction, so that with crossed beams, two independent directions are simultaneously measured and therefore the vector velocity (both magnitude and direction) are captured. The vector velocity is readily related to the strain rates on the surface (after removing the rigid rotation rates), and the equations are integrated to obtain the strains.

  15. Ultrasonic Backscatter Imaging by Shear-Wave-Induced Echo Phase Encoding of Target Locations

    Science.gov (United States)

    McAleavey, Stephen

    2011-01-01

    We present a novel method for ultrasound backscatter image formation wherein lateral resolution of the target is obtained by using traveling shear waves to encode the lateral position of targets in the phase of the received echo. We demonstrate that the phase modulation as a function of shear wavenumber can be expressed in terms of a Fourier transform of the lateral component of the target echogenicity. The inverse transform, obtained by measurements of the phase modulation over a range of shear wave spatial frequencies, yields the lateral scatterer distribution. Range data are recovered from time of flight as in conventional ultrasound, yielding a B-mode-like image. In contrast to conventional ultrasound imaging, where mechanical or electronic focusing is used and lateral resolution is determined by aperture size and wavelength, we demonstrate that lateral resolution using the proposed method is independent of the properties of the aperture. Lateral resolution of the target is achieved using a stationary, unfocused, single-element transducer. We present simulated images of targets of uniform and non-uniform shear modulus. Compounding for speckle reduction is demonstrated. Finally, we demonstrate image formation with an unfocused transducer in gelatin phantoms of uniform shear modulus. PMID:21244978

  16. Examination of nanosecond laser melting thresholds in refractory metals by shear wave acoustics

    Directory of Open Access Journals (Sweden)

    A. Abdullaev

    2017-07-01

    Full Text Available Nanosecond laser pulse-induced melting thresholds in refractory (Nb, Mo, Ta and W metals are measured using detected laser-generated acoustic shear waves. Obtained melting threshold values were found to be scaled with corresponding melting point temperatures of investigated materials displaying dissimilar shearing behavior. The experiments were conducted with motorized control of the incident laser pulse energies with small and uniform energy increments to reach high measurement accuracy and real-time monitoring of the epicentral acoustic waveforms from the opposite side of irradiated sample plates. Measured results were found to be in good agreement with numerical finite element model solving coupled elastodynamic and thermal conduction governing equations on structured quadrilateral mesh. Solid-melt phase transition was handled by means of apparent heat capacity method. The onset of melting was attributed to vanished shear modulus and rapid radial molten pool propagation within laser-heated metal leading to preferential generation of transverse acoustic waves from sources surrounding the molten mass resulting in the delay of shear wave transit times. Developed laser-based technique aims for applications involving remote examination of rapid melting processes of materials present in harsh environment (e.g. spent nuclear fuels with high spatio-temporal resolution.

  17. The radiation of sound by the instability waves of a compressible plane turbulent shear layer

    Science.gov (United States)

    Tam, C. K. W.; Morris, P. J.

    1980-01-01

    The problem of acoustic radiation generated by instability waves of a compressible plane turbulent shear layer is solved. The solution provided is valid up to the acoustic far-field region. It represents a significant improvement over the solution obtained by classical hydrodynamic-stability theory which is essentially a local solution with the acoustic radiation suppressed. The basic instability-wave solution which is valid in the shear layer and the near-field region is constructed in terms of an asymptotic expansion using the method of multiple scales. This solution accounts for the effects of the slightly divergent mean flow. It is shown that the multiple-scales asymptotic expansion is not uniformly valid far from the shear layer. Continuation of this solution into the entire upper half-plane is described. The extended solution enables the near- and far-field pressure fluctuations associated with the instability wave to be determined. Numerical results show that the directivity pattern of acoustic radiation into the stationary medium peaks at 20 degrees to the axis of the shear layer in the downstream direction for supersonic flows. This agrees qualitatively with the observed noise-directivity patterns of supersonic jets.

  18. Examination of nanosecond laser melting thresholds in refractory metals by shear wave acoustics

    Science.gov (United States)

    Abdullaev, A.; Muminov, B.; Rakhymzhanov, A.; Mynbayev, N.; Utegulov, Z. N.

    2017-07-01

    Nanosecond laser pulse-induced melting thresholds in refractory (Nb, Mo, Ta and W) metals are measured using detected laser-generated acoustic shear waves. Obtained melting threshold values were found to be scaled with corresponding melting point temperatures of investigated materials displaying dissimilar shearing behavior. The experiments were conducted with motorized control of the incident laser pulse energies with small and uniform energy increments to reach high measurement accuracy and real-time monitoring of the epicentral acoustic waveforms from the opposite side of irradiated sample plates. Measured results were found to be in good agreement with numerical finite element model solving coupled elastodynamic and thermal conduction governing equations on structured quadrilateral mesh. Solid-melt phase transition was handled by means of apparent heat capacity method. The onset of melting was attributed to vanished shear modulus and rapid radial molten pool propagation within laser-heated metal leading to preferential generation of transverse acoustic waves from sources surrounding the molten mass resulting in the delay of shear wave transit times. Developed laser-based technique aims for applications involving remote examination of rapid melting processes of materials present in harsh environment (e.g. spent nuclear fuels) with high spatio-temporal resolution.

  19. Ultrasound viscoelasticity assessment using an adaptive torsional shear wave propagation method

    Energy Technology Data Exchange (ETDEWEB)

    Ouared, Abderrahmane [Laboratory of Biorheology and Medical Ultrasonics, University of Montréal Hospital Research Center (CRCHUM), Montréal, Québec H2X 0A9, Canada and Institute of Biomedical Engineering, University of Montréal, Montréal, Québec H3T 1J4 (Canada); Kazemirad, Siavash; Montagnon, Emmanuel [Laboratory of Biorheology and Medical Ultrasonics, University of Montréal Hospital Research Center (CRCHUM), Montréal, Québec H2X 0A9 (Canada); Cloutier, Guy, E-mail: guy.cloutier@umontreal.ca [Laboratory of Biorheology and Medical Ultrasonics, University of Montréal Hospital Research Center (CRCHUM), Montréal, Québec H2X 0A9 (Canada); Department of Radiology, Radio-Oncology and Nuclear Medicine, University of Montréal, Montréal, Québec H3T 1J4 (Canada); Institute of Biomedical Engineering, University of Montréal, Montréal, Québec H3T 1J4 (Canada)

    2016-04-15

    Purpose: Different approaches have been used in dynamic elastography to assess mechanical properties of biological tissues. Most techniques are based on a simple inversion based on the measurement of the shear wave speed to assess elasticity, whereas some recent strategies use more elaborated analytical or finite element method (FEM) models. In this study, a new method is proposed for the quantification of both shear storage and loss moduli of confined lesions, in the context of breast imaging, using adaptive torsional shear waves (ATSWs) generated remotely with radiation pressure. Methods: A FEM model was developed to solve the inverse wave propagation problem and obtain viscoelastic properties of interrogated media. The inverse problem was formulated and solved in the frequency domain and its robustness to noise and geometric constraints was evaluated. The proposed model was validated in vitro with two independent rheology methods on several homogeneous and heterogeneous breast tissue-mimicking phantoms over a broad range of frequencies (up to 400 Hz). Results: Viscoelastic properties matched benchmark rheology methods with discrepancies of 8%–38% for the shear modulus G′ and 9%–67% for the loss modulus G″. The robustness study indicated good estimations of storage and loss moduli (maximum mean errors of 19% on G′ and 32% on G″) for signal-to-noise ratios between 19.5 and 8.5 dB. Larger errors were noticed in the case of biases in lesion dimension and position. Conclusions: The ATSW method revealed that it is possible to estimate the viscoelasticity of biological tissues with torsional shear waves when small biases in lesion geometry exist.

  20. Ultrasound viscoelasticity assessment using an adaptive torsional shear wave propagation method.

    Science.gov (United States)

    Ouared, Abderrahmane; Kazemirad, Siavash; Montagnon, Emmanuel; Cloutier, Guy

    2016-04-01

    Different approaches have been used in dynamic elastography to assess mechanical properties of biological tissues. Most techniques are based on a simple inversion based on the measurement of the shear wave speed to assess elasticity, whereas some recent strategies use more elaborated analytical or finite element method (FEM) models. In this study, a new method is proposed for the quantification of both shear storage and loss moduli of confined lesions, in the context of breast imaging, using adaptive torsional shear waves (ATSWs) generated remotely with radiation pressure. A FEM model was developed to solve the inverse wave propagation problem and obtain viscoelastic properties of interrogated media. The inverse problem was formulated and solved in the frequency domain and its robustness to noise and geometric constraints was evaluated. The proposed model was validated in vitro with two independent rheology methods on several homogeneous and heterogeneous breast tissue-mimicking phantoms over a broad range of frequencies (up to 400 Hz). Viscoelastic properties matched benchmark rheology methods with discrepancies of 8%-38% for the shear modulus G' and 9%-67% for the loss modulus G″. The robustness study indicated good estimations of storage and loss moduli (maximum mean errors of 19% on G' and 32% on G″) for signal-to-noise ratios between 19.5 and 8.5 dB. Larger errors were noticed in the case of biases in lesion dimension and position. The ATSW method revealed that it is possible to estimate the viscoelasticity of biological tissues with torsional shear waves when small biases in lesion geometry exist.

  1. Use of shear horizontal waves to distinguish adhesive thickness variation from reduction in bonding strength.

    Science.gov (United States)

    Predoi, Mihai Valentin; Ech Cherif El Kettani, Mounsif; Leduc, Damien; Pareige, Pascal; Coné, Khadidiatou

    2015-08-01

    The capability of shear horizontal (SH) guided waves, to evaluate geometrical imperfections in a bonding layer, is investigated. SH waves are used in a three-layer structure in which the adhesive layer has variable thickness. It is proven that the SH waves are adapting to the local thickness of the adhesive layer (adiabatic waves). This is particularly useful in case of small thickness variations, which is of technical interest. The influence of thickness and stiffness of the adhesive layer on the wavenumbers are investigated. The selected SH2 mode is proven to be very sensitive to the adhesive layer thickness variation in the given frequency range and considerably less sensitive to the adhesive stiffness variation. This property is due to its specific displacement field and is important in practical applications, such as inspection techniques based on SH waves, in order to avoid false alarms.

  2. Propagation of thickness shear waves in a periodically corrugated quartz crystal plate and its application exploration in acoustic wave filters.

    Science.gov (United States)

    Li, Peng; Cheng, Li

    2017-05-01

    The propagation of thickness shear waves in a periodically corrugated quartz crystal plate is investigated in the present paper using a power series expansion technique. In the proposed simulation model, an equivalent continuity of shear stress moment is introduced as an approximation to handle sectional interfaces with abrupt thickness changes. The Bloch theory is applied to simulate the band structures for three different thickness variation patterns. It is shown that the power series expansion method exhibits good convergence and accuracy, in agreement with results by finite element method (FEM). A broad stop band can be obtained in the power transmission spectra owing to the trapped thickness shear modes excited by the thickness variation, whose physical mechanism is totally different from the well-known Bragg scattering effect and is insensitive to the structural periodicity. Based on the observed energy trapping phenomenon, an acoustic wave filter is proposed in a quartz plate with sectional decreasing thickness, which inhibits wave propagation in different regions. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. In vivo evaluation of the elastic anisotropy of the human Achilles tendon using shear wave dispersion analysis

    Science.gov (United States)

    Brum, J.; Bernal, M.; Gennisson, J. L.; Tanter, M.

    2014-02-01

    Non-invasive evaluation of the Achilles tendon elastic properties may enhance diagnosis of tendon injury and the assessment of recovery treatments. Shear wave elastography has shown to be a powerful tool to estimate tissue mechanical properties. However, its applicability to quantitatively evaluate tendon stiffness is limited by the understanding of the physics on the shear wave propagation in such a complex medium. First, tendon tissue is transverse isotropic. Second, tendons are characterized by a marked stiffness in the 400 to 1300 kPa range (i.e. fast shear waves). Hence, the shear wavelengths are greater than the tendon thickness leading to guided wave propagation. Thus, to better understand shear wave propagation in tendons and consequently to properly estimate its mechanical properties, a dispersion analysis is required. In this study, shear wave velocity dispersion was measured in vivo in ten Achilles tendons parallel and perpendicular to the tendon fibre orientation. By modelling the tendon as a transverse isotropic viscoelastic plate immersed in fluid it was possible to fully describe the experimental data (deviation<1.4%). We show that parallel to fibres the shear wave velocity dispersion is not influenced by viscosity, while it is perpendicularly to fibres. Elasticity (found to be in the range from 473 to 1537 kPa) and viscosity (found to be in the range from 1.7 to 4 Pa.s) values were retrieved from the model in good agreement with reported results.

  4. Transmission, attenuation and reflection of shear waves in the human brain.

    Science.gov (United States)

    Clayton, Erik H; Genin, Guy M; Bayly, Philip V

    2012-11-07

    Traumatic brain injuries (TBIs) are caused by acceleration of the skull or exposure to explosive blast, but the processes by which mechanical loads lead to neurological injury remain poorly understood. We adapted motion-sensitive magnetic resonance imaging methods to measure the motion of the human brain in vivo as the skull was exposed to harmonic pressure excitation (45, 60 and 80 Hz). We analysed displacement fields to quantify the transmission, attenuation and reflection of distortional (shear) waves as well as viscoelastic material properties. Results suggest that internal membranes, such as the falx cerebri and the tentorium cerebelli, play a key role in reflecting and focusing shear waves within the brain. The skull acts as a low-pass filter over the range of frequencies studied. Transmissibility of pressure waves through the skull decreases and shear wave attenuation increases with increasing frequency. The skull and brain function mechanically as an integral structure that insulates internal anatomic features; these results are valuable for building and validating mathematical models of this complex and important structural system.

  5. A Numerical Simulation of Base Shear Forces and Moments Exerted by Waves on Large Diameter Pile

    Directory of Open Access Journals (Sweden)

    You-liang Cheng

    2017-01-01

    Full Text Available To solve the problem of the dynamic variation of wave force diameter of pile foundation for offshore wind turbines, wave force and moment of large diameter pile foundation can be calculated. In this paper, simulation technique is used to calculate the wave force and moment of different large diameter pile foundation, and the base shear force and moment of the interval 20-degree phase angle are obtained by the base line of the pile. Under the action of a certain load, the complete stress variation of the pile foundation is obtained. According to the basic principle of diffraction theory, the process curve of large diameter pile, and analysis of wave force, diffraction force changes in a certain period of time interval. The results show that the wave after the large diameter pile formed around the vortex, large diameter pile base shear, and moment dynamic change is nonlinear in a complete cycle, the diameter of the pile increases by 0.5 m, and the wave force increases by about 5%, the results show that it provides certain reference value for the offshore pile foundation pile with large diameter primary site. Some significant results for practical application are discussed.

  6. Site response, shallow shear-wave velocity, and wave propagation at the San Jose, California, dense seismic array

    Science.gov (United States)

    Hartzell, S.; Carver, D.; Williams, R.A.; Harmsen, S.; Zerva, A.

    2003-01-01

    Ground-motion records from a 52-element dense seismic array near San Jose, California, are analyzed to obtain site response, shallow shear-wave velocity, and plane-wave propagation characteristics. The array, located on the eastern side of the Santa Clara Valley south of the San Francisco Bay, is sited over the Evergreen basin, a 7-km-deep depression with Miocene and younger deposits. Site response values below 4 Hz are up to a factor of 2 greater when larger, regional records are included in the analysis, due to strong surface-wave development within the Santa Clara Valley. The pattern of site amplification is the same, however, with local or regional events. Site amplification increases away from the eastern edge of the Santa Clara Valley, reaching a maximum over the western edge of the Evergreen basin, where the pre-Cenozoic basement shallows rapidly. Amplification then decreases further to the west. This pattern may be caused by lower shallow shear-wave velocities and thicker Quaternary deposits further from the edge of the Santa Clara Valley and generation/trapping of surface waves above the shallowing basement of the western Evergreen basin. Shear-wave velocities from the inversion of site response spectra based on smaller, local earthquakes compare well with those obtained independently from our seismic reflection/refraction measurements. Velocities from the inversion of site spectra that include larger, regional records do not compare well with these measurements. A mix of local and regional events, however, is appropriate for determination of site response to be used in seismic hazard evaluation, since large damaging events would excite both body and surface waves with a wide range in ray parameters. Frequency-wavenumber, plane-wave analysis is used to determine the backazimuth and apparent velocity of coherent phases at the array. Conventional, high-resolution, and multiple signal characterization f-k power spectra and stacked slowness power spectra are

  7. Ultrasound Shear Wave Simulation of Breast Tumor Using Nonlinear Tissue Elasticity

    Directory of Open Access Journals (Sweden)

    Dae Woo Park

    2016-01-01

    Full Text Available Shear wave elasticity imaging (SWEI can assess the elasticity of tissues, but the shear modulus estimated in SWEI is often less sensitive to a subtle change of the stiffness that produces only small mechanical contrast to the background tissues. Because most soft tissues exhibit mechanical nonlinearity that differs in tissue types, mechanical contrast can be enhanced if the tissues are compressed. In this study, a finite element- (FE- based simulation was performed for a breast tissue model, which consists of a circular (D: 10 mm, hard tumor and surrounding tissue (soft. The SWEI was performed with 0% to 30% compression of the breast tissue model. The shear modulus of the tumor exhibited noticeably high nonlinearity compared to soft background tissue above 10% overall applied compression. As a result, the elastic modulus contrast of the tumor to the surrounding tissue was increased from 0.46 at 0% compression to 1.45 at 30% compression.

  8. Ultrasound Shear Wave Simulation of Breast Tumor Using Nonlinear Tissue Elasticity.

    Science.gov (United States)

    Park, Dae Woo

    2015-01-01

    Shear wave elasticity imaging (SWEI) can assess the elasticity of tissues, but the shear modulus estimated in SWEI is often less sensitive to a subtle change of the stiffness that produces only small mechanical contrast to the background tissues. Because most soft tissues exhibit mechanical nonlinearity that differs in tissue types, mechanical contrast can be enhanced if the tissues are compressed. In this study, a finite element- (FE-) based simulation was performed for a breast tissue model, which consists of a circular (D: 10 mm, hard) tumor and surrounding tissue (soft). The SWEI was performed with 0% to 30% compression of the breast tissue model. The shear modulus of the tumor exhibited noticeably high nonlinearity compared to soft background tissue above 10% overall applied compression. As a result, the elastic modulus contrast of the tumor to the surrounding tissue was increased from 0.46 at 0% compression to 1.45 at 30% compression.

  9. Piecewise parabolic method for simulating one-dimensional shear shock wave propagation in tissue-mimicking phantoms

    Science.gov (United States)

    Tripathi, B. B.; Espíndola, D.; Pinton, G. F.

    2017-06-01

    The recent discovery of shear shock wave generation and propagation in the porcine brain suggests that this new shock phenomenology may be responsible for a broad range of traumatic injuries. Blast-induced head movement can indirectly lead to shear wave generation in the brain, which could be a primary mechanism for injury. Shear shock waves amplify the local acceleration deep in the brain by up to a factor of 8.5, which may tear and damage neurons. Currently, there are numerical methods that can model compressional shock waves, such as comparatively well-studied blast waves, but there are no numerical full-wave solvers that can simulate nonlinear shear shock waves in soft solids. Unlike simplified representations, e.g., retarded time, full-wave representations describe fundamental physical behavior such as reflection and heterogeneities. Here we present a piecewise parabolic method-based solver for one-dimensional linearly polarized nonlinear shear wave in a homogeneous medium and with empirical frequency-dependent attenuation. This method has the advantage of being higher order and more directly extendable to multiple dimensions and heterogeneous media. The proposed numerical scheme is validated analytically and experimentally and compared to other shock capturing methods. A Riemann step-shock problem is used to characterize the numerical dissipation. This dissipation is then tuned to be negligible with respect to the physical attenuation by choosing an appropriate grid spacing. The numerical results are compared to ultrasound-based experiments that measure planar polarized shear shock wave propagation in a tissue-mimicking gelatin phantom. Good agreement is found between numerical results and experiment across a 40 mm propagation distance. We anticipate that the proposed method will be a starting point for the development of a two- and three-dimensional full-wave code for the propagation of nonlinear shear waves in heterogeneous media.

  10. Piecewise parabolic method for simulating one-dimensional shear shock wave propagation in tissue-mimicking phantoms

    Science.gov (United States)

    Tripathi, B. B.; Espíndola, D.; Pinton, G. F.

    2017-11-01

    The recent discovery of shear shock wave generation and propagation in the porcine brain suggests that this new shock phenomenology may be responsible for a broad range of traumatic injuries. Blast-induced head movement can indirectly lead to shear wave generation in the brain, which could be a primary mechanism for injury. Shear shock waves amplify the local acceleration deep in the brain by up to a factor of 8.5, which may tear and damage neurons. Currently, there are numerical methods that can model compressional shock waves, such as comparatively well-studied blast waves, but there are no numerical full-wave solvers that can simulate nonlinear shear shock waves in soft solids. Unlike simplified representations, e.g., retarded time, full-wave representations describe fundamental physical behavior such as reflection and heterogeneities. Here we present a piecewise parabolic method-based solver for one-dimensional linearly polarized nonlinear shear wave in a homogeneous medium and with empirical frequency-dependent attenuation. This method has the advantage of being higher order and more directly extendable to multiple dimensions and heterogeneous media. The proposed numerical scheme is validated analytically and experimentally and compared to other shock capturing methods. A Riemann step-shock problem is used to characterize the numerical dissipation. This dissipation is then tuned to be negligible with respect to the physical attenuation by choosing an appropriate grid spacing. The numerical results are compared to ultrasound-based experiments that measure planar polarized shear shock wave propagation in a tissue-mimicking gelatin phantom. Good agreement is found between numerical results and experiment across a 40 mm propagation distance. We anticipate that the proposed method will be a starting point for the development of a two- and three-dimensional full-wave code for the propagation of nonlinear shear waves in heterogeneous media.

  11. Shear-wave velocity structure of young Atlantic Lithosphere from dispersion analysis and waveform modelling of Rayleigh waves

    Science.gov (United States)

    Grevemeyer, Ingo; Lange, Dietrich; Schippkus, Sven

    2016-04-01

    The lithosphere is the outermost solid layer of the Earth and includes the brittle curst and brittle uppermost mantle. It is underlain by the asthenosphere, the weaker and hotter portion of the mantle. The boundary between the brittle lithosphere and the asthenosphere is call the lithosphere-asthenosphere boundary, or LAB. The oceanic lithosphere is created at spreading ridges and cools and thickens with age. Seismologists define the LAB by the presence of a low shear wave velocity zone beneath a high velocity lid. Surface waves from earthquakes occurring in young oceanic lithosphere should sample lithospheric structure when being recorded in the vicinity of a mid-ocean ridge. Here, we study group velocity and dispersion of Rayleigh waves caused by earthquakes occurring at transform faults in the Central Atlantic Ocean. Earthquakes were recorded either by a network of wide-band (up to 60 s) ocean-bottom seismometers (OBS) deployed at the Mid-Atlantic Ridge near 15°N or at the Global Seismic Network (GSN) Station ASCN on Ascension Island. Surface waves sampling young Atlantic lithosphere indicate systematic age-dependent changes of group velocities and dispersion of Rayleigh waves. With increasing plate age maximum group velocity increases (as a function of period), indicating cooling and thickening of the lithosphere. Shear wave velocity is derived inverting the observed dispersion of Rayleigh waves. Further, models derived from the OBS records were refined using waveform modelling of vertical component broadband data at periods of 15 to 40 seconds, constraining the velocity structure of the uppermost 100 km and hence in the depth interval of the mantle where lithospheric cooling is most evident. Waveform modelling supports that the thickness of lithosphere increases with age and that velocities in the lithosphere increase, too.

  12. Shear wave velocity models retrieved using Rg wave dispersion data in shallow crust in some regions of southern Ontario, Canada

    Science.gov (United States)

    Ma, Shutian; Motazedian, Dariush; Corchete, Victor

    2013-04-01

    Many crucial tasks in seismology, such as locating seismic events and estimating focal mechanisms, need crustal velocity models. The velocity models of shallow structures are particularly important in the simulation of ground motions. In southern Ontario, Canada, many small shallow earthquakes occur, generating high-frequency Rayleigh ( Rg) waves that are sensitive to shallow structures. In this research, the dispersion of Rg waves was used to obtain shear-wave velocities in the top few kilometers of the crust in the Georgian Bay, Sudbury, and Thunder Bay areas of southern Ontario. Several shallow velocity models were obtained based on the dispersion of recorded Rg waves. The Rg waves generated by an m N 3.0 natural earthquake on the northern shore of Georgian Bay were used to obtain velocity models for the area of an earthquake swarm in 2007. The Rg waves generated by a mining induced event in the Sudbury area in 2005 were used to retrieve velocity models between Georgian Bay and the Ottawa River. The Rg waves generated by the largest event in a natural earthquake swarm near Thunder Bay in 2008 were used to obtain a velocity model in that swarm area. The basic feature of all the investigated models is that there is a top low-velocity layer with a thickness of about 0.5 km. The seismic velocities changed mainly within the top 2 km, where small earthquakes often occur.

  13. Joint analysis of shear wave velocity from SH-wave refraction and MASW techniques for SPT-N estimation

    Directory of Open Access Journals (Sweden)

    Sawasdee Yordkayhun

    2014-06-01

    Full Text Available Horizontally polarized shear wave (SH refraction and multichannel analysis of surface wave (MASW methods have been carried out in Hatyai City, southern Thailand, a pilot study for site classification, part of the National Earthquake Hazards Reduction Program (NEHRP. The objectives of this study are the comparison of the efficiencies of different shear wave velocity (Vs determination techniques and the use of Vs measurements of the prediction of standard penetration resistance (SPT-N. Good correlation between all Vs profiles and SPT-N values and local lithology are observed. However, there are systematic differences between SH-refraction based-Vs and MASW based-Vs, which might be explained by possible converted waves, limitations of the assumptions used, poor quality of the acquired data, and limitations of the inversion procedures of the methods applied. From the integrated use of Vs from both methods an empirical formula to describe the correlation between Vs and SPT-N values has been proposed and can be used to estimate geotechnical parameters in areas where no borehole or geophysical investigation exist.

  14. Three-dimensional Single-Track-Location Shear Wave Elasticity Imaging (STL-SWEI).

    Science.gov (United States)

    Hollender, Peter; Lipman, Samantha; Trahey, Gregg

    2017-09-06

    Conventional multiple track location shear wave elasticity imaging (MTL-SWEI) is a powerful tool for noninvasively estimating tissue elasticity. The resolution and noise levels of MTL-SWEI systems, however, are limited by ultrasound speckle. Single track location SWEI (STL-SWEI) is a novel variant which fixes the position of the tracking beam and modulates the push location to effectively cancel out the effects of speckle-induced bias. We present here a three-dimensional STL-SWEI system which provides full suppression of lateral and elevation speckle bias for high resolution volumetric elasticity imaging, and requires no spatial smoothing to make accurate measurements of shear wave speed. We demonstrate and analyze the system's performance in homogeneous and layered elasticity phantoms.

  15. Correlation between Shear Wave Velocity and Porosity in Porous Solids and Rocks

    Directory of Open Access Journals (Sweden)

    J. Kováčik

    2013-01-01

    Full Text Available The shear wave velocity dependence on porosity was modelled using percolation theory model for the shear modulus porosity dependence. The obtained model is not a power law dependence (no simple scaling with porosity, but a more complex equation. Control parameters of this equation are shear wave velocity of bulk solid, percolation threshold of the material and the characteristic power law exponent for shear modulus porosity dependence. This model is suitable for all porous materials, mortars and porous rocks filled with liquid or gas. In the case of pores filled with gas the model can be further simplified: The term for the ratio of the gas density to the density of solid material can be omitted in the denominator (the ratio is usually in the range of (10−4, 10−3 for all solids. This simplified equation was then tested on the experimental data set for porous ZnO filled with air. Due to lack of reasonable data the scientists are encouraged to test the validity of proposed model using their experimental data.

  16. Influence of shear wave velocity reversals on one-dimensional site response of spatially varied profiles

    OpenAIRE

    Pehlivan, M; Hashash, YMA; Harmon, JA; Rathje, EM; Stewart, JP; Silva, SJ; Campbell, KW; Nikolaou, S

    2015-01-01

    Spatial variability and uncertainties that exist in natural deposits are often modeled in one-dimensional (1D) site response analysis through multiple spatially varied shear wave velocity (VS) profiles. These spatially varied VS profiles usually exhibit VS reversals that might not be observed in the natural deposits. This study investigates the consequences of allowing VS reversals in spatially varied VS on the 1D site response characteristics. Two sets of sixty (60) spatially varied VS profi...

  17. Acoustic radiation force impulse shear wave elastography (ARFI) of acute and chronic pancreatitis and pancreatic tumor.

    Science.gov (United States)

    Goertz, Ruediger S; Schuderer, Johanna; Strobel, Deike; Pfeifer, Lukas; Neurath, Markus F; Wildner, Dane

    2016-12-01

    Acoustic Radiation Force Impulse (ARFI) elastography evaluates tissue stiffness non-invasively and has rarely been applied to pancreas examinations so far. In a prospective and retrospective analysis, ARFI shear wave velocities of healthy parenchyma, pancreatic lipomatosis, acute and chronic pancreatitis, adenocarcinoma and neuroendocrine tumor (NET) of the pancreas were evaluated and compared. In 95 patients ARFI elastography of the pancreatic head, and also of the tail for a specific group, was analysed retrospectively. Additionally, prospectively in 100 patients ARFI was performed in the head and tail of the pancreas. A total of 195 patients were included in the study. Healthy parenchyma (n=21) and lipomatosis (n=30) showed similar shear wave velocities of about 1.3m/s. Acute pancreatitis (n=35), chronic pancreatitis (n=53) and adenocarcinoma (n=52) showed consecutively increasing ARFI values, respectively. NET (n=4) revealed the highest shear wave velocities amounting to 3.62m/s. ARFI elastography showed relevant differences between acute pancreatitis and chronic pancreatitis or adenocarcinoma. With a cut-off value of 1.74m/s for the diagnosis of a malignant disease the sensitivity was 91.1% whereas the specificity amounted to 60.4%. ARFI shear wave velocities present differences in various pathologies of the pancreas. Acute and chronic pancreatitis as well as neoplastic lesions show high ARFI values. Very high elasticity values may indicate malignant disease of the pancreas. However, there is a considerable overlap between the entities. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  18. Comparative study of shear wave-based elastography techniques in optical coherence tomography

    Science.gov (United States)

    Zvietcovich, Fernando; Rolland, Jannick P.; Yao, Jianing; Meemon, Panomsak; Parker, Kevin J.

    2017-03-01

    We compare five optical coherence elastography techniques able to estimate the shear speed of waves generated by one and two sources of excitation. The first two techniques make use of one piezoelectric actuator in order to produce a continuous shear wave propagation or a tone-burst propagation (TBP) of 400 Hz over a gelatin tissue-mimicking phantom. The remaining techniques utilize a second actuator located on the opposite side of the region of interest in order to create three types of interference patterns: crawling waves, swept crawling waves, and standing waves, depending on the selection of the frequency difference between the two actuators. We evaluated accuracy, contrast to noise ratio, resolution, and acquisition time for each technique during experiments. Numerical simulations were also performed in order to support the experimental findings. Results suggest that in the presence of strong internal reflections, single source methods are more accurate and less variable when compared to the two-actuator methods. In particular, TBP reports the best performance with an accuracy error TBP was tested in a fresh chicken tibialis anterior muscle with a localized thermally ablated lesion in order to evaluate its performance in biological tissue.

  19. Longitudinal and shear wave velocities in pure tungsten and tungsten fiber-reinforced tungsten composites

    Science.gov (United States)

    Lee, H. T.; Ando, S.; Coenen, J. W.; Mao, Y.; Riesch, J.; Gietl, H.; Kasada, R.; Hamaji, Y.; Ibano, K.; Ueda, Y.

    2017-12-01

    Longitudinal and shear wave velocities in pure tungsten and tungsten fiber-reinforced tungsten (Wf/W) composites were studied by laser ultrasonic measurements. The samples were produced from powders or powder/fiber mixtures by spark plasma sintering process. It was found that sintering temperature, as a processing parameter, has the largest effect. Higher sintering temperatures result in faster wave velocities. For example, longitudinal wave velocities and their standard deviations in sintered W at 1800 °C and 2000 °C were 4834 ± 53 m s-1 and 5043 ± 47 m s-1. In comparison, the average longitudinal wave velocity for a polycrystalline reference W was 5227 ± 5 m s-1. The values for Wf/W composites fall between the two sintered samples. However, the thicker Yttria (Y2O3) fiber/matrix interface resulted in faster wave velocities. The elastic moduli were calculated from the sound velocities using average density measurements. The standard relations for isotropic, homogeneous material were used. It was found that the shear, bulk, Young’s modulus are 80%-90% of the values for polycrystalline tungsten, while the temperature dependency from 25 °C to 450 °C is similar.

  20. Arterial waveguide model for shear wave elastography: implementation and in vitro validation

    Science.gov (United States)

    Vaziri Astaneh, Ali; Urban, Matthew W.; Aquino, Wilkins; Greenleaf, James F.; Guddati, Murthy N.

    2017-07-01

    Arterial stiffness is found to be an early indicator of many cardiovascular diseases. Among various techniques, shear wave elastography has emerged as a promising tool for estimating local arterial stiffness through the observed dispersion of guided waves. In this paper, we develop efficient models for the computational simulation of guided wave dispersion in arterial walls. The models are capable of considering fluid-loaded tubes, immersed in fluid or embedded in a solid, which are encountered in in vitro/ex vivo, and in vivo experiments. The proposed methods are based on judiciously combining Fourier transformation and finite element discretization, leading to a significant reduction in computational cost while fully capturing complex 3D wave propagation. The developed methods are implemented in open-source code, and verified by comparing them with significantly more expensive, fully 3D finite element models. We also validate the models using the shear wave elastography of tissue-mimicking phantoms. The computational efficiency of the developed methods indicates the possibility of being able to estimate arterial stiffness in real time, which would be beneficial in clinical settings.

  1. Shear wave velocity of the healthy thyroid gland in children with acoustic radiation force impulse elastography.

    Science.gov (United States)

    Ceyhan Bilgici, Meltem; Sağlam, Dilek; Delibalta, Semra; Yücel, Serap; Tomak, Leman; Elmalı, Muzaffer

    2018-01-01

    Acoustic radiation force impulse imaging is a kind of shear wave elastography that can be used in children for differentiating thyroid pathologies. Possible changes in the healthy thyroid gland in children may create difficulties in the use of shear wave velocities (SWV) in thyroid pathologies. The aim of this study was to define the normal values of SWV for the healthy thyroid gland in children, elucidate the correlation of the SWV values with potential influencing factors, and evaluate intra-operator reproducibility of the SWV. Between January 2015 and December 2015, a total of 145 healthy children (81 girls, 64 boys; mean age, 10.5 ± 3.14 years; range 6-17 years) were enrolled in the study. The SWV and volume of the thyroid gland were determined. The mean shear wave velocity of the thyroid gland was 1.22 ± 0.20 m/s. There was no correlation between age and the mean SWV of the thyroid gland (Spearman Rho = 0.049, p = 0.556). There was also no correlation between the thyroid gland volume or BSA and the mean SWV. The only correlation detected was between BSA and total thyroid gland volume (p thyroid gland in children was determined. There was no correlation between the SWV of the thyroid gland and age, BSA, or thyroid gland volume.

  2. Model benchmarking and reference signals for angled-beam shear wave ultrasonic nondestructive evaluation (NDE) inspections

    Science.gov (United States)

    Aldrin, John C.; Hopkins, Deborah; Datuin, Marvin; Warchol, Mark; Warchol, Lyudmila; Forsyth, David S.; Buynak, Charlie; Lindgren, Eric A.

    2017-02-01

    For model benchmark studies, the accuracy of the model is typically evaluated based on the change in response relative to a selected reference signal. The use of a side drilled hole (SDH) in a plate was investigated as a reference signal for angled beam shear wave inspection for aircraft structure inspections of fastener sites. Systematic studies were performed with varying SDH depth and size, and varying the ultrasonic probe frequency, focal depth, and probe height. Increased error was observed with the simulation of angled shear wave beams in the near-field. Even more significant, asymmetry in real probes and the inherent sensitivity of signals in the near-field to subtle test conditions were found to provide a greater challenge with achieving model agreement. To achieve quality model benchmark results for this problem, it is critical to carefully align the probe with the part geometry, to verify symmetry in probe response, and ideally avoid using reference signals from the near-field response. Suggested reference signals for angled beam shear wave inspections include using the `through hole' corner specular reflection signal and the full skip' signal off of the far wall from the side drilled hole.

  3. Shear wave prediction using committee fuzzy model constrained by lithofacies, Zagros basin, SW Iran

    Science.gov (United States)

    Shiroodi, Sadjad Kazem; Ghafoori, Mohammad; Ansari, Hamid Reza; Lashkaripour, Golamreza; Ghanadian, Mostafa

    2017-02-01

    The main purpose of this study is to introduce the geological controlling factors in improving an intelligence-based model to estimate shear wave velocity from seismic attributes. The proposed method includes three main steps in the framework of geological events in a complex sedimentary succession located in the Persian Gulf. First, the best attributes were selected from extracted seismic data. Second, these attributes were transformed into shear wave velocity using fuzzy inference systems (FIS) such as Sugeno's fuzzy inference (SFIS), adaptive neuro-fuzzy inference (ANFIS) and optimized fuzzy inference (OFIS). Finally, a committee fuzzy machine (CFM) based on bat-inspired algorithm (BA) optimization was applied to combine previous predictions into an enhanced solution. In order to show the geological effect on improving the prediction, the main classes of predominate lithofacies in the reservoir of interest including shale, sand, and carbonate were selected and then the proposed algorithm was performed with and without lithofacies constraint. The results showed a good agreement between real and predicted shear wave velocity in the lithofacies-based model compared to the model without lithofacies especially in sand and carbonate.

  4. Reduced Patellar Tendon Elasticity with Aging: In Vivo Assessment by Shear Wave Elastography.

    Science.gov (United States)

    Hsiao, Ming-Yen; Chen, Yi-Ching; Lin, Che-Yu; Chen, Wen-Shian; Wang, Tyng-Guey

    2015-11-01

    How aging affects the elasticity of tendons has long been debated, partly because of the limited methods for in vivo evaluation, which differ vastly from those for in vitro animal studies. In this study, we tested the reliability of shear wave elastography (SWE) in the evaluation of patellar tendons and their change in elasticity with age. We recruited 62 healthy participants in three age groups: 20-30 years (group 1), 40-50 years (group 2) and 60-70 years (group 3). Shear wave velocity and elastic modulus were measured at the proximal, middle and distal areas of the patellar tendon. Reliability was excellent at the middle area and fair to good at both ends. Compared with the other groups, group 3 had significantly decreased elastic modulus and shear wave velocity values (p ≤ 0.001 vs. group 1 or 2), with significant increased side-to-side differences. SWE may be valuable in detecting aging tendons before visible abnormalities are observed on B-mode ultrasonography. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  5. Stochastic piecewise linear function fitting with application to ultrasound shear wave imaging.

    Science.gov (United States)

    Ingle, Atul; Varghese, Tomy; Sethares, William; Bucklew, James

    2014-01-01

    Piecewise linear function fitting is ubiquitous in many signal processing applications. Inspired by an application to shear wave velocity imaging in ultrasound elastography, this paper presents a discrete state-space Markov model for noisy piecewise linear data and also proposes a tractable algorithm for maximum a posteriori estimation of the slope of each segment in the piecewise linear function. The number and locations of breaks is handled indirectly by the stochastics of the Markov model. In the ultrasound shear wave imaging application, these slope values have concrete physical interpretation as being the reciprocal of the shear wave velocities in the imaged medium. Data acquired on an ellipsoidal inclusion phantom shows that this algorithm can provide good contrast of around 6 dB and contrast to noise ratio of 25 dB between the stiff inclusion and surrounding soft background. The phantom validation study also shows that this algorithm can be used to preserve sharp boundary details, which would otherwise be blurred out if a sliding window least squares filter is applied.

  6. Real-Time Monitoring of Shear Wave Traveling in Liver Tissue In Vivo

    Science.gov (United States)

    Machida, Hideyuki; Yagi, Shin-ichi; Kondo, Yuji; Murata, Yutaka; Akimoto, Shin

    2004-05-01

    Real-time imaging of tissue dynamic response caused by internal or external stress forces acting across a living tissue is promising for improving diagnostic quality and accuracy of clinical palpation as an “ultrasonic visualized palpation”. Thus we have investigated a real-time imaging system of local tissue displacement along an ultrasonic beam scanned across the living tissue, which realized straightforward but tissue-oriented physiological and dynamic color imaging on a conventional B-mode screen. System performance is fairly supported by a flexible design of a digital signal processor for real-time local cross correlation between successive two-dimensional complex speckle echo frames. Propagation of shear waves raised by external stress in a tissue phantom was clearly observed, so that real-time observation of shear wave traveling across a physiological liver tissue locally stressed by heartbeats was studied. As a result, we could confirm the characteristic shear wave propagation pattern by internal stress synchronous with heartbeat.

  7. Shear wave velocity versus quality factor: results from seismic noise recordings

    Science.gov (United States)

    Boxberger, Tobias; Pilz, Marco; Parolai, Stefano

    2017-08-01

    The assessment of the shear wave velocity (vs) and shear wave quality factor (Qs) for the shallow structure below a site is necessary to characterize its site response. In the past, methods based on the analysis of seismic noise have been shown to be very efficient for providing a sufficiently accurate estimation of the vs versus depth at reasonable costs for engineering seismology purposes. In addition, a slight modification of the same method has proved to be able to provide realistic Qs versus depth estimates. In this study, data sets of seismic noise recorded by microarrays of seismic stations in different geological environments of Europe and Central Asia are used to calculate both vs and Qs versus depth profiles. Analogous to the generally adopted approach in seismic hazard assessment for mapping the average shear wave velocity in the uppermost 30 m (vs30) as a proxy of the site response, this approach was also applied to the quality factor within the uppermost 30 m (Qs30). A slightly inverse correlation between both parameters is found based on a methodological consistent determination for different sites. Consequently, a combined assessment of vs and Qs by seismic noise analysis has the potential to provide a more comprehensive description of the geological structure below a site.

  8. An EMAT-based shear horizontal (SH) wave technique for adhesive bond inspection

    Science.gov (United States)

    Arun, K.; Dhayalan, R.; Balasubramaniam, Krishnan; Maxfield, Bruce; Peres, Patrick; Barnoncel, David

    2012-05-01

    The evaluation of adhesively bonded structures has been a challenge over the several decades that these structures have been used. Applications within the aerospace industry often call for particularly high performance adhesive bonds. Several techniques have been proposed for the detection of disbonds and cohesive weakness but a reliable NDE method for detecting interfacial weakness (also sometimes called a kissing bond) has been elusive. Different techniques, including ultrasonic, thermal imaging and shearographic methods, have been proposed; all have had some degree of success. In particular, ultrasonic methods, including those based upon shear and guided waves, have been explored for the assessment of interfacial bond quality. Since 3-D guided shear horizontal (SH) waves in plates have predominantly shear displacement at the plate surfaces, we conjectured that SH guided waves should be influenced by interfacial conditions when they propagate between adhesively bonded plates of comparable thickness. This paper describes a new technique based on SH guided waves that propagate within and through a lap joint. Through mechanisms we have yet to fully understand, the propagation of an SH wave through a lap joint gives rise to a reverberation signal that is due to one or more reflections of an SH guided wave mode within that lap joint. Based upon a combination of numerical simulations and measurements, this method shows promise for detecting and classifying interfacial bonds. It is also apparent from our measurements that the SH wave modes can discriminate between adhesive and cohesive bond weakness in both Aluminum-Epoxy-Aluminum and Composite-Epoxy-Composite lap joints. All measurements reported here used periodic permanent magnet (PPM) Electro-Magnetic Acoustic Transducers (EMATs) to generate either or both of the two lowest order SH modes in the plates that comprise the lap joint. This exact configuration has been simulated using finite element (FE) models to

  9. Shallow shear-wave velocity profiles and site response characteristics from microtremor array measurements in Metro Manila, the Philippines

    Science.gov (United States)

    Grutas, Rhommel; Yamanaka, Hiroaki

    2012-07-01

    This paper presents the outcome of reconnaissance surveys in metropolitan Manila (Metro Manilla), the Philippines, with the aim of mapping shallow shear-wave velocity structures. Metro Manila is a seismically active and densely populated region that is in need of detailed investigation of the subsurface structures, to assess local site effects in seismic hazard estimation. We conducted microtremor array observations and used the spatial autocorrelation method to estimate the shear-wave profiles at 32 sites in major geological settings in Metro Manila. We applied a hybrid genetic simulated annealing algorithm to invert phase velocity data from the spatial autocorrelation method to generate shear-wave velocity models near the global best-fit solution. The comparison between the inferred shear-wave velocity profiles and PS logging showed good agreement in terms of the fundamental mode of Rayleigh waves and site responses. Then, we utilised the inferred shear-wave velocity profiles to compute the site amplifications with reference to the motion in engineering bedrock. Subsequently, the site amplifications have been grouped, based on NEHRP site classes. The amplification factor has also been compared with the average shear-wave velocity of the upper 30m at each site, to produce a power-law regression equation that can be used as a starting basis for further site-effects evaluation in the metropolis.

  10. Investigation of mantle kinematics beneath the Hellenic-subduction zone with teleseismic direct shear waves

    Science.gov (United States)

    Confal, Judith M.; Eken, Tuna; Tilmann, Frederik; Yolsal-Çevikbilen, Seda; Çubuk-Sabuncu, Yeşim; Saygin, Erdinc; Taymaz, Tuncay

    2016-12-01

    The subduction and roll-back of the African plate beneath the Eurasian plate along the arcuate Hellenic trench is the dominant geodynamic process in the Aegean and western Anatolia. Mantle flow and lithospheric kinematics in this region can potentially be understood better by mapping seismic anisotropy. This study uses direct shear-wave splitting measurements based on the Reference Station Technique in the southern Aegean Sea to reveal seismic anisotropy in the mantle. The technique overcomes possible contamination from source-side anisotropy on direct S-wave signals recorded at a station pair by maximizing the correlation between the seismic traces at reference and target stations after correcting the reference stations for known receiver-side anisotropy and the target stations for arbitrary splitting parameters probed via a grid search. We obtained splitting parameters at 35 stations with good-quality S-wave signals extracted from 81 teleseismic events. Employing direct S-waves enabled more stable and reliable splitting measurements than previously possible, based on sparse SKS data at temporary stations, with one to five events for local SKS studies, compared with an average of 12 events for each station in this study. The fast polarization directions mostly show NNE-SSW orientation with splitting time delays between 1.15 s and 1.62 s. Two stations in the west close to the Hellenic Trench and one in the east show N-S oriented fast polarizations. In the back-arc region three stations exhibit NE-SW orientation. The overall fast polarization variations tend to be similar to those obtained from previous SKS splitting studies in the region but indicate a more consistent pattern, most likely due to the usage of a larger number of individual observations in direct S-wave derived splitting measurements. Splitting analysis on direct shear waves typically resulted in larger split time delays compared to previous studies, possibly because S-waves travel along a longer path

  11. On the Dynamics of Two-Dimensional Capillary-Gravity Solitary Waves with a Linear Shear Current

    Directory of Open Access Journals (Sweden)

    Dali Guo

    2014-01-01

    Full Text Available The numerical study of the dynamics of two-dimensional capillary-gravity solitary waves on a linear shear current is presented in this paper. The numerical method is based on the time-dependent conformal mapping. The stability of different kinds of solitary waves is considered. Both depression wave and large amplitude elevation wave are found to be stable, while small amplitude elevation wave is unstable to the small perturbation, and it finally evolves to be a depression wave with tails, which is similar to the irrotational capillary-gravity waves.

  12. Quantitative shear wave ultrasound elastography: initial experience in solid breast masses

    Science.gov (United States)

    2010-01-01

    Introduction Shear wave elastography is a new method of obtaining quantitative tissue elasticity data during breast ultrasound examinations. The aims of this study were (1) to determine the reproducibility of shear wave elastography (2) to correlate the elasticity values of a series of solid breast masses with histological findings and (3) to compare shear wave elastography with greyscale ultrasound for benign/malignant classification. Methods Using the Aixplorer® ultrasound system (SuperSonic Imagine, Aix en Provence, France), 53 solid breast lesions were identified in 52 consecutive patients. Two orthogonal elastography images were obtained of each lesion. Observers noted the mean elasticity values in regions of interest (ROI) placed over the stiffest areas on the two elastography images and a mean value was calculated for each lesion. A sub-set of 15 patients had two elastography images obtained by an additional operator. Reproducibility of observations was assessed between (1) two observers analysing the same pair of images and (2) findings from two pairs of images of the same lesion taken by two different operators. All lesions were subjected to percutaneous biopsy. Elastography measurements were correlated with histology results. After preliminary experience with 10 patients a mean elasticity cut off value of 50 kilopascals (kPa) was selected for benign/malignant differentiation. Greyscale images were classified according to the American College of Radiology (ACR) Breast Imaging Reporting and Data System (BI-RADS). BI-RADS categories 1-3 were taken as benign while BI-RADS categories 4 and 5 were classified as malignant. Results Twenty-three benign lesions and 30 cancers were diagnosed on histology. Measurement of mean elasticity yielded an intraclass correlation coefficient of 0.99 for two observers assessing the same pairs of elastography images. Analysis of images taken by two independent operators gave an intraclass correlation coefficient of 0.80. Shear

  13. Quantitative evaluation of atrial radio frequency ablation using intracardiac shear-wave elastography.

    Science.gov (United States)

    Kwiecinski, Wojciech; Provost, Jean; Dubois, Rémi; Sacher, Frédéric; Haïssaguerre, Michel; Legros, Mathieu; Nguyen-Dinh, An; Dufait, Rémi; Tanter, Mickaël; Pernot, Mathieu

    2014-11-01

    Radio frequency catheter ablation (RFCA) is a well-established clinical procedure for the treatment of atrial fibrillation (AF) but suffers from a low single-procedure success rate. Recurrence of AF is most likely attributable to discontinuous or nontransmural ablation lesions. Yet, despite this urgent clinical need, there is no clinically available imaging modality that can reliably map the lesion transmural extent in real time. In this study, the authors demonstrated the feasibility of shear-wave elastography (SWE) to map quantitatively the stiffness of RFCA-induced thermal lesions in cardiac tissues in vitro and in vivo using an intracardiac transducer array. SWE was first validated in ex vivo porcine ventricular samples (N = 5). Both B-mode imaging and SWE were performed on normal cardiac tissue before and after RFCA. Areas of the lesions were determined by tissue color change with gross pathology and compared against the SWE stiffness maps. SWE was then performed in vivo in three sheep (N = 3). First, the stiffness of normal atrial tissues was assessed quantitatively as well as its variation during the cardiac cycle. SWE was then performed in atrial tissue after RFCA. A large increase in stiffness was observed in ablated ex vivo regions (average shear modulus across samples in normal tissue: 22 ± 5 kPa, average shear-wave speed (ct): 4.5 ± 0.4 m s(-1) and in determined ablated zones: 99 ± 17 kPa, average ct: 9.0 ± 0.5 m s(-1) for a mean shear modulus increase ratio of 4.5 ± 0.9). In vivo, a threefold increase of the shear modulus was measured in the ablated regions, and the lesion extension was clearly visible on the stiffness maps. By its quantitative and real-time capabilities, Intracardiac SWE is a promising intraoperative imaging technique for the evaluation of thermal ablation during RFCA.

  14. Characterizing wave- and current- induced bottom shear stress: U.S. middle Atlantic continental shelf

    Science.gov (United States)

    Dalyander, P. Soupy; Butman, Bradford; Sherwood, Christopher R.; Signell, Richard P.; Wilkin, John L.

    2013-01-01

    Waves and currents create bottom shear stress, a force at the seabed that influences sediment texture distribution, micro-topography, habitat, and anthropogenic use. This paper presents a methodology for assessing the magnitude, variability, and driving mechanisms of bottom stress and resultant sediment mobility on regional scales using numerical model output. The analysis was applied to the Middle Atlantic Bight (MAB), off the U.S. East Coast, and identified a tidally-dominated shallow region with relatively high stress southeast of Massachusetts over Nantucket Shoals, where sediment mobility thresholds are exceeded over 50% of the time; a coastal band extending offshore to about 30 m water depth dominated by waves, where mobility occurs more than 20% of the time; and a quiescent low stress region southeast of Long Island, approximately coincident with an area of fine-grained sediments called the “Mud Patch”. The regional high in stress and mobility over Nantucket Shoals supports the hypothesis that fine grain sediment winnowed away in this region maintains the Mud Patch to the southwest. The analysis identified waves as the driving mechanism for stress throughout most of the MAB, excluding Nantucket Shoals and sheltered coastal bays where tides dominate; however, the relative dominance of low-frequency events varied regionally, and increased southward toward Cape Hatteras. The correlation between wave stress and local wind stress was lowest in the central MAB, indicating a relatively high contribution of swell to bottom stress in this area, rather than locally generated waves. Accurate prediction of the wave energy spectrum was critical to produce good estimates of bottom shear stress, which was sensitive to energy in the long period waves.

  15. Propagation of ultrasonic guided waves in lap-shear adhesive joints: Case of incident a0 Lamb wave

    Science.gov (United States)

    Lanza di Scalea, Francesco; Rizzo, Piervincenzo; Marzani, Alessandro

    2004-01-01

    This paper deals with the propagation of ultrasonic guided waves in adhesively bonded lap-shear joints. The topic is relevant to bond inspection by ultrasonic testing. Specifically, the propagation of the lowest-order, antisymmetric a0 mode through the joint is examined. An important aspect is the mode conversion at the boundaries between the single-plate adherents and the multilayer overlap. The a0 strength of transmission is studied for three different bond states in aluminum joints, namely a fully cured adhesive bond, a poorly cured adhesive bond, and a slip bond. Theoretical predictions indicate that the dispersive behavior of the guided waves in the multilayer overlap is highly dependent on bond state. Experimental tests are conducted in lap-shear joints by a hybrid, broadband laser/air-coupled ultrasonic setup in a through-transmission configuration. The Gabor wavelet transform is employed to extract energy transmission coefficients in the 100 kHz 1.4 MHz range for the three different bond states examined. The cross-sectional mode shapes of the guided waves are shown to have a substantial role in the energy transfer through the joint.

  16. Shear wave velocities in deformed Al-stishovite and seismic heterogeneities in the mid-mantle

    Science.gov (United States)

    Sanchez-Valle, C.; Rosa, A. D.; Bolfan-Casanova, N.; Evans, S.; Merkel, S.

    2012-12-01

    Seismic observations show extensive evidence for negative shear wave anomalies of 2 to 6% in the shallow to middle parts of the lower mantle (800 to 1850 km depths) in the vicinity of subduction zones [e.g., 1-4]. Although the origin of these anomalies is still under debate, shear softening related to the stishovite (rutile structure) to post-stishovite (CaCl2 structure) in subducted MORB may be a plausible explanation for these features [5]. The broad range of depths over which the heterogeneities span may be related to compositional effects on the transition pressure [5,6]. To better deciphering the observed seismic heterogeneities, a more detailed evaluation of the seismic properties of deformed stishovite due to mantle flow is required. In this contribution, we report investigations of the effect of texture development on the shear wave velocities of Al-bearing stishovite containing 5wt% of Al2O3, a plausible composition for subducted slabs. Experiments were conducted using synchrotron radial x-ray diffraction at ESRF ID09A and a panoramic diamond anvil cell as deformation apparatus. The samples were synthesized at 20 GPa and 1700 °C in a multianvil apparatus. The recovered Al-Stishovite crystals were reduced to fine-grained powders and loaded in x-ray transparent boron gaskets for experiments up to 50 GPa. Upon compression, changes in the texture are observed across the stishovite to post-stishovite transition. The results from the deformation experiments are used with available elasticity data obtained by Brillouin scattering spectroscopy in similar samples [5] to evaluate the effect of texture on the shear wave anomalies in stishovite. Ultimately, the implications of these results for the interpretation of seismic heterogeneities in the mid-mantle will be discussed. [1] Stunff et al., (1995); [2]Kaneshima and Helffrich (1999); [3] Vinnik et al., (2001); [4] Niu et al., (2003); [5] Lakshtanov et al., (2007); [6] Nomura et al. [2010].

  17. Measurement of elastic constants by simultaneously sensing longitudinal and shear waves as an overlapped signal

    Energy Technology Data Exchange (ETDEWEB)

    Seo, Ho Geon; Song, Dong Gi; Jhang, Kyoung Young [Hanyang University, Seoul (Korea, Republic of)

    2016-04-15

    Measurement of elastic constants is crucial for engineering aspects of predicting the behavior of materials under load as well as structural health monitoring of material degradation. Ultrasonic velocity measurement for material properties has been broadly used as a nondestructive evaluation method for material characterization. In particular, pulse-echo method has been extensively utilized as it is not only simple but also effective when only one side of the inspected objects is accessible. However, the conventional technique in this approach measures longitudinal and shear waves individually to obtain their velocities. This produces a set of two data for each measurement. This paper proposes a simultaneous sensing system of longitudinal waves and shear waves for elastic constant measurement. The proposed system senses both these waves simultaneously as a single overlapped signal, which is then analyzed to calculate both the ultrasonic velocities for obtaining elastic constants. Therefore, this system requires just half the number of data to obtain elastic constants compared to the conventional individual measurement. The results of the proposed simultaneous measurement had smaller standard deviations than those in the individual measurement. These results validate that the proposed approach improves the efficiency and reliability of ultrasonic elastic constant measurement by reducing the complexity of the measurement system, its operating procedures, and the number of data.

  18. Shear-wave sonoelastography for assessing masseter muscle hardness in comparison with strain sonoelastography: study with phantoms and healthy volunteers.

    Science.gov (United States)

    Ariji, Yoshiko; Nakayama, Miwa; Nishiyama, Wataru; Nozawa, Michihito; Ariji, Eiichiro

    2016-01-01

    Objectives Shear-wave sonoelastography is expected to facilitate low operator dependency, high reproducibility and quantitative evaluation, whereas there are few reports on available normative values of in vivo tissue in head and neck fields. The purpose of this study was to examine the reliabilities on measuring hardness using shear-wave sonoelastography and to clarify normal values of masseter muscle hardness in healthy volunteers. Methods Phantoms with known hardness ranging from 20 to 140 kPa were scanned with shear-wave sonoelastography, and inter- and intraoperator reliabilities were examined compared with strain sonoelastography. The relationships between the actual and measured hardness were analyzed. The masseter muscle hardness in 30 healthy volunteers was measured using shear-wave sonoelastography. The inter- and intraoperator intraclass correlation coefficients were almost perfect. Strong correlations were seen between the actual and measured hardness. The mean hardness of the masseter muscles in healthy volunteers was 42.82 ± 5.56 kPa at rest and 53.36 ± 8.46 kPa during jaw clenching. The hardness measured with shear-wave sonoelastography showed high-level reliability. Shear-wave sonoelastography may be suitable for evaluation of the masseter muscles.

  19. A uniform-sensitivity omnidirectional shear-horizontal (SH) wave transducer based on a thickness poled, thickness-shear (d15) piezoelectric ring

    Science.gov (United States)

    Huan, Qiang; Miao, Hongchen; Li, Faxin

    2017-08-01

    The fundamental shear horizontal (SH0) wave in plates is of great importance in the field of nondestructive testing (NDT) and structural health monitoring (SHM) since it is the unique non-dispersive guided wave mode. For practical applications, a phased array system based on omnidirectional SH0 wave transducers is most useful as it can cover a wide range of a plate. However, so far very few omnidirectional SH wave transducers have been developed. In this work, we proposed an omnidirectional SH wave piezoelectric transducer (OSH-PT) based on a thickness poled piezoelectric ring. The ring is equally divided into twelve sectors and the electric field is circumferentially applied, resulting in a new thickness-shear (d15) mode. Finite element analysis shows that the proposed OSH-PT can excite single-mode SH0 wave and receive the SH0 wave only. Experiments were then conducted to examine the performance of the proposed OSH-PT. Results indicated that it can generate and receive single-mode SH0 wave in a wide frequency range with nearly uniform sensitivities along all directions. Considering its quite simple configuration, compact size and low cost, the proposed OSH-PT is expected to greatly promote the applications of SH waves in the field of NDT and SHM.

  20. Towards a new tool to develop a 3-D shear-wave velocity model from converted waves

    Science.gov (United States)

    Colavitti, Leonardo; Hetényi, György

    2017-04-01

    The main target of this work is to develop a new method in which we exploit converted waves to construct a fully 3-D shear-wave velocity model of the crust. A reliable 3-D model is very important in Earth sciences because geological structures may vary significantly in their lateral dimension. In particular, shear-waves provide valuable complementary information with respect to P-waves because they usually guarantee a much better correlation in terms of rock density and mechanical properties, reducing the interpretation ambiguities. Therefore, it is fundamental to develop a new technique to improve structural images and to describe different lithologies in the crust. In this study we start from the analysis of receiver functions (RF, Langston, 1977), which are nowadays largely used for structural investigations based on passive seismic experiments, to map Earth discontinuities at depth. The RF technique is also commonly used to invert for velocity structure beneath single stations. Here, we plan to combine two strengths of RF method: shear-wave velocity inversion and dense arrays. Starting from a simple 3-D forward model, synthetic RFs are obtained extracting the structure along a ray to match observed data. During the inversion, thanks to a dense stations network, we aim to build and develop a multi-layer crustal model for shear-wave velocity. The initial model should be chosen simple to make sure that the inversion process is not influenced by the constraints in terms of depth and velocity posed at the beginning. The RFs inversion represents a complex problem because the amplitude and the arrival time of different phases depend in a non-linear way on the depth of interfaces and the characteristics of the velocity structure. The solution we envisage to manage the inversion problem is the stochastic Neighbourhood Algorithm (NA, Sambridge, 1999a, b), whose goal is to find an ensemble of models that sample the good data-fitting regions of a multidimensional parameter

  1. Development of oil-in-gelatin phantoms for viscoelasticity measurement in ultrasound shear wave elastography.

    Science.gov (United States)

    Nguyen, Man M; Zhou, Shiwei; Robert, Jean-Luc; Shamdasani, Vijay; Xie, Hua

    2014-01-01

    Because tissues consist of solid and fluid materials, their mechanical properties should be characterized in terms of both elasticity and viscosity. Although the elastic properties of tissue-mimicking phantoms have been extensively studied and well characterized in commercially available phantoms, their viscous properties have not been fully investigated. In this article, a set of 14 tissue-mimicking phantoms with different concentrations of gelatin and castor oil were fabricated and characterized in terms of acoustic and viscoelastic properties. The results indicate that adding castor oil to gelatin phantoms decreases shear modulus, but increases shear wave dispersion. For 3% gelatin phantoms containing 0%, 10%, 20% and 40% oil, the measured shear moduli are 2.01 ± 0.26, 1.68 ± 0.25, 1.10 ± 0.22 and 0.88 ± 0.17 kPa, and the Voigt-model coupled shear viscosities are 0.60 ± 0.11, 0.89 ± 0.07, 1.05 ± 0.11 and 1.06 ± 0.13 Pa·s, respectively. The results also confirm that increasing the gelatin concentration increases shear modulus. For phantoms containing 3%, 4%, 5%, 6% and 7% gelatin, the measured shear moduli are 2.01 ± 0.26, 3.10 ± 0.34, 4.18 ± 0.84, 8.05 ± 1.00 and 10.24 ± 1.80 kPa at 0% oil and 1.10 ± 0.22, 1.97 ± 0.20, 3.13 ± 0.63, 4.60 ± 0.60 and 8.43 ± 1.39 kPa at 20% oil, respectively. The phantom recipe developed in this study can be used in validating ultrasound shear wave elastography techniques for soft tissues. Copyright © 2014 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  2. Monitoring the lesion formation during histotripsy treatment using shear wave imaging

    Science.gov (United States)

    Arnal, Bastien; Lee, Wei-Ning; Pernot, Mathieu; Fink, Mathias; Tanter, Mickael

    2012-11-01

    Monitoring the lesion formation induced by histotripsy has mainly relied on the quantitative change in backscatter intensity using ultrasound B-mode imaging. However, how the mechanical properties of the histotripsy-treated tissue region alter during the procedure is yet to be fully investigated. We thus proposed here to monitor such a therapeutic process based on shear modulus estimated by shear wave imaging (SWI). In the therapeutic procedure, a single-element piezo-composite focused transducer (Imasonic, Besançon, France) with a center frequency of 660 kHz, a focal length of 45 mm, and an fnumber of 1 was driven by a function generator (AFG 3101, Tektronix, Beaverton, OR) and a gated RF power amplifier (GA-2500A, RITEC Inc., USA) to generate ultrasound histotripsy pulses. Histotripsy pulses were delivered for 20 seconds and then followed by a 30-second pause and a rapid monitoring step. Such a treatment and monitoring scheme was repeated for 10 mins. Both the reference measurement and monitoring were realized by SWI, where plane shear waves were generated by an 8 MHz linear array probe connected to a prototype ultrasound scanner, and acquired at a frame rate of 10000 Hz. Shear modulus was estimated and mapped in 2D through a time-of-flight algorithm. Gelatin (8%)-agar (2%) phantoms and ex-vivo porcine liver samples were tested. Regions of interests (ROI's) of 2 mm-by-2 mm in both untreated and treated regions were selected to compute the contrast-to-noise ratio (CNR). In all three scenarios where different PD's and PRF's were implemented, during the first 100 seconds of the treatment, 50% decrease in the shear modulus within the histotripsy-targeted zone was already observed, and the CNR of the shear modulus increased by 18 dB. In contrast, the backscatter intensity began to reduce and the corresponding CNR was found to increase by 6 dB only after 120 seconds of treatment. The results demonstrated that SWI can map quantitatively the change of mechanical

  3. Shallow shear-wave reflection seismics in the tsunami struck Krueng Aceh River Basin, Sumatra

    Directory of Open Access Journals (Sweden)

    U. Polom

    2008-01-01

    Full Text Available As part of the project "Management of Georisk" (MANGEONAD of the Federal Institute for Geosciences and Natural Resources (BGR, Hanover, high resolution shallow shear-wave reflection seismics was applied in the Indonesian province Nanggroe Aceh Darussalam, North Sumatra in cooperation with the Government of Indonesia, local counterparts, and the Leibniz Institute for Applied Geosciences, Hanover. The investigations were expected to support classification of earthquake site effects for the reconstruction of buildings and infrastructure as well as for groundwater exploration. The study focussed on the city of Banda Aceh and the surroundings of Aceh Besar. The shear-wave seismic surveys were done parallel to standard geoengineering investigations like cone penetrometer tests to support subsequent site specific statistical calibration. They were also partly supplemented by shallow p-wave seismics for the identification of (a elastic subsurface parameters and (b zones with abundance of groundwater. Evaluation of seismic site effects based on shallow reflection seismics has in fact been found to be a highly useful method in Aceh province. In particular, use of a vibratory seismic source was essential for successful application of shear-wave seismics in the city of Banda Aceh and in areas with compacted ground like on farm tracks in the surroundings, presenting mostly agricultural land use areas. We thus were able to explore the mechanical stiffness of the subsurface down to 100 m depth, occasionally even deeper, with remarkably high resolution. The results were transferred into geotechnical site classification in terms of the International Building Code (IBC, 2003. The seismic images give also insights into the history of the basin sedimentation processes of the Krueng Aceh River delta, which is relevant for the exploration of new areas for construction of safe foundations of buildings and for identification of fresh water aquifers in the tsunami

  4. On the Origin of High Shear Wave Velocities in the Deep Roots of Cratons

    Science.gov (United States)

    Zeng, L.; Duncan, M. S.; Garber, J. M.; Hernandez, J. A.; Maurya, S.; Zhang, H.; Faul, U.; McCammon, C. A.; Montagner, J. P.; Moresi, L. N.; Romanowicz, B. A.; Rudnick, R. L.; Stixrude, L. P.

    2016-12-01

    Some seismic models derived from tomographic studies indicate very high shear wave velocities around 150 km depth, which cannot be explained by standard cratonic peridotite compositions derived from kimberlites, even under the assumption of very cold geotherms (i.e. 28mW/m3 surface heat flux). We present the results of a multi-disciplinary study conducted at the CIDER Summer 2016 program in Santa Barbara (CA), in which we have reviewed various geophysical and petrological constraints on the nature of cratonic roots (seismic velocities, electrical conductivity, gravity, lithologies) and explored a range of possible solutions. We find that matching the high shear wave velocities requires a large proportion of eclogite that is not matched by observed eclogite proportions in kimberlite samples. The high shear velocity of diamond makes it a viable candidate to account for such high velocities, in a proportion that is compatible with the global carbon budget. Our most recent results will be presented as well as suggestions for possible mechanisms for diamond formation and emplacement.

  5. Subsurface structure of the Nojima fault from dipole shear velocity/anisotropy and borehole Stoneley wave

    Energy Technology Data Exchange (ETDEWEB)

    Ito, H. [Geological Survey of Japan, Tsukuba (Japan); Yamamoto, H.; Brie, A.

    1996-10-01

    Fracture and permeability in the fault zone of the active fault drilling at the Nojima fault were evaluated from acoustic waveforms. There were several permeable intervals in the fault zone. There was strong Stoneley wave attenuation, very large S-Se below the fault and in the interval above the fault. In the fault zone, there were also several short intervals where S-Se was very large; 667 m-674 m and 706 m-710 m. In these intervals, the Stoneley attenuation was large, but there was no Stoneley reflection from within the interval. Reflections were observed at the upper and lower boundaries, going away from the bed up above, and down below. In this well, the shear wave was very strongly attenuated at and below the fault zone. The fast shear azimuth changed at the fault. The slowness anisotropy was fairly strong above the fault from 602 m to 612 m, but smaller below the fault. The changes in fast shear azimuth were much more pronounced near the fault, which suggested a strong influence of the fault. 6 refs., 5 figs.

  6. Shear wave elastography reveals different degrees of passive and active stiffness of the neck extensor muscles.

    Science.gov (United States)

    Dieterich, Angela V; Andrade, Ricardo J; Le Sant, Guillaume; Falla, Deborah; Petzke, Frank; Hug, François; Nordez, Antoine

    2017-01-01

    The neck extensor muscles contribute to spinal support and posture while performing head and neck motion. Muscle stiffness relates to passive elasticity (support) and active tensioning (posture and movement) of muscle. It was hypothesized that support and motion requirements are reflected in the distribution of stiffness between superficial and deep neck extensor muscles. In ten healthy participants, shear modulus (stiffness) of five neck extensor muscles was determined in prone at rest and during isometric head lift at three intensities using shear wave elastography. Shear modulus differed between muscles (P muscles: (median (interquartile range)) trapezius 7.7 kPa (4.4), splenius capitis 6.5 kPa (2.5), semispinalis capitis 8.9 kPa (2.8), semispinalis cervicis 9.5 kPa (2.5), multifidus 14.9 kPa (1.4). Shear modulus differed between the resting condition and head lift (P muscles most close to the spine. The highest active increase of stiffness during the head lift was found in the semispinalis cervicis muscle. The non-invasive, clinically applicable estimates of muscle stiffness have potential for the assessment of muscular changes associated with neck pain/injury.

  7. Direct Numerical Simulations of Small-Scale Gravity Wave Instability Dynamics in Variable Stratification and Shear

    Science.gov (United States)

    Mixa, T.; Fritts, D. C.; Laughman, B.; Wang, L.; Kantha, L. H.

    2015-12-01

    Multiple observations provide compelling evidence that gravity wave dissipation events often occur in multi-scale environments having highly-structured wind and stability profiles extending from the stable boundary layer into the mesosphere and lower thermosphere. Such events tend to be highly localized and thus yield local energy and momentum deposition and efficient secondary gravity wave generation expected to have strong influences at higher altitudes [e.g., Fritts et al., 2013; Baumgarten and Fritts, 2014]. Lidars, radars, and airglow imagers typically cannot achieve the spatial resolution needed to fully quantify these small-scale instability dynamics. Hence, we employ high-resolution modeling to explore these dynamics in representative environments. Specifically, we describe numerical studies of gravity wave packets impinging on a sheet of high stratification and shear and the resulting instabilities and impacts on the gravity wave amplitude and momentum flux for various flow and gravity wave parameters. References: Baumgarten, Gerd, and David C. Fritts (2014). Quantifying Kelvin-Helmholtz instability dynamics observed in noctilucent clouds: 1. Methods and observations. Journal of Geophysical Research: Atmospheres, 119.15, 9324-9337. Fritts, D. C., Wang, L., & Werne, J. A. (2013). Gravity wave-fine structure interactions. Part I: Influences of fine structure form and orientation on flow evolution and instability. Journal of the Atmospheric Sciences, 70(12), 3710-3734.

  8. Shear-Wave Velocity Structure Around the Korean Peninsula Using the Rayleigh Wave Signature of the North Korea Underground Nuclear Explosion on May 25, 2009

    Science.gov (United States)

    Kim, G.; Shin, J.; Chi, H. C.; Sheen, D.; Park, J.; Cho, C.

    2011-12-01

    The crustal structure around the Korean Peninsula was investigated by analyzing the Rayleigh waves generated from the 2nd North Korea underground nuclear explosion on May 25, 2009. Group velocity dispersion curves were measured from vertical component waveforms of 20 broadband stations in the range of 194 to 1183 km from the test site. The measured dispersion curves were inverted to get shear-wave velocity models for depths from 0 to 50 km. The dispersion curves and the velocity models clearly show lateral variations in the crustal structure, which could be more clearly classified into the North Korea-Northeast China group, the Western Margin of the East Sea group, and the Japan Basin group. For each group, an averaged dispersion curve and an averaged velocity model were measured. The averaged shear-wave velocity model of the North Korea-Northeast China group shows that the mean shear-wave velocity of the Moho discontinuity, which is known to be located at approximately 35 km, is 4.37 km/s with a standard deviation of 0.15 km/s. The averaged shear-wave velocity model of the Japan Basin group shows a mean shear-wave velocity of 4.26 km/s with a standard deviation of 0.14 km/s in the layer between 16 and 22 km. The averaged shear-wave velocity model of the Western Margin of the East Sea group shows characteristics of a transition zone between the North Korea-Northeast China group, which represents continental crust, and the Japan Basin group, which represents oceanic crust. The mean shear-wave velocity in the layer between 16 and 22 km is 4.12 km/s with a standard deviation of 0.05 km/s.

  9. Investigation of sinkhole areas in Germany using 2D shear wave reflection seismics and zero-offset VSP

    Science.gov (United States)

    Tschache, Saskia; Wadas, Sonja; Polom, Ulrich; Krawczyk, Charlotte M.

    2017-04-01

    Sinkholes pose a serious geohazard for humans and infrastructure in populated areas. The Junior Research Group Subrosion within the Leibniz Institute for Applied Geophysics and the joint project SIMULTAN work on the multi-scale investigation of subrosion processes in the subsurface, which cause natural sinkholes. In two case studies in sinkhole areas of Thuringia in Germany, we applied 2D shear wave reflection seismics using SH-waves with the aim to detect suitable parameters for the characterisation of critical zones. This method has the potential to image near-surface collapse and faulting structures in improved resolution compared to P-wave surveys resulting from the shorter wavelength of shear waves. Additionally, the shear wave velocity field derived by NMO velocity analysis is a basis to calculate further physical parameters, as e.g. the dynamic shear modulus. In both investigation areas, vertical seismic profiles (VSP) were acquired by generating P- and SH-waves (6 component VSP) directly next to a borehole equipped with a 3C downhole sensor. They provide shear and compressional wave velocity profiles, which are used to improve the 2D shear wave velocity field from surface seismics, to perform a depth calibration of the seismic image and to calculate the Vp/Vs ratio. The signals in the VSP data are analysed with respect to changes in polarisation and attenuation with depth and/or azimuth. The VSP data reveal low shear wave velocities of 200-300 m/s in rock layers known to be heavily affected by subrosion and confirm the low velocities calculated from the surface seismic data. A discrepancy of the shear wave velocities is observed in other intervals probably due to unsymmetrical travel paths in the surface seismics. In some VSP data dominant conversion of the direct SH-wave to P-wave is observed that is assumed to be caused by an increased presence of cavities. A potential fault distorting the vertical travel paths was detected by abnormal P-wave first

  10. Concurrent Visualization of Acoustic Radiation Force Displacement and Shear Wave Propagation with 7T MRI.

    Directory of Open Access Journals (Sweden)

    Yu Liu

    Full Text Available Manual palpation is a common and very informative diagnostic tool based on estimation of changes in the stiffness of tissues that result from pathology. In the case of a small lesion or a lesion that is located deep within the body, it is difficult for changes in mechanical properties of tissue to be detected or evaluated via palpation. Furthermore, palpation is non-quantitative and cannot be used to localize the lesion. Magnetic Resonance-guided Focused Ultrasound (MRgFUS can also be used to evaluate the properties of biological tissues non-invasively. In this study, an MRgFUS system combines high field (7T MR and 3 MHz focused ultrasound to provide high resolution MR imaging and a small ultrasonic interrogation region (~0.5 x 0.5 x 2 mm, as compared with current clinical systems. MR-Acoustic Radiation Force Imaging (MR-ARFI provides a reliable and efficient method for beam localization by detecting micron-scale displacements induced by ultrasound mechanical forces. The first aim of this study is to develop a sequence that can concurrently quantify acoustic radiation force displacements and image the resulting transient shear wave. Our motivation in combining these two measurements is to develop a technique that can rapidly provide both ARFI and shear wave velocity estimation data, making it suitable for use in interventional radiology. Secondly, we validate this sequence in vivo by estimating the displacement before and after high intensity focused ultrasound (HIFU ablation, and we validate the shear wave velocity in vitro using tissue-mimicking gelatin and tofu phantoms. Such rapid acquisitions are especially useful in interventional radiology applications where minimizing scan time is highly desirable.

  11. Detection of placenta elasticity modulus by quantitative real-time shear wave imaging.

    Science.gov (United States)

    Li, W J; Wei, Z T; Yan, R L; Zhang, Y L

    2012-01-01

    To explore the clinical values in detecting the placental elastic modulus using real-time quantitative shear wave elasticity imaging. A total of 30 women in the late pregnancy stage without complications and having normal, single pregnancies, as well as normal fetal growth, amniotic fluid index, and anterior placenta were selected. A real-time elasticity imaging shear wave ultrasonic diagnostic apparatus was used to randomly select regions of interest at the central and edge of the placenta. The elastography imaging mode was launched to measure the elasticity of the elastic modulus of these placental parts. A total of 15 measured values were obtained at the placental center and edge for each pregnancy case. Umbilical artery and uterine artery pulsatility index (PI) values for 18 cases were also randomly measured. The average value of 30 placental edges of the elastic modulus (n = 15) was (7.60 +/- 1.71) kPa. The average value of the 30 placental central elastic modulus (n = 15 ) was (7.84 +/- 1.68) kPa. No significant difference was observed between placenta central and edge elastic modulus. The PI mean value of umbilical artery in 18 cases was 0.94, whereas the average PI values of the uterine artery was 0.83. No linear correlation was found among the elastic modulus, the placental uterine artery PI values, and the umbilical artery PI values (p > 0.05). No difference between the placental center of normal pregnancies and the edge of the elastic modulus was detected. The elastic modulus of the placenta could be obtained in the best position. The placenta varied greatly between elastic modulus. No correlation was found between the placental elastic modulus, the uterine artery, and umbilical artery PI values. Real-time shear wave elasticity imaging technology can provide morphological evidence of placental function, which may emerge as a new clinical assessment approach.

  12. Reproducibility of real-time shear wave elastography in the evaluation of liver elasticity

    Energy Technology Data Exchange (ETDEWEB)

    Ferraioli, Giovanna, E-mail: giovanna.ferraioli@unipv.it [Ultrasound Unit, Infectious Diseases Department, IRCCS San Matteo Hospital Foundation, University of Pavia, Via Taramelli 5, 27100 Pavia (Italy); Tinelli, Carmine, E-mail: ctinelli@smatteo.pv.it [Clinical Epidemiology and Biometric Unit, IRCCS San Matteo Hospital Foundation, Viale Golgi 19, 27100 Pavia (Italy); Zicchetti, Mabel, E-mail: mabel.zicchetti@unipv.it [Ultrasound Unit, Infectious Diseases Department, IRCCS San Matteo Hospital Foundation, University of Pavia, Via Taramelli 5, 27100 Pavia (Italy); Above, Elisabetta, E-mail: betta.above@gmail.com [Ultrasound Unit, Infectious Diseases Department, IRCCS San Matteo Hospital Foundation, University of Pavia, Via Taramelli 5, 27100 Pavia (Italy); Poma, Gianluigi, E-mail: gigi.poma@libero.it [Ultrasound Unit, Infectious Diseases Department, IRCCS San Matteo Hospital Foundation, University of Pavia, Via Taramelli 5, 27100 Pavia (Italy); Di Gregorio, Marta, E-mail: martadigregorio@virgilio.it [Ultrasound Unit, Infectious Diseases Department, IRCCS San Matteo Hospital Foundation, University of Pavia, Via Taramelli 5, 27100 Pavia (Italy); Filice, Carlo, E-mail: carfil@unipv.it [Ultrasound Unit, Infectious Diseases Department, IRCCS San Matteo Hospital Foundation, University of Pavia, Via Taramelli 5, 27100 Pavia (Italy)

    2012-11-15

    Objective: To evaluate the reproducibility of real-time shear wave elastography in assessing liver elasticity in healthy volunteers. Methods: Forty-two volunteers were studied in day 1. Shear wave elastography studies were performed by using the ultrasound system Aixplorer Trade-Mark-Sign (SuperSonic Imagine S.A., Aix-en-Provence, France) with a convex broadband probe. Measurements were carried by two operators, an expert (operator 1) and a novice (operator 2). Examinations were performed on the right lobe of the liver. Each operator performed 10 consecutive measurements in each volunteer. In a subset of volunteers (n = 18) measurements were performed twice on two different days (day 1 and day 2). Intraobserver and interobserver agreement were assessed by intraclass correlation coefficient. Results: Intraobserver agreement between measurements performed in the same subject in the same day (day 1 or day 2) showed intraclass correlation coefficient values of 0.95 (95% confidence interval, 0.93-0.98) and 0.93 (95% confidence interval, 0.90-0.96) for operator 1 and operator 2, respectively. Intraobserver agreement between measurements performed in the same subject in different days showed intraclass correlation coefficient values of 0.84 (95% confidence interval, 0.69-0.98) and 0.65 (95% confidence interval, 0.39-0.91) for operator 1 and operator 2, respectively. Interobserver agreement was 0.88 (95% confidence interval, 0.82-0.94). Conclusions: The results of this study show that shear wave elastography is a reliable and reproducible noninvasive method for the assessment of liver elasticity. Expert operator had higher reproducibility of measurements over time than novice operator.

  13. Evaluation of Liver, Kidney, and Spleen Elasticity in Healthy Newborns and Infants Using Shear Wave Elastography.

    Science.gov (United States)

    Palabiyik, Figen Bakirtas; Inci, Ercan; Turkay, Rustu; Bas, Derya

    2017-10-01

    Elasticity measurements of tissues can be valuable in the diagnosis and management of various diseases. The aim of this study was to determine the elasticity values for normal liver, kidney, and spleen of healthy newborns and infants using shear wave elastography (SWE) imaging. A total of 50 healthy term newborns and infants (19 girls and 31 boys; mean age 20.1 days, range 1 to 70 days) were examined by an experienced pediatric radiologist using SWE. None of them had any liver, kidney or spleen disease, or any other systemic disease that could affect these organs secondarily. All newborns and infants had a normal abdominal ultrasound scan. Age, sex, weight, height, and body mass index had no significant effects on shear wave velocity (SWV) values of liver and spleen. The SWV values of both kidneys decreased with age, weight, height, and body mass index. The mean SWV values were 1.70 m/s (range: 1.23-2.43 m/s) for the liver, 1.69 m/s (range: 0.8-2.40 m/s) for the right kidney, 1.70 m/s (range: 0.9-2.49 m/s) for the left kidney, and 2.03 m/s (range: 1.28-2.48 m/s) for the spleen. Shear wave elastography can be used to measure liver, kidney, and spleen elasticity in newborns and infants. The standard values for abdominal organs allow differentiation of healthy versus pathological tissue. We measured the normal values of SWE in healthy newborns and infants as reference data. © 2017 by the American Institute of Ultrasound in Medicine.

  14. Measuring the linear and nonlinear elastic properties of brain tissue with shear waves and inverse analysis.

    Science.gov (United States)

    Jiang, Yi; Li, Guoyang; Qian, Lin-Xue; Liang, Si; Destrade, Michel; Cao, Yanping

    2015-10-01

    We use supersonic shear wave imaging (SSI) technique to measure not only the linear but also the nonlinear elastic properties of brain matter. Here, we tested six porcine brains ex vivo and measured the velocities of the plane shear waves induced by acoustic radiation force at different states of pre-deformation when the ultrasonic probe is pushed into the soft tissue. We relied on an inverse method based on the theory governing the propagation of small-amplitude acoustic waves in deformed solids to interpret the experimental data. We found that, depending on the subjects, the resulting initial shear modulus [Formula: see text] varies from 1.8 to 3.2 kPa, the stiffening parameter [Formula: see text] of the hyperelastic Demiray-Fung model from 0.13 to 0.73, and the third- [Formula: see text] and fourth-order [Formula: see text] constants of weakly nonlinear elasticity from [Formula: see text]1.3 to [Formula: see text]20.6 kPa and from 3.1 to 8.7 kPa, respectively. Paired [Formula: see text] test performed on the experimental results of the left and right lobes of the brain shows no significant difference. These values are in line with those reported in the literature on brain tissue, indicating that the SSI method, combined to the inverse analysis, is an efficient and powerful tool for the mechanical characterization of brain tissue, which is of great importance for computer simulation of traumatic brain injury and virtual neurosurgery.

  15. Shear wave elastography using amplitude-modulated acoustic radiation force and phase-sensitive optical coherence tomography

    Science.gov (United States)

    Nguyen, Thu-Mai; Arnal, Bastien; Song, Shaozhen; Huang, Zhihong; Wang, Ruikang K.; O'Donnell, Matthew

    2015-01-01

    Investigating the elasticity of ocular tissue (cornea and intraocular lens) could help the understanding and management of pathologies related to biomechanical deficiency. In previous studies, we introduced a setup based on optical coherence tomography for shear wave elastography (SWE) with high resolution and high sensitivity. SWE determines tissue stiffness from the propagation speed of shear waves launched within tissue. We proposed acoustic radiation force to remotely induce shear waves by focusing an ultrasound (US) beam in tissue, similar to several elastography techniques. Minimizing the maximum US pressure is essential in ophthalmology for safety reasons. For this purpose, we propose a pulse compression approach. It utilizes coded US emissions to generate shear waves where the energy is spread over a long emission, and then numerically compressed into a short, localized, and high-energy pulse. We used a 7.5-MHz single-element focused transducer driven by coded excitations where the amplitude is modulated by a linear frequency-swept square wave (1 to 7 kHz). An inverse filter approach was used for compression. We demonstrate the feasibility of performing shear wave elastography measurements in tissue-mimicking phantoms at low US pressures (mechanical index <0.6).

  16. Comparison of shear-wave and strain ultrasound elastography in the differentiation of benign and malignant breast lesions.

    Science.gov (United States)

    Chang, Jung Min; Won, Jae-Kyung; Lee, Kyoung-Bun; Park, In Ae; Yi, Ann; Moon, Woo Kyung

    2013-08-01

    The purpose of this article is to compare the diagnostic performances of shearwave and strain elastography for the differentiation of benign and malignant breast lesions. B-mode ultrasound and shear-wave and strain elastography were performed in 150 breast lesions; 71 were malignant. BI-RADS final assessment, elasticity values in kilopascals, and elasticity scores on a 5-point scale were assessed before biopsy. The results were compared using the area under the receiver operating characteristic curve (AUC). The AUC for shear-wave elastography was similar to that of strain elastography (0.928 vs 0.943). The combined use of B-mode ultrasound and either elastography technique improved diagnostic performance in the differentiation of benign and malignant breast lesions compared with the use of B-mode ultrasound alone (B-mode alone, AUC = 0.851; B-mode plus shear-wave elastography, AUC = 0.964; B-mode plus strain elastography, AUC = 0.965; p < 0.001). With the best cutoff points of 80 kPa on shear-wave elastography and a score between 3 and 4 on strain elastography, the sensitivity was higher in shear-wave elastography, and specificity was higher in strain elastography (95.8% vs 81.7%, p = 0.002; 93.7% vs 84.8%, p = 0.016). In cases of infiltrating ductal carcinoma, mean elasticity scores were lower in grade 3 than in grade 1 and 2 cancers (p = 0.017) with strain elastography causing false-negative findings. The diagnostic performance of shear-wave and strain elastography was similar. Either elastography technique can improve overall diagnostic performance in the differentiation of benign and malignant lesions when combined with B-mode ultrasound. However, the sensitivity and specificity of shear-wave and strain elastography were different according to lesion histologic profile, tumor grade, and breast thickness.

  17. Diagnosis of Fibrosis and Activity by a Combined Use of Strain and Shear Wave Imaging in Patients with Liver Disease.

    Science.gov (United States)

    Yada, Norihisa; Tamaki, Nobuhura; Koizumi, Yohei; Hirooka, Masashi; Nakashima, Osamu; Hiasa, Yoichi; Izumi, Namiki; Kudo, Masatoshi

    2017-01-01

    Performing shear wave imaging is simple, but can be difficult when inflammation, jaundice, and congestion are present. Therefore, the correct diagnosis of liver fibrosis using shear wave imaging alone might be difficult in mild-to-moderate fibrosis cases. Strain imaging can diagnose liver fibrosis without the influence of inflammation. Therefore, the combined use of strain and shear wave imaging (combinational elastography) for cases without jaundice and congestion might be useful for evaluating fibrosis and inflammation. We enrolled consecutive patients with liver disease, without jaundice or liver congestion. Strain and shear wave imaging, blood tests, and liver biopsy were performed on the same day. The liver fibrosis index (LF index) was calculated by strain imaging; real-time tissue elastography, and the shear wave velocity (Vs) was calculated by shear wave imaging. Fibrosis index (F index) and activity index (A index) were calculated as a multiple regression equation for determining hepatic fibrosis and inflammation using histopathological diagnosis as the gold standard. The diagnostic ability of F index for fibrosis and A index for inflammation were compared using LF index and Vs. The total number of enrolled cases was 388. The area under the receiver operating characteristic (AUROC) was 0.87, 0.80, 0.83, and 0.80, at diagnosis of fibrosis stage with an F index of F1 or higher, F2 or higher, F3 or higher, and F4, respectively. The AUROC was 0.94, 0.74, and 0.76 at diagnosis of activity grade with an A index of A1 or higher, A2 or higher, and A3, respectively. The diagnostic ability of F index for liver fibrosis and A index for inflammation was higher than for other conventional diagnostic values. The combined use of strain and shear wave imaging (combinational elastography) might increase the positive diagnosis of liver fibrosis and inflammation. © 2017 S. Karger AG, Basel.

  18. Geothermal exploration in the German Molasse Basin - Supplementary exploration using integrated 3-component data and shear wave measurements

    Science.gov (United States)

    Wawerzinek, Britta; Buness, Hermann; Lüschen, Ewald; Thomas, Rüdiger

    2017-04-01

    To establish a dense area-wide network of geothermal facilities, the Stadtwerke München initiated the joint research project GRAME together with the Leibniz Institute for Applied Geophysics (GeoParaMoL*). As a database for the project, a 3D seismic survey was acquired from November 1015 to March 2016 and covers 170 km2 of the southern part of Munich. 3D seismic exploration is a well-established method to explore geothermal reservoirs, and its value for reservoir characterization of the Malm has been proven by several projects. A particular challenge often is the determination of geophysical parameters for facies interpretation without any borehole information, which is needed for calibration. A new approach to facilitate a reliable interpretation is to include shear waves in the interpretation workflow, which helps to tie down the range of lithological and petrophysical parameters. Shear wave measurements were conducted during the regular 3D seismic survey in Munich. In a passive experiment, the survey was additionally recorded on 467 single, 3-component (3C), digital receivers that were deployed along one main line (15 km length) and two crosslines (4 km length). In this way another 3D P-wave as well as a 3D shear wave dataset were acquired. In the active shear wave experiment the SHOVER technique (Edelmann, 1981) was applied to directly excite shear waves using standard vertical vibrators. The 3C recordings of both datasets show, in addition to the P-wave reflections on the vertical component, clear shear-wave signals on the horizontal components. The structural image of the P-waves recorded on the vertical component of the 3C receivers displays clear reflectors within the Molasse Basin down to the Malm and correlates well with the structural image of the regular survey. Taking into account a travel time ratio of 1.6 the reflection patterns of horizontal and vertical components approximately coincide. This indicates that Molasse sediments and the Malm can also

  19. Tunable rejection filters with ultra-wideband using zeroth shear mode plate wave resonators

    Science.gov (United States)

    Kadota, Michio; Sannomiya, Toshio; Tanaka, Shuji

    2017-07-01

    This paper reports wide band rejection filters and tunable rejection filters using ultra-wideband zeroth shear mode (SH0) plate wave resonators. The frequency range covers the digital TV band in Japan that runs from 470 to 710 MHz. This range has been chosen to meet the TV white space cognitive radio requirements of rejection filters. Wide rejection bands were obtained using several resonators with different frequencies. Tunable rejection filters were demonstrated using Si diodes connected to the band rejection filters. Wide tunable ranges as high as 31% were measured by applying a DC voltage to the Si diodes.

  20. Shear-wave elastography of the liver and spleen identifies clinically significant portal hypertension

    DEFF Research Database (Denmark)

    Jansen, Christian; Bogs, Christopher; Verlinden, Wim

    2017-01-01

    BACKGROUND & AIMS: Clinically significant portal hypertension (CSPH) is associated with severe complications and decompensation of cirrhosis. Liver stiffness measured either by transient elastography (TE) or Shear-wave elastography (SWE) and spleen stiffness by TE might be helpful in the diagnosis...... correlate with portal pressure and can both be used as a non-invasive method to investigate CSPH. Even though external validation is still missing, these algorithms to rule-out and rule-in CSPH using sequential SWE of liver and spleen might change the clinical practice....

  1. Shear-wave elastography in breast ultrasonography: the state of the art

    Directory of Open Access Journals (Sweden)

    Ji Hyun Youk

    2017-10-01

    Full Text Available Shear-wave elastography (SWE is a recently developed ultrasound technique that can visualize and measure tissue elasticity. In breast ultrasonography, SWE has been shown to be useful for differentiating benign breast lesions from malignant breast lesions, and it has been suggested that SWE enhances the diagnostic performance of ultrasonography, potentially improving the specificity of conventional ultrasonography using the Breast Imaging Reporting and Data System criteria. More recently, not only has SWE been proven useful for the diagnosis of breast cancer, but has also been shown to provide valuable information that can be used as a preoperative predictor of the prognosis or response to chemotherapy.

  2. Shear-wave elastography in breast ultrasonography: the state of the art

    Energy Technology Data Exchange (ETDEWEB)

    Youk, Ji Hyun; Gweon, Hye Mi; Son, Eun Ju [Dept. of Radiology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul (Korea, Republic of)

    2017-10-15

    Shear-wave elastography (SWE) is a recently developed ultrasound technique that can visualize and measure tissue elasticity. In breast ultrasonography, SWE has been shown to be useful for differentiating benign breast lesions from malignant breast lesions, and it has been suggested that SWE enhances the diagnostic performance of ultrasonography, potentially improving the specificity of conventional ultrasonography using the Breast Imaging Reporting and Data System criteria. More recently, not only has SWE been proven useful for the diagnosis of breast cancer, but has also been shown to provide valuable information that can be used as a preoperative predictor of the prognosis or response to chemotherapy.

  3. Brillouin light scattering from shear waves in an epoxy resin through the glass transition

    Science.gov (United States)

    Comez, L.; Fioretto, D.; Verdini, L.; Rolla, P. A.

    1997-05-01

    The temperature dependences of the characteristic frequency and lifetime of hypersonic transverse acoustic waves in the epoxy system EPON 828 have been probed by means of the Brillouin light scattering technique. Evidence has been found of a very broad dispersion region, together with a discontinuity close to the glass transition temperature 0953-8984/9/19/016/img7. For temperatures higher than 0953-8984/9/19/016/img7, the shear loss data obtained from Brillouin spectra are in quantitative agreement with dielectric data for the same system. For lower temperatures, the Brillouin data deviate from the dielectric ones, the former being more sensitive to the secondary relaxation processes.

  4. Shear wave reflection seismic surveying in the Trondheim harbour area - imaging of land slide processes

    Science.gov (United States)

    Polom, U.; Hansen, L.; L'Heureux, S.; Longva, O.; Lecomte, I.; Krawczyk, C. M.

    2008-12-01

    The harbour area of Trondheim, Norway, was build on man-made land fillings at the coast of the Trondheim Fjord in several expansions since the last 80 years. The whole area is located on the deltaic sediments of the river Nidelven, which are overlying marine sediments that reach the bed rock in nearly 150 m depth. Some submarine land slides at the border of the sediment body nearby the harbour area were reported during the last decades. Therefore, many geological and geophysical investigations were carried out in recent years to explore the structure of the sediment body and its stability onshore and offshore in detail. Whereas high-resolution marine seismic methods archieved excellent results in the offshore area, common seismic investigations for the mostly paved harbour area itself were a difficult challenge. Therefore, SH polarized shear wave reflection seismics using a land streamer combined with a newly developed shear wave vibrator buggy of 30 kN peak force was applied, because this method is advantageous for paved surfaces. Overall 4.2 km 2.5D profiling was carried out in the harbour area along roads and parking places after optimizing of the field procedure. The whole operation was done at night in time slots from midnight to 5 am by road closures due to savety reasons and to minimize the noise from surrounding heavy traffic of trains, trucks and other heavy equipment. The field measurements achieved high resolution results of the sediment body structure, clear detection of the bedrock, and probably deeper structures within the bedrock. Due to the clear and continuous reflection events, also the shear wave velocity could be calculated at least down to the bedrock to indicate the stiffness of the sediment layers. The results of these onshore seismic profiles will be integrated in a combined onshore-offshore seismic profile grid for structural interpretation. Furthermore, the derived shear wave velocities will be combined with cone penetrometer testings and

  5. Shear-wave elastography in breast ultrasonography: the state of the art

    Science.gov (United States)

    2017-01-01

    Shear-wave elastography (SWE) is a recently developed ultrasound technique that can visualize and measure tissue elasticity. In breast ultrasonography, SWE has been shown to be useful for differentiating benign breast lesions from malignant breast lesions, and it has been suggested that SWE enhances the diagnostic performance of ultrasonography, potentially improving the specificity of conventional ultrasonography using the Breast Imaging Reporting and Data System criteria. More recently, not only has SWE been proven useful for the diagnosis of breast cancer, but has also been shown to provide valuable information that can be used as a preoperative predictor of the prognosis or response to chemotherapy. PMID:28513127

  6. Shear horizontal wave propagation in a periodic stubbed plate and its application in rainbow trapping.

    Science.gov (United States)

    Li, Peng; Cheng, Li

    2018-03-01

    The high-order waveguide modal theory, usually used in electromagnetics and acoustics, is adopted to investigate the propagation properties of shear horizontal waves in a periodic stubbed plate. Beyond the sub-wavelength regime, higher-order modes are included to calculate the exact band structures caused by the stubs. Theoretical solutions are obtained in a closed form, in which both the dynamic governing equations and the boundary conditions are strictly satisfied. It is shown that the proposed modelling approach exhibits good convergence and accuracy, in agreement with results obtained from the finite element method. After a systematic investigation on the influence of the stub on the evolution of the band structures, the so-called rainbow trapping phenomenon of SH waves is revealed and explored in a graded stubbed plate with monotonously increasing height or width of the stubs, featuring an obvious reduction of the group velocity and blocking of the wave propagation at different locations for SH waves of different frequencies. The proposed model is expected to provide a useful theoretical tool for the physical mechanism exploration, structural design and eventually system optimization to guide various engineering applications of SH waves. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Propagation of shear elastic and electromagnetic waves in one dimensional piezoelectric and piezomagnetic composites.

    Science.gov (United States)

    Shi, P; Chen, C Q; Zou, W N

    2015-01-01

    Coupled shear (SH) elastic and electromagnetic (EM) waves propagating oblique to a one dimensional periodic piezoelectric and piezomagnetic composite are investigated using the transfer matrix method. Closed-form expression of the dispersion relations is derived. We find that the band structures of the periodic composite show simultaneously the features of phononic and photonic crystals. Strong interaction between the elastic and EM waves near the center of the Brillouin zone (i.e., phonon-polariton) is revealed. It is shown the elastic branch of the band structures is more sensitive to the piezoelectric effect while the phonon-polariton is more sensitive to the piezomagnetic effect of the composite. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Nonresonant absorption of shear Alfven waves. [in solar coronal heating and solar wind acceleration

    Science.gov (United States)

    Strauss, H. R.

    1991-01-01

    Resonant absorption of shear Alfven waves is thought to be a likely candidate to explain heating of the solar corona and acceleration of the solar wind. A difficulty with the theory is that the absorption process is slow. Moreover, heating occurs in a very thin layer. A faster absorption mechanism is nonresonant absorption by compressional viscosity, in a curved magnetic field. Heating is nonresonant and is not localized to a narrow layer. The effect could be quite important where the solar coronal magnetic field is strongly curved, in the chromosphere. It could also be important on open field lines in the upper corona, where the compressional viscosity is large. It might imply that a significant part of outgoing Alfven waves are absorbed in the corona.

  9. Estimating site effects for seismic hazard assessment in Portugal using shear wave and geotechnical data

    Science.gov (United States)

    Cancela Pinto, C.; Carvalho, J.; Vilanova, S.; Borges, J.

    2012-04-01

    The estimation of seismic ground motion requires a simultaneous understanding of the effects of earthquake sources, propagation effects in the earth and local geological site conditions. In this work we address the latter issue in Portugal mainland. The SCENE project has the main goal to improve the seismic hazard assessment in Portugal by taking into account the site effects. To achieve this purpose, the project was divided into two main goals: 1) to estimate the shear-wave profiles at the seismic stations in order to correct the recorded ground motions for site effects and 2)to produce a regional soil classification based on shear-wave velocity averaged on the upper 30m (VS30) that will be used to include first order site effects in seismic hazard maps. This parameter was calculated using seismic refraction and reflection data, interpreted with the aid of nearby wells. The refraction interpretation was carried out using the generalized reciprocal and first break tomographic methods. Using reflection seismic software, the velocities measured from the reflection hyperbolae occasionally observed in the shot gathers were used to obtain an average velocity until the respective reflector and complement the refraction data. The soil classification is based on the eurocode 8, which uses only shear wave velocities, but the classification presented here includes also standard penetration test (SPT) data. The seismic acquisition was carried out next to the accelerometer and broadband stations located in the regions center and south of Portugal. To produce a soil classification, 30 P-wave and 30 S-wave profiles were acquired and data collected under the scope of other projects was also used. The classification takes into consideration not only the geological units on which the seismic profiles were acquired but lithological information and has been generalized to each unit using 1: 200.000 scale geological cartography. This classification for southern Portugal is presented

  10. A variable-frequency structural health monitoring system based on omnidirectional shear horizontal wave piezoelectric transducers

    Science.gov (United States)

    Huan, Qiang; Miao, Hongchen; Li, Faxin

    2018-02-01

    Structural health monitoring (SHM) is of great importance for engineering structures as it may detect the early degradation and thus avoid life and financial loss. Guided wave based inspection is very useful in SHM due to its capability for long distance and wide range monitoring. The fundamental shear horizontal (SH0) wave based method should be most promising since SH0 is the unique non-dispersive wave mode in plate-like structures. In this work, a sparse array SHM system based on omnidirectional SH wave piezoelectric transducers (OSH-PT) was proposed and the multi data fusion method was used for defect inspection in a 2 mm thick aluminum plate. Firstly, the performances of three types OSH-PTs was comprehensively compared and the thickness-poled d15 mode OSH-PT used in this work was demonstrated obviously superior to the other two. Then, the signal processing method and imaging algorithm for this SHM system was presented. Finally, experiments were carried out to examine the performance of the proposed SHM system in defect localization and imaging. Results indicated that this SHM system can locate a through hole as small as 0.12λ (4 mm) in diameter (where λ is the wavelength corresponding to the central operation frequency) under frequencies from 90 to 150 kHz. It can also locate multiple defects accurately based on the baseline subtraction method. Obviously, this SHM system can detect larger areas with sparse sensors because of the adopted single mode, non-dispersive and low frequency SH0 wave which can propagate long distance with small attenuation. Considering its good performances, simple data processing and sparse array, this SH0 wave-based SHM system is expected to greatly promote the applications of guided wave inspection.

  11. Temperature-dependent elastic properties of brain tissues measured with the shear wave elastography method.

    Science.gov (United States)

    Liu, Yan-Lin; Li, Guo-Yang; He, Ping; Mao, Ze-Qi; Cao, Yanping

    2017-01-01

    Determining the mechanical properties of brain tissues is essential in such cases as the surgery planning and surgical training using virtual reality based simulators, trauma research and the diagnosis of some diseases that alter the elastic properties of brain tissues. Here, we suggest a protocol to measure the temperature-dependent elastic properties of brain tissues in physiological saline using the shear wave elastography method. Experiments have been conducted on six porcine brains. Our results show that the shear moduli of brain tissues decrease approximately linearly with a slope of -0.041±0.006kPa/°C when the temperature T increases from room temperature (~23°C) to body temperature (~37°C). A case study has been further conducted which shows that the shear moduli are insensitive to the temperature variation when T is in the range of 37 to 43°C and will increase when T is higher than 43°C. With the present experimental setup, temperature-dependent elastic properties of brain tissues can be measured in a simulated physiological environment and a non-destructive manner. Thus the method suggested here offers a unique tool for the mechanical characterization of brain tissues with potential applications in brain biomechanics research. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Shear wave splitting measurements and interpretation beneath Acapulco-Tampico transect in Mexico

    Science.gov (United States)

    Stubailo, I.; Davis, P.

    2007-12-01

    We have examined shear wave splitting in teleseismic shear waves from 100 broadband stations installed from Acapulco to Tampico in Mexico over a period of 1.5 years (2005-2007). The instruments were part of the MASE (Middle America Subduction Experiment) which has the objective to build a geodynamical model of the subduction process beneath the Middle America Trench. The stations had a 5-6 km spacing and provided a unique data set which allows examination of the variation in splitting in high detail. Tomographic and receiver function studies in this area (done by MASE colleagues) show the presence of a flat slab under the western part of the array, and a steeply dipping slab beneath its center. According to geochronological data, the onset of flat slab subduction took place ~15-20 Ma, after the Cocos plate broke off the Farallon plate. We observe large splitting delay times with, on average, a fast direction in the northeast-southwest direction, but with considerable variation along the network. We compare the splitting results with the three dimensional structure inferred from the geochemistry and seismic analyses.

  13. Effect of Vertically Propagating Shear Waves on Seismic Behavior of Circular Tunnels

    Directory of Open Access Journals (Sweden)

    Tohid Akhlaghi

    2014-01-01

    Full Text Available Seismic design loads for tunnels are characterized in terms of the deformations imposed on the structure by surrounding ground. The free-field ground deformations due to a seismic event are estimated, and the tunnel is designed to accommodate these deformations. Vertically propagating shear waves are the predominant form of earthquake loading that causes the ovaling deformations of circular tunnels to develop, resulting in a distortion of the cross sectional shape of the tunnel lining. In this paper, seismic behavior of circular tunnels has been investigated due to propagation of shear waves in the vertical direction using quasi-static analytical approaches as well as numerical methods. Analytical approaches are based on the closed-form solutions which compute the forces in the lining due to equivalent static ovaling deformations, while the numerical method carries out dynamic, nonlinear soil-structure interaction analysis. Based on comparisons made, the accuracy and reliability of the analytical solutions are evaluated and discussed. The results show that the axial forces determined using the analytical approaches are in acceptable agreement with numerical analysis results, while the computed bending moments are less comparable and show significant discrepancies. The differences between the analytical approaches are also investigated and addressed.

  14. Added value of point shear-wave elastography in the diagnosis of acute cholecystitis.

    Science.gov (United States)

    Kim, Ji Eun; Choi, Dae Seob; Bae, Kyungsoo; Cho, Jae Min; Jeong, Chi Young; Kim, Hyun Ok

    2017-04-01

    To evaluate the added value of point shear-wave elastography (pSWE) in the diagnostic performance of conventional US for diagnosis of acute cholecystitis. B-mode and colour Doppler US and pSWE were performed prospectively in 216 patients with clinically suspected acute cholecystitis. The morphology and mural vascularity of the gallbladder and median shear wave velocity (SWV) of the right liver were evaluated. Two observers independently reviewed conventional US images and subsequently reviewed combined conventional US and pSWE images. Mean SWVs of the acute cholecystitis group (n = 91) were significantly higher than those of the control group (n = 85) in the right liver within 2 cm lateral to the gallbladder (1.56 versus 1.03 m/s, 1.39 versus 1.04 m/s, P acute cholecystitis improved significantly from 0.790 and 0.777 to 0.963 and 0.962, respectively, after additional review of pSWE images (P acute cholecystitis when compared with conventional US alone. • In acute cholecystitis, stiffness of the right liver increases adjacent to the gallbladder. • The cut-off value for diagnosing acute cholecystitis was 1.29 or 1.16 m/s. • Adding pSWE to conventional US improves the diagnosis of acute cholecystitis.

  15. Effect of vertically propagating shear waves on seismic behavior of circular tunnels.

    Science.gov (United States)

    Akhlaghi, Tohid; Nikkar, Ali

    2014-01-01

    Seismic design loads for tunnels are characterized in terms of the deformations imposed on the structure by surrounding ground. The free-field ground deformations due to a seismic event are estimated, and the tunnel is designed to accommodate these deformations. Vertically propagating shear waves are the predominant form of earthquake loading that causes the ovaling deformations of circular tunnels to develop, resulting in a distortion of the cross sectional shape of the tunnel lining. In this paper, seismic behavior of circular tunnels has been investigated due to propagation of shear waves in the vertical direction using quasi-static analytical approaches as well as numerical methods. Analytical approaches are based on the closed-form solutions which compute the forces in the lining due to equivalent static ovaling deformations, while the numerical method carries out dynamic, nonlinear soil-structure interaction analysis. Based on comparisons made, the accuracy and reliability of the analytical solutions are evaluated and discussed. The results show that the axial forces determined using the analytical approaches are in acceptable agreement with numerical analysis results, while the computed bending moments are less comparable and show significant discrepancies. The differences between the analytical approaches are also investigated and addressed.

  16. Mantle upwelling beneath Madagascar: evidence from receiver function analysis and shear wave splitting

    Science.gov (United States)

    Paul, Jonathan D.; Eakin, Caroline M.

    2017-07-01

    Crustal receiver functions have been calculated from 128 events for two three-component broadband seismomenters located on the south coast (FOMA) and in the central High Plateaux (ABPO) of Madagascar. For each station, crustal thickness and V p / V s ratio were estimated from H- κ plots. Self-consistent receiver functions from a smaller back-azimuthal range were then selected, stacked and inverted to determine shear wave velocity structure as a function of depth. These results were corroborated by guided forward modeling and by Monte Carlo error analysis. The crust is found to be thinner (39 ± 0.7 km) beneath the highland center of Madagascar compared to the coast (44 ± 1.6 km), which is the opposite of what would be expected for crustal isostasy, suggesting that present-day long wavelength topography is maintained, at least in part, dynamically. This inference of dynamic support is corroborated by shear wave splitting analyses at the same stations, which produce an overwhelming majority of null results (>96 %), as expected for vertical mantle flow or asthenospheric upwelling beneath the island. These findings suggest a sub-plate origin for dynamic support.

  17. EVALUATION OF IRIDOCILIARY AND LENTICULAR ELASTICITY USING SHEAR-WAVE ELASTOGRAPHY IN RABBIT EYES

    Directory of Open Access Journals (Sweden)

    Efstathios T. Detorakis

    2014-01-01

    Full Text Available Introduction: A previous study has employed shear-wave ultrasound elastographic imaging to assess corneal rigidity in an ex-vivo porcine eye model. This study employs the same modality in vivo in a rabbit eye model in order to assess lens, ciliary body and total ocular rigidity changes following the instillation of atropine and pilocarpine. Methods: Ten non-pigmented female rabbits were examined. Measurements of the lens, ciliary body and total ocular rigidity as well as lens thickness and anterior chamber depth were taken with the Aixplorer system (SuperSonic Imagine, Aix-en-Provence, France with the SuperLinear™ SL 15-4 transducer in both eyes at baseline as well as after pilocarpine and atropine instillation. The IOP was also measured with the TonoPen tonometer. Results: Changes in rigidity in the examined areas following atropine instillation were statistically not significant. Ciliary body rigidity was significantly increased whereas lens and total ocular rigidity were significantly reduced following pilocarpine instillation. The decrease in lens rigidity following pilocarpine was significantly associated with the respective increase in ciliary body rigidity. Conclusions: Shear-wave ultrasound elastography can detect in vivo rigidity changes in the anterior segment of the rabbit eye model and may potentially be applied in human eyes, providing useful clinical information on conditions in which rigidity changes play an important role, such as glaucoma, pseudoexfoliation syndrome or presbyopia.

  18. Elastic Characteristics of the Normal Achilles Tendon Assessed by Virtual Touch Imaging Quantification Shear Wave Elastography.

    Science.gov (United States)

    Fu, Shuai; Cui, Ligang; He, Xiaoxi; Sun, Yang

    2016-09-01

    To assess the elastic properties of the normal Achilles tendon in different age groups by Virtual Touch imaging quantification (VTIQ; Siemens Medical Solutions, Malvern, PA) shear wave elastography. A total of 326 healthy volunteers older than 18 years were divided into different groups by sex and age. The thickness, shear wave velocity (SWV) in sagittal and axial sections, and anisotropic coefficient of the Achilles tendon in a state of relaxation were obtained by conventional sonography and Virtual Touch imaging quantification elastography. These parameters were compared in different age and sex groups, and their correlations with age were evaluated. The thickness of the Achilles tendon in men and women increased gradually with age, and it was larger in men than in women in each age group (P tendon in the sagittal section decreased slightly with age, but the sagittal and axial SWVs and anisotropic coefficient had no significant differences among different age groups (P > .05), and they also had no significant differences between men and women within any group (P > .05). The SWVs in the sagittal and axial sections and anisotropic coefficient had no correlation with age. Intraclass correlation coefficients for sagittal and axial SWVs obtained by 2 independent observers were 0.923 and 0.870, respectively. The thickness of the Achilles tendon increased gradually with age. We confirmed that tendinous elastographic anisotropy and the stiffness of the tendon had no significant correlation with age.

  19. Shear wave elastography contribution in ultrasound diagnosis management of breast lesions.

    Science.gov (United States)

    Klotz, T; Boussion, V; Kwiatkowski, F; Dieu-de Fraissinette, V; Bailly-Glatre, A; Lemery, S; Boyer, L

    2014-09-01

    To determine the diagnosis performance of shear wave elastography in the differentiation of benign and malignant breast lesions and the factors influencing the elasticity values. To suggest an appropriate management of breast lesions using the ultrasound-elastography combination. Monocentric retrospective study of 167 breast lesions classified by conventional ultrasound as BI-RADS category 3 or higher that underwent an elastography study and histological analysis. The analysis of qualitative parameters, according to the classification established in this study, allows us to obtain a sensitivity of 91.1% and a specificity of 92.3%. These values are very close to or better than the quantitative parameters Emax and Emean. Different Emax thresholds values were established based on the long axis of the lesion and its palpable character, which appeared to be significant factors influencing elasticity. The management of breast lesions by combining ultrasound and elastography, as proposed here, allows us to keep the sensitivity of an ultrasound (96%), while doubling its specificity (86.2% versus 43.1%). With the complementary nature of their performance, the combination of conventional ultrasound and shear wave elastography can improve the management of breast lesions. The qualitative classification proposed appears to be relevant assistance in lesion characterization. Copyright © 2014 Éditions françaises de radiologie. Published by Elsevier Masson SAS. All rights reserved.

  20. Shear-wave elastographic features of breast cancers: comparison with mechanical elasticity and histopathologic characteristics.

    Science.gov (United States)

    Lee, Su Hyun; Moon, Woo Kyung; Cho, Nariya; Chang, Jung Min; Moon, Hyeong-Gon; Han, Wonshik; Noh, Dong-Young; Lee, Jung Chan; Kim, Hee Chan; Lee, Kyoung-Bun; Park, In-Ae

    2014-03-01

    The objective of this study was to compare the quantitative and qualitative shear-wave elastographic (SWE) features of breast cancers with mechanical elasticity and histopathologic characteristics. This prospective study was conducted with institutional review board approval, and written informed consent was obtained. Shear-wave elastography was performed for 30 invasive breast cancers in 30 women before surgery. The mechanical elasticity of a fresh breast tissue section, correlated with the ultrasound image, was measured using an indentation system. Quantitative (maximum, mean, minimum, and standard deviation of elasticity in kilopascals) and qualitative (color heterogeneity and presence of signal void areas in the mass) SWE features were compared with mechanical elasticity and histopathologic characteristics using the Pearson correlation coefficient and the Wilcoxon signed rank test. Maximum SWE values showed a moderate correlation with maximum mechanical elasticity (r = 0.530, P = 0.003). There were no significant differences between SWE values and mechanical elasticity in histologic grade I or II cancers (P = 0.268). However, SWE values were significantly higher than mechanical elasticity in histologic grade III cancers (P elasticity (r = 0.469, P = 0.009). Signal void areas in the masses were present in 43% of breast cancers (13 of 30) and were correlated with dense collagen depositions (n = 11) or intratumoral necrosis (n = 2). Quantitative and qualitative SWE features reflect both the mechanical elasticity and histopathologic characteristics of breast cancers.

  1. Finite element modeling of impulsive excitation and shear wave propagation in an incompressible, transversely isotropic medium.

    Science.gov (United States)

    Rouze, Ned C; Wang, Michael H; Palmeri, Mark L; Nightingale, Kathy R

    2013-11-15

    Elastic properties of materials can be measured by observing shear wave propagation following localized, impulsive excitations and relating the propagation velocity to a model of the material. However, characterization of anisotropic materials is difficult because of the number of elasticity constants in the material model and the complex dependence of propagation velocity relative to the excitation axis, material symmetries, and propagation directions. In this study, we develop a model of wave propagation following impulsive excitation in an incompressible, transversely isotropic (TI) material such as muscle. Wave motion is described in terms of three propagation modes identified by their polarization relative to the material symmetry axis and propagation direction. Phase velocities for these propagation modes are expressed in terms of five elasticity constants needed to describe a general TI material, and also in terms of three constants after the application of two constraints that hold in the limit of an incompressible material. Group propagation velocities are derived from the phase velocities to describe the propagation of wave packets away from the excitation region following localized excitation. The theoretical model is compared to the results of finite element (FE) simulations performed using a nearly incompressible material model with the five elasticity constants chosen to preserve the essential properties of the material in the incompressible limit. Propagation velocities calculated from the FE displacement data show complex structure that agrees quantitatively with the theoretical model and demonstrates the possibility of measuring all three elasticity constants needed to characterize an incompressible, TI material. © 2013 Elsevier Ltd. All rights reserved.

  2. Multi-mode surface wave tomography of the North American upper mantle: 3-D shear wave speed model and radial anisotropy

    Science.gov (United States)

    Yoshizawa, K.; Ekström, G.

    2009-04-01

    The three dimensional shear wave speed structure and radial anisotropy of the upper mantle beneath the North American continent is investigated from automatic measurements of multi-mode phase speeds of Love and Rayleigh waves. We have employed a fully automated method of a nonlinear waveform fitting based on a direct model-parameter search with the neighbourhood algorithm (Yoshizawa and Kennett, 2002a GJI). This method has been applied to long-period three-component records of seismic stations in North America, which mostly comprise the GSN and US regional networks including USArray stations distributed by the IRIS DMC. We have collected over 30,000 path-specific phase speeds of fundamental-mode and higher-mode surface waves in the period range from 30 to 200 seconds. These path-specific phase speeds are then inverted for multi-mode phase speed maps incorporating approximate effects of finite-frequency via the surface-wave influence zone (Yoshizawa and Kennett, 2002b GJI, 2004 JGR), within which surface waves are assumed to be coherent in phase. A 3-D radially anisotropic shear wave speed model is obtained from simultaneous inversions of local dispersion curves of both Love and Rayleigh waves. The preliminary high-resolution 3-D model of North America indicates a large-scale strong velocity contrast between the western and central United States with slow anomalies beneath the Rocky Mountain Range down to 150 km depth and fast anomalies beneath the cratonic areas. Radial anisotropy model shows fast anomalies of vertically polarized shear waves (SV waves) relative to horizontally polarized shear waves (SH waves) beneath the Cascade Range volcanoes down to about 70-100 km, and a similar anomaly beneath the Yellowstone hotspot seems to persist down to about 200-250 km.

  3. Development of site class and site coefficient maps of Semarang, Indonesia using field shear wave velocity data

    OpenAIRE

    Partono Windu; Irsyam Masyhur; Prabandiyani Retno Wardani Sri

    2017-01-01

    The new Indonesian National Code for seismic resistance design (SNI-03-1726-2012) issued recently utilizes seismic response spectra for the whole area of the country. Site class and site coefficient are two parameters needed for designing response spectra. Site class can be estimated using average standard penetration test (N-SPT), average shear wave velocity (Vs) and average un-drained shear strength (Su) of top 30 meter soil deposit. Site coefficients can be predicted using probabilistic se...

  4. Modulation of Atmospheric Nonisothermality and Wind Shears on the Propagation of Seismic Tsunami-Excited Gravity Waves

    Directory of Open Access Journals (Sweden)

    John Z. G. Ma

    2016-01-01

    Full Text Available We study the modulation of atmospheric nonisothermality and wind shears on the propagation of seismic tsunami-excited gravity waves by virtue of the vertical wavenumber, m (with its imaginary and real parts, m i and m r , respectively, within a correlated characteristic range of tsunami wave periods in tens of minutes. A generalized dispersion relation of inertio-acoustic-gravity (IAG waves is obtained by relaxing constraints on Hines’ idealized locally-isothermal, shear-free and rotation-free model to accommodate a realistic atmosphere featured by altitude-dependent nonisothermality (up to 100 K/km and wind shears (up to 100 m/s per km. The obtained solutions recover all of the known wave modes below the 200-km altitude where dissipative terms are assumed negligible. Results include: (1 nonisothermality and wind shears divide the atmosphere into a sandwich-like structure of five layers within the 200-km altitude in view of the wave growth in amplitudes: Layer I (0–18 km, Layer II (18–87 km, Layer III (87–125 km, Layer IV (125–175 km and Layer V (175–200 km; (2 in Layers I, III and V, the magnitude of m i is smaller than Hines’ imaginary vertical wavenumber ( m i H , referring to an attenuated growth in the amplitudes of upward propagating waves; on the contrary, in Layers II and IV, the magnitude of m i is larger than that of m i H , providing a pumped growth from Hines’ model; (3 nonisothermality and wind shears enhance m r substantially at an ∼100-km altitude for a tsunami wave period T t s longer than 30 min. While Hines’ model provides that the maximal value of m r 2 is ∼0.05 (1/km 2 , this magnitude is doubled by the nonisothermal effect and quadrupled by the joint nonisothermal and wind shear effect. The modulations are weaker at altitudes outside 80–140-km heights; (4 nonisothermality and wind shears expand the definition of the observation-defined “damping factor”, β: relative to Hines’ classical wave

  5. Shear wave velocity structure in North America from large-scale waveform inversions of surface waves

    Science.gov (United States)

    Alsina, D.; Woodward, R.L.; Snieder, R.K.

    1996-01-01

    A two-step nonlinear and linear inversion is carried out to map the lateral heterogeneity beneath North America using surface wave data. The lateral resolution for most areas of the model is of the order of several hundred kilometers. The most obvious feature in the tomographic images is the rapid transition between low velocities in the technically active region west of the Rocky Mountains and high velocities in the stable central and eastern shield of North America. The model also reveals smaller-scale heterogeneous velocity structures. A high-velocity anomaly is imaged beneath the state of Washington that could be explained as the subducting Juan de Fuca plate beneath the Cascades. A large low-velocity structure extends along the coast from the Mendocino to the Rivera triple junction and to the continental interior across the southwestern United States and northwestern Mexico. Its shape changes notably with depth. This anomaly largely coincides with the part of the margin where no lithosphere is consumed since the subduction has been replaced by a transform fault. Evidence for a discontinuous subduction of the Cocos plate along the Middle American Trench is found. In central Mexico a transition is visible from low velocities across the Trans-Mexican Volcanic Belt (TMVB) to high velocities beneath the Yucatan Peninsula. Two elongated low-velocity anomalies beneath the Yellowstone Plateau and the eastern Snake River Plain volcanic system and beneath central Mexico and the TMVB seem to be associated with magmatism and partial melting. Another low-velocity feature is seen at depths of approximately 200 km beneath Florida and the Atlantic Coastal Plain. The inversion technique used is based on a linear surface wave scattering theory, which gives tomographic images of the relative phase velocity perturbations in four period bands ranging from 40 to 150 s. In order to find a smooth reference model a nonlinear inversion based on ray theory is first performed. After

  6. Diagnostic performance of quantitative shear wave elastography in the evaluation of solid breast masses: determination of the most discriminatory parameter.

    Science.gov (United States)

    Au, Frederick Wing-Fai; Ghai, Sandeep; Moshonov, Hadas; Kahn, Harriette; Brennan, Cressida; Dua, Hemi; Crystal, Pavel

    2014-09-01

    The purpose of this article is to assess the diagnostic performance of quantitative shear wave elastography in the evaluation of solid breast masses and to determine the most discriminatory parameter. B-mode ultrasound and shear wave elastography were performed before core biopsy of 123 masses in 112 women. The diagnostic performance of ultrasound and quantitative shear wave elastography parameters (mean elasticity, maximum elasticity, and elasticity ratio) were compared. The added effect of shear wave elastography on the performance of ultrasound was determined. The mean elasticity, maximum elasticity, and elasticity ratio were 24.8 kPa, 30.3 kPa, and 1.90, respectively, for 79 benign masses and 130.7 kPa, 154.9 kPa, and 11.52, respectively, for 44 malignant masses (p elasticity ratio (0.943) was the highest. By adding shear wave elastography parameters to the evaluation of BI-RADS category 4a masses, about 90% of masses could be downgraded to BI-RADS category 3. The numbers of downgraded masses were 40 of 44 (91%) for mean elasticity, 39 of 44 (89%) for maximum elasticity, and 42 of 44 (95%) for elasticity ratio. The numbers of correctly downgraded masses were 39 of 40 (98%) for mean elasticity, 38 of 39 (97%) for maximum elasticity, and 41 of 42 (98%) for elasticity ratio. There was improvement in the diagnostic performance of ultrasound of mass assessment with shear wave elastography parameters added to BI-RADS category 4a masses compared with ultrasound alone. Combined ultrasound and elasticity ratio had the highest improvement, from 35.44% to 87.34% for specificity, from 45.74% to 80.77% for positive predictive value, and from 57.72% to 90.24% for accuracy (p elasticity ratio (0.914) was the highest compared with the other combined parameters. There was a statistically significant difference in the values of the quantitative shear wave elastography parameters of benign and malignant solid breast masses. By adding shear wave elastography parameters to BI

  7. Shear Wave Anisotropy in the Deep Crust of the Donez Basin (Ukraine)

    Science.gov (United States)

    Rabbel, W.; Landerer, F.; Janik, T.; Dobrefraction Working Group; Dobreflection Working Group

    2003-04-01

    The DOBRE profile is a seismic refraction (1999) and reflection (2000, 2001) traverse across the SE part of the Donez Basin (Ukraine) performed in cooperation of Danish, Dutch, German, Polish and Ukrainian partners. After Devonian and Permian extension, the Donez Basin was compressed and finally inverted in the Cretacious and early Tertiary. Today, the crust is about 40 km thick carrying more than 20 km thick sedimentary layers. In the lower crust a 20 km thick high velocity body is found asymmetrically displaced with respect to the basin centre suggesting the existence (ultra-?) mafic intrusives. The basin strikes NW-SE and is bounded in the N and S by the Voronezh-Massif and the Ukrainian Shield, respectively. Today, maximum horizontal stress is oriented NE and influenced by the Caucasian and the Carpathian orogeny. So, the basin and its adjacent crustal units represent heterogeneous blocks in both structure and evolution. In this context we analyzed shear wave arrivals observed on the profile at distance of ca. 100km, parallel to the DOBRE line in order to investigate whether the deformation processes mentioned above have left a crustal signature in terms of seismic anisotropy. If yes, the following properties and questions are of interest: the orientation of the axes of symmetry, regional and depth variations of anisotropy, and whether the cause of anisotropy such as layering or ductile deformation can be identified from the anisotropy pattern. We observed shear wave splitting of Sg and SmS arrivals showing up to 750 ms delay between the split waves.A close inspection of travel time differences and polarization directions showed that differences in the anisotropy of the upper and lower crust and between Donez basin and Voronezh Massif. The observations are compatible with a N110E stiking symmetry axis corresponding to the strike direction of the basin and major boundary faults. S-wave splitting of Sg is less than 0.5% in the upper crust. SmS splitting is

  8. Selection of Shear Horizontal Wave Transducers for Robotic Nondestructive Inspection in Harsh Environments

    Directory of Open Access Journals (Sweden)

    Sungho Choi

    2016-12-01

    Full Text Available Harsh environments and confined spaces require that nondestructive inspections be conducted with robotic systems. Ultrasonic guided waves are well suited for robotic systems because they can provide efficient volumetric coverage when inspecting for various types of damage, including cracks and corrosion. Shear horizontal guided waves are especially well suited for robotic inspection because they are sensitive to cracks oriented perpendicular or parallel to the wave propagation direction and can be generated with electromagnetic acoustic transducers (EMATs and magnetostrictive transducers (MSTs. Both types of transducers are investigated for crack detection in a stainless steel plate. The MSTs require the robot to apply a compressive normal force that creates frictional force coupling. However, the coupling is observed to be very dependent upon surface roughness and surface debris. The EMATs are coupled through the Lorentz force and are thus noncontact, although they depend on the lift off between transducer and substrate. After comparing advantages and disadvantages of each transducer for robotic inspection the EMATs are selected for application to canisters that store used nuclear fuel.

  9. Excitation and reception of non-dispersive guided waves using face-shear d24 mode piezoelectric transducers

    Science.gov (United States)

    Miao, Hongchen; Li, Faxin

    2017-04-01

    The non-dispersive fundamental shear horizontal (SH0) and torsional [T(0,1)] waves are extremely useful in guidedwave-based inspection techniques. However, excitation of SH0 and T(0,1) waves using piezoelectrics is always a challenge. In this work, firstly, a newly defined face-shear d24 PZT wafer is proposed to excite and receive SH0 wave mode. The d24 wafer is in-plane poled and its working electric field is applied along another orthogonal in-plane direction. Both finite element simulations and experiments show that single SH0 mode can be excited by using the d24 wafer along two orthogonal directions (0° and 90°). Then an omnidirectional SH0 wave piezoelectric transducer (OSHPT) is developed which consists of a circular array of twelve face-shear d24 trapezoidal PZT elements. Results show that the proposed OSH-PT exhibits good omnidirectional properties, no matter it is used as a SH0 wave transmitter or receiver. Finally, the development of a T(0,1) wave transducer for pipes based on a ring array of d24 PZT elements is described. Both finite element simulations and experiments show that the d24 elements ring can excite single T(0,1) mode and suppress all the unwanted non-axisymmetric modes. This work may greatly promote the applications of SH0 and T(0,1) waves in nondestructive testing (NDT) and structural health monitoring (SHM).

  10. Comparison and Combination of Strain and Shear Wave Elastography of Breast Masses for Differentiation of Benign and Malignant Lesions by Quantitative Assessment: Preliminary Study.

    Science.gov (United States)

    Seo, Mirinae; Ahn, Hye Shin; Park, Sung Hee; Lee, Jong Beum; Choi, Byung Ihn; Sohn, Yu-Mee; Shin, So Youn

    2018-01-01

    To compare the diagnostic performance of strain and shear wave elastography of breast masses for quantitative assessment in differentiating benign and malignant lesions and to evaluate the diagnostic accuracy of combined strain and shear wave elastography. Between January and February 2016, 37 women with 45 breast masses underwent both strain and shear wave ultrasound (US) elastographic examinations. The American College of Radiology Breast Imaging Reporting and Data System (BI-RADS) final assessment on B-mode US imaging was assessed. We calculated strain ratios for strain elastography and the mean elasticity value and elasticity ratio of the lesion to fat for shear wave elastography. Diagnostic performances were compared by using the area under the receiver operating characteristic curve (AUC). The 37 women had a mean age of 47.4 years (range, 20-79 years). Of the 45 lesions, 20 were malignant, and 25 were benign. The AUCs for elasticity values on strain and shear wave elastography showed no significant differences (strain ratio, 0.929; mean elasticity, 0.898; and elasticity ratio, 0.868; P > .05). After selectively downgrading BI-RADS category 4a lesions based on strain and shear wave elastographic cutoffs, the AUCs for the combined sets of B-mode US and elastography were improved (B-mode + strain, 0.940; B-mode + shear wave; 0.964; and B-mode, 0.724; P < .001). Combined strain and shear wave elastography showed significantly higher diagnostic accuracy than each individual elastographic modality (P = .031). These preliminary results showed that strain and shear wave elastography had similar diagnostic performance. The addition of strain and shear wave elastography to B-mode US improved diagnostic performance. The combination of strain and shear wave elastography results in a higher diagnostic yield than each individual elastographic modality. © 2017 by the American Institute of Ultrasound in Medicine.

  11. Assessment of biopsy-proven liver fibrosis by two-dimensional shear wave elastography

    DEFF Research Database (Denmark)

    Herrmann, Eva; de Lédinghen, Victor; Cassinotto, Christophe

    2018-01-01

    equipment were contacted to share their data. Retrospective statistical analysis used direct and paired receiver operating characteristic (ROC) and area under the ROC curve (AUROC) analysis accounting for random effects. RESULTS: Data on both 2D-SWE and liver biopsy was available in 1134 patients from 13......BACKGROUND AND AIMS: 2D shear wave elastography (2D-SWE) has proven to be efficient for the evaluation of liver fibrosis in small to moderate size clinical trials. We aimed at running a larger scale meta-analysis of individual data. METHODS: Centers which have worked with Aixplorer ultrasound...... sites, as well as on successful transient elastography (TE) in 665 patients. Most patients had chronic hepatitis C (HCV, n = 379), hepatitis B (HBV, n = 400) or non-alcoholic fatty liver disease (NAFLD, n = 156). AUROCs of 2D-SWE in patients with HCV, HBV and NAFLD were 86.3%, 90.6% and 85...

  12. Smooth muscle cells of penis in the rat: noninvasive quantification with shear wave elastography.

    Science.gov (United States)

    Zhang, Jia-Jie; Qiao, Xiao-Hui; Gao, Feng; Bai, Ming; Li, Fan; Du, Lian-Fang; Xing, Jin-Fang

    2015-01-01

    Smooth muscle cells (SMCs) of cavernosum play an important role in erection. It is of great significance to quantitatively analyze the level of SMCs in penis. In this study, we investigated the feasibility of shear wave elastography (SWE) on evaluating the level of SMCs in penis quantitatively. Twenty healthy male rats were selected. The SWE imaging of penis was carried out and then immunohistochemistry analysis of penis was performed to analyze the expression of alpha smooth muscle actin in penis. The measurement index of SWE examination was tissue stiffness (TS). The measurement index of immunohistochemistry analysis was positive area percentage of alpha smooth muscle actin (AP). Sixty sets of data of TS and AP were obtained. The results showed that TS was significantly correlated with AP and the correlation coefficient was -0.618 (p penis was successfully quantified in vivo with SWE. SWE can be used clinically for evaluating the level of SMCs in penis quantitatively.

  13. A preliminary study of shear wave elastography for the evaluation of unilateral palpable undescended testes.

    Science.gov (United States)

    Ucar, Ayse Kalyoncu; Alis, Deniz; Samanci, Cesur; Aslan, Mine; Habibi, Hatice Arioz; Dikici, Atilla Suleyman; Namdar, Yesim; Gultekin, Mehmet Hamza; Onal, Bulent; Adaletli, Ibrahim

    2017-01-01

    We sought to compare unilateral palpable undescended testes and contralateral descended testes using shear wave elastography (SWE) to show potential quantitative differences in elasticity patterns, which might reflect the histologic features. Approval for this prospective study was obtained from the local ethics committee. A total of 29 patients (mean age, 7.52 years; range, 1-18 years) with unilateral palpable undescended testes and contralateral descended testes were examined by greyscale ultrasonography and SWE between February 2015 and April 2016. The volume and the elasticity of each testicle were the main factors evaluated. There was no difference between undescended testes and contralateral descended testes in terms of volume. However, a significant difference was evident in SWE-derived quantitative data. SWE seems to be a useful sonographic technique to predict histologic features of the undescended testicle, which might replace testicular biopsy in modern management of the undescended testis. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  14. Shear wave elastography of the placenta in patients with gestational diabetes mellitus.

    Science.gov (United States)

    Yuksel, Mehmet Aytac; Kilic, Fahrettin; Kayadibi, Yasemin; Alici Davutoglu, Ebru; Imamoglu, Metehan; Bakan, Selim; Mihmanli, Ismail; Kantarci, Fatih; Madazli, Riza

    2016-07-01

    To evaluate placental elasticty in women with gestational diabetes mellitus (GDM) and non-diabetic controls. Thirty-three pregnant women with GDM according to the current criteria of the American Diabetes Association and 43 healthy pregnant women who were admitted to the antenatal clinic were recruited for this case-control study. Elasticity values of both the peripheral and the central parts of the placentas of the patients in both groups were determined by shear wave elastography (SWE) imaging. Mean elasticity values of both the central and the peripheral part of the placentas were significantly higher in GDM pregnancies (p  0.05). SWE imaging technology might provide a quantitative assessment of the morphological pathologies of placentas in pregnant women with GDM.

  15. Calculation of high frequency ultrasonic signals for shear wave insonification in solid material.

    Science.gov (United States)

    Schmitz, V; Langenberg, K J; Chakhlov, S

    2004-04-01

    The goal of the theoretical part is to simulate an automatic ultrasonic inspection with contact technique shear wave probes, where the high frequency signals are captured and used to perform a reconstruction based on the synthetic aperture focusing method "SAFT". Therefore the ultrasonic probe, the scanning path and the defects are parameters in a CAD model. The scattering behavior of the defect is calculated by the Kirchhoff approximation in its elastodynamic version. The result of the simulation--the high frequency data--and the result of the SAFT-reconstructions are compared with experimental results on a steel test block with side drilled and flat bottom holes. The model is validated by the experiment. One of the applications of the model is to identify multiple reflections.

  16. Effect of Calcifications on Breast Ultrasound Shear Wave Elastography: An Investigational Study.

    Directory of Open Access Journals (Sweden)

    Adriana Gregory

    Full Text Available To investigate the effects of macrocalcifications and clustered microcalcifications associated with benign breast masses on shear wave elastography (SWE.SuperSonic Imagine (SSI and comb-push ultrasound shear elastography (CUSE were performed on three sets of phantoms to investigate how calcifications of different sizes and distributions influence measured elasticity. To demonstrate the effect in vivo, three female patients with benign breast masses associated with mammographically-identified calcifications were evaluated by CUSE.Apparent maximum elasticity (Emax estimates resulting from individual macrocalcifications (with diameters of 2mm, 3mm, 5mm, 6mm, 9mm, 11mm, and 15mm showed values over 50 kPa for all cases, which represents more than 100% increase over background (~21kPa. We considered a 2cm-diameter circular region of interest for all phantom experiments. Mean elasticity (Emean values varied from 26 kPa to 73 kPa, depending on the macrocalcification size. Highly dense clusters of microcalcifications showed higher Emax values than clusters of microcalcification with low concentrations, but the difference in Emean values was not significant.Our results demonstrate that the presence of large isolated macrocalcifications and highly concentrated clusters of microcalcifications can introduce areas with apparent high elasticity in SWE. Considering that benign breast masses normally have significantly lower elasticity values than malignant tumors, such areas with high elasticity appearing due to presence of calcification in benign breast masses may lead to misdiagnosis.

  17. Measurement of tissue-radiation dosage using a thermal steady-state elastic shear wave.

    Science.gov (United States)

    Chang, Sheng-Yi; Hsieh, Tung-Sheng; Chen, Wei-Ru; Chen, Jin-Chung; Chou, Chien

    2017-08-01

    A biodosimeter based on thermal-induced elastic shear wave (TIESW) in silicone acellular porcine dermis (SAPD) at thermal steady state has been proposed and demonstrated. A square slab SAPD treated with ionizing radiation was tested. The SAPD becomes a continuous homogeneous and isotropic viscoelastic medium due to the generation of randomly coiled collagen fibers formed from their bundle-like structure in the dermis. A harmonic TIESW then propagates on the surface of the SAPD as measured by a nanometer-scaled strain-stress response under thermal equilibrium conditions at room temperature. TIESW oscillation frequency was noninvasively measured in real time by monitoring the transverse displacement of the TIESW on the SAPD surface. Because the elastic shear modulus is highly sensitive to absorbed doses of ionizing radiation, this proposed biodosimeter can become a highly sensitive and noninvasive method for quantitatively determining tissue-absorbed dosage in terms of TIESW’s oscillation frequency. Detection sensitivity at 1 cGy and dynamic ranges covering 1 to 40 cGy and 80 to 500 cGy were demonstrated.

  18. Effect of Calcifications on Breast Ultrasound Shear Wave Elastography: An Investigational Study

    Science.gov (United States)

    Gregory, Adriana; Mehrmohammadi, Mohammad; Denis, Max; Bayat, Mahdi; Stan, Daniela L.; Fatemi, Mostafa; Alizad, Azra

    2015-01-01

    Purpose To investigate the effects of macrocalcifications and clustered microcalcifications associated with benign breast masses on shear wave elastography (SWE). Methods SuperSonic Imagine (SSI) and comb-push ultrasound shear elastography (CUSE) were performed on three sets of phantoms to investigate how calcifications of different sizes and distributions influence measured elasticity. To demonstrate the effect in vivo, three female patients with benign breast masses associated with mammographically-identified calcifications were evaluated by CUSE. Results Apparent maximum elasticity (Emax) estimates resulting from individual macrocalcifications (with diameters of 2mm, 3mm, 5mm, 6mm, 9mm, 11mm, and 15mm) showed values over 50 kPa for all cases, which represents more than 100% increase over background (~21kPa). We considered a 2cm-diameter circular region of interest for all phantom experiments. Mean elasticity (Emean) values varied from 26 kPa to 73 kPa, depending on the macrocalcification size. Highly dense clusters of microcalcifications showed higher Emax values than clusters of microcalcification with low concentrations, but the difference in Emean values was not significant. Conclusions Our results demonstrate that the presence of large isolated macrocalcifications and highly concentrated clusters of microcalcifications can introduce areas with apparent high elasticity in SWE. Considering that benign breast masses normally have significantly lower elasticity values than malignant tumors, such areas with high elasticity appearing due to presence of calcification in benign breast masses may lead to misdiagnosis. PMID:26368939

  19. A Uniform Shear-Wave Splitting Database for Africa and Arabia

    Science.gov (United States)

    Elsheikh, A. A.; Gao, S. S.; Liu, K. H.

    2014-12-01

    Splitting of P-to-S converted phases at the core-mantle boundary (XKS, including SKS, PKS, and SKKS) is a very effective tool to measure seismic anisotropy, which is mostly caused by deformational processes in the Earth's lithosphere and asthenosphere. Consequently, patterns of seismic anisotropy revealed by shear-wave splitting (SWS) measurements are widely used in constraining the strength and direction of mantle flow. However, the currently available SWS measurements were obtained by a large number of research groups using different methods, resulting in a heterogeneous database. Specifically, different data selection and ranking criteria were employed, which led to many controversial results. In addition, splitting parameters obtained by the majority of the previous studies were presented as station-averages, which prevent the identification of complex anisotropy. This presentation reports preliminary results from an ongoing study using all the broadband XKS data available at the IRIS Data Management Center recorded in Africa and Arabia. More than 360 stations located in the region were used to produce a uniform SWS database. A robust process to reliably assess and objectively rank XKS splitting parameters is used to produce these results [Liu and Gao, 2013, Making reliable shear-wave splitting measurements, BSSA, 2680-2693]. Manual screening is applied to ensure that no high quality events are ignored and no low quality results are selected. The result is a homogeneous database of individual rather than station-averaged splitting parameters that can be used by a variety of geoscientists for the understanding of the structure and dynamics of the Earth's deep interior beneath the Africa and Arabia. The effort is still in progress and so far about 4455 high-quality measurements, including 2878 from SKS, 708 from PKS, and 869 from SKKS have been made. The ultimate goal is to establish a searchable and growing database for public access for Africa and Arabia.

  20. Shear wave velocity-based evaluation and design of stone column improved ground for liquefaction mitigation

    Science.gov (United States)

    Zhou, Yanguo; Sun, Zhengbo; Chen, Jie; Chen, Yunmin; Chen, Renpeng

    2017-04-01

    The evaluation and design of stone column improvement ground for liquefaction mitigation is a challenging issue for the state of practice. In this paper, a shear wave velocity-based approach is proposed based on the well-defined correlations of liquefaction resistance (CRR)-shear wave velocity ( V s)-void ratio ( e) of sandy soils, and the values of parameters in this approach are recommended for preliminary design purpose when site specific values are not available. The detailed procedures of pre- and post-improvement liquefaction evaluations and stone column design are given. According to this approach, the required level of ground improvement will be met once the target V s of soil is raised high enough (i.e., no less than the critical velocity) to resist the given earthquake loading according to the CRR- V s relationship, and then this requirement is transferred to the control of target void ratio (i.e., the critical e) according to the V s- e relationship. As this approach relies on the densification of the surrounding soil instead of the whole improved ground and is conservative by nature, specific considerations of the densification mechanism and effect are given, and the effects of drainage and reinforcement of stone columns are also discussed. A case study of a thermal power plant in Indonesia is introduced, where the effectiveness of stone column improved ground was evaluated by the proposed V s-based method and compared with the SPT-based evaluation. This improved ground performed well and experienced no liquefaction during subsequent strong earthquakes.

  1. Shear wave elastography for detection of prostate cancer: A preliminary study

    Energy Technology Data Exchange (ETDEWEB)

    Woo, Sung Min; Kim, Sang Youn; Cho, Jeong Yeon; KIm, Seung Hyup [Dept. of Radiology, Seoul National University Hospital, Seoul (Korea, Republic of)

    2014-06-15

    To assess the diagnostic value of shear wave elastography (SWE) for prostate cancer detection. In this retrospective study, 87 patients with the suspicion of prostate cancer (prostate-specific antigen > 4 ng/mL and abnormal digital rectal examination) underwent a protocol-based systematic 12-core biopsy followed by targeted biopsy at hypoechoic areas on grey-scale ultrasound. Prior to biopsy, SWE was performed by placing two circular 5 mm-sized regions of interest (ROIs) along the estimated biopsy tract in each sector and one ROI for hypoechoic lesions. SWE parameters, S (mean stiffness) and R (mean stiffness ratio), were calculated and compared regarding different histopathologic tissues and their accuracy for diagnosing prostate cancer was analyzed. SWE parameters were correlated with Gleason score and were compared between indolent (< 8) and aggressive (≥ 8) tissues in prostate cancer patients. Prostate cancer was detected in 7.5% of 1058 cores in 29.9% of 87 patients. Seven (43.8%) of 16 hypoechoic lesions were confirmed as prostate cancer. SWE parameters were significantly different among the histopathologic entities (p < 0.001). Prostate cancer was stiffer than benign tissues (p ≤ 0.003). Sensitivity, specificity and receiver operating characteristic curve area for diagnosing cancer were 43%, 80.8%, and 0.599, respectively, for a cutoff of S > 43.9 kPa and 60.8%, 66.4%, and 0.653, respectively, for R > 3. Both, S and R showed a significant correlation with Gleason score (r ≥ 0.296, p ≤ 0.008) and were significantly different between indolent and aggressive prostate cancer (p ≤ 0.006). Shear wave elastographic parameters are significantly different between prostate cancer and benign prostate tissue and correlate with Gleason score.

  2. Ultrasound and Point Shear Wave Elastography in Livers of Patients with Primary Sclerosing Cholangitis.

    Science.gov (United States)

    Mjelle, Anders Batman; Mulabecirovic, Anesa; Hausken, Trygve; Havre, Roald Flesland; Gilja, Odd Helge; Vesterhus, Mette

    2016-09-01

    Point shear wave elastography (pSWE) is an ultrasound-based method for non-invasive quantification of liver fibrosis. The objective of this study was to explore liver pSWE in patients with primary sclerosing cholangitis (PSC) for assessment of fibrosis. Fifty-five non-transplant patients with PSC (38 males, 17 females; mean age: 46.4 y) were included and compared with 24 matched controls. Median (range) PSC duration was 8.1 (0-33) y. Ultrasonographic scanning followed by liver stiffness measurement by pSWE was performed using a conventional ultrasound system (Philips iU22). Signs of liver fibrosis on B-mode were identified in 21 patients (38%). Splenomegaly was found in 19 patients (35%) and ascites in two patients (4%). Successful pSWE measurements were achieved in the right liver lobe of all individuals and in the left liver lobe of 36 patients (65.5%). PSC patients had significantly higher median shear wave velocity (SWV) than controls in the right liver (median [range] SWV 1.26 [0.73-2.57] m/s vs. 1.09 [0.88-1.25] m/s, p liver lobe and spleen did not differ between PSC patients and controls. Our findings indicate that PSC patients have increased median SWV, indicating more fibrosis compared with controls; however, a wide range of SWV values were obtained among PSC patients, possibly reflecting the various stages in disease development. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  3. Characterizing Seismic Anisotropy across the Peruvian Flat-Slab Subduction Zone: Shear Wave Splitting from PULSE

    Science.gov (United States)

    Eakin, C. M.; Long, M. D.; Beck, S. L.; Wagner, L. S.; Tavera, H.

    2013-12-01

    Although 10% of subduction zones worldwide today exhibit shallow or flat subduction, we are yet to fully understand how and why these slabs go flat. An excellent study location for such a problem is in Peru, where the largest region of flat-subduction currently exists, extending ~1500 km in length (from 3 °S to 15 °S) and ~300 km in width. Across this region we investigate the pattern of seismic anisotropy, an indicator for past and/or ongoing deformation in the upper mantle. To achieve this we conduct shear wave splitting analyzes at 40 broadband stations from the PULSE project (PerU Lithosphere and Slab Experiment). These stations were deployed for 2+ years across the southern half of the Peruvian flat-slab region. We present detailed shear wave splitting results for deep and teleseismic events, making use of a wide variety of available phases that sample the upper mantle directly beneath the stations (such as SKS, SKKS, PKS, sSKS, SKiKS, ScS and local/direct S). We analyze the variability of our results with respect to initial polarizations and ray paths, as well as spatial variability between stations as the underlying slab morphology changes. Preliminary results show predominately NW-SE fast polarizations (trench oblique to sub-parallel) over the flat-slab region east of Lima. These results are consistent with observations of more complex multi-layered anisotropy beneath a nearby permanent station (NNA). Further south, towards the transition to steeper subduction, the splitting pattern becomes increasingly dominated by null measurements. Over to the east however, beyond Cuzco, where the mantle wedge might begin to play a role, we record fast polarizations quasi-parallel to the local slab contours. We carefully evaluate the different possible source locations within the subduction zone for this seismic anisotropy and observe increasing evidence for distinct anisotropy within the slab as well as the sub-slab mantle.

  4. Diagnostic performance of shear wave elastography of the breast according to scanning orientation.

    Science.gov (United States)

    Kim, Solip; Choi, SeonHyeong; Choi, Yoonjung; Kook, Shin-Ho; Park, Hee Jin; Chung, Eun Chul

    2014-10-01

    To evaluate the influence of the scanning orientation on diagnostic performance measured by the mean elasticity, maximum elasticity, and fat-to-lesion elasticity ratio on ultrasound-based shear wave elastography in differentiating breast cancers from benign lesions. In this study, a total of 260 breast masses from 235 consecutive patients were observed from March 2012 to November 2012. For each lesion, the mean elasticity value, maximum elasticity value, and fat-to-lesion ratio were measured along two orthogonal directions, and all values were compared with pathologic results. There were 59 malignant and 201 benign lesions. Malignant masses showed higher mean elasticity, maximum elasticity, and fat-to-lesion ratio values than benign lesions (P elasticity on both views, 0.870; mean elasticity on the transverse view, 0.866; maximum elasticity on both views, 0.865; maximum elasticity on the transverse view, 0.864; mean elasticity on the longitudinal view, 0.849; fat-to-lesion ratio on both views, 0.849; maximum elasticity on the longitudinal view, 0.845; fat-to-lesion ratio on the transverse view, 0.841; and fat-to-lesion ratio on the longitudinal view, 0.814. Intraclass correlation coefficients for agreement between the scanning directions were as follows: mean elasticity, 0.852; maximum elasticity, 0.842; fat-to-lesion ratio, 0.746, for masses; and mean elasticity, 0.392, for anterior mammary fat. Mean elasticity, maximum elasticity, and fat-to-lesion elasticity ratio values were helpful in differentiating benign and malignant breast masses. The scanning orientation did not significantly affect the diagnostic performance of shear wave elastography for breast masses. © 2014 by the American Institute of Ultrasound in Medicine.

  5. Effect of particle size distribution on the correlation between liquefaction resistance and shear wave velocity of granular soils

    Science.gov (United States)

    Zhou, Changtao; Xu, Xiao Min; Cheng, Yi Pik

    2017-06-01

    Shear wave method has been increasingly popular in assessing the liquefaction potential of granular soils. Two particle-scale parameters, the inter-particle friction and the shear modulus of grains, play vital roles in correlation between Cyclic Resistance Ratio (CRR) and shear wave velocity corrected by overburden stress (Vs1). Series of drained one-dimensional compression tests were simulated on samples of different inter-particle friction angles assigned during preparation stage. Uniformity coefficients of these Particle Size Distribution (PSD) curves are 2 and 4 whose average particle size d50 are identical. The shearing results, as well as their assigned inter-particle friction angles form calibration curves for real sands. Dissimilar PSD curves result in different calibration outcomes. For Silica sand no.8, these curves give divergent inter-particle friction angles. This study calibrates particle shear modulus for Silica sand no.8 as well. Different PSD curves give divergent values of particle shear modulus. PSDs show impacts on calibrations of both vital parameters, which have converse effects on CRR-Vs1 curves. This study suggests that the CRR-Vs1 correlation should be independent of PSDs.

  6. Non-invasive assessment of sciatic nerve stiffness during human ankle motion using ultrasound shear wave elastography

    NARCIS (Netherlands)

    Andrade, R.J.; Nordez, A.; Hug, F.; Coppieters, M.W.J.; Pezarat-Correia, P.; de Freitas, S.R.

    2015-01-01

    Peripheral nerves are exposed to mechanical stress during movement. However the in vivo mechanical properties of nerves remain largely unexplored. The primary aim of this study was to characterize the effect of passive dorsiflexion on sciatic nerve shear wave velocity (an index of stiffness) when

  7. Evaluating the Benefit of Elevated Acoustic Output in Harmonic Motion Estimation in Ultrasonic Shear Wave Elasticity Imaging.

    Science.gov (United States)

    Deng, Yufeng; Palmeri, Mark L; Rouze, Ned C; Haystead, Clare M; Nightingale, Kathryn R

    2018-02-01

    Harmonic imaging techniques have been applied in ultrasonic elasticity imaging to obtain higher-quality tissue motion tracking data. However, harmonic tracking can be signal-to-noise ratio and penetration depth limited during clinical imaging, resulting in decreased yield of successful shear wave speed measurements. A logical approach is to increase the source pressure, but the in situ pressures used in diagnostic ultrasound have been subject to a de facto upper limit based on the Food and Drug Administration guideline for the mechanical index (MI harmonic motion tracking for hepatic shear wave elasticity imaging. The studies indicate that high-MI harmonic tracking increased shear wave speed estimation yield by 27% at a focal depth of 5 cm, with larger yield increase in more difficult-to-image patients. High-MI tracking improved harmonic tracking data quality by increasing the signal-to-noise ratio and decreasing jitter in the tissue motion data. We conclude that there is clinical benefit to use of elevated acoustic output in shear wave tracking, particularly in difficult-to-image patients. Copyright © 2018 World Federation for Ultrasound in Medicine and Biology. Published by Elsevier Inc. All rights reserved.

  8. Investigation of the acute plantar fasciitis with contrast-enhanced ultrasound and shear wave elastography - first results.

    Science.gov (United States)

    Putz, Franz Josef; Hautmann, Matthias G; Banas, Miriam; Jung, Ernst Michael

    2017-09-04

    The plantar fasciitis is a common disease with a high prevalence in public and a frequent cause of heel pain. In our pilot study, we wanted to characterise the feasibility of shear-wave elastography and contrast-enhanced ultrasound (CEUS) in the assessment of the plantar fasciitis. 23 cases of painful heels were examined by B-Mode ultrasound, Power Doppler (PD), shear wave elastography and contrast-enhanced ultrasound before anti-inflammatory radiation. Time-intensity-curves were analysed by the integrated software. The results for area-under-the-curve (AUC), peak, time-to-peak (TTP) and mean-transit-time (MTT) were compared between the plantar fascia and the surrounding tissue. All cases showed thickening of the plantar fascia, in most cases with interstitial oedema (87.0%). Shear wave elastography showed inhomogeneous stiffness of the plantar fascia. 83.3% of cases showed a visible hyperperfusion in CEUS at the proximal plantar fascia in comparison to the surrounding tissue. This hyperperfusion could also be found in 75.0% of cases with no signs of vascularisation in PD. AUC (p = 0.0005) and peak (p = 0.037) were significantely higher in the plantar fascia than in the surrounding tissue. CEUS and shear wave elastography are new diagnostic tools in the assessment of plantar fasciitis and can provide quantitative parameters for monitoring therapy.

  9. In Vivo Evaluation of the Biomechanical Properties of Optic Nerve and Peripapillary Structures by Ultrasonic Shear Wave Elastography in Glaucoma

    OpenAIRE

    Dikici; Mihmanli; Kilic; Ozkok; Kuyumcu; Sultan,; Samanci; Halit Yilmaz; Rafiee; Tamcelik; Isik Hasiloglu; Kantarci

    2016-01-01

    Background Primary open-angle glaucoma is a multifactorial serious disease characterized by progressive retinal ganglion cell death and loss of visual field. Objectives The purposes of this study were to investigate shear wave elastography (SWE) use in the evaluation of the optic nerve (ON) and peripapillary structures, and to compare the findings between glaucomatous and control eyes. Patients...

  10. Detailed three-dimensional shear wave velocity structure of the northwestern United States from Rayleigh wave tomography

    Science.gov (United States)

    Wagner, Lara; Forsyth, Donald W.; Fouch, Matthew J.; James, David E.

    2010-11-01

    Since the mid-Miocene, the northwestern United States has experienced extensive flood basalt volcanism, followed by the formation of two time-progressive tracks of silicic volcanism: the Yellowstone/Snake River Plains (YSRP) and the High Lava Plains (HLP). The YSRP track progresses towards the northeast, parallel to North American plate motion, and has therefore often been attributed to a deep mantle plume source. However, the HLP track progresses to the northwest over the same time frame in a direction not consistent with any regional plate motion. The causes of the mid-Miocene flood basalts and the tracks of the YSRP and HLP are a matter of ongoing debate. We present results of Rayleigh wave phase velocity inversions and inversions for 3-D shear wave velocity structure of the northwestern United States using data collected from the High Lava Plains seismic experiment and the EarthScope USArray Transportable Array (TA). The large number of stations used in these inversions allows us to show an unprecedented level of detail in the seismic velocity structures of this tectonically complex area. Our velocity images indicate that low S-wave velocities in the uppermost mantle do not well match the track of HLP volcanism. While at the surface the Newberry caldera appears to anchor the NW end of the HLP hotspot track, the seismic results show that it lies in a separate, north-south trending low velocity band just east of the Cascades that is distinct from the main HLP trace. The ultra-low S-wave velocities beneath the YSRP track extend locally to at least 175 km depth and are by far the most prominent seismic anomalies in the region. Along axis, the YSRP hotspot track is characterized by a discrete low velocity channel in the upper mantle that shallows, narrows and intensifies to the northeast, but then deepens rapidly to the north beneath Yellowstone. The shallowing of the low velocity anomaly to the northeast is consistent with a stationary heat source beneath a moving

  11. The lithospheric shear-wave velocity structure of Saudi Arabia: Young volcanism in an old shield

    KAUST Repository

    Tang, Zheng

    2016-05-11

    We investigate the lithospheric shear-wave velocity structure of Saudi Arabia by conducting H-κ stacking analysis and jointly inverting teleseismic P-receiver functions and fundamental-mode Rayleigh wave group velocities at 56 broadband stations deployed by the Saudi Geological Survey (SGS). The study region, the Arabian plate, is traditionally divided into the western Arabian shield and the eastern Arabian platform: The Arabian shield itself is a complicated mélange of crustal material, composed of several Proterozoic terrains separated by ophiolite-bearing suture zones and dotted by outcropping Cenozoic volcanic rocks (locally known as harrats). The Arabian platform is primarily covered by 8 to 10 km of Paleozoic, Mesozoic and Cenozoic sedimentary rocks. Our results reveal high Vp/Vs ratios in the region of Harrat Lunayyir, which are interpreted as solidified magma intrusions from old magmatic episodes in the shield. Our results also indicate slow velocities and large upper mantle lid temperatures below the southern and northern tips of the Arabian shield, when compared with the values obtained for the central shield. We argue that our inferred patterns of lid velocity and temperature are due to heating by thermal conduction from the Afar plume (and, possibly, the Jordan plume), and that volcanism in western Arabia may result from small-scale adiabatic ascent of magma diapirs.

  12. Analytical study of dispersion relations for shear horizontal wave propagation in plates with periodic stubs.

    Science.gov (United States)

    Xu, Yanlong

    2015-08-01

    The coupled mode theory with coupling of diffraction modes and waveguide modes is usually used on the calculations of transmission and reflection coefficients for electromagnetic waves traveling through periodic sub-wavelength structures. In this paper, I extend this method to derive analytical solutions of high-order dispersion relations for shear horizontal (SH) wave propagation in elastic plates with periodic stubs. In the long wavelength regime, the explicit expression is obtained by this theory and derived specially by employing an effective medium. This indicates that the periodical stubs are equivalent to an effective homogenous layer in the long wavelength. Notably, in the short wavelength regime, high-order diffraction modes in the plate and high-order waveguide modes in the stubs are considered with modes coupling to compute the band structures. Numerical results of the coupled mode theory fit pretty well with the results of the finite element method (FEM). In addition, the band structures' evolution with the height of the stubs and the thickness of the plate shows clearly that the method can predict well the Bragg band gaps, locally resonant band gaps and high-order symmetric and anti-symmetric thickness-twist modes for the periodically structured plates. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Analytical study of dispersion relations for shear horizontal wave propagation in plates with periodic stubs

    KAUST Repository

    Xu, Yanlong

    2015-08-01

    The coupled mode theory with coupling of diffraction modes and waveguide modes is usually used on the calculations of transmission and reflection coefficients for electromagnetic waves traveling through periodic sub-wavelength structures. In this paper, I extend this method to derive analytical solutions of high-order dispersion relations for shear horizontal (SH) wave propagation in elastic plates with periodic stubs. In the long wavelength regime, the explicit expression is obtained by this theory and derived specially by employing an effective medium. This indicates that the periodical stubs are equivalent to an effective homogenous layer in the long wavelength. Notably, in the short wavelength regime, high-order diffraction modes in the plate and high-order waveguide modes in the stubs are considered with modes coupling to compute the band structures. Numerical results of the coupled mode theory fit pretty well with the results of the finite element method (FEM). In addition, the band structures\\' evolution with the height of the stubs and the thickness of the plate shows clearly that the method can predict well the Bragg band gaps, locally resonant band gaps and high-order symmetric and anti-symmetric thickness-twist modes for the periodically structured plates. © 2015 Elsevier B.V.

  14. PICASSO: Shear velocities in the Western Mediterranean from Rayleigh Wave tomography

    Science.gov (United States)

    Palomeras, I.; Thurner, S.; Levander, A.

    2012-12-01

    The Western Mediterranean has been affected by complex subduction and slab rollback, simultaneously with compression due to African-European convergence. The deformed region occupies a wide area from the intra-continental Atlas mountain belt in Morocco to the southern Iberian Massif in Spain. Evolutionary models of the Western Mediterranean invoke extensive slab rollback and compression in the Cenozoic, as well as likely upper mantle delamination scenarios during formation of the Alboran domain, the Betics, Rif, and Atlas Mountains. PICASSO (Program to Investigate Convective Alboran Sea System Overturn) is a multidisciplinary, international investigation of the Alboran System and surrounding areas. In this study we have analyzed data from the 95 PICASSO broadband stations with data from the Spanish IberArray and Siberia Array in Spain and Morocco, the University of Muenster array in the Atlas Mountains and the permanent Spanish and Portuguese networks. We present Rayleigh wave tomography results made from 168 teleseimic events recorded by 237 stations from April 2009 to April 2011. We measured Rayleigh phase velocities using the two-plane-wave method to remove complications due to multi-pathing, and finite-frequency kernels to improve lateral resolution. Phase velocities were then inverted for shear velocity structure on a grid of 0.5 by 0.5 degree to form a well-resolved 3D shear velocity model to 230 km depth. Our results show low S-velocities (2.9 km/s) in the crust beneath the Gibraltar Strait. Low upper mantle S-velocities are mapped beneath the Middle and High Atlas at ~60 km depth suggesting an elevated asthenosphere beneath these young mountain belts, in agreement with receiver functions analysis (Thurner et al, this session). Beneath the Western Alboran Sea, upper-mantle velocities change laterally from high velocities (>4.5 km/s) in the east to lower velocities to the west (~4.3 km/s). The Rayleigh wave tomography is consistent with P-tomography that

  15. Shear-wave velocity of marine sediments offshore Taiwan using ambient seismic noise

    Science.gov (United States)

    Lin, Yu-Tse; Lin, Jing-Yi; Kuo-Chen, Hao; Yeh, Yi-Chin; Cheng, Win-Bin

    2017-04-01

    Seismic ambient noise technology has many advantages over the traditional two-station method. The most important one is that noise is happening all the time and it can be widely and evenly distributed. Thus, the Green's Function of any station pair can be obtained through the data cross-correlation process. Many related studies have been performed to estimate the velocity structures based on the inland area. Only a few studies were reported for the marine area due to the relatively shorter recording time of ocean bottom seismometers (OBS) deployment and the high cost of the marine experiment. However, the understanding about the shear-wave velocity (Vs) of the marine sediments is very crucial for the hazard assessment related to submarine landslides, particularly with the growing of submarine resources exploration. In this study, we applied the ambient noise technique to four OBS seismic networks located offshore Taiwan in the aim of getting more information about the noise sources and having the preliminary estimation for the Vs of the marine sediments. Two of the seismic networks were deployed in the NE part of Taiwan, near the Ryukyu subduction system, whereas the others were in the SW area, on the continental margin rich in gas hydrate. Generally, ambient seismic noise could be associated with wind, ocean waves, rock fracturing and anthropogenic activity. In the southwestern Taiwan, the cross-correlation function obtained from two seismic networks indicate similar direction, suggestion that the source from the south part of the network could be the origin of the noise. However, the two networks in the northeastern Taiwan show various source direction, which could be caused by the abrupt change of bathymetry or the volcanic degassing effect frequently observed by the marine geophysical method in the area. The Vs determined from the dispersion curve shows a relatively higher value for the networks in the Okinawa Trough (OT) off NE Taiwan than that in the

  16. Liquefaction assessment based on combined use of CPT and shear wave velocity measurements

    Science.gov (United States)

    Bán, Zoltán; Mahler, András; Győri, Erzsébet

    2017-04-01

    Soil liquefaction is one of the most devastating secondary effects of earthquakes and can cause significant damage in built infrastructure. For this reason liquefaction hazard shall be considered in all regions where moderate-to-high seismic activity encounters with saturated, loose, granular soil deposits. Several approaches exist to take into account this hazard, from which the in-situ test based empirical methods are the most commonly used in practice. These methods are generally based on the results of CPT, SPT or shear wave velocity measurements. In more complex or high risk projects CPT and VS measurement are often performed at the same location commonly in the form of seismic CPT. Furthermore, VS profile determined by surface wave methods can also supplement the standard CPT measurement. However, combined use of both in-situ indices in one single empirical method is limited. For this reason, the goal of this research was to develop such an empirical method within the framework of simplified empirical procedures where the results of CPT and VS measurements are used in parallel and can supplement each other. The combination of two in-situ indices, a small strain property measurement with a large strain measurement, can reduce uncertainty of empirical methods. In the first step by careful reviewing of the already existing liquefaction case history databases, sites were selected where the records of both CPT and VS measurement are available. After implementing the necessary corrections on the gathered 98 case histories with respect to fines content, overburden pressure and magnitude, a logistic regression was performed to obtain the probability contours of liquefaction occurrence. Logistic regression is often used to explore the relationship between a binary response and a set of explanatory variables. The occurrence or absence of liquefaction can be considered as binary outcome and the equivalent clean sand value of normalized overburden corrected cone tip

  17. Diffraction of picosecond bulk longitudinal and shear waves in micron thick films. Application to their nondestructive evaluation.

    Science.gov (United States)

    Audoin, B; Perton, M; Chigarev, N; Rossignol, C

    2008-11-01

    In this paper, acute focusing of the laser pump beam ( approximately 0.5 microm) on the sample surface allows picosecond acoustic diffraction in thin metallic films. The resulting wavefronts propagate at a group velocity which differs from phase velocities in anisotropic films. Waveforms have been experimentally recorded in a gold layer (2.1 microm thick) for several distances between pump and probe on the sample surface. A specified signal processing based on a Synthetic Focalization Technique allows analyzing the space repartition of the acoustic wave vectors for both longitudinal and shear waves. Stiffness coefficients of the gold layer are then identified from wave arrival times.

  18. Propagation of ultrasonic guided waves in lap-shear adhesive joints

    Science.gov (United States)

    Lanza di Scalea, Francesco; Rizzo, Piervincenzo; Marzani, Alessandro

    2004-07-01

    This paper deals with the propagation of ultrasonic guided waves in adhesively-bonded lap-shear joints. The topic is relevant to ultrasonic bond inspection in aerospace components. Specifically, the propagation of the lowest-order, antisymmetric a0 mode through the joint is examined. This mode can be easily generated and detected in the field due to the predominant out-of-plane displacements at the surface of the test piece. An important aspect is the mode conversion at the boundaries between the single-plate adherends and the multilayer overlap. The a0 strength of transmission is studied for three different bond states in aluminum joints, namely a fully cured adhesive bond, a poorly cured adhesive bond, and a slip bond. Theoretical predictions based on the Global Matrix Method indicate that the dispersive behavior of the guided waves in the multilayer overlap is highly dependent on bond state. Experimental tests of the joints are conducted by a hybrid, broadband laser/air-coupled ultrasonic setup in a through-transmission configuration. This system does not require any wet coupling and it can be moved flexibly across the test piece. The Gabor Wavelet transform is employed to extract energy transmission coefficients in the 100 kHz - 1.4 MHz range for the three different bond states examined. The cross-sectional mode shapes of the guided waves are shown to have a substantial role in the energy transfer through the joint. A rationale for the selection of the a0 excitation frequencies highly sensitive to bond state will be given.

  19. An investigation on the deicing of helicopter blades using shear horizontal guided waves

    Science.gov (United States)

    Ramanathan, Srinivasan

    Despite all the advances that have made air travel safer than ever, the accumulation of ice on airplane and rotorcraft wings continues to be one of aviation's most challenging problems. Hence the presence of a reliable and efficient deicing or anti-icing system is imperative for their safe operation. The current method used to deice helicopter blades is similar to that available in automobile rear windows. These electro-thermal systems consist of heating coils that run along the span or chord of the rotor-blade. A current source connected via a slip ring configuration heats the coils, which in turn melt the ice on the surface. Due to their enormous power consumption, electro-thermal systems are generally configured to deice one foot of one blade at a time. This makes it hazardous to fly the helicopters under severe icing conditions. Even with the energy saving deicing procedure the electrical power required substantially exceeds the normal helicopter electrical system capacity, necessitating a large secondary electrical system with redundant, dual alternator features. The electro-thermal system for the Bell 412 helicopter weighed 162 lbs and required 26 kW of power for 2 blades! Various types of deicing systems were compared in chapter 1 and electromechanical systems were found to be the most energy efficient and practical for in-flight conditions. A novel approach of breaking the ice-substrate bonds by exceeding their adhesive strength using guided shear horizontal waves was chosen as the deicing mechanism. A comparison of the different electro-mechanical actuation systems pointed towards monolithic shear mode piezoelectric actuators as the choice that would satisfy the energy and dimensional requirements. A survey of literature on the mechanics of ice adhesion, in chapter 2, led to the selection of 1.42MPa as the target adhesive bond strength for the refrigerated icealuminum interface. The static adhesive strength of naturally occurring forms of ice such as rime

  20. Performance of shear wave elastography for differentiation of benign and malignant solid breast masses.

    Directory of Open Access Journals (Sweden)

    Guiling Li

    Full Text Available OBJECTIVES: To perform a meta-analysis assessing the ability of shear wave elastography (SWE to identify malignant breast masses. METHODS: PubMed, the Cochrane Library, and the ISI Web of Knowledge were searched for studies evaluating the accuracy of SWE for identifying malignant breast masses. The diagnostic accuracy of SWE was evaluated according to sensitivity, specificity, and hierarchical summary receiver operating characteristic (HSROC curves. An analysis was also performed according to the SWE mode used: supersonic shear imaging (SSI and the acoustic radiation force impulse (ARFI technique. The clinical utility of SWE for identifying malignant breast masses was evaluated using analysis of Fagan plot. RESULTS: A total of 9 studies, including 1888 women and 2000 breast masses, were analyzed. Summary sensitivities and specificities were 0.91 (95% confidence interval [CI], 0.88-0.94 and 0.82 (95% CI, 0.75-0.87 by SSI and 0.89 (95% CI, 0.81-0.94 and 0.91 (95% CI, 0.84-0.95 by ARFI, respectively. The HSROCs for SSI and ARFI were 0.92 (95% CI, 0.90-0.94 and 0.96 (95% CI, 0.93-0.97, respectively. SSI and ARFI were both very informative, with probabilities of 83% and 91%, respectively, for correctly differentiating between benign and malignant breast masses following a "positive" measurement (over the threshold value and probabilities of disease as low as 10% and 11%, respectively, following a "negative" measurement (below the threshold value when the pre-test probability was 50%. CONCLUSIONS: SWE could be used as a good identification tool for the classification of breast masses.

  1. A threshold value in Shear Wave elastography to rule out malignant thyroid nodules: A reality?

    Energy Technology Data Exchange (ETDEWEB)

    Veyrieres, J.-B., E-mail: jbveyrieres@hotmail.fr [Département d’imagerie médicale, Hôpital d’Instruction des Armées St Anne, Bd Saint Anne, BP 20545 Toulon cedex (France); Albarel, F., E-mail: frederique.albarel@ap-hm.fr [Département médical d’endocrinologie et des pathologies métaboliques, Hôpital Universitaire la Timone, Assistance publique des Hôpitaux de Marseille, 264 rue Saint Pierre, 13385 Marseille cedex 5 (France); Lombard, J. Vaillant, E-mail: Josiane.vaillant@ap-hm.fr [Département d’imagerie médicale, Hôpital Universitaire la Timone, Assistance publique des Hôpitaux de Marseille, 264 rue Saint Pierre, 13385 Marseille cedex 5 (France); Berbis, J., E-mail: Julie.berbis@ap-hm.fr [Département de santé publique, Université de Médecine, 27, Bd Jean Moulin, 13385 Marseille cedex 5 (France); Sebag, F., E-mail: frederic.sebag@ap-hm.fr [Département de chirurgie des pathologies endocriniennes et métaboliques, Hôpital Universitaire la Timone, Assistance publique des Hôpitaux de Marseille, 264 rue Saint Pierre, 13385 Marseille cedex 5 (France); and others

    2012-12-15

    Objectives: To evaluate hability of a threshold value in ShearWave™ elastography to rule out malignant thyroid nodules while studying its pertinence in association with morphological signs. Equipment and methods: 148 patients (110 women and 38 men; 52.5 y.o. 15.8) referred for surgery of thyroid nodules underwent standard ultrasound as well as elastography. Characteristics of the morphological signs and maximum elastographic index were calculated in relation to histology. Association of morphological signs alone and then of elastography was also evaluated. One hundred and fifty one nodules were studied on a double-blind basis. Results: 297 nodules were studied. Thirty-five cancers were detected (11.6%). Elastographic index was higher in malignant nodules (115 kPa 60.4) than in benign nodules (41 kPa 25.8) (p < 0.001, Student's t-test). Cut off value of 66 kPa was the best to discriminate malignant nodules with a sensitivity of 80% (CI 95%, 62.5; 90.9) and a specificity of 90.5% (CI 95%, 86.1; 93.6) (p = 0.0001). Association of elastography and morphological ultrasound signs presented a sensitivity of 97% (CI 95%, 83.3; 99.8) and a negative predictive value of 99.5% (CI 95%, 95.6; 99.9). Interobserver reproducibility proved to be excellent with an interclass correlation of 0.97 (CI 95%, 0.96; 0.98) (p < 0.001). Conclusion: The 66 kPa threshold in Shear Wave elastography is the best ultrasound sign to rule out malignant thyroid nodules. The method is simple, quantitative, reproducible and usable in the study of nodules larger than 3 cm. Progress must still be made in the study of calcified nodules and follicular tumors.

  2. Feasibility assessment of shear wave elastography to lumbar back muscles: A Radioanatomic Study.

    Science.gov (United States)

    Creze, Maud; Nyangoh Timoh, Krystel; Gagey, Olivier; Rocher, Laurence; Bellin, Marie-France; Soubeyrand, Marc

    2017-09-01

    Low back pain is often associated with tensional changes in the paraspinal muscles detected by palpatory procedures. Shear wave elastography (SWE), recently introduced, allows the stiffness of muscles to be assessed noninvasively. The aim of this work was to study the feasibility of using SWE on the three main lumbar back muscles (multifidus, longissimus, and iliocostalis) in vivo after analyzing their muscular architecture ex vivo. We determined the orientation of fibers in the multifidus, longissimus, and iliocotalis muscles in seven fresh cadavers using gross anatomy and B-Mode ultrasound imaging. We then quantified the stiffness of these three muscles at the L3 level ex vivo and in 16 healthy young adults. Little pennation was observed in the longissimus and iliocostalis, in which the direction of fibers was almost parallel to the line of spinous processes. The multifidus appeared as a multiceps and multipennate muscle. Given the random layering of millimetric fascicles, tendons, and fatty spaces, the multifidus had multiple fiber orientations. Muscular fascicles and fibers were oriented from 9° to 22° to the line of spinous processes. The shear moduli related to stiffness were 6.9 ± 2.7 kPa for the longissimus, 4.9 ± 1.4 kPa for the iliocostalis, and 5.4 ± 1.6 kPa for the multifidus. SWE is a feasible method for quantifying the stiffness of the lumbar back muscles. Clin. Anat. 30:774-780, 2017. © 2017Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  3. Wave-induced bottom shear stress estimation in shallow water exemplified by using deep water wind statistics

    Directory of Open Access Journals (Sweden)

    Dag Myrhaug

    2017-04-01

    Full Text Available The paper provides a simple and analytical method which can be used to give estimates of the wave-induced bottom shear stress for very rough beds and mud beds in shallow water based on wind statistics in deep water. This is exemplified by using long-term wind statistics from the northern North Sea, and by providing examples representing realistic field conditions. Based on, for example, global wind statistics, the present results can be used to make estimates of the bottom shear stress in shallow water.

  4. Ultrasound-Based Shear Wave Elastography in the Assessment of Patients with Diabetic Kidney Disease.

    Science.gov (United States)

    Bob, Flaviu; Grosu, Iulia; Sporea, Ioan; Bota, Simona; Popescu, Alina; Sima, Alexandra; Şirli, Roxana; Petrica, Ligia; Timar, Romulus; Schiller, Adalbert

    2017-10-01

    In previous studies of acoustic radiation force impulse (ARFI) elastography, using Virtual Touch tissue quantification (VTQ) (Siemens Acuson S2000), it was reported that the measurement of renal shear wave speed in patients with chronic kidney disease (CKD) is not influenced exclusively by renal fibrosis. The purpose of the present study was to analyze the role of VTQ in patients with diabetic kidney disease, considered the main cause of CKD. The study group included 164 patients: 80 patients with diabetic kidney disease (DKD) and 84 without renal disease or diabetes mellitus. In each subject in lateral decubitus, five valid VTQ measurements were performed in each kidney and a median value was calculated, the result being expressed in meters/second. The following means of the median values were obtained In DKD patients, the means of the median values were for VTQ right kidney, 2.21 ± 0.71 m/s, and for VTQ left kidney, 2.13 ± 0.72 m/s, whereas in the normal controls statistically significant higher values were obtained: 2.58 ± 0.78 m/s for VTQ right kidney (p = 0.0017) and 2.46 ± 0.81 m/s for VTQ left kidney (p = 0.006). Patients with an estimated glomerular filtration rate (eGFR) >60 mL/min (DKD stages 1 and 2 together with normal controls) had a significantly higher kidney shear wave speed compared with patients with an eGFR 60 mL/min (either normal controls or diabetic patients with DKD stages 1 and 2), and values decrease with the decrease in eGFR. However, proteinuria, diabetic retinopathy and glycated hemoglobin have no influence on VTQ. Copyright © 2017 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  5. Constraints on the Dip of the Anisotropic Symmetry Axis Beneath Japan From Shear Wave Splitting

    Science.gov (United States)

    Long, M. D.; Chevrot, S.; van der Hilst, R.

    2001-12-01

    Shear wave splitting is widely used as a tool to characterize deformational signatures in the upper mantle. However, we nearly always make the simplifying assumption that the axis of symmetry of the anisotropy is horizontal, which may not always be correct. Due to the nearly vertical incidence angles of the SKS phases typically used in splitting studies, the dip of the symmetry axis is difficult to characterize. However, if phases with varying angles of incidence are used, constraints may be placed on the dip of the symmetry axis. Splitting measurements made on upgoing shear waves with different incidence angles should exhibit discrepancies if the axis of symmetry is not horizontal. Therefore, recordings of SKKS, S, and ScS phases in addition to SKS may be used to constrain the dip of the axis of anisotropic symmetry. Japan is an excellent candidate region to potentially exhibit such discrepancies; deformation associated with the subduction beneath Japan could reasonably be expected to produce a dipping axis of symmetry. In addition, Japan is favorably located with respect to suitable source regions and data from several dense broadband seismic networks are available. We examine data from several high-quality, low-noise stations from the FREESIA network, a network of 62 broadband stations in Japan. We search for good recordings of events in the 0o-60o distance range for ScS, from 40o-80o for S, from 90o-130ofor SKS, and beyond 105o for SKKS. Only deep (>200km) events are used for S and ScS to eliminate contamination from source-side anisotropy. The multichannel method of Chevrot (JGR 2000) is used to determine splitting parameters (φ , δ t) at each station for each phase. Splitting parameters are determined from the azimuthal dependence of the splitting intensity; the method is therefore limited by the azimuthal coverage. Japan has relatively poor azimuthal coverage for SKS and SKKS, and this limits the usefulness of the multichannel method for this dataset

  6. Observation and modeling of mixing-layer development in HED blast-wave-driven shear flow

    Science.gov (United States)

    di Stefano, Carlos

    2013-10-01

    This talk describes work exploring the sensitivity to initial conditions of hydrodynamic mixing-layer growth due to shear flow in the high-energy-density regime. This work features an approach in two parts, experimental and theoretical. First, an experiment, conducted at the OMEGA-60 laser facility, seeks to measure the development of such a mixing layer. This is accomplished by placing a layer of low-density (initially of either 0.05 or 0.1 g/cm3, to vary the system's Atwood number) carbon foam against a layer of higher-density (initially 1.4 g/cm3) polyamide-imide that has been machined to a nominally-flat surface at its interface with the foam. Inherent roughness of this surface's finish is precisely measured and varied from piece to piece. Ten simultaneous OMEGA beams, comprising a 4.5 kJ, 1-ns pulse focused to a roughly 1-mm-diameter spot, irradiate a thin polycarbonate ablator, driving a blast wave into the foam, parallel to its interface with the polyamide-imide. The ablator is framed by a gold washer, such that the blast wave is driven only into the foam, and not into the polyamide-imide. The subsequent forward motion of the shocked foam creates the desired shear effect, and the system is imaged by X-ray radiography 35 ns after the beginning of the driving laser pulse. Second, a simulation is performed, intending to replicate the flow observed in the experiment as closely as possible. Using the resulting simulated flow parameters, an analytical model can be used to predict the evolution of the mixing layer, as well as track the motion of the fluid in the experiment prior to the snapshot seen in the radiograph. The ability of the model to predict growth of the mixing layer under the various conditions observed in the experiment is then examined. This work is funded by the Predictive Sciences Academic Alliances Program in NNSA-ASC via grant DEFC52- 08NA28616, by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, grant number DE

  7. Urban shear-wave reflection seismics: Reconstruction support by combined shallow seismic and engineering geology investigations

    Science.gov (United States)

    Polom, U.; Guenther, A.; Arsyad, I.; Wiyono, P.; Krawczyk, C. M.

    2009-12-01

    After the big 2004 Sumatra-Andaman earthquake, the massive reconstruction activities in the Aceh province (Northern Sumatra) were promoted by the Republic of Indonesia and the Federal Ministry of Economic Cooperation and Development. The aims of the project MANGEONAD (Management of Georisk Nanggroe Aceh Darussalam). are to establish geoscientific on the ground support for a sustainable development and management of save building constructions, lifelines, infrastructure and also natural resources. Therefore, shallow shear-wave reflection seismics was applied in close combination to engineering geology investigations in the period between 2005-2009 since depth and internal structure of the Krueng Aceh River delta (mainly young alluvial sediments) were widely unknown. Due to the requirements in the densely populated Banda Aceh region, lacking also traffic infrastructure, a small and lightweight engineering seismic setup of high mobility and high subsurface resolution capability was chosen. The S-wave land streamer system with 48 channels was applied successfully together with the ELVIS vibratory source using S- and P-waves on paved roads within the city of Banda Aceh. The performance of the S-wave system enabled the detailed seismic investigation of the shallow subsurface down to 50-150 m depth generating shaking frequencies between 20 Hz to 200 Hz. This also provides depth information extending the maximum depths of boreholes and Standard Penetrometer Testings (SPT), which could only be applied to max. 20 m depth. To integrate the results gained from all three methods, and further to provide a fast statistical analysis tool for engineering use, the Information System Engineering Geology (ISEG, BGR) was developed. This geospatial information tool includes the seismic data, all borehole information, geotechnical SPT and laboratory results from samples available in the investigation area. Thereby, the geotechnical 3D analysis of the subsurface units is enabled. The

  8. Crustal Anisotropy Beneath the Western Segment of North Anatolian Fault Zone from Local Shear-Wave Splitting

    Science.gov (United States)

    Altuncu Poyraz, S.; Teoman, U.; Kahraman, M.; Turkelli, N.; Rost, S.; Thompson, D. A.; Houseman, G.

    2014-12-01

    Shear-wave splitting from local earthquakes provides valuable knowledge on anisotropy of the upper crust. Upper-crustal anisotropy is widely interpreted as due to aligned fluid-filled cracks or pores. Differential stress is thought to close cracks aligned perpendicular to the maximum principal stress and leaves cracks open that are aligned perpendicular to the minimum horizontal compressional stress. In other cases local shear-wave splitting has been found to be aligned with regional faulting. Temporal variations in local splitting patterns might provide hints of changes in stress orientation related to earthquakes or volcanoes. North Anatolian Fault Zone (NAFZ) is a large-scale continental strike slip fault system originating at the Karlıova Junction in the east where it intersects the East Anatolian Fault (EAF) and extends west cutting across the entire Northern Turkey towards the Aegean Sea and the mainland Greece. Our primary focus is to provide constraints on the crustal anisotropy beneath the western segment of the North Anatolian Fault Zone with the use of a data set collected from a dense temporary seismic network consisting of 70 stations that was deployed in early May 2012 and operated for 18 months in the Sakarya region and the surroundings during the Faultlab experiment. For the local shear wave splitting analysis, out of 1344 events, we extracted 90 well located earthquakes with magnitudes greater than 2.0. Local shear-wave splitting makes use of earthquakes close to and nearly directly below the recording station. Incidence angles of less than 45 degrees were used to avoid the free-surface effect and resulting non-linear particle motion. Basically, two essential parameters for each station-event pair is needed for shear wave splitting calculations. One of them is fast polarization direction (ɸ) and the other is delay time (δt) between the fast and slow components of the shear wave. In this study, delay times vary between 0,02 and 0,25 seconds

  9. Quantitative Assessment of In-situ Salt Karstification Using Shear Wave Velocity, Dead Sea

    Science.gov (United States)

    Ezersky, Michael; Legchenko, Anatoly

    2014-09-01

    The Dead Sea (DS) coastal areas have been dramatically affected by sinkhole formation since around 1990. Such sinkholes along both Israeli and Jordanian shores are linked to karst cavities that form through slow salt dissolution. A quantitative estimate of such in-situ salt karstification would be an important indicator of sinkhole hazard. One of the indications of salt karstification is its increased hydraulic conductivity, caused by the development of dissolution cavities forming conducting channels within the salt layer. We measured the hydraulic conductivity (K) versus shear-wave velocity (Vs) of DS salt in situ for estimating the actual salt karstification in areas of sinkhole development. These parameters were measured with the Magnetic Resonance Sounding (MRS) and Multichannel Analysis of Surface Waves (MASW) methods, respectively. Understanding of the field relationships was augmented by similar inter-relations obtained in the laboratory on samples of DS salt. In-situ salt velocities Vs vary from 750 m/s to over 1650 m/s, while hydraulic conductivity (K) in the same zones varies between about 10- 4 m/s to slightly over 10- 8 m/s. Both field and laboratory K and Vs values fit the exponential function ln(K) = - 0.0045 ∗ Vs - 5.416 with a determination coefficient (R2) of 0.88. A classification based on Vs and K was generated for salt conditions and the corresponding degrees of sinkhole hazard, which was verified in the Mineral Beach sinkhole development area. The mapping of sinkhole sites shows that they form within highly conductive zones with K ≥ 5.5 ∗ 10- 5. It is suggested that this methodology, with some modification, can be used for evaluating the conductive properties of karstified rock and associated sinkhole hazards.

  10. Shear Wave Structure Beneath Texas and Its Implication for the Opening of The Gulf of Mexico

    Science.gov (United States)

    Yao, Y.; Li, A.

    2016-12-01

    It has been widely accepted that the Gulf of Mexico (GOM) was opened by the counterclockwise rotation of the Yucatan block away from the Texas-Louisiana margin during 140-160 Ma. However, little is known about the geodynamic cause of this rotation. We aim to find clues about the opening of the GOM using a high-resolution, 3D model in Texas with a focus on the coastal plane. We have conducted Rayleigh wave tomography using ambient noise and earthquake data recorded at the USArray TA stations and obtained phase velocity maps for 25 periods from 6 s to 166 s, which are utilized to build a 3-D shear wave velocity model in the crust and upper mantle above 200 km. The Laurentian craton is characterized by high-velocity anomalies, and the low-velocity anomalies mainly appear in the coastal plane. High-velocity maximums are observed following the Ouachita Belt in the entire crust and the uppermost mantle and are correlated with known uplifts. We interpreted these deep-rooted uplifts as accreted island arc materials during the Ouachita collision, which supports the argument of a strong Ouachita lithosphere that helped to confine the thin transition crust to its east and south in the Gulf coast. The most significant low-velocity region is imaged in southeast Texas from the lower crust to at least 200 km depth. This anomaly aligns on the Keathley Canyon hotspot track in the GOM and could be caused by a combination of high temperature, partial melting, and high volatile content. We associate this low-velocity column with a past asthenosphere upwelling that could have originated from the tear of the subducted slab during the Ouachita orogeny. The plume-like upwelling in southeast Texas is probably the main driving force for the opening of the Gulf of Mexico.

  11. Shear horizontal surface acoustic wave microsensor for Class A viral and bacterial detection.

    Energy Technology Data Exchange (ETDEWEB)

    Branch, Darren W.; Huber, Dale L.; Brozik, Susan Marie; Edwards, Thayne L.

    2008-10-01

    The rapid autonomous detection of pathogenic microorganisms and bioagents by field deployable platforms is critical to human health and safety. To achieve a high level of sensitivity for fluidic detection applications, we have developed a 330 MHz Love wave acoustic biosensor on 36{sup o} YX Lithium Tantalate (LTO). Each die has four delay-line detection channels, permitting simultaneous measurement of multiple analytes or for parallel detection of single analyte containing samples. Crucial to our biosensor was the development of a transducer that excites the shear horizontal (SH) mode, through optimization of the transducer, minimizing propagation losses and reducing undesirable modes. Detection was achieved by comparing the reference phase of an input signal to the phase shift from the biosensor using an integrated electronic multi-readout system connected to a laptop computer or PDA. The Love wave acoustic arrays were centered at 330 MHz, shifting to 325-328 MHz after application of the silicon dioxide waveguides. The insertion loss was -6 dB with an out-of-band rejection of 35 dB. The amplitude and phase ripple were 2.5 dB p-p and 2-3{sup o} p-p, respectively. Time-domain gating confirmed propagation of the SH mode while showing suppression of the triple transit. Antigen capture and mass detection experiments demonstrate a sensitivity of 7.19 {+-} 0.74{sup o} mm{sup 2}/ng with a detection limit of 6.7 {+-} 0.40 pg/mm{sup 2} for each channel.

  12. Lithospheric deformation inferred from teleseismic shear wave splitting observations in the Scottish Highlands

    Science.gov (United States)

    Bastow, I. D.; Owens, T. J.; Helffrich, G.; Knapp, J. H.

    2006-05-01

    The Scottish Highlands is an area that has experienced intense tectonic deformation over a recorded geological history that dates back to the Precambrian. Evidence for large scale deformation during the Caledonian orogeny is evident, for example, at the Great Glen and Highland Boundary faults, which have been investigated by field based studies of surface geology. The RUSH (Reflections Under the Scottish Highlands) broadband seismic network of 24 stations recorded continuously for 2 years in 2001-3 and traversed several of the major tectonic terrane boundaries in Scotland. Here we employ the method of Silver and Chan (1991) to estimate splitting parameters (dt, phi) using teleseismic shear waves recorded by these stations. The problem of large amounts of microseismic noise in our data is overcome by stacking individual results using the approach of Restivo and Helffrich (1999); high signal-to-noise ratio results are given more weight in the stack. We explore the relationship between splitting and structural fabric and find that fast polarisation directions are most commonly parallel to geological features such as the NE-SW trending Great Glen and Highland Boundary faults. In the north west part of the study area, towards the Moine thust zone, a change from NE- SW to E-W oriented polarisation direction is noted but dt is unchanged. dt increases markedly towards the NE-SW terrane boundaries. The results confirm that lithospheric scale deformation in Scotland has a preserved "fossil" anisotropic signature, up to hundreds of millions of years after the last tectonic episode.

  13. Smooth Muscle Cells of Penis in the Rat: Noninvasive Quantification with Shear Wave Elastography

    Directory of Open Access Journals (Sweden)

    Jia-Jie Zhang

    2015-01-01

    Full Text Available Purpose. Smooth muscle cells (SMCs of cavernosum play an important role in erection. It is of great significance to quantitatively analyze the level of SMCs in penis. In this study, we investigated the feasibility of shear wave elastography (SWE on evaluating the level of SMCs in penis quantitatively. Materials and Methods. Twenty healthy male rats were selected. The SWE imaging of penis was carried out and then immunohistochemistry analysis of penis was performed to analyze the expression of alpha smooth muscle actin in penis. The measurement index of SWE examination was tissue stiffness (TS. The measurement index of immunohistochemistry analysis was positive area percentage of alpha smooth muscle actin (AP. Results. Sixty sets of data of TS and AP were obtained. The results showed that TS was significantly correlated with AP and the correlation coefficient was −0.618 (p<0.001. The result of TS had been plotted against the AP measurements. The relation between the two results has been fitted with quadric curve; the goodness-of-fit index was 0.364 (p<0.001. Conclusions. The level of SMCs in penis was successfully quantified in vivo with SWE. SWE can be used clinically for evaluating the level of SMCs in penis quantitatively.

  14. Intra-and interobserver reproducibility of shear wave elastography for evaluation of the breast lesions

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Min Ji [Dept. of Radiology, Gil Hospital, Gachon University of Medicine and Science, Incheon (Korea, Republic of); Kim, Hak Hee [Dept. of Radiology, and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul (Korea, Republic of)

    2017-03-15

    To evaluate reproducibility of shear wave elastography (SWE) for breast lesions within and between observers and compare the reproducibility of SWE features. For intraobserver reproducibility, 225 masses with 208 patients were included; and two consecutive SWE images were acquired by each observer. For interobserver reproducibility, SWE images of the same mass were obtained by another observer before surgery in 40 patients. Intraclass correlation coefficients (ICC) were used to determine intra- and interobserver reproducibility. Intraobserver reliability for mean elasticity (Emean) and maximum elasticity (Emax) were excellent (ICC = 0.803, 0.799). ICC for SWE ratio and minimum elasticity (Emin) were fair to good (ICC = 0.703, 0.539). Emean showed excellent ICC regardless of histopathologic type and tumor size. Emax, SWE ratio and Emin represented excellent or fair to good reproducibility based on histopathologic type and tumor size. In interobserver study, ICC for Emean, Emax and SWE ratio were excellent. Emean, Emax and SWE ratio represented excellent ICC irrespective of histopathologic type. ICC for Emean was excellent regardless of tumor size. SWE ratio and Emax showed fair to good interobserver reproducibility based on tumor size. Emin represented poor interobserver reliability. Emean in SWE was highly reproducible within and between observers.

  15. Liver Stiffness Assessed by Shear Wave Elastography Predicts Postoperative Liver Failure in Patients with Hepatocellular Carcinoma.

    Science.gov (United States)

    Shen, Yinghao; Zhou, Chenhao; Zhu, Guodong; Shi, Guoming; Zhu, Xiaodong; Huang, Cheng; Zhou, Jian; Fan, Jia; Ding, Hong; Ren, Ning; Sun, Hui-Chuan

    2017-09-01

    Cirrhosis increases a patient's risk of developing postoperative liver failure (PLF). Liver stiffness (LS), assessed by two-dimensional shear wave elastography (SWE), indicates liver fibrosis with high accuracy. Whether LS is superior to portal hypertension (PHT) in predicting PLF remains to be studied. The study enrolled 280 patients who underwent hepatectomy for hepatocellular carcinoma from July 2015 to July 2016. All patients received preoperative assessments for LS, PHT, and serum markers of liver fibrosis in addition to other clinicopathological tests. Risk factors for grade A and grade B (or greater) PLF were subjected to univariate and multivariate analysis and receiver operating characteristic curve analysis. Fifty-five patients (19.6%) experienced PLF. The cutoff value of LS for predicting cirrhosis was 10.1 kPa. Multivariate analysis identified LS, hyaluronic acid, IV collagen, and the presence of splenomegaly as independent predictors of PLF. The cutoff value of LS for predicting PLF and grade B (or greater) PLF was 11.75 and 11.9 kPa, respectively. LS was superior to PHT in predicting PLF or greater than grade B PLF (0.72 vs. 0.60, 0.76 vs. 0.59, P < 0.05). LS measured by SWE can predict risk of PLF with greater accuracy than PHT.

  16. Qualitative pattern classification of shear wave elastography for breast masses: How it correlates to quantitative measurements

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Jung Hyun, E-mail: lvjenny0417@gmail.com [Department of Radiology, CHA Bundang Medical Center, CHA University, School of Medicine (Korea, Republic of); Department of Radiology, Research Institute of Radiological Science, Yonsei University, College of Medicine (Korea, Republic of); Ko, Kyung Hee, E-mail: yourheeya@cha.ac.kr [Department of Radiology, CHA Bundang Medical Center, CHA University, School of Medicine (Korea, Republic of); Jung, Hae Kyoung, E-mail: AA40501@cha.ac.kr [Department of Radiology, CHA Bundang Medical Center, CHA University, School of Medicine (Korea, Republic of); Lee, Jong Tae, E-mail: jtlee@cha.ac.kr [Department of Radiology, CHA Bundang Medical Center, CHA University, School of Medicine (Korea, Republic of)

    2013-12-01

    Objective: To determine the correlation of qualitative shear wave elastography (SWE) pattern classification to quantitative SWE measurements and whether it is representative of quantitative SWE values with similar performances. Methods: From October 2012 to January 2013, 267 breast masses of 236 women (mean age: 45.12 ± 10.54 years, range: 21–88 years) who had undergone ultrasonography (US), SWE, and subsequent biopsy were included. US BI-RADS final assessment and qualitative and quantitative SWE measurements were recorded. Correlation between pattern classification and mean elasticity, maximum elasticity, elasticity ratio and standard deviation were evaluated. Diagnostic performances of grayscale US, SWE parameters, and US combined to SWE values were calculated and compared. Results: Of the 267 breast masses, 208 (77.9%) were benign and 59 (22.1%) were malignant. Pattern classifications significantly correlated with all quantitative SWE measurements, showing highest correlation with maximum elasticity, r = 0.721 (P < 0.001). Sensitivity was significantly decreased in US combined to SWE measurements to grayscale US: 69.5–89.8% to 100.0%, while specificity was significantly improved: 62.5–81.7% to 13.9% (P < 0.001). Area under the ROC curve (A{sub z}) did not show significant differences between grayscale US to US combined to SWE (P > 0.05). Conclusion: Pattern classification shows high correlation to maximum stiffness and may be representative of quantitative SWE values. When combined to grayscale US, SWE improves specificity of US.

  17. Use of shear wave elastography to differentiate benign and malignant breast lesions.

    Science.gov (United States)

    Çebi Olgun, Deniz; Korkmazer, Bora; Kılıç, Fahrettin; Dikici, Atilla Süleyman; Velidedeoğlu, Mehmet; Aydoğan, Fatih; Kantarcı, Fatih; Yılmaz, Mehmet Halit

    2014-01-01

    We aimed to determine the correlations between the elasticity values of solid breast masses and histopathological findings to define cutoff elasticity values differentiating malignant from benign lesions. A total of 115 solid breast lesions of 109 consecutive patients were evaluated prospectively using shear wave elastography (SWE). Two orthogonal elastographic images of each lesion were obtained. Minimum, mean, and maximum elasticity values were calculated in regions of interest placed over the stiffest areas on the two images; we also calculated mass/fat elasticity ratios. Correlation of elastographic measurements with histopathological results were studied. Eighty-three benign and thirty-two malignant lesions were histopathologically diagnosed. The minimum, mean, and maximum elasticity values, and the mass/fat elasticity ratios of malignant lesions, were significantly higher than those of benign lesions. The cutoff value was 45.7 kPa for mean elasticity (sensitivity, 96%; specificity, 95%), 54.3 kPa for maximum elasticity (sensitivity, 95%; specificity, 94%), 37.1 kPa for minimum elasticity (sensitivity, 96%; specificity, 95%), and 4.6 for the mass/fat elasticity ratio (sensitivity, 97%; specificity, 95%). SWE yields additional valuable quantitative data to ultrasonographic examination on solid breast lesions. SWE may serve as a complementary tool for diagnosis of breast lesions. Long-term clinical studies are required to accurately select lesions requiring biopsy.

  18. Anisotropy of Solid Breast Lesions in 2D Shear Wave Elastography is an Indicator of Malignancy.

    Science.gov (United States)

    Skerl, Katrin; Vinnicombe, Sarah; Thomson, Kim; McLean, Denis; Giannotti, Elisabetta; Evans, Andrew

    2016-01-01

    To investigate if anisotropy at two-dimensional shear wave elastography (SWE) suggests malignancy and whether it correlates with prognostic and predictive factors in breast cancer. Study group A of 244 solid breast lesions was imaged with SWE between April 2013 and May 2014. Each lesion was imaged in radial and in antiradial planes, and the maximum elasticity, mean elasticity, and standard deviation were recorded and correlated with benign/malignant status, and if malignant, correlated with conventional predictive and prognostic factors. The results were compared to a study group B of 968 solid breast lesions, which were imaged in sagittal and in axial planes between 2010 and 2013. Neither benign nor malignant lesion anisotropy is plane dependent. However, malignant lesions are more anisotropic than benign lesions (P ≤ 0.001). Anisotropy correlates with increasing elasticity parameters, breast imaging-reporting and data system categories, core biopsy result, and tumor grade. Large cancers are significantly more anisotropic than small cancers (P ≤ 0.001). The optimal anisotropy cutoff threshold for benign/malignant differentiation of 150 kPa(2) achieves the best sensitivity (74%) with a reasonable specificity (63%). Anisotropy may be useful during benign/malignant differentiation of solid breast masses using SWE. Anisotropy also correlates with some prognostic factors in breast cancer. Crown Copyright © 2016. Published by Elsevier Inc. All rights reserved.

  19. Performance of Ultrasonic Shear Wave Elastography in Assessing Benign and Malignant Breast Lesions.

    Science.gov (United States)

    Shi, Xian-Quan; Li, Jun-Lai; Li, Qiu-Yang; Huang, Yan; Wan, Wen-Bo; Tang, Jie

    2015-06-01

    To determine the best shear wave elastography (SWE) quantitative parameters including the maximum elasticity (Emax), mean elasticity(Emean), minimum elasticity, standard deviation and ratio of Emean (Eratio) in assessing benign and malignant breast lesions. Totally 302 breast lesions underwent conventional ultrasound and SWE. Each lesion was classified according to ultrasound Breast Imaging Reporting and Data System (BI-RADS). The receiver operating characteristic(ROC) curves were used to determine the cut-off values of SWE quantitative parameters and to suggest breast lesions as benign or malignant. The sensitivity,specificity and the Youden index (sum of sensitivity and specificity minus 1) of SWE quantitative parameters were compared,and then the sensitivity,specificity and the Youden index of the combinations of each SWE parameters in assessing breast lesions were compared. The sensitivity,specificity and the Youden index of the Emax were 0.87,0.97 and 0.84,which were higher than other SWE parameters (all Pbreast lesions. It can be used as an important quantitative indicator for the evaluation of benign and malignant breast lesions.

  20. Changes in ultrasound shear wave elastography properties of normal breast during menstrual cycle.

    Science.gov (United States)

    Rzymski, P; Skórzewska, A; Opala, T

    2011-01-01

    Elastography is a novel technique capable of noninvasively assessing the elastic properties of breast tissue. Because the risk factors for breast cancer include hormonal status and proliferation, the aim of our study was to estimate the intensity of sonoelastographic changes during the menstrual cycle. Eight women aged 20-23 years with regular menstrual cycles underwent B-mode sonography and sonoelastography (ShearWave on Aixplorer, France) on days 3, 10, 17 and 24. Mean values of glandular and fat tissue elasticity did not change statistically significantly during the menstrual cycle as well as glandular to fat tissue ratio. During almost the whole cycle differences between outer and inner quadrants in glandular and fat tissue were statistically significant. The lowest values of elasticity occurred on the 10th day and the highest on the 24th of the menstrual cycle. There were statistically significant differences in elasticity between inner and outer quadrants of both breasts close to day 3 and 17 of the menstrual cycle.

  1. Lymphangiogenesis in Breast Cancer Correlates with Matrix Stiffness on Shear-Wave Elastography.

    Science.gov (United States)

    Cha, Yoon Jin; Youk, Ji Hyun; Kim, Baek Gil; Jung, Woo Hee; Cho, Nam Hoon

    2016-05-01

    To correlate tumor stiffness and lymphangiogenesis in breast cancer and to find its clinical implications. A total of 140 breast cancer patients were evaluated. Tumor stiffness was quantitatively measured by shear-wave elastography in preoperative ultrasound examination, calculated as mean elasticity value (kPa). Slides of resected breast cancer specimens were reviewed for most fibrotic area associated with tumor. D2-40 immunohistochemical staining was applied for fibrotic areas to detect the lymphatic spaces. Microlymphatic density, tumor stiffness, and clinicopathologic data were analyzed. Higher elasticity value was associated with invasive size of tumor, microlymphatic density, histologic grade 3, absence of extensive intraductal component, presence of axillary lymph node metastasis, and Ki-67 labeling index (LI) in univariate regression analysis, and associated with Ki-67 LI and axillary lymph node metastasis in multivariate regression analysis. Microlymphatic density was associated histologic grade 3, mean elasticity value, and Ki-67 LI in univariate regression analysis. In multivariate regression analysis, microlymphatic density was correlated with mean elasticity value. In breast cancer, tumor stiffness correlates with lymphangiogenesis and poor prognostic factors.

  2. Shear-horizontal vibration modes of an oblate elliptical cylinder and energy trapping in contoured acoustic wave resonators.

    Science.gov (United States)

    He, Huijing; Yang, Jiashi; Kosinski, John A

    2012-08-01

    We study shear-horizontal free vibrations of an elastic cylinder with an oblate elliptical cross section and a traction-free surface. Exact vibration modes and frequencies are obtained. The results show the existence of thickness-shear and thickness-twist modes. The energy-trapping behavior of these modes is examined. Trapped modes are found wherein the vibration energy is largely confined to the central portion of the cross section and little vibration energy is found at the edges. It is also shown that face-shear modes are not allowed in such a cylinder. The results are useful for the understanding of the energy trapping phenomenon in contoured acoustic wave resonators.

  3. Rheological assessment of a polymeric spherical structure using a three-dimensional shear wave scattering model in dynamic spectroscopy elastography.

    Science.gov (United States)

    Montagnon, Emmanuel; Hadj-Henni, Anis; Schmitt, Cédric; Cloutier, Guy

    2014-02-01

    With the purpose of assessing localized rheological behavior of pathological tissues using ultrasound dynamic elastography, an analytical shear wave scattering model was used in an inverse problem framework. The proposed method was adopted to estimate the complex shear modulus of viscoelastic spheres from 200 to 450 Hz. The inverse problem was formulated and solved in the frequency domain, allowing assessment of the complex viscoelastic shear modulus at discrete frequencies. A representative rheological model of the spherical obstacle was determined by comparing storage and loss modulus behaviors with Kelvin-Voigt, Maxwell, Zener, and Jeffrey models. The proposed inversion method was validated by using an external vibrating source and acoustic radiation force. The estimation of viscoelastic properties of three-dimensional spheres made softer or harder than surrounding tissues did not require a priori rheological assumptions. The proposed method is intended to be applied in the context of breast cancer imaging.

  4. A design procedure for an acoustic mirror providing dual reflection of longitudinal and shear waves in Solidly Mounted BAW Resonators (SMRs)

    NARCIS (Netherlands)

    Jose, Sumy; Jansman, Andreas; Hueting, Raymond Josephus Engelbart

    The quality factor of the traditional Solidly Mounted Resonator (SMR) is limited by substrate losses, as the traditionally employed acoustic mirror reflects longitudinal waves but not shear waves. Modern mirrors do reflect both waves, but design rules for such mirrors have not been published so far.

  5. [IMPORTANCE OF SHEAR WAVE ELASTOGRAPHY OF LIVERS IN PRACTICALLY HEALTHY PREGNANT WOMEN].

    Science.gov (United States)

    Sariyeva, E; Salahova, S; Bayramov, N

    2017-01-01

    .082, p=0.571), but a significant inverse correlation was found between the body mass index (BMI) and liver density (ρ=-0.317; p=0.025). Easy application, non-invasiveness, maximum exactness within the real time, repeatedly application of procedure and no risk to fetus by Shear Wave elastography of liver allow applying this method in pregnant women. Study of liver elasticity in pregnant women allows assessing the grades of hepatic fibrosis and differentiating liver disease.

  6. Scalar evolution equations for shear waves in incompressible solids: a simple derivation of the Z, ZK, KZK and KP equations

    KAUST Repository

    Destrade, M.

    2010-12-08

    We study the propagation of two-dimensional finite-amplitude shear waves in a nonlinear pre-strained incompressible solid, and derive several asymptotic amplitude equations in a simple, consistent and rigorous manner. The scalar Zabolotskaya (Z) equation is shown to be the asymptotic limit of the equations of motion for all elastic generalized neo-Hookean solids (with strain energy depending only on the first principal invariant of Cauchy-Green strain). However, we show that the Z equation cannot be a scalar equation for the propagation of two-dimensional shear waves in general elastic materials (with strain energy depending on the first and second principal invariants of strain). Then, we introduce dispersive and dissipative terms to deduce the scalar Kadomtsev-Petviashvili (KP), Zabolotskaya-Khokhlov (ZK) and Khokhlov- Zabolotskaya-Kuznetsov (KZK) equations of incompressible solid mechanics. © 2010 The Royal Society.

  7. Quaternary layer anomalies around the Carlsberg Fault zone mapped with high-resolution shear-wave seismics south of Copenhagen

    DEFF Research Database (Denmark)

    Kammann, Janina; Hübscher, Christian; Nielsen, Lars

    The Carlsberg Fault zone is located in the N-S striking Höllviken Graben and traverses the city of Copenhagen. The fault zone is a NNW-SSE striking structure in direct vicinity to the transition zone of the Danish Basin and the Baltic Shield. Recent small earthquakes indicate activity in the area......, although none of the mapped earthquakes appear to have occurred on the Carlsberg Fault. We examined the fault evolution by a combination of very high resolution onshore shear-wave seismic data, one conventional onshore seismic profile and marine reflection seismic profiles. The chalk stratigraphy....... In the Upper Cretaceous growth faulting documents continued rifting. This finding contrasts the Late Cretaceous to Paleogene inversion tectonics in neighboring structures, as the Tornquist Zone. The high-resolution shear-wave seismic method was used to image structures in Quaternary layers in the Carlsberg...

  8. The value of shear wave elastography in the quantification of corpus cavernosum penis rigidity and its alteration with age.

    Science.gov (United States)

    Inci, Ercan; Turkay, Rustu; Nalbant, Mustafa Orhan; Yenice, Mustafa Gurkan; Tugcu, Volkan

    2017-04-01

    The goal of this study was to measure corpus cavernosum (CC) penis rigidity with shear wave elastography (SWE) in healthy volunteers and to evaluate the change of rigidity with age. SWE was performed in 60 healthy volunteers (age range 20-71, mean 47±12,83 years). Volunteers were divided into 2 groups by age (Group 1 age penis (proximal, middle and glans penis) on both sides of CC. All values of SWE (in kilo Pascal) were noted along with volunteers' ages. The measurements were done both with transverse (T) and longitudinal (L) sections. We compared all SW values of penis parts and their alterations with age. The shear wave elastography values of CC penis increased with increasing age (ppenis (ppenis (ppenis rigidity and its alteration with age. These data may create a new approach in the evaluation process and treatment options for penile pathologies. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Reproducibility of shear wave velocity measurements by acoustic radiation force impulse imaging of the liver: a study in healthy volunteers.

    Science.gov (United States)

    Guzmán-Aroca, Florentina; Reus, Manuel; Berná-Serna, Juan D; Serrano, Laura; Serrano, Cristina; Gilabert, Amparo; Cepero, Angela

    2011-07-01

    The purposes of this study were to investigate interobserver reproducibility using acoustic radiation force impulse imaging and to develop an acoustic radiation force impulse scoring system. Fifty healthy volunteers with normal liver function test values were selected for the study. Shear wave velocity measurements, expressed in meters per second, were taken in a deep portion of liver segment 6. Two observers with different levels of experience performed the measurements independently and blindly. All of the measurements taken by the 2 observers were valid, even in volunteers with a body mass index of greater than 28 kg/m(2). The results point to very good interobserver reproducibility of shear wave velocity measurements, with an intraclass coefficient correlation of 0.86 (P measurements using the acoustic radiation force impulse technique and a standardized protocol are accurate and reproducible.

  10. Shear Wave Elastography in Thyroid Nodules with Indeterminate Cytology: Results of a Prospective Bicentric Study : SWE in indeterminate thyroid nodules

    OpenAIRE

    Bardet, Stéphane; Ciappuccini, Renaud; Pellot‐barakat, Claire; Monpeyssen, Hervé; Michels, Jean‐jacques; Tissier, Frédérique; Blanchard, David; Menegaux, Fabrice; De Raucourt, Dominique; Lefort, Muriel; Reznik, Yves; Rouxel, Agnes; Heutte, Natacha; Brenac, Frédérique; Leconte, Alexandra

    2017-01-01

    International audience; BACKGROUND:The clinical management of thyroid nodules with indeterminate cytology (IC) remains challenging. The role of shear wave elastography (SWE) in this setting is controversial. The aim of the study was to assess the performances of SWE in terms of prediction of malignancy, reproducibility, and combined analysis with ultrasound (US) examination in thyroid nodules with IC.METHODS:This prospective study was conducted in two referral centers. Eligible patients had a...

  11. Wave propagation against current : a study of the effects of vertical shears of the mean current on the geometrical focusing of water waves

    Science.gov (United States)

    Charland, Jenna; Touboul, Julien; Rey, Vincent

    2013-04-01

    Wave propagation against current : a study of the effects of vertical shears of the mean current on the geometrical focusing of water waves J. Charland * **, J. Touboul **, V. Rey ** jenna.charland@univ-tln.fr * Direction Générale de l'Armement, CNRS Délégation Normandie ** Université de Toulon, 83957 La Garde, France Mediterranean Institute of Oceanography (MIO) Aix Marseille Université, 13288 Marseille, France CNRS/INSU, IRD, MIO, UM 110 In the nearshore area, both wave propagation and currents are influenced by the bathymetry. For a better understanding of wave - current interactions in the presence of a 3D bathymetry, a large scale experiment was carried out in the Ocean Basin FIRST, Toulon, France. The 3D bathymetry consisted of two symmetric underwater mounds on both sides in the mean wave direction. The water depth at the top the mounds was hm=1,5m, the slopes of the mounds were of about 1:3, the water depth was h=3 m elsewhere. For opposite current conditions (U of order 0.30m/s), a huge focusing of the wave up to twice its incident amplitude was observed in the central part of the basin for T=1.4s. Since deep water conditions are verified, the wave amplification is ascribed to the current field. The mean velocity fields at a water depth hC=0.25m was measured by the use of an electromagnetic current meter. The results have been published in Rey et al [4]. The elliptic form of the "mild slope" equation including a uniform current on the water column (Chen et al [1]) was then used for the calculations. The calculated wave amplification of factor 1.2 is significantly smaller than observed experimentally (factor 2). So, the purpose of this study is to understand the physical processes which explain this gap. As demonstrated by Kharif & Pelinovsky [2], geometrical focusing of waves is able to modify significantly the local wave amplitude. We consider this process here. Since vertical velocity profiles measured at some locations have shown significant

  12. Hepatic Venous Outflow Stenosis After Auxiliary Left Hemiliver Transplantation Diagnosed by Ultrasonic Shear Wave Elastography Combined With Doppler Ultrasonography

    Science.gov (United States)

    Li, Jia-Wu; Lu, Qiang; Luo, Yan

    2017-01-01

    Abstract Hepatic vein stenosis after liver transplantation is a relatively rare complication that could even result in graft loss. However, it is difficult to arrive at a definite diagnosis at the early stage of postoperation, and there are few researches on ultrasonic shear wave elastography in the diagnosis of hepatic vein stenosis. We report the case of an 11-year-old male patient with cirrhosis due to hepatolenticular degeneration who received an auxiliary left hemiliver graft from his uncle. Massive ascites developed in 4 days after the operation. Stenosis was suspected at the site of anastomosis by Doppler ultrasonography when elevating the velocity of the left hepatic vein. Meanwhile, increased stiffness of the graft was revealed by ultrasonic shear wave elastography. The stenosis was confirmed by subsequent digital subtraction angiography. Ascites decreased gradually after the stent implantation. Our case indicates that ultrasonic shear wave elastography combined with Doppler ultrasonography is a promising method for noninvasive diagnosis of hepatic venous outflow stenosis following liver transplantation. PMID:29190228

  13. A combined analysis of basaltic melting and shear wave velocity anomalies to constrain dynamic support of western North America

    Science.gov (United States)

    Klöcking, Marthe; White, Nicky; Maclennan, John; Fitton, Godfrey

    2017-04-01

    The region of western North America that encompasses the Basin and Range Province, the Snake River Plain and the Colorado Plateau is about 2 km higher than cratonic North America. This topographic difference broadly coincides with variations in lithospheric thickness (i.e. 260 samples from volcanic centers throughout western North America for major, trace and rare earth elements using ICP-MS and XRF techniques. For asthenospheric samples, we observe a correlation between slow shear wave velocity anomalies and basaltic geochemistry. Using a combination of petrologic observations, forward and inverse modeling of major and rare earth elements, and shear wave velocity anomalies from tomographic models, we determine depth of melting and melt fraction. We explore the possibility that volatiles, anomalous source composition and/or temperature can give rise to basaltic magmatism and regional uplift. We then calculate mantle temperatures from shear wave velocity profiles beneath each volcanic field. In this way, we exploit a variety of approaches to constrain lithospheric thickness and mantle potential temperature. Our combined geochemical and geophysical results yield excess temperatures of 50-80 °C beneath a 60 km thin lithospheric plate. A dynamic topographic model of progressive lithospheric erosion over anomalously hot upper mantle can account for regional uplift as well as the temporal and spatial distribution of magmatism across western North America.

  14. Comparison Between Neck and Shoulder Stiffness Determined by Shear Wave Ultrasound Elastography and a Muscle Hardness Meter.

    Science.gov (United States)

    Akagi, Ryota; Kusama, Saki

    2015-08-01

    The goals of this study were to compare neck and shoulder stiffness values determined by shear wave ultrasound elastography with those obtained with a muscle hardness meter and to verify the correspondence between objective and subjective stiffness in the neck and shoulder. Twenty-four young men and women participated in the study. Their neck and shoulder stiffness was determined at six sites. Before the start of the measurements, patients rated their present subjective symptoms of neck and shoulder stiffness on a 6-point verbal scale. At all measurement sites, the correlation coefficients between the values of muscle hardness indices determined by the muscle hardness meter and shear wave ultrasound elastography were not significant. Furthermore, individuals' subjective neck and shoulder stiffness did not correspond to their objective symptoms. These results suggest that the use of shear wave ultrasound elastography is essential to more precisely assess neck and shoulder stiffness. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  15. Insight into NE Tibetan Plateau expansion from crustal and upper mantle anisotropy revealed by shear-wave splitting

    Science.gov (United States)

    Huang, Zhouchuan; Tilmann, Frederik; Xu, Mingjie; Wang, Liangshu; Ding, Zhifeng; Mi, Ning; Yu, Dayong; Li, Hua

    2017-11-01

    The northeastern Tibetan plateau margin is the current expansion border, where growth of the plateau is ongoing. We analyze shear-wave splitting at ChinArray stations in the NE Tibetan Plateau and its margin with the stable North Chine Craton. The measurements provide important information on the seismic anisotropy and deformations patterns in the crust and upper mantle, which can be used to constrain the expansion mechanism of the plateau. Along the margin and within the craton, the dominant NW-SE fast polarization direction (FPD) is NW-SE, subparallel to the boundary between the plateau and the North China Craton. The shear-wave splitting measurements on the NE Tibetan Plateau itself generally reflect two-layer anisotropy. The lower-layer anisotropy (with NW-SE FPDs) is consistent in the whole region and FPDs are the same as those in the North China Craton. The upper-layer FPDs are parallel to crustal motion rather than surface structures within the high plateau. The two-layer anisotropy implies the presence of deformed Tibetan lithosphere above the underthrusting North China Craton. The NE Tibetan shows similar deformation patterns at the surface (inferred from GPS) and within the mantle (inferred from shear-wave splitting), but significant crustal anisotropy (parallel to crustal motion) requires mid-lower crustal channel flow or detachment to drive further tectonic uplift of the plateau.

  16. A finite element model to study the effect of tissue anisotropy on ex vivo arterial shear wave elastography measurements

    Science.gov (United States)

    Shcherbakova, D. A.; Debusschere, N.; Caenen, A.; Iannaccone, F.; Pernot, M.; Swillens, A.; Segers, P.

    2017-07-01

    Shear wave elastography (SWE) is an ultrasound (US) diagnostic method for measuring the stiffness of soft tissues based on generated shear waves (SWs). SWE has been applied to bulk tissues, but in arteries it is still under investigation. Previously performed studies in arteries or arterial phantoms demonstrated the potential of SWE to measure arterial wall stiffness—a relevant marker in prediction of cardiovascular diseases. This study is focused on numerical modelling of SWs in ex vivo equine aortic tissue, yet based on experimental SWE measurements with the tissue dynamically loaded while rotating the US probe to investigate the sensitivity of SWE to the anisotropic structure. A good match with experimental shear wave group speed results was obtained. SWs were sensitive to the orthotropy and nonlinearity of the material. The model also allowed to study the nature of the SWs by performing 2D FFT-based and analytical phase analyses. A good match between numerical group velocities derived using the time-of-flight algorithm and derived from the dispersion curves was found in the cross-sectional and axial arterial views. The complexity of solving analytical equations for nonlinear orthotropic stressed plates was discussed.

  17. Parametric decay of linearly polarized shear Alfvén waves in oblique propagation: One and two-dimensional hybrid simulations

    National Research Council Canada - National Science Library

    Lorenzo Matteini; Simone Landi; Luca Del Zanna; Marco Velli; Petr Hellinger

    2010-01-01

      The parametric instability of a monochromatic shear Alfvén wave in oblique propagation with respect the ambient magnetic field is investigated in a kinetic regime, performing one-dimensional (1-D...

  18. Differentiating benign from malignant solid breast masses: value of shear wave elastography according to lesion stiffness combined with greyscale ultrasound according to BI-RADS classification

    National Research Council Canada - National Science Library

    Evans, A; Whelehan, P; Thomson, K; Brauer, K; Jordan, L; Purdie, C; McLean, D; Baker, L; Vinnicombe, S; Thompson, A

    2012-01-01

    The aim of this study was to assess the performance of shear wave elastography combined with BI-RADS classification of greyscale ultrasound images for benign/malignant differentiation in a large group of patients...

  19. On the source-frequency dependence of fracture-orientation estimates from shear-wave transmission experiments

    Science.gov (United States)

    Santos, Leo K.; de Figueiredo, J. J. S.; Omoboya, Bode; Schleicher, Jörg; Stewart, Robert R.; Dyaur, Nikolay

    2015-03-01

    Shear-wave propagation through anisotropic fractured or cracked media can provide valuable information about these fracture swarms and their orientations. The main goal of this work is to recover information about fracture orientation based on the shear waveforms (S-waveforms). For this study, we carried out ultrasonic S-wave measurements in a synthetic physical model made of epoxy resin (isotropic matrix proxy), with small cylindrical rubber strips as inclusions (artificial cracks) inserted in it to simulate a homogeneous anisotropic medium. In these experiments, we used low, intermediate, and high frequency shear-wave sources, with frequencies 90, 431, and 840 kHz. We integrated and interpreted the resulting S-wave seismograms, cross-correlation panels and anisotropic parameter-analysis curves. We were able to estimate the crack orientation in single-orientation fracture zones. The high frequency peaks associated with scattered S-waves provided interpretable information about the fracture orientations when the propagation direction was parallel to the fracture plane. The analysis was possible utilizing results from frequency-versus-polarization-angle curves. Moreover, we applied a bandpass filtering process to the intermediate and high frequency seismograms in order to obtain low frequency seismograms. A spectral analysis using frequency-wavenumber (F-K) spectra supports this filtering process. The results obtained using an analysis of cross-correlograms and the Thomsen parameter γ extracted from filtered high-frequency data were quite similar to those obtained using a low-frequency source. This highlighted the possibility of using less expensive high-frequency sources to recover information about the fracture set.

  20. Seismic anisotropy and mantle deformation in western Iran inferred from shear-wave splitting analysis

    Science.gov (United States)

    Sadeghi-Bagherabadi, Amir; Sobouti, Farhad; Ghods, Abdolreza; Chen, Ling; Talebian, Morteza; Motaghi, Khalil; Jiang, Mingming; He, Yumei; Ai, Yinshuang

    2017-04-01

    The Iranian plateau as a part of the Alpine-Himalayan mountain belt is comprised of several tectonic units. These are; the Zagros, Alborz, Talesh and Kopeh-Dagh active thrust and fold belts, the Sannandaj-Sirjan and Urmieh-Dhoktar metamorphic and magmatic belts, and the Makran subduction zone. Much of the structural and deformational characteristics of these units have been formed during the subduction of the Neo-Tethys in the Mesozoic and the subsequent Arabia - Eurasia collision in the Cenozoic. Understanding the pattern of past and present deformation at depth provides a valuable key for enhancing our knowledge about the evolution of the collisional boundary in the Iran region. Here we use measurements of seismic anisotropy to understand this pattern. We use data from a temporary seismic network in western Iran to calculate shear-wave splitting parameters. The network was in operation for one year in 2013 and 2014 and consisted of 63 broadband seismometers installed along three parallel profiles that crossed the western Zagros Mountains, central Iran and the western Alborz Mountains.We present ourresults as splitting measurements of the teleseismic SKS/SKKS core-refracted phases. Our results show an average delay time of about 1.3 sec. The fast polarization orientation of the measurements varies significantly along the profile, indicating important changes in style of deformation across different tectonic units. A range-parallel trend is observed in the Zagros, while the orientations of the fast axes are perpendicular to the strike in the Alborz. We compared our fast polarization orientations with GPS velocity vectors in different reference frames. The fast directions in the Alborz are subparallel to the absolute plate motion GPS directions, indicating that the asthenospheric flow might be the influencing factor in the observed anisotropy. The complicated splitting pattern in the Zagros can be either due to contributions from both lithospheric and asthenospheric

  1. Electrode modification and the response of the acoustic shear wave device operating in liquids.

    Science.gov (United States)

    Ghafouri, S; Thompson, M

    2001-12-01

    The effect of electrode polarity, geometry, and stray capacitance on the performance of the thickness-shear mode acoustic wave sensor operating in electrolytes and solutions of biomolecules has been studied. In contrast to the well-known mass-based response of the device operating in the gas phase, the response in a liquid is governed by several factors including acoustoelectric and fringing field effects, which are known to be active at the edges of the electrodes. In order to investigate and utilize these effects, we modified the electrode geometry to increase the edge length, which, in turn, raises the sensitivity of the device. These changes which constituted either complete coverage of the back of the device with electrode material, or the removal of disks and lines from the electrode surface, resulted in a two to three times enhancement of sensor response. Such modifications that extend device sensitivity beyond the electrode area to the quartz region of the sensing structure also provide a better surface for the immobilization of various probes. We verified the enhancing ability of the modified electrodes for the case of adsorption of the protein avidin and neutravidin, followed by their affinity reactions with biotinylated biomolecules. It was found that the active electrode in contact with electrolyte exhibits a sensitivity of about twice that of the grounded electrode. The existence of stray capacitance around the cell was confirmed by shielding the cell assembly with a bath of concentrated KCl solution. This shielding effect was measured to be about 25-60 Hz in series resonant frequency and -1000 Hz in parallel resonant frequency.

  2. Shear wave elastography evaluation in pediatric testicular microlithiasis: a comparative study.

    Science.gov (United States)

    Bayramoglu, Zuhal; Kandemirli, Sedat Giray; Comert, Rana Gunoz; Akpinar, Yunus Emre; Caliskan, Emine; Yilmaz, Ravza; Oktar, Tayfun Mevlut; Cetin, Bilal; Cingoz, Mehmet; Adaletli, Ibrahim

    2017-10-26

    The aim of this study was to evaluate the testicular parenchyma in pediatric patients with testicular microlithiasis by shear wave elastography (SWE) and compare the values with normal control subjects. Twenty-three patients previously diagnosed with testicular microlithiasis under follow-up for 20 ± 11 months were included in the study group. In the control group, 31 patients with no medical history that could affect testicular tissue were prospectively included. Forty-six testes in the study group and 62 testes in the control group were evaluated with gray-scale ultrasound and SWE. There were no differences in age and testes volume between the study and control groups. The mean SWE values of all testes based on elasticity and speed parameters in the study group were 8.84 ± 2.86 kPa and 1.66 ± 0.26 m/s, respectively. In the control group, mean SWE values were 5.26 ± 1.17 kPa and 1.31 ± 0.14 m/s, respectively. Elasticity values were significantly higher in testes with microlithiasis as compared with the control group (p < 0.001). SWE evaluation demonstrates the effects of ultrastructural changes in elasticity that are not detected on gray-scale ultrasound. SWE is a more reliable method in follow-up examinations for pediatric testicular microlithiasis.

  3. [Application of shear wave elastography in the evaluation of neck-shoulder myofascial pain syndrome].

    Science.gov (United States)

    Guo, Ling; Zhang, Chen; Zhang, Ding-ding; Gao, Jing-hua; Liu, Guang-hui; Wang, Shang-quan

    2016-02-01

    To study clinical value of shear wave elastography (SWE) in the evaluation of neck-shoulder myofascial pain syndrome. From December 2013 to July 2014,30 patients diagnosed as neck-shoulder myofascial pain syndrome were in the treatment group,including 17 males and 13 females, with an average age of (44 ± 3) years old. Thirty healthy people were in the control group, including 22 males and 8 females, with a mean age of (37 ± 5) years old. The patients in the treatment group were treated with manipulation, once every other day, total 7 times. The SWE was used to detect tension part of trapezius muscle of patients in the treatment group before and after treatment, as well as to detect muscle belly at the descending part of trapezius muscle in the control group. The tissue elasticity and Yang's modulus value were recorded and compared. The tissue elasticity chart of patients in the treatment group before treatment was mainly greenish blue with the score of 3.70 ± 1.53, and the Yang's modulus was (43.4 ± 15.6) kPa. The tissue elasticity figure after treatment was mainly blue with the score of 2.40 ± 0.87, and the Yang's modulus was (29.0 ± 5.9) kPa. Whereas in the control group, the tissue elasticity figure was mainly blue with the score of 1.60 ± 0.72, and the Yang's modulus was (24.0 ± 7.6) kPa. These were statistical differences between the two groups (P = 0.000). SWE can be used as an evaluation method of manipulation treatment for neck-shoulder myofascial pain syndrome, which is an objective and sensitive detection method.

  4. The influence of precompression on elasticity of thyroid nodules estimated by ultrasound shear wave elastography.

    Science.gov (United States)

    Lam, A C L; Pang, S W A; Ahuja, A T; Bhatia, K S S

    2016-08-01

    To investigate the influence of variations in resting pressure (precompression) on thyroid ultrasound supersonic shear wave elastography (SWE). Thirty-five normal thyroid glands (Norm), 55 benign hyperplastic nodules (BHN), and 17 papillary thyroid cancers (PTC) in 96 subjects underwent thyroid SWE. Four precompression levels were applied manually by the operator, ranging from A (baseline, 0 % strain) to D (high, 22-30 % strain). SWE results at each precompression level were compared using ANOVA tests with P < 0.05 indicating significance. SWE indices were highest in PTC, followed by BHN and Norm at each precompression level (P < 0.05). All tissue types showed successive increases in SWE results as precompression increased, although the rate was higher for PTC than BHN and Norm (Ps < 0.05). SWE values (kPa) of Norm, BHN, and PTC at baseline precompression (A) were 10.3 ± 3.3, 17.7 ± 7.6, and 22.2 ± 11.9 compared with 21.1 ± 4.2, 42.3 ± 16.0, and 97.6 ± 46.8 at high precompression (D). SWE index differences between precompression levels A and D were 10.8 kPa for Norm, 24.6 kPa for BHN, and 75.4 kPa for PTC. PTCs show greater SWE stiffening than BHN as precompression rises. Precompression effects on thyroid nodules are not negligible and may account for wide discrepancies in published SWE discriminatory performance results for thyroid malignancy. • Increases in resting pressure (precompression) applied by the operator increases thyroid stiffness. • Papillary cancers show greater increases in stiffness (strain hardening) than benign nodules. • Precompression may affect the diagnostic performance of shearwave elastography for thyroid malignancy.

  5. Quantitative assessment of rotator cuff muscle elasticity: Reliability and feasibility of shear wave elastography.

    Science.gov (United States)

    Hatta, Taku; Giambini, Hugo; Uehara, Kosuke; Okamoto, Seiji; Chen, Shigao; Sperling, John W; Itoi, Eiji; An, Kai-Nan

    2015-11-05

    Ultrasound imaging has been used to evaluate various shoulder pathologies, whereas, quantification of the rotator cuff muscle stiffness using shear wave elastography (SWE) has not been verified. The purpose of this study was to investigate the reliability and feasibility of SWE measurements for the quantification of supraspinatus (SSP) muscle elasticity. Thirty cadaveric shoulders (18 intact and 12 with torn rotator cuff) were used. Intra- and inter-observer reliability was evaluated on an established SWE technique for measuring the SSP muscle elasticity. To assess the effect of overlying soft tissues above the SSP muscle, SWE values were measured with the transducer placed on the skin, on the subcutaneous fat after removing the skin, on the trapezius muscle after removing the subcutaneous fat, and directly on the SSP muscle. In addition, SWE measurements on 4 shoulder positions (0°, 30°, 60°, and 90° abduction) were compared in those with/without rotator cuff tears. Intra- and inter-observer reliability of SWE measurements were excellent for all regions in SSP muscle. Also, removing the overlying soft tissue showed no significant difference on SWE values measured in the SSP muscle. The SSP muscle with 0° abduction showed large SWE values, whereas, shoulders with large-massive tear showed smaller variation throughout the adduction-abduction positions. SWE is a reliable and feasible tool for quantitatively assessing the SSP muscle elasticity. This study also presented SWE measurements on the SSP muscle under various shoulder abduction positions which might help characterize patterns in accordance to the size of rotator cuff tears. Copyright © 2015 Elsevier Ltd. All rights reserved.

  6. Shear wave elastography versus real-time elastography on evaluation thyroid nodules: A preliminary study

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Bao-Xian, E-mail: xian_1121@163.com [Department of Medical Ultrasonics, the First Affiliated Hospital of Sun Yat-sen University, Institute of Diagnostic and Interventional Ultrasound, Sun Yat-Sen University, 58 Zhong Shan Road 2, Guangzhou 510080 (China); Xie, Xiao-Yan, E-mail: xxy1992@21cn.com [Department of Medical Ultrasonics, the First Affiliated Hospital of Sun Yat-sen University, Institute of Diagnostic and Interventional Ultrasound, Sun Yat-Sen University, 58 Zhong Shan Road 2, Guangzhou 510080 (China); Liang, Jin-Yu, E-mail: fishgrace1124@gmail.com [Department of Medical Ultrasonics, the First Affiliated Hospital of Sun Yat-sen University, Institute of Diagnostic and Interventional Ultrasound, Sun Yat-Sen University, 58 Zhong Shan Road 2, Guangzhou 510080 (China); Zheng, Yan-Ling, E-mail: zhyanl@mail.sysu.edu.cn [Department of Medical Ultrasonics, the First Affiliated Hospital of Sun Yat-sen University, Institute of Diagnostic and Interventional Ultrasound, Sun Yat-Sen University, 58 Zhong Shan Road 2, Guangzhou 510080 (China); Huang, Guang-Liang, E-mail: venice0016@163.com [Department of Medical Ultrasonics, the First Affiliated Hospital of Sun Yat-sen University, Institute of Diagnostic and Interventional Ultrasound, Sun Yat-Sen University, 58 Zhong Shan Road 2, Guangzhou 510080 (China); Zhou, Lu-Yao, E-mail: 5454kill@163.com [Department of Medical Ultrasonics, the First Affiliated Hospital of Sun Yat-sen University, Institute of Diagnostic and Interventional Ultrasound, Sun Yat-Sen University, 58 Zhong Shan Road 2, Guangzhou 510080 (China); Wang, Zhu, E-mail: 160395191@qq.com [Department of Medical Ultrasonics, the First Affiliated Hospital of Sun Yat-sen University, Institute of Diagnostic and Interventional Ultrasound, Sun Yat-Sen University, 58 Zhong Shan Road 2, Guangzhou 510080 (China); and others

    2014-07-15

    Objective: To comparatively evaluate shear wave elastography (SWE) and real-time elastography (RTE) in distinguishing malignant from benign thyroid nodules. Methods: 49 patients with 64 focal thyroid nodules were enrolled and underwent SWE and RTE before surgery. SWE elasticity indices (mean, minimum and maximum value of 2-mm region of interest) of nodules were measured. For RTE, elastograms were assessed by Rago criteria and nodules with scores of 4 or 5 were classified as suspicious for malignancy. Surgery histopathologic results were adopted as diagnostic standard. Results: Of the 64 nodules, 19 were papillary thyroid carcinomas and 45 were benign. SWE indices were significantly higher in malignant than benign nodules (P < 0.05). Areas under the ROC curves (AUC) of SWE parameters were 0.840, 0.831 and 0.788, which were not significantly different from that of RTE showed as 0.880 (P = 0.148–0.482). When the most accurate cut-off, 38.3 kPa for mean value was applied to predict malignancy, the diagnostic specificity, sensitivity, accuracy, positive predictive value and negative predictive value of SWE and RTE were 68.4% versus 79.0%, 86.7% versus 84.4%, 81.3% versus 78.1%, 68.4% versus 64.7% and 86.7% versus 83.3%, respectively (P = 0.683–1.000). Conclusion: SWE as a promising tool can be performed in differentiating thyroid nodules with comparable results to RTE.

  7. Role of shear wave sonoelastography in differentiation between focal breast lesions.

    Science.gov (United States)

    Dobruch-Sobczak, Katarzyna; Nowicki, Andrzej

    2015-02-01

    Our goal in this study was to evaluate the relevance of shear wave sonoelastography (SWE) in the differential diagnosis of masses in the breast with respect to ultrasound (US). US and SWE were performed (Aixplorer System, SuperSonic Imagine, Aix en Provence, France) in 76 women (aged 24 to 85) with 84 lesions (43 malignant, 41 benign). The study included BI-RADS-US (Breast Imaging Reporting and Data System for Ultrsound) category 3-5 lesions. In elastograms, the following values were calculated: mean elasticity in lesions (E(av.l)) and in fat tissue (E(av.f.)) and maximal (E(max.adj.)) and mean (E(av.adj.)) elasticity in lesions and adjacent tissues. The sensitivity and specificity of the BI-RADS category 4a/4b cutoff value were 97.7% and 90.2%. For an E(av.adj.) of 68.5 kPa, the cutoff sensitivity was 86.1% and the specificity was 87.8%, and for an E(max.adj.) of 124.1 kPa, 74.4% and 92.7%, respectively. For BI-RADS-US category 3 lesions, E(av.l), E(max.adj.) and E(av.adj.) were below cutoff levels. On the basis of our findings, E(av.adj.) had lower sensitivity and specificity compared with US. Emax.adj. improved the specificity of breast US with loss of sensitivity. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  8. Time-lapse changes of P- and S-wave velocities and shear wave splitting in the first year after the 2011 Tohoku earthquake, Japan: shallow subsurface

    Science.gov (United States)

    Sawazaki, Kaoru; Snieder, Roel

    2013-04-01

    We detect time-lapse changes in P- and S-wave velocities (hereafter, VP and VS, respectively) and shear wave splitting parameters associated with the 2011 Tohoku earthquake, Japan, at depths between 0 and 504 m. We estimate not only medium parameters but also the 95 per cent confidence interval of the estimated velocity change by applying a new least squares inversion scheme to the deconvolution analysis of KiK-net vertical array records. Up to 6 per cent VS reduction is observed at more than half of the analysed KiK-net stations in northeastern Japan with over 95 per cent confidence in the first month after the main shock. There is a considerable correlation between the S-wave traveltime delay and the maximum horizontal dynamic strain (MDS) by the main shock motion when the strain exceeds 5 × 10- 4 on the ground surface. This correlation is not clearly observed for MDS at the borehole bottom. On the contrary, VP and shear wave splitting parameters do not show systematic changes after the Tohoku earthquake. These results indicate that the time-lapse change is concentrated near the ground surface, especially in loosely packed soil layers. We conclude that the behaviour of VP, VS and shear wave splitting parameters are explained by the generation of omnidirectional cracks near the ground surface and by the diffusion of water in the porous subsurface. Recovery of VS should be related to healing of the crack which is proportional to the logarithm of the lapse time after the main shock and/or to decompaction after shaking.

  9. Shear wave velocity, seismic attenuation, and thermal structure of the continental upper mantle

    Science.gov (United States)

    Artemieva, I.M.; Billien, M.; Leveque, J.-J.; Mooney, W.D.

    2004-01-01

    Seismic velocity and attenuation anomalies in the mantle are commonly interpreted in terms of temperature variations on the basis of laboratory studies of elastic and anelastic properties of rocks. In order to evaluate the relative contributions of thermal and non-thermal effects on anomalies of attenuation of seismic shear waves, QS-1, and seismic velocity, VS, we compare global maps of the thermal structure of the continental upper mantle with global QS-1 and Vs maps as determined from Rayleigh waves at periods between 40 and 150 S. We limit the comparison to three continental mantle depths (50, 100 and 150 km), where model resolution is relatively high. The available data set does not indicate that, at a global scale, seismic anomalies in the upper mantle are controlled solely by temperature variations. Continental maps have correlation coefficients of seismic and thermal anomalies of the opposite sign. The strongest inverse correlation is found at a depth of 100 km, where the attenuation model is best resolved. Significantly, at this depth, the contours of near-zero QS anomalies approximately correspond to the 1000 ??C isotherm, in agreement with laboratory measurements that show a pronounced increase in seismic attenuation in upper mantle rocks at 1000-1100 ??C. East-west profiles of VS, QS and T where continental data coverage is best (50??N latitude for North America and 60??N latitude for Eurasia) further demonstrate that temperature plays a dominant, but non-unique, role in determining the value of lithospheric VS and QS. At 100 km depth, where the resolution of seismic models is the highest, we compare observed seismic VS and QS with theoretical VST and QST values, respectively, that are calculated solely from temperature anomalies and constrained by experimental data on temperature dependencies of velocity and attenuation. This comparison shows that temperature variations alone are sufficient to explain seismic VS and QS in ca 50 per cent of continental

  10. Shear-wave velocity structure of the Tongariro Volcanic Centre, New Zealand: Fast Rayleigh and slow Love waves indicate strong shallow anisotropy

    Science.gov (United States)

    Godfrey, Holly J.; Fry, Bill; Savage, Martha K.

    2017-04-01

    Models of the velocity structure of volcanoes can help define possible magma pathways and contribute to calculating more accurate earthquake locations, which can help with monitoring volcanic activity. However, shear-wave velocity of volcanoes is difficult to determine from traditional seismic techniques, such as local earthquake tomography (LET) or refraction/reflection surveys. Here we use the recently developed technique of noise cross correlation of continuous seismic data to investigate the subsurface shear-wave velocity structure of the Tongariro Volcanic Centre (TgVC) of New Zealand, focusing on the active Ruapehu and Tongariro Volcanoes. We observe both the fundamental and first higher-order modes of Rayleigh and Love waves within our noise dataset, made from stacks of 15 min cross-correlation functions. We manually pick group velocity dispersion curves from over 1900 correlation functions, of which we consider 1373 to be high quality. We subsequently invert a subset of the fundamental mode Rayleigh- and Love-wave dispersion curves both independently and jointly for one dimensional shear-wave velocity (Vs) profiles at Ruapehu and Tongariro Volcanoes. Vs increases very slowly at a rate of approximately 0.2 km/s per km depth beneath Ruapehu, suggesting that progressive hydrothermal alteration mitigates the effects of compaction driven velocity increases. At Tongariro, we observe larger Vs increases with depth, which we interpret as different layers within Tongariro's volcanic system above altered basement greywacke. Slow Vs, on the order of 1-2 km/s, are compatible with P-wave velocities (using a Vp/Vs ratio of 1.7) from existing velocity profiles of areas within the TgVC, and the observations of worldwide studies of shallow volcanic systems that used ambient noise cross-correlation methods. Most of the measured group velocities of fundamental mode Love-waves across the TgVC are 0.1-0.4 km/s slower than those of fundamental mode Rayleigh-waves in the

  11. Shear wave elastography for localization of prostate cancer lesions and assessment of elasticity thresholds: implications for targeted biopsies and active surveillance protocols.

    Science.gov (United States)

    Boehm, Katharina; Salomon, Georg; Beyer, Burkhard; Schiffmann, Jonas; Simonis, Kathrin; Graefen, Markus; Budaeus, Lars

    2015-03-01

    Shear wave elastography allows the detection of cancer by using focused ultrasound pulses for locally deforming tissue. The differences in tissue elasticity and stiffness have been used increasingly in breast cancer imaging and help detect potential tumor lesions in the prostate. In this study we localized prostate cancer lesions using shear wave elastography before radical prostatectomy and assessed the examiner independent elasticity threshold for cancer foci detection. Shear wave elastography scanning of the whole prostate was performed before radical prostatectomy in 60 consecutive patients with high, intermediate and low risk disease. Localization of suspected lesions and density threshold (kPa) were recorded in up to 12 areas and resulted in 703 different fields. Shear wave elastography findings were correlated with final pathology. Initially 381 areas were used to establish shear wave elastography cutoffs (development cohort 32 patients). Subsequently these cutoffs were validated in 322 areas (validation cohort 28 patients). Using shear wave elastography significant differences were recorded for the elasticity of benign tissue vs prostate cancer nodules at 42 kPa (range 29 to 71.3) vs 88 kPa (range 54 to 132) (all p <0.001). Median cancer lesion diameter was 26 mm (range 18 to 41). Applying the most informative cutoff of 50 kPa to the validation cohort resulted in 80.9% and 69.1% sensitivity and specificity, respectively, and 74.2% accuracy for detecting cancer nodules based on final pathological finding. The corresponding positive and negative predictive values were 67.1% and 82.2%, respectively. Shear wave elastography allows the identification of cancer foci based on shear wave elastography differences. Moreover, reliable cutoffs for this approach can be established, allowing examiner independent localization of prostate cancer foci. Copyright © 2015 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights

  12. Simulation of nonlinear transient elastography: finite element model for the propagation of shear waves in homogeneous soft tissues.

    Science.gov (United States)

    Ye, W; Bel-Brunon, A; Catheline, S; Combescure, A; Rochette, M

    2018-01-01

    In this study, visco-hyperelastic Landau's model, which is widely used in acoustical physic field, is introduced into a finite element formulation. It is designed to model the nonlinear behaviour of finite amplitude shear waves in soft solids, typically, in biological tissues. This law is used in finite element models based on elastography, experiments reported in Jacob et al, the simulations results show a good agreement with the experimental study: It is observed in both that a plane shear wave generates only odd harmonics and a nonplane wave generates both odd and even harmonics in the spectral domain. In the second part, a parametric study is performed to analyse the influence of different factors on the generation of odd harmonics of plane wave. A quantitative relation is fitted between the odd harmonic amplitudes and the non-linear elastic parameter of Landau's model, which provides a practical guideline to identify the non-linearity of homogeneous tissues using elastography experiment. Copyright © 2017 John Wiley & Sons, Ltd.

  13. Differentiating benign from malignant solid breast masses: value of shear wave elastography according to lesion stiffness combined with greyscale ultrasound according to BI-RADS classification.

    Science.gov (United States)

    Evans, A; Whelehan, P; Thomson, K; Brauer, K; Jordan, L; Purdie, C; McLean, D; Baker, L; Vinnicombe, S; Thompson, A

    2012-07-10

    The aim of this study was to assess the performance of shear wave elastography combined with BI-RADS classification of greyscale ultrasound images for benign/malignant differentiation in a large group of patients. One hundred and seventy-five consecutive patients with solid breast masses on routine ultrasonography undergoing percutaneous biopsy had the greyscale findings classified according to the American College of Radiology BI-RADS. The mean elasticity values from four shear wave images were obtained. For mean elasticity vs greyscale BI-RADS, the performance results against histology were sensitivity: 95% vs 95%, specificity: 77% vs 69%, Positive Predictive Value (PPV): 88% vs 84%, Negative Predictive Value (NPV): 90% vs 91%, and accuracy: 89% vs 86% (all P>0.05). The results for the combination (positive result from either modality counted as malignant) were sensitivity 100%, specificity 61%, PPV 82%, NPV 100%, and accuracy 86%. The combination of BI-RADS greyscale and shear wave elastography yielded superior sensitivity to BI-RADS alone (P=0.03) or shear wave alone (P=0.03). The NPV was superior in combination compared with either alone (BI-RADS P=0.01 and shear wave P=0.02). Together, BI-RADS assessment of greyscale ultrasound images and shear wave ultrasound elastography are extremely sensitive for detection of malignancy.

  14. Application of time-lapse seismic shear wave inversion to characterize the stimulated rock volume in the Niobrara and Codell Reservoirs, Wattenberg Field, CO

    Science.gov (United States)

    Mueller, Staci K.

    Advances in horizontal drilling and completions in shale reservoirs have allowed operators to extract hydrocarbons within low permeability reservoirs that were once impossible to access. The integration of time-lapse multicomponent seismic data with engineering technology aids in the characterization of these reservoirs through monitoring. This thesis investigates the fast and slow shear wave components of a time-lapse, nine-component seismic survey to determine the stimulated volume in the Niobrara and Codell reservoir intervals. The time-lapse post-stack inversions of the shear wave datasets provide insight into how the shear impedance is affected by hydraulic fracturing through the work of cross-equalized seismic shear impedances and shear wave splitting. The study area is the Wishbone Section within Wattenberg Field, CO, which is owned and operated by Anadarko Petroleum Corporation and contains eleven horizontal wells that vary in spacing and completion methods. Shear seismic data sets were acquired over this section before and after hydraulic stimulation. The time-lapse shear seismic inversions show an increase in fast shear wave velocity and a decrease in slow shear velocity after stimulation. The sensitivity of both the fast and slow shear seismic to stimulation correlates with the net pressure trends at each stage. Borehole image log interpretations are compared to the inversions to analyze the affect that a complex fracture network has on induced anisotropy. The stimulated volume for the Niobrara and Codell reservoir intervals are now more accurately defined. Time-lapse shear seismic is the only technology that is able to define the stimulated rock volume and reveal areas that are not being accessed by the wells currently drilled. These areas are now detected within the Wishbone section, and may be candidates for future re-completion.

  15. Fjord-valley fill stratigraphy from onshore high-resolution shear-wave seismics, Trondheim harbour area, central Norway

    Science.gov (United States)

    Hansen, L.; Polom, U.; L'Heureux, J.; Sauvin, G.; Lecomte, I.; Krawczyk, C. M.; Longva, O.

    2009-12-01

    To obtain information on the stratigraphic variability within the underlying fjord-valley fill, a shallow, shear-wave reflection seismic survey was successfully carried out on land in the Trondheim harbor area, central Norway. Since the last deglaciation, the region has been subjected to a fall of relative sea level of totally 175 m due to glacioisostatic rebound. The relative sea-level fall was accompanied by river erosion of emerging (glacio) marine deposits, several, large landslides, and delta progradation into the fjord. The infilled harbour area is located on the submerged part of a delta plain, and land reclamation is still going on. Historic and older submarine landslides are known to have taken place along the shoreline and an improved understanding of the ground conditions is therefore valuable for engineering purposes. In addition, the unique, S-wave seismic record gives insight into the overall architecture and long-term development of a fjord-valley filling influenced by relative sea level fall accompanied by occasional major mass-wasting events. Shear-wave reflection seismics was applied using a land streamer of 120 channels combined with a newly developed shear-wave vibrator from LIAG. Overall, 4.2 profile-km were acquired in a 2.5-D grid along paved roads and parking lots during night to minimize environmental noise. The investigations achieved a highly resolved image of the fjord-valley fill and clear bedrock detection. Vertical resolution is within a few meters over the entire profile whereas horizontal resolution decreases with depth. The entire fjord-valley fill is up to 160 m thick and five main stratigraphic units have been identified including bedrock. The fjord-valley fill is interpreted as consisting of glaciomarine deposits overlain by marine fjord sediments grading upwards into deltaic deposits. The change from continuous to more discontinuous or irregular reflection patterns reflects a progressive influence of delta-derived processes and

  16. Shear Wave Velocity Structure of Southern African Crust: Evidence for Compositional Heterogeneity within Archaean and Proterozoic Terrains

    Energy Technology Data Exchange (ETDEWEB)

    Kgaswane, E M; Nyblade, A A; Julia, J; Dirks, P H H M; Durrheim, R J; Pasyanos, M E

    2008-11-11

    Crustal structure in southern Africa has been investigated by jointly inverting receiver functions and Rayleigh wave group velocities for 89 broadband seismic stations spanning much of the Precambrian shield of southern Africa. 1-D shear wave velocity profiles obtained from the inversion yield Moho depths that are similar to those reported in previous studies and show considerable variability in the shear wave velocity structure of the lower part of the crust between some terrains. For many of the Archaean and Proterozoic terrains in the shield, S velocities reach 4.0 km/s or higher over a substantial part of the lower crust. However, for most of the Kimberley terrain and adjacent parts of the Kheis Province and Witwatersrand terrain, as well as for the western part of the Tokwe terrain, mean shear wave velocities of {le} 3.9 km/s characterize the lower part of the crust along with slightly ({approx}5 km) thinner crust. These findings indicate that the lower crust across much of the shield has a predominantly mafic composition, except for the southwest portion of the Kaapvaal Craton and western portion of the Zimbabwe Craton, where the lower crust is intermediate-to-felsic in composition. The parts of the Kaapvaal Craton underlain by intermediate-to-felsic lower crust coincide with regions where Ventersdorp rocks have been preserved, and thus we suggest that the intermediate-to-felsic composition of the lower crust and the shallower Moho may have resulted from crustal melting during the Ventersdorp tectonomagmatic event at c. 2.7 Ga and concomitant crustal thinning caused by rifting.

  17. Sediment and Crustal Shear Velocity Structure offshore New Zealand from Seafloor Compliance, Receiver Functions and Rayleigh Wave Dispersion

    Science.gov (United States)

    Ball, J. S.; Sheehan, A. F.; Stachnik, J. C.; Lin, F.; Collins, J. A.

    2013-12-01

    We have developed a joint Monte Carlo inversion of teleseismic receiver functions, seafloor compliance, and Rayleigh wave dispersion and apply it here to ocean bottom seismic (OBS) data from offshore New Zealand. With this method we estimate sediment and crustal thickness and shear velocity structure beneath the Bounty Trough and the Tasman Sea flanking the South Island of New Zealand. Teleseismic receiver functions and surface wave dispersion measurements provide complementary constraints on shear velocity structure and interface depths beneath seismic stations. At ocean bottom seismic (OBS) stations the interpretation of these measurements is complicated by strong sediment reverberations that obscure deeper impedance contrasts such as the Moho. In principle, the seafloor's response to ocean loading from infragravity waves (seafloor compliance) can be used to determine shallow shear velocity information. This velocity information can subsequently be used to better model the receiver function reverberations, allowing deeper interfaces of tectonic interest to be resolved. Data for this study were acquired in 2009-2010 by the Marine Observations of Anisotropy Near Aotearoa (MOANA) experiment, which deployed 30 broadband OBS and differential pressure gauges (DPGs) off the South Island of New Zealand. High-frequency (5Hz) receiver functions were estimated using multitaper cross-correlation for events in a 30-90 degree epicentral distance range. Coherence-weighted stacks binned by epicentral distance were produced in the frequency domain to suppress noise. Seafloor compliance was measured using multitaper pressure and acceleration spectra averaged from 120 days of continuous data without large transient events. Seafloor compliance measurements on the order of 10-9 Pa-1 are sensitive to shear velocity structure in the uppermost 5km of the crust and sediments. Rayleigh dispersion measurements were obtained at periods of 6-27s from ambient noise cross correlation. Sediment

  18. Effect of Graphite Concentration on Shear-Wave Speed in Gelatin-Based Tissue-Mimicking Phantoms

    Science.gov (United States)

    Anderson, Pamela G.; Rouze, Ned C.; Palmeri, Mark L.

    2011-01-01

    Elasticity-based imaging modalities are becoming popular diagnostic tools in clinical practice. Gelatin-based, tissue mimicking phantoms that contain graphite as the acoustic scattering material are commonly used in testing and validating elasticity-imaging methods to quantify tissue stiffness. The gelatin bloom strength and concentration are used to control phantom stiffness. While it is known that graphite concentration can be modulated to control acoustic attenuation, the impact of graphite concentrationon phantom elasticity has not been characterized in these gelatin phantoms. This work investigates the impact of graphite concentration on phantom shear stiffness as characterized by shear-wave speed measurements using impulsive acoustic-radiation-force excitations. Phantom shear-wave speed increased by 0.83 (m/s)/(dB/(cm MHz)) when increasing the attenuation coefficient slope of the phantom material through increasing graphite concentration. Therefore, gelatin-phantom stiffness can be affected by the conventional ways that attenuation is modulated through graphite concentration in these phantoms. PMID:21710828

  19. Propagation of sound waves through a linear shear layer: A closed form solution

    Science.gov (United States)

    Scott, J. N.

    1978-01-01

    Closed form solutions are presented for sound propagation from a line source in or near a shear layer. The analysis was exact for all frequencies and was developed assuming a linear velocity profile in the shear layer. This assumption allowed the solution to be expressed in terms of parabolic cyclinder functions. The solution is presented for a line monopole source first embedded in the uniform flow and then in the shear layer. Solutions are also discussed for certain types of dipole and quadrupole sources. Asymptotic expansions of the exact solutions for small and large values of Strouhal number gave expressions which correspond to solutions previously obtained for these limiting cases.

  20. Propagation of sound waves through a linear shear layer - A closed form solution

    Science.gov (United States)

    Scott, J. N.

    1978-01-01

    Closed form solutions are presented for sound propagation from a line source in or near a shear layer. The analysis is exact for all frequencies and is developed assuming a linear velocity profile in the shear layer. This assumption allows the solution to be expressed in terms of parabolic cylinder functions. The solution is presented for a line monopole source first embedded in the uniform flow and then in the shear layer. Solutions are also discussed for certain types of dipole and quadrupole sources. Asymptotic expansions of the exact solutions for small and large values of Strouhal number give expressions which correspond to solutions previously obtained for these limiting cases.

  1. The role of viscosity estimation for oil-in-gelatin phantom in shear wave based ultrasound elastography.

    Science.gov (United States)

    Zhu, Ying; Dong, Changfeng; Yin, Yin; Chen, Xin; Guo, Yanrong; Zheng, Yi; Shen, Yuanyuan; Wang, Tianfu; Zhang, Xinyu; Chen, Siping

    2015-02-01

    Shear wave based ultrasound elastography utilizes mechanical excitation or acoustic radiation force to induce shear waves in deep tissue. The tissue response is monitored to obtain elasticity information about the tissue. During the past two decades, tissue elasticity has been extensively studied and has been used in clinical disease diagnosis. However, biological soft tissues are viscoelastic in nature. Therefore, they should be simultaneously characterized in terms of elasticity and viscosity. In this study, two shear wave-based elasticity imaging methods, shear wave dispersion ultrasound vibrometry (SDUV) and acoustic radiation force impulsive (ARFI) imaging, were compared. The discrepancy between the measurements obtained by the two methods was analyzed, and the role of viscosity was investigated. To this end, four types of gelatin phantoms containing 0%, 20%, 30% and 40% castor oil were fabricated to mimic different viscosities of soft tissue. For the SDUV method, the shear elasticity μ1 was 3.90 ± 0.27 kPa, 4.49 ± 0.16 kPa, 2.41 ± 0.33 kPa and 1.31 ± 0.09 kPa; and the shear viscosity μ2 was 1.82 ± 0.31 Pa•s, 2.41 ± 0.35 Pa•s, 2.65 ± 0.13 Pa•s and 2.89 ± 0.14 Pa•s for 0%, 20%, 30% and 40% oil, respectively in both cases. For the ARFI measurements, the shear elasticity μ was 7.30 ± 0.20 kPa, 8.20 ± 0.31 kPa, 7.42 ± 0.21 kPa and 5.90 ± 0.36 kPa for 0%, 20%, 30% and 40% oil, respectively. The SDUV results demonstrated that the elasticity first increased from 0% to 20% oil and then decreased for the 30% and 40% oil. The viscosity decreased consistently as the concentration of castor oil increased from 0% to 40%. The elasticity measured by ARFI showed the same trend as that of the SDUV but exceeded the results measured by SDUV. To clearly validate the impact of viscosity on the elasticity estimation, an independent measurement of the elasticity and viscosity by dynamic mechanical analysis (DMA) was conducted on these four types of gelatin

  2. Variability of Liver Shear Wave Measurements Using a New Ultrasound Elastographic Technique.

    Science.gov (United States)

    Nadebaum, David P; Nicoll, Amanda J; Sood, Siddharth; Gorelik, Alexandra; Gibson, Robert N

    2017-09-29

    A new 2-dimensional (2D) shear wave elastographic (SWE) device has been developed for the noninvasive assessment of liver fibrosis. Guidelines on measurement acquisition parameters are not yet well established for this technique. Our study aimed to assess 2D SWE measurement variability and to determine the number of measurements required per patient to reliably assess liver stiffness. Two-dimensional SWE was assessed in 55 patients with mixed-etiology chronic liver disease on an Aplio 500 ultrasound system (Toshiba Medical Systems Corporation, Tochigi, Japan). Ten measurements were obtained per patient by an operator blinded to all preceding readings. Results were analyzed with clinical information obtained from medical records. The median interquartile range/median ratio for 2D SWE was 0.131 (quartiles 1-3, 0.089-0.174). Five readings provided an approximation within 0.11 m/s, or 4.2% of the median velocity of 10 measurements. Factors associated with increased measurement variability included body mass index (ρ = 0.388; P = .01), increased skin-to-liver capsule distance (ρ = 0.426; P = .002), and measurements taken within 1.5 cm of the liver capsule (P  0.15) showed greater deviation from the set's median velocity than those with an ROI SD/speed ratio of 0.15 or lower (0.42 versus 0.22 m/s; P = .001). Two-dimensional SWE showed low overall measurement variability, with a minimum of 5 readings providing equivalent precision to the existing method using 10 samples. Obesity, increasing abdominal wall thickness, subcapsular measurements and an ROI SD/speed ratio of greater than 0.15 were all associated with increased measurement variability. The ROI SD/speed ratio warrants further evaluation as a quality assessment metric, to allow objective operator assessment of individual 2D SWE measurement reliability in real time. © 2017 by the American Institute of Ultrasound in Medicine.

  3. Computer-aided diagnosis based on quantitative elastographic features with supersonic shear wave imaging.

    Science.gov (United States)

    Xiao, Yang; Zeng, Jie; Niu, Lili; Zeng, Qingjing; Wu, Tao; Wang, Congzhi; Zheng, Rongqin; Zheng, Hairong

    2014-02-01

    Supersonic shear wave imaging (SSI) has recently been explored as a technique to evaluate tissue elasticity modulus and has become a valuable tool for tumor characterization. The purpose of this study was to develop a novel computer-aided diagnosis (CAD) system that can acquire quantitative elastographic information from color SSI elastography images automatically and objectively for the purpose of classifying benign and malignant breast tumors. Conventional ultrasonography (US) and SSI elastography images of 125 breast tumors (81 benign, 44 malignant), in 93 consecutive patients (mean age: 40 y, age range: 16-75 y), were obtained. After reconstruction of tissue elasticity data and automatic segmentation of each breast tumor, 10 quantitative elastographic features of the tumor and peri-tumoral areas, respectively (elasticity modulus mean, maximum and standard deviation, hardness degree and elasticity ratio), were computed and evaluated. A support vector machine (SVM) classifier was used for optimum classification via combination of these features. The B-mode Breast Imaging Reporting and Data System (BI-RADS) was used to compare gray-scale US and SSI elastography with respect to diagnostic performance. Histopathologic examination was used as the reference standard. Student's t-test, the Mann-Whitney U-test, the point biserial correlation coefficient and receiver operating characteristic curve analysis were performed for statistical analysis. As a result, the accuracy, sensitivity, specificity, positive predictive value and negative predictive value of benign/malignant classification were 95.2% (119/125), 90.9% (40/44), 97.5% (79/81), 95.2% (40/42) and 95.2% (79/83) for the CAD scheme, respectively, and 79.2% (99/125), 90.9% (40/44), 72.8% (59/81), 64.5% (40/62) and 93.7% (59/63) for BI-RADS assessment, respectively. The area under the receiver operating characteristic curve (Az value) for the proposed CAD system using the combination of elastographic features was

  4. A new qualitative pattern classification of shear wave elastograghy for solid breast mass evaluation.

    Science.gov (United States)

    Cong, Rui; Li, Jing; Guo, Song

    2017-02-01

    To examine the efficacy of qualitative shear wave elastography (SWE) in the classification and evaluation of solid breast masses, and to compare this method with conventional ultrasonograghy (US), quantitative SWE parameters and qualitative SWE classification proposed before. From April 2015 to March 2016, 314 consecutive females with 325 breast masses who decided to undergo core needle biopsy and/or surgical biopsy were enrolled. Conventional US and SWE were previously performed in all enrolled subjects. Each mass was classified by two different qualitative classifications. One was established in our study, herein named the Qual1. Qual1 could classify the SWE images into five color patterns by the visual evaluations: Color pattern 1 (homogeneous pattern); Color pattern 2 (comparative homogeneous pattern); Color pattern 3 (irregularly heterogeneous pattern); Color pattern 4 (intralesional echo pattern); and Color pattern 5 (the stiff rim sign pattern). The second qualitative classification was named Qual2 here, and included a four-color overlay pattern classification (Tozaki and Fukuma, Acta Radiologica, 2011). The Breast Imaging Reporting and Data System (BI-RADS) assessment and quantitative SWE parameters were recorded. Diagnostic performances of conventional US, SWE parameters, and combinations of US and SWE parameters were compared. With pathological results as the gold standard, of the 325 examined breast masses, 139 (42.77%) samples were malignant and 186 (57.23%) were benign. The Qual1 showed a higher Az value than the Qual2 and quantitative SWE parameters (all P<0.05). When applying Qual1=Color pattern 1 for downgrading and Qual1=Color pattern 5 for upgrading the BI-RADS categories, we obtained the highest Az value (0.951), and achieved a significantly higher specificity (86.56%, P=0.002) than that of the US (81.18%) with the same sensitivity (94.96%). The qualitative classification proposed in this study may be representative of SWE parameters and has

  5. Shear Wave Elastography in Thyroid Nodules with Indeterminate Cytology: Results of a Prospective Bicentric Study.

    Science.gov (United States)

    Bardet, Stéphane; Ciappuccini, Renaud; Pellot-Barakat, Claire; Monpeyssen, Hervé; Michels, Jean-Jacques; Tissier, Frédérique; Blanchard, David; Menegaux, Fabrice; de Raucourt, Dominique; Lefort, Muriel; Reznik, Yves; Rouxel, Agnès; Heutte, Natacha; Brenac, Frédérique; Leconte, Alexandra; Buffet, Camille; Clarisse, Bénédicte; Leenhardt, Laurence

    2017-11-01

    The clinical management of thyroid nodules with indeterminate cytology (IC) remains challenging. The role of shear wave elastography (SWE) in this setting is controversial. The aim of the study was to assess the performances of SWE in terms of prediction of malignancy, reproducibility, and combined analysis with ultrasound (US) examination in thyroid nodules with IC. This prospective study was conducted in two referral centers. Eligible patients had a thyroid nodule ≥15 mm with IC (Bethesda class III-V) for which surgery had been recommended. Patients underwent a standardized US evaluation combined with a SWE exam followed by surgery. SWE parameters included mean (meanEI; kPa) and max (maxEI) elasticity values, and ratio (meanEI nodule/parenchyma). One hundred and thirty-one nodules (median size 30 mm) in 131 patients were studied. IC was class III in 28%, class IV in 64%, and class V in 8% of cases. After surgery, 21 (16%) nodules were malignant, including nine papillary thyroid cancers (PTC), six follicular thyroid cancers, five poorly differentiated carcinomas, and one large B-cell lymphoma. SWE parameters were similar in benign and malignant nodules, including meanEI (20.2 vs. 19.6 kPa), maxEI (34.3 vs. 32.5 kPa), and ratio (1.57 vs. 1.38). In malignant nodules, meanEI, maxEI, and ratio were higher in the classic PTC variants (n = 4) than in the other PTC variants (n = 5; p < 0.02) and in non-PTC tumors (n = 12; p < 0.005). Intra- and inter-observer coefficients of variations for meanEI in nodules were 23% and 26%, respectively. The French Thyroid Imaging Reporting and Data System score, the American Thyroid Association US classification, and the EU-Thyroid Imaging Reporting and Data System were not associated with malignancy. Despite high elasticity values in classic PTC variants, conventional SWE indexes failed to discriminate between benign and malignant tumors in thyroid nodules with IC.

  6. Effect of pathological heterogeneity on shear wave elasticity imaging in the staging of deep venous thrombosis.

    Directory of Open Access Journals (Sweden)

    Xiaona Liu

    Full Text Available We aimed to observe the relationship between the pathological components of a deep venous thrombus (DVT, which was divided into three parts, and the findings on quantitative ultrasonic shear wave elastography (SWE to increase the accuracy of thrombus staging in a rabbit model.A flow stenosis-induced vein thrombosis model was used, and the thrombus was divided into three parts (head, body and tail, which were associated with corresponding observation points. Elasticity was quantified in vivo using SWE over a 2-week period. A quantitative pathologic image analysis (QPIA was performed to obtain the relative percentages of the components of the main clots.DVT maturity occurred at 2 weeks, and the elasticity of the whole thrombus and the three parts (head, body and tail showed an increasing trend, with the Young's modulus values varying from 2.36 ± 0.41 kPa to 13.24 ± 1.71 kPa; 2.01 ± 0.28 kPa to 13.29 ± 1.48 kPa; 3.27 ± 0.57 kPa to 15.91 ± 2.05 kPa; and 1.79 ± 0.36 kPa to 10.51 ± 1.61 kPa, respectively. Significant increases occurred on different days for the different parts: the head showed significant increases on days 4 and 6; the body showed significant increases on days 4 and 7; and the tail showed significant increases on days 3 and 6. The QPIA showed that the thrombus composition changed dynamically as the thrombus matured, with the fibrin and calcium salt deposition gradually increasing and the red blood cells (RBCs and platelet trabecula gradually decreasing. Significant changes were observed on days 4 and 7, which may represent the transition points for acute, sub-acute and chronic thrombi. Significant heterogeneity was observed between and within the thrombi.Variations in the thrombus components were generally consistent between the SWE and QPIA. Days 4 and 7 after thrombus induction may represent the transition points for acute, sub-acute and chronic thrombi in rabbit models. A dynamic examination of the same part of the thrombus

  7. Numerical Simulation of Focused Shock Shear Waves in Soft Solids and a Two-Dimensional Nonlinear Homogeneous Model of the Brain.

    Science.gov (United States)

    Giammarinaro, B; Coulouvrat, F; Pinton, G

    2016-04-01

    Shear waves that propagate in soft solids, such as the brain, are strongly nonlinear and can develop into shock waves in less than one wavelength. We hypothesize that these shear shock waves could be responsible for certain types of traumatic brain injuries (TBI) and that the spherical geometry of the skull bone could focus shear waves deep in the brain, generating diffuse axonal injuries. Theoretical models and numerical methods that describe nonlinear polarized shear waves in soft solids such as the brain are presented. They include the cubic nonlinearities that are characteristic of soft solids and the specific types of nonclassical attenuation and dispersion observed in soft tissues and the brain. The numerical methods are validated with analytical solutions, where possible, and with self-similar scaling laws where no known solutions exist. Initial conditions based on a human head X-ray microtomography (CT) were used to simulate focused shear shock waves in the brain. Three regimes are investigated with shock wave formation distances of 2.54 m, 0.018 m, and 0.0064 m. We demonstrate that under realistic loading scenarios, with nonlinear properties consistent with measurements in the brain, and when the shock wave propagation distance and focal distance coincide, nonlinear propagation can easily overcome attenuation to generate shear shocks deep inside the brain. Due to these effects, the accelerations in the focal are larger by a factor of 15 compared to acceleration at the skull surface. These results suggest that shock wave focusing could be responsible for diffuse axonal injuries.

  8. SplitRacer - a semi-automatic tool for the analysis and interpretation of teleseismic shear-wave splitting

    Science.gov (United States)

    Reiss, Miriam Christina; Rümpker, Georg

    2017-04-01

    We present a semi-automatic, graphical user interface tool for the analysis and interpretation of teleseismic shear-wave splitting in MATLAB. Shear wave splitting analysis is a standard tool to infer seismic anisotropy, which is often interpreted as due to lattice-preferred orientation of e.g. mantle minerals or shape-preferred orientation caused by cracks or alternating layers in the lithosphere and hence provides a direct link to the earth's kinematic processes. The increasing number of permanent stations and temporary experiments result in comprehensive studies of seismic anisotropy world-wide. Their successive comparison with a growing number of global models of mantle flow further advances our understanding the earth's interior. However, increasingly large data sets pose the inevitable question as to how to process them. Well-established routines and programs are accurate but often slow and impractical for analyzing a large amount of data. Additionally, shear wave splitting results are seldom evaluated using the same quality criteria which complicates a straight-forward comparison. SplitRacer consists of several processing steps: i) download of data per FDSNWS, ii) direct reading of miniSEED-files and an initial screening and categorizing of XKS-waveforms using a pre-set SNR-threshold. iii) an analysis of the particle motion of selected phases and successive correction of the sensor miss-alignment based on the long-axis of the particle motion. iv) splitting analysis of selected events: seismograms are first rotated into radial and transverse components, then the energy-minimization method is applied, which provides the polarization and delay time of the phase. To estimate errors, the analysis is done for different randomly-chosen time windows. v) joint-splitting analysis for all events for one station, where the energy content of all phases is inverted simultaneously. This allows to decrease the influence of noise and to increase robustness of the measurement

  9. Deep ReMi Imaging - Mapping Shear-Wave Velocities to 1 km Depth and Greater Using Refraction Microtremor

    Science.gov (United States)

    Louie, J. N.; Pancha, A.; Munger, D.; Law, C.; Adams, D.; Mick, T. M.; Pullammanappallil, S. K.

    2016-12-01

    The Refraction Microtremor (ReMi) surface-wave technique, in use since 2002, has become a standard tool for assessing urban shear-wave velocities for engineering applications. ReMi is effective for site-class studies as well as assessing ground conditions, including 1D and 2D velocity-depth profiling to shallow depths of approximately 100 m. Over the last few years, we have successfully extended the application of the method to depths greater than 1 km. The use of deep ReMi, which relies primarily on ambient noise, for estimation of shear-wave velocities to kilometer depths, allows for mapping the thickness and velocity of deep urban basins. Accurate 3D modeling and calibration of recorded earthquake ground motions in urban areas is one use of deep ReMi results. Such models have the potential to be an essential part of seismic hazard evaluation. We present results from several deep ReMi studies conducted in the Reno-area and Tahoe basins of Nevada and California. Wireless instruments coupled with low-frequency geophones deployed in 3-km-long arrays across the densely populated urban environment acquired data in 2012, 2014, and 2015. In addition to mapping basement as deep as 900 m, the lateral velocity variations reveal deep-seated fault structure in the initial studies. A study of the Reno-area basin in 2016 employed arrays of 90 IRIS-PASSCAL Texans, 15 and 22 km long. This data set appears to constrain a sub-basin interface between Tertiary volcanics and Mesozoic basement at 1-2 km depth. Characterization of shear velocity at greater than 100 m depth, to basement, along with previously unknown faults, is vital towards quantifying earthquake ground motion and seismic hazard potential in geologically complex urban basins. Our measurements will allow Nevada communities to become more resilient against natural hazards.

  10. The association of muscle and tendon elasticity with passive joint stiffness: In vivo measurements using ultrasound shear wave elastography.

    Science.gov (United States)

    Chino, Kentaro; Takahashi, Hideyuki

    2015-12-01

    Passive joint stiffness is associated with various tissues, including muscles, tendons, ligaments, and joint capsules. The specific elasticity of muscles or tendons can be measured using ultrasound shear wave elastography. To examine the association of muscle and tendon elasticity with passive joint stiffness, in vivo measurements of muscle and tendon elasticity were performed using ultrasound shear wave elastography. In 25 subjects, passive ankle joint stiffness was determined using the joint angle-passive torque relationship. The stiffness index of the muscle belly of the medial gastrocnemius (MG)--influenced by the muscle fascicles, its aponeuroses, and the proximal tendon--was quantified by the displacement of the muscle-tendon junction, which was visualized using B-mode ultrasonography during passive dorsiflexion. The stiffness index of the Achilles tendon--influenced by the tendon and the ligaments and joint capsule of the ankle--was similarly determined. The MG and Achilles tendon elasticity was measured using ultrasound shear wave elastography. Simple regression indicated a significant correlation between passive joint stiffness and stiffness index of the MG muscle belly (r=0.80) and Achilles tendon (r=0.60), but no correlation with elasticity of the MG (r=-0.37) or Achilles tendon (r=-0.39). Individual variations in the elasticity of either the MG or Achilles tendon are not associated with variations in passive ankle joint stiffness; however, variations in the elasticity of other tissues, including MG aponeuroses or the ligaments and joint capsule of the ankle, would be associated with the variations in joint stiffness. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Superficial Ultrasound Shear Wave Speed Measurements in Soft and Hard Elasticity Phantoms: Repeatability and Reproducibility Using Two Different Ultrasound Systems

    Science.gov (United States)

    Dillman, Jonathan R.; Chen, Shigao; Davenport, Matthew S.; Zhao, Heng; Urban, Matthew W.; Song, Pengfei; Watcharotone, Kuanwong; Carson, Paul L.

    2014-01-01

    Background There is a paucity of data available regarding the repeatability and reproducibility of superficial shear wave speed (SWS) measurements at imaging depths relevant to the pediatric population. Purpose To assess the repeatability and reproducibility of superficial shear wave speed (SWS) measurements acquired from elasticity phantoms at varying imaging depths using three different imaging methods, two different ultrasound systems, and multiple operators. Methods and Materials Soft and hard elasticity phantoms manufactured by Computerized Imaging Reference Systems, Inc. (Norfolk, VA) were utilized for our investigation. Institution #1 used an Acuson S3000 ultrasound system (Siemens Medical Solutions USA, Inc.) and three different shear wave imaging method/transducer combinations, while institution #2 used an Aixplorer ultrasound system (Supersonic Imagine) and two different transducers. Ten stiffness measurements were acquired from each phantom at three depths (1.0, 2.5, and 4.0 cm) by four operators at each institution. Student’s t-test was used to compare SWS measurements between imaging techniques, while SWS measurement agreement was assessed with two-way random effects single measure intra-class correlation coefficients and coefficients of variation. Mixed model regression analysis determined the effect of predictor variables on SWS measurements. Results For the soft phantom, the average of mean SWS measurements across the various imaging methods and depths was 0.84 ± 0.04 m/s (mean ± standard deviation) for the Acuson S3000 system and 0.90 ± 0.02 m/s for the Aixplorer system (p=0.003). For the hard phantom, the average of mean SWS measurements across the various imaging methods and depths was 2.14 ± 0.08 m/s for the Acuson S3000 system and 2.07 ± 0.03 m/s Aixplorer system (p>0.05). The coefficients of variation were low (0.5–6.8%), and inter-operator agreement was near-perfect (ICCs ≥0.99). Shear wave imaging method and imaging depth

  12. Pressure-induced forces and shear stresses on rubble mound breakwater armour layers in regular waves

    DEFF Research Database (Denmark)

    Jensen, Bjarne; Christensen, Erik Damgaard; Sumer, B. Mutlu

    2014-01-01

    measurements in the core material: (1) core material with an idealized armour layer made out of spherical objects that also allowed for detailed velocity measurements between and above the armour, and (2) core material with real rock armour stones. The same core material was applied through the entire...... and turbulence measurements showed that the large outward directed pressure gradients in general coincide, both in time and space, with the maximum bed-shear stresses on the armour layer based on the Reynolds-stresses. The bed-shear stresses were found to result in a Shields parameter in the same order......This paper presents the results from an experimental investigation of the pressure-induced forces in the core material below the main armour layer and shear stresses on the armour layer for a porous breakwater structure. Two parallel experiments were performed which both involved pore pressure...

  13. Acute effect of static stretching on passive stiffness of the human gastrocnemius fascicle measured by ultrasound shear wave elastography.

    Science.gov (United States)

    Hirata, Kosuke; Kanehisa, Hiroaki; Miyamoto, Naokazu

    2017-03-01

    Passive muscle stiffness and muscle architecture at a given joint angle, as well as slack angle of the muscle have been shown to change after an acute bout of stretching. However, it remains unclear whether passive muscle stiffness at a given fascicle length is reduced after stretching. We aimed to elucidate the acute effect of static stretching on the passive fascicle stiffness using ultrasound shear wave elastography. Shear modulus, fascicle length, and slack angle of the medial gastrocnemius (MG) as well as passive plantar flexion torque during passive dorsiflexion were measured before and after a 5-min static stretching in 14 healthy males. After stretching, passive torques were significantly reduced at >50% of range of motion (ROM). Shear modulus at a given fascicle length was significantly reduced at >80% of the change in fascicle length during passive dorsiflexion. Slack angle of MG was observed at the middle part of ROM and significantly shifted toward more dorsiflexed position after stretching. The present study showed the significant effectiveness of static stretching on the passive fascicle stiffness. Furthermore, the present results suggest that both the shift in slack angle and the reduction in passive fascicle stiffness contribute to produce the change in passive torque-joint angle relationship during passive dorsiflexion. Notably, the contribution of the reduced passive fascicle stiffness to the decrease in passive torque is substantial over the latter part of ROM.

  14. Two-dimensional shear wave elastography of breast lesions: Comparison of two different systems.

    Science.gov (United States)

    Ren, Wei-Wei; Li, Xiao-Long; He, Ya-Ping; Li, Dan-Dan; Wang, Dan; Zhao, Chong-Ke; Bo, Xiao-Wan; Liu, Bo-Ji; Yue, Wen-Wen; Xu, Hui-Xiong

    2017-01-01

    To evaluate the diagnostic performance of two different shear wave elastography (SWE) techniques in distinguishing malignant breast lesions from benign ones. From March 2016 to May 2016, a total of 153 breast lesions (mean diameter, 16.8 mm±10.5; range 4.1-90.0 mm) in 153 patients (mean age, 46.4 years±15.1; age range 20-86 years) were separately performed by two different SWE techniques (i.e. T-SWE, Aplio500, Toshiba Medical System, Tochigi, Japan; and S-SWE, the Aixplorer US system, SuperSonic Imagine, Provence, France). The maximum (Emax), mean (Emean) and standard deviation (ESD) of elasticity modulus values in T-SWE and S-SWE were analyzed. All the lesions were confirmed by ultrasound (US)-guided core needle biopsy (n = 26), surgery (n = 122), or both (n = 5), with pathological results as the gold standard. The areas under the receiver operating characteristic curves (AUROCs) were calculated. Sensitivity, specificity, accuracy, positive predictive value (PPV), negative predictive value (NPV) were calculated to assess the diagnostic performance between T-SWE and S-SWE. Operator consistency was also evaluated. Among the 153 lesions, 41 (26.8%) were malignant and 112 (73.2%) were benign. Emax (T-SWE: 40.10±37.14 kPa vs. 118.78±34.41 kPa; S-SWE: 41.22±22.54 kPa vs. 134.77±60.51 kPa), Emean (T-SWE: 19.75±16.31 kPa vs. 52.93±25.75 kPa; S-SWE: 20.95±10.98 kPa vs. 55.95±22.42 kPa) and ESD (T-SWE: 9.00±8.55 kPa vs. 38.44±12.30 kPa; S-SWE: 8.17±6.14 kPa vs. 29.34±13.88 kPa) showed statistical differences in distinguishing malignant lesions from benign ones both in T-SWE and S-SWE (all p  0.05 in comparison with Emax) and Emean (AUROC = 0.930, p = 0.034 in comparison with Emax). AUROC-max (T-SWE: 0.909 vs. 0.967), AUROC-mean (T-SWE: 0.892 vs. 0.930) and AUROC-SD (T-SWE: 0.958 vs. 0.962) showed no significant difference between T-SWE and S-SWE (all p > 0.05). The intra-class correlation coefficients

  15. In Vitro Comparison of Five Different Elastography Systems for Clinical Applications, Using Strain and Shear Wave Technology.

    Science.gov (United States)

    Mulabecirovic, Anesa; Vesterhus, Mette; Gilja, Odd Helge; Havre, Roald Flesland

    2016-11-01

    Several different platforms providing ultrasound elastography have emerged in recent years. In this in vitro study on a single tissue-mimicking phantom (CIRS Model 49), we aimed to compare the performance of quantitative elastography measurements from platforms running strain elastography and others running shear wave elastography. We evaluated five different elastography platforms using both linear and curvilinear probes. All measurements were performed in parallel by two independent investigators who recorded the elasticity quantitatively. We investigated intra- and inter-observer agreement by intra-class correlation analysis and coefficient of variation, by correlation and limits of agreement. The reproducibility of elasticity measurements was good to excellent for shear wave and strain elastography. All five elastography platforms had high intra-observer (intra-class correlation coefficient: 0.932-1.0) and inter-observer correlation (intra-class correlation coefficient: 0.845-0.996). All inclusions could be differentiated by quantitative elastography by all systems (p < 0.001). The use of a linear probe yielded more reproducible measurements compared with use of a convex probe in 3/4 platforms. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  16. A study on crustal shear wave splitting in the western part of the Banda arc-continent collision

    Energy Technology Data Exchange (ETDEWEB)

    Syuhada, E-mail: hadda9@gmail.com [Graduate Research on Earthquake and Active Tectonics-ITB, Jl. Ganesha 10, Bandung 40132 (Indonesia); Research Centre for Physics - Indonesian Institute of Sciences (LIPI), Puspiptek Serpong 15314,Indonesia (Indonesia); Hananto, Nugroho D. [Research Centre for Geotechnology -LIPI, Jl. Sangkuriang (Kompleks LIPI) Bandung 40135 (Indonesia); Puspito, Nanang T.; Yudistira, Tedi [Faculty of Mining and Petroleum Engineering ITB, Jalan Ganesha 10, Bandung 40132 (Indonesia); Anggono, Titi [Research Centre for Physics - Indonesian Institute of Sciences (LIPI), Puspiptek Serpong 15314,Indonesia (Indonesia)

    2016-03-11

    We analyzed shear wave splitting parameters from local shallow (< 30 km) earthquakes recorded at six seismic stations in the western part of the Banda arc-continent collision. We determined fast polarization and delay time for 195 event-stations pairs calculated from good signal-to-noise ratio waveforms. We observed that there is evidence for shear wave splitting at all stations with dominant fast polarization directions oriented about NE-SW, which are parallel to the collision direction of the Australian plate. However, minor fast polarization directions are oriented around NW-SE being perpendicular to the strike of Timor through. Furthermore, the changes in fast azimuths with the earthquake-station back azimuth suggest that the crustal anisotropy in the study area is not uniform. Splitting delay times are within the range of 0.05 s to 0.8 s, with a mean value of 0.29±0.18 s. Major seismic stations exhibit a weak tendency increasing of delay times with increasing hypocentral distance suggesting the main anisotropy contribution of the shallow crust. In addition, these variations in fast azimuths and delay times indicate that the crustal anisotropy in this region might not only be caused by extensive dilatancy anisotropy (EDA), but also by heterogeneity shallow structure such as the presence of foliations in the rock fabric and the fracture zones associated with active faults.

  17. Measurement of gastrocnemius muscle elasticity by shear wave elastography: association with passive ankle joint stiffness and sex differences.

    Science.gov (United States)

    Chino, Kentaro; Takahashi, Hideyuki

    2016-04-01

    Passive joint stiffness is an important quantitative measure of flexibility, but is affected by muscle volume and all of the anatomical structures located within and over the joint. Shear wave elastography can assess muscle elasticity independent of the influences of muscle volume and the other nearby anatomical structures. We determined how muscle elasticity, as measured using shear wave elastography, is associated with passive joint stiffness and patient sex. Twenty-six healthy men (24.4 ± 5.9 years) and 26 healthy women (25.2 ± 4.8 years) participated in this study. The passive ankle joint stiffness and tissue elasticity of the medial gastrocnemius (MG) were quantified with the ankle in 30° plantar flexion (PF), a neutral anatomical position (NE), and 20° dorsiflexion (DF). No significant difference in passive joint stiffness by sex was observed with the ankle in PF, but significantly greater passive ankle joint stiffness in men than in women was observed in NE and DF. The MG elasticity was not significantly associated with joint stiffness in PF or NE, but it was significantly associated with joint stiffness in DF. There were no significant differences in MG elasticity by sex at any ankle position. Muscle elasticity, measured independent of the confounding effects of muscle volume and the other nearby anatomical structures, is associated with passive joint stiffness in the joint position where the muscle is sufficiently lengthened, but does not vary by sex in any joint position tested.

  18. Site response, shallow shear-wave velocity, and damage in Los Gatos, California, from the 1989 Loma Prieta earthquake

    Science.gov (United States)

    Hartzell, S.; Carver, D.; Williams, R.A.

    2001-01-01

    Aftershock records of the 1989 Loma Prieta earthquake are used to calculate site response in the frequency band of 0.5-10 Hz at 24 locations in Los Gatos, California, on the edge of the Santa Clara Valley. Two different methods are used: spectral ratios relative to a reference site on rock and a source/site spectral inversion method. These two methods complement each other and give consistent results. Site amplification factors are compared with surficial geology, thickness of alluvium, shallow shear-wave velocity measurements, and ground deformation and structural damage resulting from the Loma Prieta earthquake. Higher values of site amplification are seen on Quaternary alluvium compared with older Miocene and Cretaceous units of Monterey and Franciscan Formation. However, other more detailed correlations with surficial geology are not evident. A complex pattern of alluvial sediment thickness, caused by crosscutting thrust faults, is interpreted as contributing to the variability in site response and the presence of spectral resonance peaks between 2 and 7 Hz at some sites. Within the range of our field measurements, there is a correlation between lower average shear-wave velocity of the top 30 m and 50% higher values of site amplification. An area of residential homes thrown from their foundations correlates with high site response. This damage may also have been aggravated by local ground deformation. Severe damage to commercial buildings in the business district, however, is attributed to poor masonry construction.

  19. Near-surface shear-wave velocity measurements in unlithified sediment

    Science.gov (United States)

    Richards, B.T.; Steeples, D.; Miller, R.; Ivanov, J.; Peterie, S.; Sloan, S.D.; McKenna, J.R.

    2011-01-01

    S-wave velocity can be directly correlated to material stiffness and lithology making it a valuable physical property that has found uses in construction, engineering, and environmental projects. This study compares different methods for measuring S-wave velocities, investigating and identifying the differences among the methods' results, and prioritizing the different methods for optimal S-wave use at the U. S. Army's Yuma Proving Grounds YPG. Multichannel Analysis of Surface Waves MASW and S-wave tomography were used to generate S-wave velocity profiles. Each method has advantages and disadvantages. A strong signal-to-noise ratio at the study site gives the MASW method promising resolution. S-wave first arrivals are picked on impulsive sledgehammer data which were then used for the tomography process. Three-component downhole seismic data were collected in-line with a locking geophone, providing ground truth to compare the data and to draw conclusions about the validity of each data set. Results from these S-wave measurement techniques are compared with borehole seismic data and with lithology data from continuous samples to help ascertain the accuracy, and therefore applicability, of each method. This study helps to select the best methods for obtaining S-wave velocities for media much like those found in unconsolidated sediments at YPG. ?? 2011 Society of Exploration Geophysicists.

  20. Acoustic and Shear-Wave Velocities in Hydrate-Bearing Sediments Offshore Southwestern Taiwan: Tomography, Converted Waves Analysis and Reverse-Time Migration of OBS Records

    Directory of Open Access Journals (Sweden)

    Philippe Schnurle

    2006-01-01

    Full Text Available A 2.5-D combined seismic reflection and refraction survey has been conducted in the accretionary complex offshore of southwestern Taiwan where BSRs (Bottom Simulating Reflectors are highly concentrated and geochemical signals for the presence of gas hydrate are strong. In this study, we perform velocity analysis of the 6 4-component OBS (Ocean-Bottom Seismometer records along the southernmost transect of this seismic experiment. We utilize 3 independent methods in order to accurately determine the acoustic and shear-wave velocities of the sediments: 1-D Root Mean Square (RMS analysis of the P-P and P-S reflected events on individual datumed components, 2-D inversion of the P-P and P-S reflected and refracted events along the in-line transect, and 3-D acoustic inversion of the first arrivals. The principal sources of bias in the determination of the velocities are the 3-dimentional nature of the topography and the complexity of the underlying structures. The three methods result in consistent velocity profiles. Rapid lateral and vertical variations of the velocities are observed. We then investigate the large scale gas hydrate content through rock physic modeling: at the vertical of each OBS, shear-waves velocities are utilized to estimate the water-filled porosities, and the acoustic velocities predicted for a set of gas hydrate, quartz and clay contents are compared to the observed profiles.

  1. AN INVESTIGATION TO DOCUMENT MORROW RESERVOIRS THAT CAN BE BETTER DETECTED WITH SEISMIC SHEAR (S) WAVES THAN WITH COMPRESSIONAL (P) WAVES

    Energy Technology Data Exchange (ETDEWEB)

    Thomas Cottman

    2001-10-19

    Pennsylvanian-age Morrow reservoirs are a key component of a large fluvial-deltaic system that extends across portions of Colorado, Kansas, Oklahoma, and Texas. A problem that operators have to solve in some Morrow plays in this multi-state area is that many of the fluvial channels within the Morrow interval are invisible to seismic compressional (P) waves. This P-wave imaging problem forces operators in such situations to site infill, field-extension, and exploration wells without the aid of 3-D seismic technology. The objective of this project was to develop and demonstrate seismic technology that can improve drilling success in Morrow plays. Current P-wave technology commonly results in 80-percent of Morrow exploration wells not penetrating economic reservoir facies. Studies at Colorado School of Mines have shown that some of the Morrow channels that are elusive as P-wave targets create robust shear (S) wave reflections (Rampton, 1995). These findings caused Visos Energy to conclude that exploration and field development of Morrow prospects should be done by a combination of P-wave and S-wave seismic imaging. To obtain expanded information about the P and S reflectivity of Morrow facies, 9-component vertical seismic profile (9-C VSP) data were recorded at three locations along the Morrow trend. These data were processed to create P and S images of Morrow stratigraphy. These images were then analyzed to determine if S waves offer an alternative to P waves, or perhaps even an advantage over P waves, in imaging Morrow reservoir targets. The study areas where these field demonstrations were done are defined in Figure 1. Well A was in Sherman County, Texas; well B in Clark County, Kansas; and well C in Cheyenne County, Colorado. Technology demonstrated at these sites can be applied over a wide geographical area and influence operators across the multi-state region spanned by Morrow channel plays. The scope of the investigation described here is significant on the

  2. Application of oil-water discrimination technology in fractured reservoirs using the differences between fast and slow shear-waves

    Science.gov (United States)

    Luo, Cong; Li, Xiangyang; Huang, Guangtan

    2017-08-01

    Oil-water discrimination is of great significance in the design and adjustment of development projects in oil fields. For fractured reservoirs, based on anisotropic S-wave splitting information, it becomes possible to effectively solve such problems which are difficult to deal with in traditional longitudinal wave exploration, due to the similar bulk modulus and density of these two fluids. In this paper, by analyzing the anisotropic character of the Chapman model (2009 Geophysics 74 97-103), the velocity and reflection coefficient differences between the fast and slow S-wave caused by fluid substitution have been verified. Then, through a wave field response analysis of the theoretical model, we found that water saturation causes a longer time delay, a larger time delay gradient and a lower amplitude difference between the fast and slow S-wave, while the oil case corresponds to a lower time delay, a lower gradient and a higher amplitude difference. Therefore, a new class attribute has been proposed regarding the amplitude energy of the fast and slow shear wave, used for oil-water distinction. This new attribute, as well as that of the time delay gradient, were both applied to the 3D3C seismic data of carbonate fractured reservoirs in the Luojia area of the Shengli oil field in China. The results show that the predictions of the energy attributes are more consistent with the well information than the time delay gradient attribute, hence demonstrating the great advantages and potential of this new attribute in oil-water recognition.

  3. Interaction of suprathermal solar wind electron fluxes with sheared whistler waves: fan instability

    Directory of Open Access Journals (Sweden)

    C. Krafft

    Full Text Available Several in situ measurements performed in the solar wind evidenced that solar type III radio bursts were some-times associated with locally excited Langmuir waves, high-energy electron fluxes and low-frequency electrostatic and electromagnetic waves; moreover, in some cases, the simultaneous identification of energetic electron fluxes, Langmuir and whistler waves was performed. This paper shows how whistlers can be excited in the disturbed solar wind through the so-called "fan instability" by interacting with energetic electrons at the anomalous Doppler resonance. This instability process, which is driven by the anisotropy in the energetic electron velocity distribution along the ambient magnetic field, does not require any positive slope in the suprathermal electron tail and thus can account for physical situations where plateaued reduced electron velocity distributions were observed in solar wind plasmas in association with Langmuir and whistler waves. Owing to linear calculations of growth rates, we show that for disturbed solar wind conditions (that is, when suprathermal particle fluxes propagate along the ambient magnetic field, the fan instability can excite VLF waves (whistlers and lower hybrid waves with characteristics close to those observed in space experiments.

    Key words. Space plasma physics (waves and instabilities – Radio Science (waves in plasma – Solar physics, astrophysics and astronomy (radio emissions

  4. Imaging feedback for histotripsy by characterizing dynamics of acoustic radiation force impulse (ARFI)-induced shear waves excited in a treated volume.

    Science.gov (United States)

    Wang, Tzu-Yin; Hall, Timothy L; Xu, Zhen; Fowlkes, J Brian; Cain, Charles A

    2014-07-01

    Our previous study indicated that shear waves decay and propagate at a lower speed as they propagate into a tissue volume mechanically fractionated by histotripsy. In this paper, we hypothesize that the change in the shear dynamics is related to the degree of tissue fractionation, and can be used to predict histotripsy treatment outcomes. To test this hypothesis, lesions with different degrees of tissue fractionation were created in agar-graphite tissue phantoms and ex vivo kidneys with increasing numbers of therapy pulses, from 0 to 2000 pulses per treatment location. The therapy pulses were 3-cycle 750-kHz focused ultrasound delivered at a peak negative/positive pressure of 17/108 MPa and a repetition rate of 50 Hz. The shear waves were excited by acoustic radiation force impulse (ARFI) focused at the center of the lesion. The spatial and temporal behavior of the propagating shear waves was measured with ultrasound plane wave imaging. The temporal displacement profile at a lateral location 10 mm offset to the shear excitation region was detected with M-mode imaging. The decay and delay of the shear waves were quantitatively characterized on the temporal displacement profile. Results showed significant changes in two characteristics on the temporal displacement profile: the peak-to-peak displacement decayed exponentially with increasing numbers of therapy pulses; the relative time-to-peak displacement increased with increasing numbers of therapy pulses, and appeared to saturate at higher numbers of pulses. Correspondingly, the degree of tissues fractionation, as indicated by the percentage of structurally intact cell nuclei, decreased exponentially with increasing numbers of therapy pulses. Strong linear correlations were found between the two characteristics and the degree of tissue fractionation. These results suggest that the characteristics of the shear temporal displacement profile may provide useful feedback information regarding the treatment outcomes.

  5. "Soft, hard, or just right?" Applications and limitations of axial-strain sonoelastography and shear-wave elastography in the assessment of tendon injuries.

    Science.gov (United States)

    Ooi, C C; Malliaras, P; Schneider, M E; Connell, D A

    2014-01-01

    Injury to a tendon leads to alterations in the mechanical properties of the tendon. Axial-strain sonoelastography and shear-wave elastography are relatively new, real-time imaging techniques that evaluate the mechanical properties of tendons in addition to the existing morphological and vascular information that is obtained with traditional imaging tools. Axial-strain sonoelastography displays the subjective distribution of strain data on an elastogram caused by tissue compression, whereas shear-wave elastography provides a more objective, quantitative measure of the intrinsic tissue elasticity using the acoustic push-pulse. Recent studies suggest that axial-strain sonoelastography is able to distinguish between asymptomatic and diseased tendons, and is potentially more sensitive than conventional ultrasound in detecting early tendinopathy. Shear-wave elastography seems to be a feasible tool for depicting elasticity and functional recovery of tendons after surgical management. While initial results have been promising, axial-strain sonoelastography and shear-wave elastography have not yet found routine use in wider clinical practice. Possible barriers to the dissemination of axial-strain sonoelastography technique include operator dependency, technical limitations such as artefacts and lack of reproducibility and quantification of sonoelastography data. Shear-wave elastography may improve the reproducibility of elastography data, although there is only one published study on the topic to date. Large-scale longitudinal studies are needed to further elucidate the clinical relevance and potential applications of axial-strain sonoelastography and shear-wave elastography in diagnosing, predicting, and monitoring the progress of tendon healing before they can be widely adopted into routine clinical practice.

  6. Optimal electrode shape and size for shear mode thin film acoustic wave resonators

    Science.gov (United States)

    Xu, L. M.; Tang, B. B.; Hu, Y. T.; Fan, H.; Yang, J. S.

    2009-12-01

    We study electrode shape and size for plates of hexagonal crystals or polarized ceramics with the sixfold axis or the poling direction parallel to the plate surfaces so that they can be excited into thickness-shear vibration by an electric field in the plate thickness direction. Electrode size and shape optimal in the sense that they satisfy the criterion of Bechmann's number in every direction are determined.

  7. 3D isotropic shear wave velocity structure of the lithosphere-asthenosphere system underneath the Alpine-Mediterranean Mobile belt

    Science.gov (United States)

    El-Sharkawy, Amr; Weidle, Christian; Christiano, Luigia; Lebedev, Sergei; Meier, Thomas

    2017-04-01

    The Alpine-Mediterranean mobile belt is, tectonically, one of the most complicated and active regions in the world. Since the Mesozoic, collisions between Gondwana-derived continental blocks and Eurasia, due to the closure of a number of rather small ocean basins, have shaped the Mediterranean geology. During the late Mesozoic, it was dominated by subduction zones (e.g., in Anatolia, the Dinarides, the Carpathians, the Alps, the Apennines, and the Betics), which inverted the extensional regime, consuming the previously formed oceanic lithosphere, the adjacent passive continental margins and presumably partly also continental lithosphere. The location, distribution, and evolution of these subduction zones were mainly controlled by the continental or oceanic nature, density, and thickness of the lithosphere inherited from the Mesozoic rift after the European Variscan Orogeny. Despite the numerous studies that have attempted to characterize the lithosphere-asthenosphere structure in that area, details of the lithospheric structure and dynamics, as well as flow in the asthenosphere are, however, poorly known. A 3D shear-wave velocity structure of the lithosphere-asthenosphere system in the Mediterranean is investigated using new tomographic images obtained from surface wave tomography. An automated algorithm for inter-station phase velocity measurements is applied here to obtain both Rayleigh and Love fundamental mode phase velocities. We utilize a database consisting of more than 4000 seismic events recorded by more than 2000 broadband seismic stations within the area, provided by the European Integrated Data Archive (WebDc/EIDA) and IRIS. Moreover, for the first time, data from the Egyptian National Seismological Network (ENSN), recorded by up to 25 broad band seismic stations, are also included in the analysis. For each station pair, approximately located on the same great circle path, the recorded waveforms are cross correlated and the dispersion curves of

  8. Angle-Beam Shear Wave Scattering from Buried Crack-like Defects in Bonded Specimens (Postprint)

    Science.gov (United States)

    2017-02-01

    corresponding depth renders guided wave methods [7,8] less useful . Ultrasonic wavefield imaging combined with signal processing can be applied to...Approved for public release (PA): distribution unlimited. Phase Velocity Filtering Fourier domain frequency-wavenumber filtering is used to separate the...Positive wavenumber filtering is done by applying a Gaussian filter to W( , kx, ky). The incident and forward scattered waves, which correspond to +ky, are

  9. Quaternary layer anomalies around the Carlsberg Fault zone mapped with high-resolution shear-wave seismics south of Copenhagen

    Science.gov (United States)

    Kammann, Janina; Hübscher, Christian; Nielsen, Lars; Boldreel, Lars Ole

    2015-04-01

    The Carlsberg Fault zone is located in the N-S striking Höllviken Graben and traverses the city of Copenhagen. The fault zone is a NNW-SSE striking structure in direct vicinity to the transition zone of the Danish Basin and the Baltic Shield. Recent small earthquakes indicate activity in the area, although none of the mapped earthquakes appear to have occurred on the Carlsberg Fault. We examined the fault evolution by a combination of very high resolution onshore shear-wave seismic data, one conventional onshore seismic profile and marine reflection seismic profiles. The chalk stratigraphy and the localization of the fault zone at depth was inferred from previous studies by other authors. We extrapolated the Jurassic and Triassic stratigraphy from the Pomeranian Bay to the area of investigation. The fault zone shows a flower structure in the Triassic as well as in Cretaceous sediments. The faulting geometry indicates strong influence of Triassic processes when subsidence and rifting prevailed in the Central European Basin System. Growth strata within the surrounding Höllviken Graben reveal syntectonic sedimentation in the lower Triassic, indicating the opening to be a result of Triassic rifting. In the Upper Cretaceous growth faulting documents continued rifting. This finding contrasts the Late Cretaceous to Paleogene inversion tectonics in neighbouring structures, as the Tornquist Zone. The high-resolution shear-wave seismic method was used to image structures in Quaternary layers in the Carlsberg Fault zone. The portable compact vibrator source ElViS III S8 was used to acquire a 1150 m long seismic section on the island Amager, south of Copenhagen. The shallow subsurface in the investigation area is dominated by Quaternary glacial till deposits in the upper 5-11 m and Danian limestone below. In the shear-wave profile, we imaged the 30 m of the upward continuation of the Carlsberg Fault zone. In our area of investigation, the fault zone appears to comprise

  10. Shear-wave elastography of the liver and spleen identifies clinically significant portal hypertension: A prospective multicentre study.

    Science.gov (United States)

    Jansen, Christian; Bogs, Christopher; Verlinden, Wim; Thiele, Maja; Möller, Philipp; Görtzen, Jan; Lehmann, Jennifer; Vanwolleghem, Thomas; Vonghia, Luisa; Praktiknjo, Michael; Chang, Johannes; Krag, Aleksander; Strassburg, Christian P; Francque, Sven; Trebicka, Jonel

    2017-03-01

    Clinically significant portal hypertension (CSPH) is associated with severe complications and decompensation of cirrhosis. Liver stiffness measured either by transient elastography (TE) or Shear-wave elastography (SWE) and spleen stiffness by TE might be helpful in the diagnosis of CSPH. We recently showed the algorithm to rule-out CSPH using sequential liver- (L-SWE) and spleen-Shear-wave elastography (S-SWE). This study investigated the diagnostic value of S-SWE for diagnosis of CSPH. One hundred and fifty-eight cirrhotic patients with pressure gradient measurements were included into this prospective multicentre study. L-SWE was measured in 155 patients, S-SWE in 112 patients, and both in 109 patients. Liver-shear-wave elastography and S-SWE correlated with clinical events and decompensation. SWE of liver and spleen revealed strong correlations with the pressure gradient and to differentiate between patients with and without CSPH. The best cut-off values were 24.6 kPa:L-SWE and 26.3 kPa:S-SWE. L-SWE ≤16.0 kPa and S-SWE ≤21.7 kPa were able to rule-out CSPH. Cut-off values of L-SWE >29.5 kPa and S-SWE >35.6 kPa were able to rule-in CSPH (specificity >92%). Patients with a L-SWE >38.0 kPa had likely CSPH. In patients with L-SWE ≤38.0 kPa, a S-SWE >27.9 kPa ruled in CSPH. This algorithm has a sensitivity of 89.2% and a specificity of 91.4% to rule-in CSPH. Patients not fulfilling these criteria may undergo HVPG measurement. Liver and spleen SWE correlate with portal pressure and can both be used as a non-invasive method to investigate CSPH. Even though external validation is still missing, these algorithms to rule-out and rule-in CSPH using sequential SWE of liver and spleen might change the clinical practice. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  11. Prediction of Compressional, Shear, and Stoneley Wave Velocities from Conventional Well Log Data Using a Committee Machine with Intelligent Systems

    Science.gov (United States)

    Asoodeh, Mojtaba; Bagheripour, Parisa

    2012-01-01

    Measurement of compressional, shear, and Stoneley wave velocities, carried out by dipole sonic imager (DSI) logs, provides invaluable data in geophysical interpretation, geomechanical studies and hydrocarbon reservoir characterization. The presented study proposes an improved methodology for making a quantitative formulation between conventional well logs and sonic wave velocities. First, sonic wave velocities were predicted from conventional well logs using artificial neural network, fuzzy logic, and neuro-fuzzy algorithms. Subsequently, a committee machine with intelligent systems was constructed by virtue of hybrid genetic algorithm-pattern search technique while outputs of artificial neural network, fuzzy logic and neuro-fuzzy models were used as inputs of the committee machine. It is capable of improving the accuracy of final prediction through integrating the outputs of aforementioned intelligent systems. The hybrid genetic algorithm-pattern search tool, embodied in the structure of committee machine, assigns a weight factor to each individual intelligent system, indicating its involvement in overall prediction of DSI parameters. This methodology was implemented in Asmari formation, which is the major carbonate reservoir rock of Iranian oil field. A group of 1,640 data points was used to construct the intelligent model, and a group of 800 data points was employed to assess the reliability of the proposed model. The results showed that the committee machine with intelligent systems performed more effectively compared with individual intelligent systems performing alone.

  12. Characteristics of wind waves in shallow tidal basins and how they affect bed shear stress, bottom erosion, and the morphodynamic evolution of coupled marsh and mudflat landforms

    Science.gov (United States)

    Tommasini, Laura; Carniello, Luca; Goodwin, Guillaume; Mudd, Simon M.; Matticchio, Bruno; D'Alpaos, Andrea

    2017-04-01

    Wind-wave induced erosion is one of the main processes controlling the morphodynamic evolution of shallow tidal basins, because wind waves promote the erosion of subtidal platforms, tidal flats and salt marshes. Our study considered zero-, one-and two-dimensional wave models. First, we analyzed the relations between wave parameters, depth and bed shear stress with constant and variable wave period considering two zero-dimensional models based on the Young and Verhagen (1996), and Carniello et al. (2005, 2011) approaches. The first one is an empirical method that computes wave height and the variable wave period from wind velocity, fetch and water depth. The second one is based on the solution of wave action conservation equation, we use this second approach for computing the bottom shear stress and wave height, considering variable and constant (t=2s) wave period. Second, we compared the wave spectral model SWAN with a fully coupled Wind-Wave Tidal Model applied to a 1D rectangular domain. These models describe both the growth and propagation of wind waves. Finally, we applied the two-dimensional Wind Wave Tidal Model (WWTM) to six different configurations of the Venice lagoon considering the same boundary conditions and we evaluated the spatial variation of mean wave power density. The analysis with zero-dimensional models show that the effects of the different model assumptions on the wave period and on the wave height computation cannot be neglected. In particular, the relationships between bottom shear stress and water depth have different shapes. Two results emerge: first, the differences are higher for small depths, and then the maximum values reached with the Young and Verhagen (1996) approach are greater than the maximum values obtained with WWTM approach. The results obtained with two-dimensional models suggest that the wave height is different in particular for small fetch, this could be due to the different formulation of the wave period. Finally, the

  13. Transient and 2-Dimensional Shear-Wave Elastography Provide Comparable Assessment of Alcoholic Liver Fibrosis and Cirrhosis

    DEFF Research Database (Denmark)

    Thiele, Maja; Detlefsen, Sönke; Møller, Linda Maria Sevelsted

    2016-01-01

    BACKGROUND & AIMS: Alcohol abuse causes half of all deaths from cirrhosis in the West, but few tools are available for noninvasive diagnosis of alcoholic liver disease. We evaluated 2 elastography techniques for diagnosis of alcoholic fibrosis and cirrhosis; liver biopsy with Ishak score...... and collagen-proportionate area were used as reference. METHODS: We performed a prospective study of 199 consecutive patients with ongoing or prior alcohol abuse, but without known liver disease. One group of patients had a high pretest probability of cirrhosis because they were identified at hospital liver...... clinics (in Southern Denmark). The second, lower-risk group, was recruited from municipal alcohol rehabilitation centers and the Danish national public health portal. All subjects underwent same-day transient elastography (FibroScan), 2-dimensional shear wave elastography (Supersonic Aixplorer), and liver...

  14. Assessment of the mechanical properties of the muscle-tendon unit by supersonic shear wave imaging elastography: a review

    Directory of Open Access Journals (Sweden)

    Kelly Mônica Marinho e Lima

    2018-01-01

    Full Text Available This review aimed to describe the state of the art in muscle-tendon unit (MTU assessment by supersonic shear wave imaging (SSI elastography in states of muscle contraction and stretching, during aging, and in response to injury and therapeutic interventions. A consensus exists that MTU elasticity increases during passive stretching or contraction, and decreases after static stretching, electrostimulation, massage, and dry needling. There is currently no agreement regarding changes in the MTU due to aging and injury. Currently, the application of SSI for the purpose of diagnosis, rehabilitation, and physical training remains limited by a number of issues, including the lack of normative value ranges, the lack of consensus regarding the appropriate terminology, and an inadequate understanding of the main technical limitations of this novel technology.

  15. Continuous monitoring of shear wave velocity at the Montevecchio earthflow (Forlì-Cesena Province, Northern Apennines)

    Science.gov (United States)

    Bertello, Lara; Berti, Matteo; Castellaro, Silvia

    2016-04-01

    The Montevecchio landslide is located about 20 km to the south - west of Cesena (Northern Italy). The landslide has a length of nearly 700 m, a maximum width of 50 m in the accumulation zone and the depth of the slip surface is around 10 m. This landslide was triggered several times in the last few years. At first on the 1th of February 2014 and at the end of February 2014 some remedial works started. From February to May 2014, the velocity of the landslide was around meters/day. At the end of May 2014, two monitoring systems were installed in the main track of the earthflow channel. The System 1 consists of a rain gauge, a pressure sensor at the depth of 1 meter, a time-lapse camera Brinno (taking photos every 30 minutes), a laser system and four geophones at 4.5Hz with a spacing of 2 meters. The System 2 consists of three GPS rover placed in the earthflow channel and the master station outside the landslide. During the 2015, the Montevecchio earth flow reactivated three times. The last reactivation was during the night between the 24th and the 25th of May. Analyzing the data acquired from the geophones, the trend of the shear wave velocity over time was detected. The data correspond to an acquisition of the ambient seismic noise (passive mode) with a sampling frequency of 300 Hz for 2min every hours and all them are collected in a Flash Memory Drive. A drop in Vs is found from the 21th-22th of May, in correspondence with a rainfall event. The video collected by the time-lapse camera shows that the landslide started to move downslope with a velocity of about 10 cm/d. Before this rainfall, the landslide was moving at a very low speed (less than 1 cm/day) and shear wave velocities were relatively high. The displacement rate increased on the 27th of May after the second rainfall event (30 mm/d) and reached the value of 10 m/day. The velocity remained apparently constant for several days, but we should consider that the data collected from the 27th of May to the 1th

  16. Double layer anisotropy beneath the New Madrid seismic zone and adjacent areas: insights from teleseismic shear wave splitting

    Directory of Open Access Journals (Sweden)

    Moikwathai Dax Moidaki

    2014-02-01

    Full Text Available A total of 93 well-defined PKS, 54 SKKS, and 126 SKS shear-wave splitting parameters are determined at 25 broadband seismic stations in an approximately 1000 by 1000 km2 area centered at the New Madrid seismic zone (NMSZ in order to test the existence of two anisotropic layers and to map the direction and strength of mantle fabrics. The individual splitting parameters suggest a significant and systematic spatial and azimuthal variation in the splitting parameters. The azimuthal variations at most stations can be explained as the results of present SW ward asthenospheric flow and NNE trending lithospheric fabrics formed during past orogenic events. In the NMSZ, rift-parallel fast directions (potentially related to a long-rift flow and rift-orthogonal fast directions from small-scale mantle convection are not observed. In addition, reduction in splitting times as a result of vertical asthenospheric flow is not observed.

  17. Mean flow stability wave models for coherent structures in open shear flows: experimental assessment of potentials and limitations

    Science.gov (United States)

    Oberleithner, Kilian; Rukes, Lothar; Paschereit, Oliver; Soria, Julio

    2014-11-01

    We report on a number of experimental and theoretical investigations of shear flow instabilities in jet flows. In these studies, linear stability analysis is employed to the time-averaged flow taken from experiments, contrasting the ``classic'' stability approach that is based on a stationary base flow. The eigenmodes of the time-averaged flow are considered as models for the nonlinearly saturated state of the instability waves. The accuracy of these models is validated through a detailed comparison with experiments. In this talk we outline the potential and limitation of these flow models for convectively and globally unstable jet flows. The first author was supported by a fellowship within the Postdoc-Program of the German Academic Exchange Service (DAAD). The support of the Australian Research Council (ARC) and the German Research Foundation (DFG) is greatfully acknowledged.

  18. Estimation of liquid properties by inverse problem analysis based on shear horizontal surface acoustic wave sensor responses

    Science.gov (United States)

    Ueda, Kento; Kondoh, Jun

    2017-07-01

    A shear horizontal surface acoustic wave (SH-SAW) sensor can detect liquid properties, such as viscosity, density, permittivity, and conductivity. The advantage of using the SH-SAW sensors is the simultaneous detection of the mechanical and electrical properties of liquids. In this paper, we proposed a method of estimating the density and viscosity of liquids based on the inverse problem analysis. Glycerol or ethanol aqueous solutions were measured. The estimated and literature values were compared. For glycerol aqueous solutions, when the concentration is low, those values agree well. However, when the concentration is high, those values did not agree because the bulk modulus of glycerin solutions cannot be assumed as constant. On the other hand, as the bulk modulus of ethanol aqueous solutions can be assumed to be the same as that of water, the deviations between those values were small. Therefore, the proposed method is effective when the bulk modulus is assumed as constant.

  19. Influence of sex hormones in women on breast elasticity measured by shear wave sonoelastography--a cross-sectional study.

    Science.gov (United States)

    Rzymski, Pawel Tomasz; Wilczak, Maciej; Opala, Tomasz

    2012-01-01

    The physiology of breast depends on age, hormonal status, menstrual cycle, lactation, and others. The aim of our study was to evaluate correlations between hormonal status and breast glandular and fat tissue elasticity in healthy women. We examined 77 women aged 20-55 with shear wave sonoelastography and estimated their hormonal levels. There were no important correlations between breast elasticity, follicle-stimulating hormone (FSH), estrogen, prolactine, and thyroid hormones (p > 0.05). Androgens negatively influenced glandular to fat elasticity ratio (Rs = -0.25, p elasticity, especially in outer-upper quadrant (Rs = 0.24, p = 0.003).

  20. Role of shear-wave elastography (SWE) in complex cystic and solid breast lesions in comparison with conventional ultrasound.

    Science.gov (United States)

    Lee, Bo Eun; Chung, Jin; Cha, Eun-Suk; Lee, Jee Eun; Kim, Jeoung Hyun

    2015-07-01

    To evaluate the additional role of shear-wave elastography (SWE) in differential diagnosis of complex cystic and solid breast lesions. From January 2013 to November 2013, 140 complex cystic and solid breast lesions from 139 consecutive patients were performed ultrasound and SWE prior to biopsy. BI-RADS ultrasound final assessment and SWE parameters were recorded for each lesion. Histopathologic diagnosis was used as the reference standard. Among the 140 lesions, 30 lesions (21.4%) were malignant. The mean maximum elasticity (Emax) of malignant lesions (184.3 kPa) was significantly higher than that of benign lesions (45.5 kPa) (Pelasticity and color pattern were significantly different from malignancy and benign lesions (Pbreast lesions. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  1. Development of site class and site coefficient maps of Semarang, Indonesia using field shear wave velocity data

    Directory of Open Access Journals (Sweden)

    Partono Windu

    2017-01-01

    Full Text Available The new Indonesian National Code for seismic resistance design (SNI-03-1726-2012 issued recently utilizes seismic response spectra for the whole area of the country. Site class and site coefficient are two parameters needed for designing response spectra. Site class can be estimated using average standard penetration test (N-SPT, average shear wave velocity (Vs and average un-drained shear strength (Su of top 30 meter soil deposit. Site coefficients can be predicted using probabilistic seismic hazard analysis (PSHA by implementing total probability theorem. To perform PSHA, Vs30 is a parameter needed for calculating ground motion at bedrock elevation. This paper presents the results of PSHA and site class analysis using Vs30 values estimated based on N-SPT results collected from 265 boring locations in Semarang. Seismic data in a radius of 500 km from Semarang were collected for PSHA. Site class and site coefficient maps are then developed for the whole study area.

  2. Lithospheric Shear Velocity Structure of South Island, New Zealand from Rayleigh Wave Tomography of Amphibious Array Data

    Science.gov (United States)

    Ball, J. S.; Sheehan, A. F.; Stachnik, J. C.; Lin, F. C.; Collins, J. A.

    2015-12-01

    We present the first 3D shear velocity model extending well offshore of New Zealand's South Island, imaging the lithosphere beneath Campbell and Challenger plateaus. Our model is constructed via linearized inversion of both teleseismic (18 -70 s period) and ambient noise-based (8 - 25 s period) Rayleigh wave dispersion measurements. We augment an array of 29 ocean-bottom instruments deployed off the South Island's east and west coasts in 2009-2010 with 28 New Zealand land-based seismometers. The ocean-bottom seismometers and 4 of the land seismometers were part of the Marine Observations of Anisotropy Near Aotearoa (MOANA) experiment, and the remaining land seismometers are from New Zealand's permanent GeoNet array. Major features of our shear wave velocity (Vs) model include a low-velocity (Vs<4.3km/s) body extending to at least 75km depth beneath the Banks and Otago peninsulas, a high-velocity (Vs~4.7km/s) upper mantle anomaly underlying the Southern Alps to a depth of 100km, and discontinuous lithospheric velocity structure between eastern and western Challenger Plateau. Using the 4.5km/s contour as a proxy for the lithosphere-asthenosphere boundary, our model suggests that the lithospheric thickness of Challenger Plateau is substantially greater than that of Campbell Plateau. The high-velocity anomaly we resolve beneath the central South Island exhibits strong spatial correlation with subcrustal earthquake hypocenters along the Alpine Fault (Boese et al., 2013). The ~400km-long low velocity zone we image beneath eastern South Island underlies Cenozoic volcanics and mantle-derived helium observations (Hoke et al., 2000) on the surface. The NE-trending low-velocity zone dividing Challenger Plateau in our model underlies a prominent magnetic discontinuity (Sutherland et al., 1999). The latter feature has been interpreted to represent a pre-Cretaceous crustal boundary, which our results suggest may involve the entire mantle lithosphere.

  3. Upper Mantle Fabrics of the Mongolian Central Asian Orogenic Belt: Observations and Inferences from Shear Wave Splitting Intensity Measurements

    Science.gov (United States)

    Russo, R. M.; Meltzer, A.; Stachnik, J. C.; Munkhuu, U.; Tsagaan, B.; Cui, Z.

    2016-12-01

    We present new results detailing upper mantle seismic anisotropy in the Mongolian portion of the diffuse zone of deformation related to the India-Asia collision. Our data derive from three temporary deployments of seismic stations, the Hangay Dome deployment, 72 stations operated in central Mongolia from 2012-2014); the Hövsgöl-Altai deployment of 26 stations around Lake Hövsgöl in northern Mongolia and 14 stations in the southwestern Mongolian Altai region, both deployed from 2014-2016; and the 20 stations of the French-Mongolian-Russian MOBAL Array deployment during 2003. These networks were deployed on lithosphere that is a collage of Precambrian microcontinents assembled by subduction and accretion during Neoproterozoic to Paleozoic. Currently, west-central Mongolia is cut by two active, generally ESE-striking sinistral strike slip fault zones, the Bulnay, in the north, and the Gobi-Altai, in the south. These faults root westward into a zone of diffuse extension, and the Bulnay fault zone and extensional Lake Hövsgöl are important active structures in the en echelon zone of extension and strike slip that includes Lake Baikal, to the north of the study region in Russia. These active structures form the southern boundary of the Siberian craton. Geodetic observations, in conjunction with the active tectonic structures mentioned, indicate that this part of Mongolia is currently undergoing eastward tectonic escape, presumably driven by the continent-continent collision to the south. The degree to which upper mantle structures beneath the study region reflect these Cenozoic tectonics - rather than older tectonics of continental assembly - is not well resolved, but can be assessed using shear wave splitting. Events suitable for this analysis (M > 5.9, of various backazimuths, epicentral distances of 87 - 150°) were well recorded at stations of all three temporary deployments. We will detail results of shear wave splitting intensity measurements and outline

  4. Effect of face fracturing on shear wave coda quality factor estimated from acoustic emission events

    CSIR Research Space (South Africa)

    Kgarume, T

    2013-10-01

    Full Text Available The dependency of the quality factor derived from S wave coda (Q(subc)) on frequency is analysed in order to understand the effect of fracturing ahead of a mining stope. Micro seismic events recorded using acoustic emission sensors in a mining...

  5. Generation of intermediately-long sea waves by weakly sheared winds

    CERN Document Server

    Chernyavski, V M; Golbraikh, E; Mond, M

    2010-01-01

    The present work concerns the numeric modeling of the sea-wave instability under the effect of the logarithmic-wind profile at hurricane conditions. Non-linear effects, such as wave breaking, foam production, etc. Powell et al. (2003), Shtemler et al. (2010) are ignored. The central point of the study is the calculation of the wave growth rate, which is proportional to the fractional input energy from the wind to the wave exponentially varied with time. The present modeling demonstrates that the Miles-type model applying Charnock's formula for roughness to the hurricane-wind parameters underestimates the growth rate from 5 to 40 times as compared with the model employing the roughness and friction velocity adopted from experimental data for hurricane winds.1 This occurs due to Charnock's formula fails at large wind speeds. The stability characteristics found on the base of the hurricane-wind experimental parameters are consistent with the other results of the observations. Obtained in the present study a maxi...

  6. Generation of intermediately-long sea waves by weakly sheared winds

    CERN Document Server

    Chernyavski, V M; Golbraikh, E; Mond, M

    2010-01-01

    The present work concerns the numeric modeling of the sea-wave instability under the effect of the logarithmic wind at hurricane conditions (ignoring non-linear effects, such as wave breaking, foam production, etc. Powell et al. (2003)^1, Shtemler et al. (2003)^2. The central point of the study is the calculation of the growth rate, which is proportional to the fractional input energy from the wind to the wave exponentially varied with time. The present modeling demonstrates that the Miles-type model applying Charnock's formula Charnock (1955)^3 for roughness to the hurricane -wind parameters underestimates the growth rate of the wind waves 5-40 times as compared with the model employing the roughness and friction velocity adopted from experimental data for hurricane winds.^1 This occurs due to Charnock's formula fails at large wind speeds. The stability characteristics obtained on the base of the hurricane-wind experimental parameters are self-consistent with the other results of the observations. A maximum ...

  7. Evaluation of healthy muscle tissue by strain and shear wave elastography – Dependency on depth and ROI position in relation to underlying bone

    DEFF Research Database (Denmark)

    Ewertsen, Caroline; Carlsen, Jonathan Frederik; Christiansen, Iben Riishede

    2016-01-01

    and methods: Ten healthy volunteers (five males and five females) had their biceps brachii, gastrocnemius, and quadriceps muscle examined with strain- and shear wave elastography at three different depths and in regions located above bone and beside bone. Strain ratios were averaged from cine-loops of 10 s...

  8. Study of the dynamic behavior of earthflows through the analysis of shear wave velocity in the landslide's body

    Science.gov (United States)

    Bertello, Lara

    2015-04-01

    Over the first year of my PhD, I carried out a literature search about earthflows features and dynamics and conducted periodic ReMi-MASW campaigns to assess the temporal variation of shear velocity for several landslides that were recently reactivated. Literature search was conducted to review recent works related to shear wave velocity as an indicator for rheological changes in clay materials (Mainsant et al., 2012). From January to August 2014 I carried out numerous ReMi-MASW surveys to characterize several active earthflows in the Emilia-Romagna Apennines. I did these measures both inside and outside the landslide's bodies, usually during the first ten days after the reactivation. At first, these measures indicate low shear waves velocity inside the landslide and high velocity outside. This is due to the different consistence of the materials, to the different water content and to the void index. Then I repeated the measures over time in the same places on the same landslide, in order to detect the variability of Vs over time in correlations with the landslide's movements. Periodic ReMi-MASW survey were conducted on the following landslides: • The Montevecchio (FC) earthflow was reactivated the 1th of February 2014 (estimated volume of 240.000 m³) and increased the movement's velocity around the 7th of February 2014, after intense precipitations. Analyzing the data collected inside the landslide's body, I observed an increase of Vs over time, due to the decrease of landslide velocity; • The Silla (BO) complex landslide reactivated the 10th of February 2014 (estimated volume of 900.000 m³), and moved downslope with a maximum velocity in the order of several m/hour. Studying the data, it is possible to notice how the Vs increase over time only in the lower portion of the landslide. In fact the upper portion is still active, so the Vs remained unchanged over time. • the Puzzola-Grizzana Morandi (BO) complex landslide. This landslide was reactivated the 10th

  9. Ultrasound shear wave elastography helps discriminate low-grade from high-grade bowel wall fibrosis in ex vivo human intestinal specimens.

    Science.gov (United States)

    Dillman, Jonathan R; Stidham, Ryan W; Higgins, Peter D R; Moons, David S; Johnson, Laura A; Keshavarzi, Nahid R; Rubin, Jonathan M

    2014-12-01

    To determine whether bowel wall fibrosis can be detected in freshly resected human intestinal specimens based on ultrasound-derived shear wave speed. Seventeen intact (>3-cm) bowel segments (15 small and 2 large intestine) from 12 patients with known or suspected inflammatory bowel disease were procured immediately after surgical resection. Ultrasound shear wave elastography of the bowel wall was performed by two methods (Virtual Touch Quantification [VTQ] and Virtual Touch-IQ [VT-IQ]; Siemens Medical Solutions USA, Inc, Mountain View, CA). Eighteen short-axis shear wave speed measurements were acquired from each specimen: 3 from the 9-, 12-, and 3-o'clock locations for each method. Imaging was performed in two areas for specimens greater than 10 cm in length (separated by ≥5 cm). A gastrointestinal pathologist scored correlative histologic slides for inflammation and fibrosis. Differences in mean shear wave speed between bowel segments with low and high inflammation/fibrosis scores were assessed by a Student t test. Receiver operating characteristic curve analysis was performed. High-fibrosis score (n = 11) bowel segments had a significantly greater mean shear wave speed than low-fibrosis score (n = 6) bowel segments (mean ± SD: VTQ, 1.59 ± 0.37 versus 1.18 ± 0.08 m/s; P= .004; VT-IQ, 1.87 ± 0.44 versus 1.50 ± 0.26 m/s; P= .049). There was no significant difference in mean shear wave speed between high-and low-inflammation score bowel segments (P > .05 for both VTQ and VT-IQ). Receiver operating characteristic curves showed areas under the curve of 0.91 (95% confidence interval, 0.67-0.99) for VTQ and 0.77 (95% confidence interval, 0.51-0.94) for VT-IQ in distinguishing low-from high-fibrosis score bowel segments. Ex vivo bowel wall shear wave speed measurements increase when transmural intestinal fibrosis is present. © 2013 by the American Institute of Ultrasound in Medicine.

  10. The Feasibility of Structural Health Monitoring Using the Fundamental Shear Horizontal Guided Wave in a Thin Aluminum Plate

    Directory of Open Access Journals (Sweden)

    Jorge Franklin Mansur Rodrigues Filho

    2017-05-01

    Full Text Available Structural health monitoring (SHM is emerging as an essential tool for constant monitoring of safety-critical engineering components. Ultrasonic guided waves stand out because of their ability to propagate over long distances and because they can offer good estimates of location, severity, and type of damage. The unique properties of the fundamental shear horizontal guided wave (SH0 mode have recently generated great interest among the SHM community. The aim of this paper is to demonstrate the feasibility of omnidirectional SH0 SHM in a thin aluminum plate using a three-transducer sparse array. Descriptions of the transducer, the finite element model, and the imaging algorithm are presented. The image localization maps show a good agreement between the simulations and experimental results. The SH0 SHM method proposed in this paper is shown to have a high resolution and to be able to locate defects within 5% of the true location. The short input signal as well the non-dispersive nature of SH0 leads to high resolution in the reconstructed images. The defect diameter estimated using the full width at half maximum was 10 mm or twice the size of the true diameter.

  11. The Feasibility of Structural Health Monitoring Using the Fundamental Shear Horizontal Guided Wave in a Thin Aluminum Plate.

    Science.gov (United States)

    Franklin Mansur Rodrigues Filho, Jorge; Tremblay, Nicolas; Soares da Fonseca, Gláucio; Belanger, Pierre

    2017-05-19

    Structural health monitoring (SHM) is emerging as an essential tool for constant monitoring of safety-critical engineering components. Ultrasonic guided waves stand out because of their ability to propagate over long distances and because they can offer good estimates of location, severity, and type of damage. The unique properties of the fundamental shear horizontal guided wave (SH₀) mode have recently generated great interest among the SHM community. The aim of this paper is to demonstrate the feasibility of omnidirectional SH₀ SHM in a thin aluminum plate using a three-transducer sparse array. Descriptions of the transducer, the finite element model, and the imaging algorithm are presented. The image localization maps show a good agreement between the simulations and experimental results. The SH₀ SHM method proposed in this paper is shown to have a high resolution and to be able to locate defects within 5% of the true location. The short input signal as well the non-dispersive nature of SH₀ leads to high resolution in the reconstructed images. The defect diameter estimated using the full width at half maximum was 10 mm or twice the size of the true diameter.

  12. Factors influencing breast elasticity measured by the ultrasound Shear Wave elastography ? preliminary results

    OpenAIRE

    Rzymski, Pawe?; Sk?rzewska, Agnieszka; Skibi?ska-Zieli?ska, Myriam; Opala, Tomasz

    2011-01-01

    Introduction Many physiological changes of breast elasticity depend on the age, hormonal status, menstrual cycle and many others. The aim of this study was to evaluate viscoelastic properties of normal breast tissues in a large group of women and to search for factors which play a role in its mechanical properties. Material and methods 101 women aged 18-74 years who underwent B-mode sonography and additionally sonoelastography. We measured viscoelasticity in 8 quadrants by a share wave ultras...

  13. Evaluation of healthy muscle tissue by strain and shear wave elastography - Dependency on depth and ROI position in relation to underlying bone.

    Science.gov (United States)

    Ewertsen, Caroline; Carlsen, Jonathan Frederik; Christiansen, Iben Riishede; Jensen, Jørgen Arendt; Nielsen, Michael Bachmann

    2016-09-01

    The aim of this study was to evaluate the influence of depth and underlying bone on strain ratios and shear wave speeds for three different muscles in healthy volunteers. For strain ratios the influence from different reference region-of-interest positions was also evaluated. Ten healthy volunteers (five males and five females) had their biceps brachii, gastrocnemius, and quadriceps muscle examined with strain- and shear wave elastography at three different depths and in regions located above bone and beside bone. Strain ratios were averaged from cine-loops of 10s length, and shear wave speeds were measured 10 times at each target point. The distance from the skin surface to the centre of each region-of-interest was measured. Measurements were evaluated with descriptive statistics and linear regression. Linear regression showed a significant influence on strain ratio measurements from the reference region-of-interest position, i.e. being above the same structures as the target region-of-interest or not (means: 1.65 and 0.78; (P<0.001)). For shear wave speeds, there was a significant influence from depth and location above or beside bone (P=0.011 and P=0.031). Strain ratio values depend significantly on reference and target region-of-interest being above the same tissue, for instance bone. Strain ratios were not influenced by depth in this study. Shear wave speeds decreased with increasing scanning depth and if there was bone below the region-of-interest. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Comparison of ultrasound B-mode, strain imaging, acoustic radiation force impulse displacement and shear wave velocity imaging using real time clinical breast images

    Science.gov (United States)

    Manickam, Kavitha; Machireddy, Ramasubba Reddy; Raghavan, Bagyam

    2016-04-01

    It has been observed that many pathological process increase the elastic modulus of soft tissue compared to normal. In order to image tissue stiffness using ultrasound, a mechanical compression is applied to tissues of interest and local tissue deformation is measured. Based on the mechanical excitation, ultrasound stiffness imaging methods are classified as compression or strain imaging which is based on external compression and Acoustic Radiation Force Impulse (ARFI) imaging which is based on force generated by focused ultrasound. When ultrasound is focused on tissue, shear wave is generated in lateral direction and shear wave velocity is proportional to stiffness of tissues. The work presented in this paper investigates strain elastography and ARFI imaging in clinical cancer diagnostics using real time patient data. Ultrasound B-mode imaging, strain imaging, ARFI displacement and ARFI shear wave velocity imaging were conducted on 50 patients (31 Benign and 23 malignant categories) using Siemens S2000 machine. True modulus contrast values were calculated from the measured shear wave velocities. For ultrasound B-mode, ARFI displacement imaging and strain imaging, observed image contrast and Contrast to Noise Ratio were calculated for benign and malignant cancers. Observed contrast values were compared based on the true modulus contrast values calculated from shear wave velocity imaging. In addition to that, student unpaired t-test was conducted for all the four techniques and box plots are presented. Results show that, strain imaging is better for malignant cancers whereas ARFI imaging is superior than strain imaging and B-mode for benign lesions representations.

  15. Shear wave velocity structure in the lithosphere and asthenosphere across the Southern California continent and Pacific plate margin using inversion of Rayleigh wave data from the ALBACORE project.

    Science.gov (United States)

    Price, A. C.; Weeraratne, D. S.; Kohler, M. D.; Rathnayaka, S.; Escobar, L., Sr.

    2015-12-01

    The North American and Pacific plate boundary is a unique example of past subduction of an oceanic spreading center which has involved oceanic plate capture and inception of a continental transform boundary that juxtaposes continental and oceanic lithosphere on a single plate. The amphibious ALBACORE seismic project (Asthenospheric and Lithospheric Broadband Architecture from the California Offshore Region Experiment) deployed 34 ocean bottom seismometers (OBS) on 15-35 Ma seafloor and offers a unique opportunity to compare the LAB in continental and oceanic lithosphere in one seismic study. Rayleigh waves were recorded simultaneously by our offshore array and 82 CISN network land stations from 2010-2011. Here we predict phase velocities for a starting shear wave velocity model for each of 5 regions in our study area and compare to observed phase velocities from our array in a least-squares sense that produces the best fit 1-D shear wave velocity structure for each region. Preliminary results for the deep ocean (seafloor 25-32 Ma) indicates high velocities reaching 4.5 km/s at depths of 50 km associated with the lithosphere for seafloor 25-32 Ma. A negative velocity gradient is observed below this which reaches a minimum of 4.0 km/s at 160 km depth. The mid-ocean region (age 13-25 Ma) indicates a slightly lower magnitude and shallower LVZ. The Inner Borderland displays the highest lithospheric velocities offshore reaching 4.8 km/s at 40 km depth indicating underplating. The base of the LVZ in the Borderland increases sharply from 4.0 km/s to 4.5 km/s at 80-150 km depth indicating partial melt and compositional changes. The LVZ displays a very gradual positive velocity gradient in all other regions such as the deep seafloor and continent reaching 4.5 km/s at 300 km depth. The deep ocean, Borderlands, and continental region each have unique lithospheric velocities, LAB depths, and LVZ character that indicate stark differences in mantle structure that occur on a

  16. Shear-wave velocity model from Rayleigh wave group velocities centered on the Sacramento/San Joaquin Delta

    Science.gov (United States)

    Fletcher, Jon Peter B.; Erdem, Jemile

    2017-01-01

    Rayleigh wave group velocities obtained from ambient noise tomography are inverted for an upper crustal model of the Central Valley, California, centered on the Sacramento/San Joaquin Delta. Two methods were tried; the first uses SURF96, a least-squares routine. It provides a good fit to the data, but convergence is dependent on the starting model. The second uses a genetic algorithm, whose starting model is random. This method was tried at several nodes in the model and compared to the output from SURF96. The genetic code is run five times and the variance of the output of all five models can be used to obtain an estimate of error. SURF96 produces a more regular solution mostly because it is typically run with a smoothing constraint. Models from the genetic code are generally consistent with the SURF96 code sometimes producing lower velocities at depth. The full model, calculated using SURF96, employed a 2-pass strategy, which used a variable damping scheme in the first pass. The resulting model shows low velocities near the surface in the Central Valley with a broad asymmetrical sedimentary basin located close to the western edge of the Central Valley near 122°W longitude. At shallow depths the Rio Vista Basin is found nestled between the Pittsburgh/Kirby Hills and Midland faults, but a significant basin also seems to exist to the west of the Kirby Hills fault. There are other possible correlations between fast and slow velocities in the Central Valley and geologic features such as the Stockton Arch, oil or gas producing regions and the fault-controlled western boundary of the Central Valley.

  17. Evaluation of the optic nerve using strain and shear wave elastography in patients with multiple sclerosis and healthy subjects.

    Science.gov (United States)

    İnal, Mikail; Tan, Sinan; Yumusak, Erhan M; Şahan, Mehmet Hamdi; Alpua, Murat; Örnek, Kemal

    2017-01-31

    Our aim was to evaluate the elasticity features of the optic nerve using strain (SE) and shear wave elastography (SWE) in multiple sclerosis (MS) patients in comparison with healthy subjects. One hundred and seven optic nerves from 54 MS patients and 118 optic nerves from 59 healthy subjects were examined prospectively by SE and SWE. Optic nerves were divided into three types in accordance to the elasticity designs, as follows: type 1 predominantly blue (hardest tissue); type 2 predominantly blue/green (hard tissue); and type 3 predominantly green (intermediate tissue). Quantitative measurements of optic nerve hardness with SWE were analyzed in kilopascals. Elastographic images from healthy volunteers showed mostly type 3 optic nerves (61.9%); type 2 was also found (38.1%), but type 1 was not observed. Elastographic examination of MS patients showed mostly type 2 optic nerves (88%), while some type 1 (4.6%) and type 3 optic nerves (6.5%) were rarely observed. There was a statistically significant difference in terms of elasticity patterns between patients and healthy volunteers (p<0.001). Statistically significant differences were observed between patients and healthy volunteers in the analysis of SWE values (10.381±3.48 kPa and 33.87±11.64 p<0.001). The receiver operating characteristic curve analysis was perfect (0.993; 95% confidence interval [CI]=0.971-0.999), and a cut-off value of 18.3 kPa shear had very high sensitivity and specificity for the patient group. No significant differences were observed between patients with and without previous optic neuritis. SE and SWE examination findings concerning the optic nerve in MS patients demonstrated remarkable differences according to the healthy group.

  18. Shear velocity model for the westernmost Mediterranean from ambient noise and ballistic finite-frequency Rayleigh wave tomography

    Science.gov (United States)

    Palomeras, I.; Villasenor, A.; Thurner, S.; Levander, A.; Gallart, J.; Harnafi, M.

    2014-12-01

    The westernmost Mediterranean comprises the Iberian Peninsula and Morocco, separated by the Alboran Sea and the Algerian Basin. From north to south this region consists of the Pyrenees, resulting from Iberia-Eurasia collision; the Iberian Massif, which has been undeformed since the end of the Paleozoic; the Central System and Iberian Chain, regions with intracontinental Oligocene-Miocene deformation; the Gibraltar Arc (Betics, Rif and Alboran terranes), resulting from post-Oligocene subduction roll-back; and the Atlas Mountains. We analyzed data from recent broad-band array deployments and permanent stations in the area (IberArray and Siberia arrays, the PICASSO array, the University of Munster array, and the Spanish, Portuguese and Moroccan National Networks) to characterize its lithospheric structure. The combined array of 350 stations has an average interstation spacing of ~60 km. We calculated the Rayleigh waves phase velocities from ambient noise (periods 4 to 40 s) and teleseismic events (periods 20 to 167 s). We inverted the phase velocities to obtain a shear velocity model for the lithosphere to ~200 km depth. Our results correlate well with the surface expression of the main structural units with higher crustal velocity for the Iberian Massif than for the Alpine Iberia and Atlas Mountains. The Gibraltar Arc has lower crustal shear velocities than the regional average at all crustal depths. It also shows an arc shaped anomaly with high upper mantle velocities (>4.6 km/s) at shallow depths (<65 km) interpreted as the subducting Alboran slab. The hanging slab is depressing the crust of the Gibraltar arc to ~55 km depth, as seen in receiver function data and active source seismic profiles. Low upper mantle velocities (<4.2 km/s) are observed beneath the Atlas, the northeastern end of the Betic Mountains and the Late Cenozoic volcanic fields in Iberia and Morocco, indicative of high temperatures at relatively shallow depths, and suggesting that the lithosphere

  19. Factors influencing breast elasticity measured by the ultrasound Shear Wave elastography – preliminary results

    Science.gov (United States)

    Rzymski, Paweł; Skórzewska, Agnieszka; Skibińska-Zielińska, Myriam; Opala, Tomasz

    2011-01-01

    Introduction Many physiological changes of breast elasticity depend on the age, hormonal status, menstrual cycle and many others. The aim of this study was to evaluate viscoelastic properties of normal breast tissues in a large group of women and to search for factors which play a role in its mechanical properties. Material and methods 101 women aged 18-74 years who underwent B-mode sonography and additionally sonoelastography. We measured viscoelasticity in 8 quadrants by a share wave ultrasonic device estimating Young modules in regions of interest. Results Mean elasticity measured in all 8 scans in glandular and fatty tissue were 11.28 ±5.79 kPa (0.1-46.26 kPa) and 9.24 ±4.48 kPa (0.1-29.78 kPa), respectively. The correlation between age and mean elasticity of glandular tissue was Rs = 0.27 (p = 0.007). The correlation between glandular tissue elasticity heterogeneity and breast mastalgia measured by VAS was Rs = –0.23 (p = 0.241). Fat tissue elasticity correlated with duration of lactation was Rs = 0.21 (p = 0.01). Conclusions There are several parameters influencing breast viscoelasticity measured by share wave sonoelastography. Glandular tissue elasticity correlates positively with age, fatty tissue elasticity correlates positively with duration of lactation and heterogeneity of the elasticity map of glandular tissue correlates with breast pain and fat tissue with BMI. PMID:22291745

  20. Factors influencing breast elasticity measured by the ultrasound Shear Wave elastography - preliminary results.

    Science.gov (United States)

    Rzymski, Paweł; Skórzewska, Agnieszka; Skibińska-Zielińska, Myriam; Opala, Tomasz

    2011-02-01

    Many physiological changes of breast elasticity depend on the age, hormonal status, menstrual cycle and many others. The aim of this study was to evaluate viscoelastic properties of normal breast tissues in a large group of women and to search for factors which play a role in its mechanical properties. 101 women aged 18-74 years who underwent B-mode sonography and additionally sonoelastography. We measured viscoelasticity in 8 quadrants by a share wave ultrasonic device estimating Young modules in regions of interest. Mean elasticity measured in all 8 scans in glandular and fatty tissue were 11.28 ±5.79 kPa (0.1-46.26 kPa) and 9.24 ±4.48 kPa (0.1-29.78 kPa), respectively. The correlation between age and mean elasticity of glandular tissue was Rs = 0.27 (p = 0.007). The correlation between glandular tissue elasticity heterogeneity and breast mastalgia measured by VAS was Rs = -0.23 (p = 0.241). Fat tissue elasticity correlated with duration of lactation was Rs = 0.21 (p = 0.01). There are several parameters influencing breast viscoelasticity measured by share wave sonoelastography. Glandular tissue elasticity correlates positively with age, fatty tissue elasticity correlates positively with duration of lactation and heterogeneity of the elasticity map of glandular tissue correlates with breast pain and fat tissue with BMI.

  1. Evaluation of Optic Nerve with Strain and Shear Wave Elastography in Patients with Behçet's Disease and Healthy Subjects.

    Science.gov (United States)

    Inal, Mikail; Tan, Sinan; Demirkan, Serkan; Burulday, Veysel; Gündüz, Özgür; Örnek, Kemal

    2017-07-01

    The objective of this study was to investigate the elasticity characteristics of the optic nerve using strain and shear wave elastography in patients with Behçet's disease and to compare the results with those of healthy volunteers. Forty-six optic nerves from patients with Behçet's disease and 54 optic nerves from healthy volunteers were investigated prospectively in this study using strain and shear wave elastography. There was a statistically significant difference in terms of elasticity patterns between patients and healthy volunteers (p < 0.001). Elastographic images of healthy volunteers revealed most optic nerves to be type 3 (51.8%); however, type 2 (40.7%) and type 1 (7.5%) were also observed. Elastographic examination of Behçet's disease patients revealed type 2 in 52.2%, type 1 in 43.5% and type 3 in 4.3% of patients. Statistically significant differences were observed between patients and healthy volunteers in the analysis of shear wave elastography values (p < 0.001). Receiver operating characteristic curve analysis was perfect (0.933) (95% CI = 0.885-0.980), and a cutoff value of 16.5 kPa shear had very high sensitivity and specificity for the patient group. Strain and shear wave elastography findings for the optic nerves of patients with Behçet's disease were significantly different from those for healthy volunteers. Copyright © 2017 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  2. Power Doppler Ultrasonography and Shear Wave Elastography as Complementary Imaging Methods for Suspected Local Breast Cancer Recurrence.

    Science.gov (United States)

    Jales, Rodrigo Menezes; Dória, Maira Teixeira; Serra, Kátia Piton; Miranda, Mila Meneguelli; Menossi, Carlos Alberto; Schumacher, Klaus; Sarian, Luis Otávio

    2017-12-04

    To prospectively investigate the diagnostic accuracy and clinical consequences of power Doppler morphologic criteria and shear wave elastography (SWE) as complementary imaging methods for evaluation of suspected local breast cancer recurrence in the ipsilateral breast or chest wall. Thirty-two breast masses with a suspicion of local breast cancer recurrence on B-mode ultrasonography underwent complementary power Doppler and SWE evaluations. Power Doppler morphologic criteria were classified as avascular, hypovascular, or hypervascular. Shear wave elastography was classified according to a 5-point scale (SWE score) and SWE maximum elasticity. Diagnostic accuracy was assessed by the sensitivity, specificity, and area under the curve. A decision curve analysis assessed clinical consequences of each method. The reference standard for diagnosis was defined as core needle or excisional biopsy. Histopathologic examinations revealed 9 (28.2%) benign and 23 (71.8%) malignant cases. Power Doppler ultrasonography (US) had sensitivity of 34.8% (95% confidence interval [CI], 6.6%-62.9%) and specificity of 45.4% (95% CI, 19.3%-71.5%). The SWE score (≥3) had sensitivity of 87.0% (95% CI, 66.4%-97.2%) and specificity of 44.4% (95% CI, 13.7%-78.8%). The SWE maximum elasticity (velocity > 6.5cm/s) had sensitivity of 87% (95% CI, 66.4%-97.2%) and specificity of 77.8% (95% CI, 40.0% to 97.2%). The areas under the curves for the SWE score and SWE maximum elasticity were 0.71 (95% CI, 0.53-0.87) and 0.82 (95% CI, 0.64-0.93), respectively (P = .32). Power Doppler US is unsuitable for discrimination between local breast cancer recurrence and fibrosis. Although the SWE score and SWE maximum elasticity can make this discrimination, the use of these methods to determine biopsy may lead to poorer clinical outcomes than the current practice of performing biopsies of all suspicious masses. © 2017 by the American Institute of Ultrasound in Medicine.

  3. Shear-wave elastography and immunohistochemical profiles in invasive breast cancer: Evaluation of maximum and mean elasticity values

    Energy Technology Data Exchange (ETDEWEB)

    Ganau, Sergi, E-mail: sganau@tauli.cat [Women' s Imaging Department, UDIAT-Centre Diagnòstic, Institut Universitari Parc Taulí – UAB, Parc Taulí, 1, 08205 Sabadell, Barcelona (Spain); Andreu, Francisco Javier, E-mail: xandreu@tauli.cat [Pathology Department, UDIAT-Centre Diagnòstic, Institut Universitari Parc Taulí – UAB, Parc Taulí, 1, 08205 Sabadell, Barcelona (Spain); Escribano, Fernanda, E-mail: fescribano@tauli.cat [Women' s Imaging Department, UDIAT-Centre Diagnòstic, Institut Universitari Parc Taulí – UAB, Parc Taulí, 1, 08205 Sabadell, Barcelona (Spain); Martín, Amaya, E-mail: amartino@tauli.cat [Women' s Imaging Department, UDIAT-Centre Diagnòstic, Institut Universitari Parc Taulí – UAB, Parc Taulí, 1, 08205 Sabadell, Barcelona (Spain); Tortajada, Lidia, E-mail: ltortajada@tauli.cat [Women' s Imaging Department, UDIAT-Centre Diagnòstic, Institut Universitari Parc Taulí – UAB, Parc Taulí, 1, 08205 Sabadell, Barcelona (Spain); Villajos, Maite, E-mail: mvillajos@tauli.cat [Women' s Imaging Department, UDIAT-Centre Diagnòstic, Institut Universitari Parc Taulí – UAB, Parc Taulí, 1, 08205 Sabadell, Barcelona (Spain); and others

    2015-04-15

    Highlights: •Shear wave elastography provides a quantitative assessment of the hardness of breast lesions. •The hardness of breast lesions correlates with lesion size: larger lesions are harder than smaller ones. •Histologic type and grade do not correlate clearly with elastography parameters. •HER2, luminal B HER2+, and triple-negative tumors have lower maximum hardness and mean hardness than other tumor types. •Half the tumors classified as BI-RADS 3 were luminal A and half were HER2. -- Abstract: Purpose: To evaluate the correlations of maximum stiffness (Emax) and mean stiffness (Emean) of invasive carcinomas on shear-wave elastography (SWE) with St. Gallen consensus tumor phenotypes. Methods: We used an ultrasound system with SWE capabilities to prospectively study 190 women with 216 histologically confirmed invasive breast cancers. We obtained one elastogram for each lesion. We correlated Emax and Emean with tumor size, histologic type and grade, estrogen and progesterone receptors, HER2 expression, the Ki67 proliferation index, and the five St. Gallen molecular subtypes: luminal A, luminal B without HER2 overexpression (luminal B HER2−), luminal B with HER2 overexpression (luminal B HER2+), HER2, and triple negative. Results: Lesions larger than 20 mm had significantly higher Emax (148.04 kPa) and Emean (118.32 kPa) (P = 0.005) than smaller lesions. We found no statistically significant correlations between elasticity parameters and histologic type and grade or molecular subtypes, although tumors with HER2 overexpression regardless whether they expressed hormone receptors (luminal B HER2+ and HER2 phenotypes) and triple-negative tumors had lower Emax and Emean than the others. We assessed the B-mode ultrasound findings of the lesions with some of the Emax or Emean values less than or equal to 80 kPa; only four of these had ultrasound findings suggestive of a benign lesion (two with luminal A phenotype and two with HER2 phenotype). Conclusions: We

  4. NA-SWS-2.1: An Updated Uniform Database of Teleseismic Shear-wave Splitting Measurements for North America

    Science.gov (United States)

    Refayee, H. A.; Liu, K.; Ray, M. A.; Purevsuren, U.; Gao, S. S.

    2011-12-01

    This updated version of shear wave splitting database for North America contains about 17000 pairs of XKS (including SKS, SKKS, and PKS) splitting parameters. The data used to generate the database were recorded by about 1800 digital broadband seismic stations over the period of 1980-2010. Those represent all the available data from both permanent and portable seismic networks at the IRIS Data Management Center. The data set was produced by following the same automated batch processing and the manual screening and ranking techniques used to create the first version of the uniform shear-wave splitting database for North America, NA-SWS1.1 (Liu, 2009, G-cubed). About 50% of the measurements were from USArray TA stations located west of 94 degree west. Approximately 12000 of the measurements were from the SKS phase, 3000 the SKKS, and 2000 the PKS phase. This study revealed several new first-order features, and enhanced some features that were previously observed in the first version of the database and/or by previous studies. These include the circular pattern of fast polarization directions in the Great Basin and in the vicinity of the San Andreas Fault in southern California. Outside the area with the circular pattern, the fast directions are dominantly parallel to the Absolute Plate Motion (APM) direction of the North American Plate, suggesting an asthenospheric origin of most of the observed anisotropy. However, inconsistency between the fast direction and the APM directions exists in a number of regions such as the southwestern US, the Black Hills region, the Snake River valley/Yellowstone area, Colorado Plateau, and the vicinity of the Rio Grande rift. Such variations reflect either lithospheric contribution to the observed anisotropy or local change in asthenospheric flow direction. Systematic spatial variation in splitting times is also evident, mostly due to the strength and depth of the mantle flow field. In particular, the average splitting time is about 1

  5. Cut-off frequencies of circumferential horizontal shear waves in various functionally graded cylinder shells.

    Science.gov (United States)

    Shen, Xiaoqin; Ren, Dawei; Cao, Xiaoshan; Wang, Ji

    2017-11-06

    In this study, cut-off frequencies of the circumferential SH waves in functionally graded piezoelectric-piezomagnetic material (FGPPM) cylinder shells with traction free, electrical and magnetic open boundary conditions are investigated analytically. The Wentzel-Kramers-Brillouin (WKB) method is employed for solving differential equations with variable coefficients for general cases. For comparison, Bessel functions and Kummer functions are used for solving cut-off frequency problems in homogenous and ideal FGPPM cylinder shells. It is shown that the WKB solution for the cut-off frequencies has good precise. The set of cut-off frequencies is a series of approximate arithmetic progressions, for which the difference is a function of the density and the effective elastic parameter. The relationship between the difference and the gradient coefficient is described. These results provide theoretical guidance for the non-destructive evaluation of curved shells based on the cut-off frequencies. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Velocity autocorrelation function in supercooled liquids: Long-time tails and anomalous shear-wave propagation.

    Science.gov (United States)

    Peng, H L; Schober, H R; Voigtmann, Th

    2016-12-01

    Molecular dynamic simulations are performed to reveal the long-time behavior of the velocity autocorrelation function (VAF) by utilizing the finite-size effect in a Lennard-Jones binary mixture. Whereas in normal liquids the classical positive t^{-3/2} long-time tail is observed, we find in supercooled liquids a negative tail. It is strongly influenced by the transfer of the transverse current wave across the period boundary. The t^{-5/2} decay of the negative long-time tail is confirmed in the spectrum of VAF. Modeling the long-time transverse current within a generalized Maxwell model, we reproduce the negative long-time tail of the VAF, but with a slower algebraic t^{-2} decay.

  7. Detection of bioagents using a shear horizontal surface acoustic wave biosensor

    Energy Technology Data Exchange (ETDEWEB)

    Larson, Richard S; Hjelle, Brian; Hall, Pam R; Brown, David C; Bisoffi, Marco; Brozik, Susan M; Branch, Darren W; Edwards, Thayne L; Wheeler, David

    2014-04-29

    A biosensor combining the sensitivity of surface acoustic waves (SAW) generated at a frequency of 325 MHz with the specificity provided by antibodies and other ligands for the detection of viral agents. In a preferred embodiment, a lithium tantalate based SAW transducer with silicon dioxide waveguide sensor platform featuring three test and one reference delay lines was used to adsorb antibodies directed against Coxsackie virus B4 or the negative-stranded category A bioagent Sin Nombre virus (SNV). Rapid detection of increasing concentrations of viral particles was linear over a range of order of magnitude for both viruses, and the sensor's selectivity for its target was not compromised by the presence of confounding Herpes Simplex virus type 1 The biosensor was able to delect SNV at doses lower than the load of virus typically found in a human patient suffering from hantavirus cardiopulmonary syndrome (HCPS).

  8. c-Axis zig-zag ZnO film ultrasonic transducers for designing longitudinal and shear wave resonant frequencies and modes.

    Science.gov (United States)

    Yanagitani, Takahiko; Morisato, Naoki; Takayanagi, Shinji; Matsukawa, Mami; Watanabe, Yoshiaki

    2011-05-01

    A method for designing frequencies and modes in ultrasonic transducers above the very-high-frequency (VHF) range is required for ultrasonic non-destructive evaluation and acoustic mass sensors. To obtain the desired longitudinal and shear wave conversion loss characteristics in the transducer, we propose the use of a c-axis zig-zag structure consisting of multilayered c-axis 23° tilted ZnO piezoelectric films. In this structure, every layer has the same thickness, and the c-axis tilt directions in odd and even layers are symmetric with respect to the film surface normal. c-axis zig-zag crystal growth was achieved by using a SiO(2) low-temperature buffer layer. The frequency characteristics of the multilayered transducer were predicted using a transmission line model based on Mason's equivalent circuit. We experimentally demonstrated two types of transducers: those exciting longitudinal and shear waves simultaneously at the same frequency, and those exciting shear waves with suppressed longitudinal waves.

  9. Ultrasound Shear Wave Elastography for Liver Disease. A Critical Appraisal of the Many Actors on the Stage.

    Science.gov (United States)

    Piscaglia, F; Salvatore, V; Mulazzani, L; Cantisani, V; Schiavone, C

    2016-02-01

    In the last 12 - 18 months nearly all ultrasound manufacturers have arrived to implement ultrasound shear wave elastography modality in their equipment for the assessment of chronic liver disease; the few remaining players are expected to follow in 2016.When all manufacturers rush to a new technology at the same time, it is evident that the clinical demand for this information is of utmost value. Around 1990, there was similar demand for color Doppler ultrasound; high demand for contrast-enhanced ultrasonography was evident at the beginning of this century, and around 2010 demand increased for strain elastography. However, some issues regarding the new shear wave ultrasound technologies must be noted to avoid misuse of the resulting information for clinical decisions. As new articles are expected to appear in 2016 reporting the findings of the new technologies from various companies, we felt that the beginning of this year was the right time to present an appraisal of these issues. We likewise expect that in the meantime EFSUMB will release a new update of the existing guidelines 1 2.The first ultrasound elastography method became available 13 years ago in the form of transient elastography with Fibroscan(®) 3. It was the first technique providing non-invasive quantitive information about the stiffness of the liver and hence regarding the amount of fibrosis in chronic liver disease 3. The innovation was enormous, since a non-invasive modality was finally available to provide findings otherwise achievable only by liver biopsy. In fact, prior to ultrasound elastography, a combination of conventional and Doppler ultrasound parameters were utilized to inform the physician about the presence of cirrhosis and portal hypertension 4. However, skilled operators were required, reproducibility and diagnostic accuracy were suboptimal, and it was not possible to differentiate the pre-cirrhotic stages of fibrosis. All these limitations were substantially improved by

  10. Differential shear wave attenuation and its lateral variation in the North Atlantic region

    Science.gov (United States)

    Sheehan, Anne F.; Solomon, Sean C.

    1992-01-01

    A digital data base of over 150 seismograms and a spectral radio technique are used to measure SS-S differential attenuation in the North Atlantic region. Differential attenuation is positively correlated with SS-S travel time residual, and both differential attentuation and travel time residual decrease with increasing seafloor age. Models are developed for seismic Q in which lateral variations include contributions from the asthenospheric low-Q zone as well as from lithospheric cooling. The Q models obtained under this assumption are in good agreement with those obtained from surface wave studies and are therefore preferred over those models with lateral variations confined to the upper 125 km. Systematic long-wavelength (1000-7000 km) variations in differential attenuation, corrected for seafloor age, are evident along the axis of the Mid-Atlantic Ridge. These variations can be qualitatively correlated with long-wavelength variations in SS-S differential travel time residuals and are attributed to along-axis differences in upper mantle temperature.

  11. Upper Mantle Seismic Anisotropy Beneath West Antarctica from Shear Wave Splitting Analysis of POLENET/ANET Data

    Science.gov (United States)

    Accardo, N.; Wiens, D. A.; Hernandez, S.; Aster, R. C.; Nyblade, A.; Anandakrishnan, S.; Huerta, A. D.; Wilson, T. J.

    2011-12-01

    We constrain azimuthal anisotropy in the Antarctic upper mantle using shear wave splitting parameters obtained from teleseismic SKS, SKKS, and PKS phases recorded at 30 broad-band seismometers deployed in West Antarctica, and the Transantarctic Mountains as a part of POLENET/ANET. The first seismometers were deployed in late 2007 and additional seismometers were deployed in 2008 and 2009. The seismometers generally operate year-round using solar power, insulated boxes, and either rechargeable AGM or primary lithium batteries. We used an eigenvalue technique to linearize the rotated and shifted shear wave particle motions and determine the best splitting parameters. Robust windows around the individual phases were chosen using the Teanby cluster-analysis algorithm. We visually inspected all results and assigned a quality rating based on factors including signal-to-noise ratios, particle motions, and error contours. The best results for each station were then stacked to get an average splitting direction and delay time. The delay times range from 0.33 to 1.33 s, but generally average about 1 s. We conclude that the splitting results from anisotropy in the upper mantle, since the large splitting times cannot be accumulated in the relatively thin crust (20-30 km) of the region. Overall, fast directions in West Antarctica are at large angles to the direction of Antarctic absolute plate motion in either hotspot or no-net rotation frameworks, showing that the anisotropic fabric does not result from shear associated with the motion of Antarctica over the mantle. The West Antarctic fast directions are also much different than those found in East Antarctica by previous studies. We suggest that the East Antarctic splitting results from anisotropy frozen into the cold cratonic continental lithosphere, whereas West Antarctic splitting is related to Cenozoic tectonism. Stations within the West Antarctic Rift System (WARS), a region of Cenozoic extension, show fast directions

  12. Acoustic radiation force impulse induced strain elastography and point shear wave elastography for evaluation of thyroid nodules.

    Science.gov (United States)

    Huang, Xian; Guo, Le-Hang; Xu, Hui-Xiong; Gong, Xue-Hao; Liu, Bo-Ji; Xu, Jun-Mei; Zhang, Yi-Feng; Li, Xiao-Long; Li, Dan-Dan; Qu, Shen; Fang, Lin

    2015-01-01

    The aim of the study was to evaluate the diagnostic performance of acoustic radiation force impulse (ARFI) induced strain elastography (SE), point shear wave elastography (p-SWE), and their combined use in differentiating thyroid nodules. This retrospective study included 155 thyroid nodules (94 benign and 61 malignant) in 136 patients. Ultrasound, ARFI-induced SE and p-SWE were performed on each nodule. Receiver operating characteristic curve (ROC) analyses were performed to assess the diagnostic efficacy of ARFI-induced SE, p-SWE and their combined use to distinguish benign from malignant thyroid nodules with histological results used as the reference standard. The areas under the ROC for ARFI-induced SE, p-SWE, and their combined use were 0.828, 0.829, and 0.840, respectively (both P > 0.05). The specificity of ARFI-induced SE was higher than that of p-SWE as well as their combined use (both P 10 mm, there were no significant differences in sensitivity and NPV among the three methods in differentiating thyroid nodules (all P > 0.05). In conclusions, ARFI-induced SE and p-SWE are both valuable tools for detecting malignant thyroid nodules. The combined use of ARFI-induced SE and p-SWE improves the diagnostic sensitivity and NPV significantly whereas ARFI-induced SE alone achieves the highest specificity.

  13. Constraints on the tectonic evolution of the westernmost Mediterranean and northwestern Africa from shear wave splitting analysis

    Science.gov (United States)

    Miller, Meghan S.; Allam, Amir A.; Becker, Thorsten W.; Di Leo, Jeanette F.; Wookey, James

    2013-08-01

    The westernmost Mediterranean mantle and lithosphere have evolved into their current configuration due to complex interactions between the African and Eurasian plates. To help unravel the regional tectonics, we use new broadband seismic data across the Gibraltar arc and into southern Morocco to infer azimuthal seismic anisotropy and flow patterns for the upper mantle based on shear wave splitting analysis. A deep (>600 km) earthquake in April 2010 was recorded by the array and allowed us to compare 31 direct S measurements with 235 teleseismic SK(K)S events from 3 years of deployment. The patterns of apparent fast polarization orientations and delay times suggest three major tectonic domains when interpreted jointly with recent tomographic images of the subducted slab: (1) a subducted slab related toroidal flow domain centered upon the Alboran Sea and southern Spain, leading to complex splits, (2), a region where the west African craton deflects mantle flow in the Anti-Atlas and High Plateaux, and, (3), an intermediate domain across the central High Atlas. Across the axis of the mountain belt a coherent, regional maximum of delay times is observed for both S and SKS splitting measurements, with polarizations predominantly parallel to the strike. We interpret this as possible SW-NE channeling of mantle flow beneath the region with a thinned lithosphere and slow seismic velocities beneath the central High Atlas Mountains.

  14. Crustal seismic anisotropy beneath Shillong plateau - Assam valley in North East India: Shear-wave splitting analysis using local earthquakes

    Science.gov (United States)

    Sharma, Antara; Baruah, Santanu; Piccinini, Davide; Saikia, Sowrav; Phukan, Manoj K.; Chetia, Monisha; Kayal, J. R.

    2017-10-01

    We present crustal anisotropy estimates constrained by shear wave splitting (SWS) analysis using local earthquakes in the Shillong plateau and Assam valley area, North East India (NE India) region. Splitting parameters are determined using an automated cross-correlation (CC) method. We located 330 earthquakes recorded by 17 broadband seismic stations during 2001-2014 in the study area. Out of these 330 events, seismograms of 163 events are selected for the SWS analysis. Relatively small average delay times (0.039-0.084 s) indicate existence of moderate crack density in the crust below the study area. It is found that fast polarization directions vary from station to station depending on the regional stress system as well as geological conditions. The spatial pattern of crustal anisotropy in the area is controlled mostly by tectonic movement of the Indian plate towards NE. Presence of several E-W and N-S trending active faults in the area also play an important role on the observed pattern of crustal anisotropy.

  15. Female striated urogenital sphincter contraction measured by shear wave elastography during pelvic floor muscle activation: Proof of concept and validation.

    Science.gov (United States)

    Aljuraifani, Rafeef; Stafford, Ryan E; Hug, François; Hodges, Paul W

    2017-04-13

    Investigation of the function of the striated urogenital sphincter (SUS) is challenging because it is difficult to access and requires invasive measures. Ultrasound shear wave elastography (SWE) is a non-invasive real-time technique used to estimate tissue stiffness. As muscle stiffness can be used as an estimate of muscle force, SWE provides an opportunity to study contraction of the peri-urethral musculature. Validation of SWE to study SUS during functional tasks, such as pelvic floor muscle contractions, is required prior to application in clinical populations. Ten healthy females (34[5] years) participated. Stiffness in a region expected to contain the SUS was quantified using SWE at rest and during a pelvic floor muscle contractions performed at 10%, 25%, and 50% of maximal voluntary contraction (MVC). Two repetitions were performed for 10 s. During contraction, stiffness increased in the region of the SUS in all participants and at all contraction intensities. Multiple regions of increased stiffness were detected, with 95.8% of regions situated ventral to the mid-urethra within the anatomical area of the SUS. The increase in stiffness was greater for 50% MVC than both 10% and 25% MVC contraction intensities (P < 0.01). Stiffness increased within the anatomical region of the SUS during voluntary pelvic floor muscle contractions with predictable response to changes in contraction intensity. These observations support the potential for ultrasound SWE to study SUS function non-invasively. © 2017 Wiley Periodicals, Inc.

  16. Shear Wave Elastography May Add a New Dimension to Ultrasound Evaluation of Thyroid Nodules: Case Series with Comparative Evaluation

    Directory of Open Access Journals (Sweden)

    Rafal Z. Slapa

    2012-01-01

    Full Text Available Although elastography can enhance the differential diagnosis of thyroid nodules, its diagnostic performance is not ideal at present. Further improvements in the technique and creation of robust diagnostic criteria are necessary. The purpose of this study was to compare the usefulness of strain elastography and a new generation of elasticity imaging called supersonic shear wave elastography (SSWE in differential evaluation of thyroid nodules. Six thyroid nodules in 4 patients were studied. SSWE yielded 1 true-positive and 5 true-negative results. Strain elastography yielded 5 false-positive results and 1 false-negative result. A novel finding appreciated with SSWE, were punctate foci of increased stiffness corresponding to microcalcifications in 4 nodules, some not visible on B-mode ultrasound, as opposed to soft, colloid-inspissated areas visible on B-mode ultrasound in 2 nodules. This preliminary paper indicates that SSWE may outperform strain elastography in differentiation of thyroid nodules with regard to their stiffness. SSWE showed the possibility of differentiation of high echogenic foci into microcalcifications and inspissated colloid, adding a new dimension to thyroid elastography. Further multicenter large-scale studies of thyroid nodules evaluating different elastographic methods are warranted.

  17. Shear Wave Elastography for Assessment of Steatohepatitis and Hepatic Fibrosis in Rat Models of Non-Alcoholic Fatty Liver Disease.

    Science.gov (United States)

    Kang, Bo-Kyeong; Lee, Seung Soo; Cheong, Hyunhee; Hong, Seung Mo; Jang, Kiseok; Lee, Moon-Gyu

    2015-12-01

    The purpose of this study was to evaluate shear wave elastography (SWE) as a method for determining the severity of non-alcoholic fatty liver disease (NAFLD) and the stage of hepatic fibrosis, as well as the major determinants of liver elasticity among the various histologic and biomolecular changes associated with NAFLD. Rat NAFLD models with various degrees of NAFLD severity were created and imaged using SWE. The explanted livers were subjected to histopathologic evaluation and RNA expression analysis. Among the histologic and biomolecular findings, the fibrosis stage and the collagen RNA level were significant independent factors associated with liver elasticity (p non-alcoholic steatohepatitis (NASH) and in determining fibrosis stage, and the corresponding areas under the receiver operating characteristic curves were 0.963 and 0.927-0.997, respectively. In conclusion, SWE is a potential non-invasive method for the detection of NASH and staging of hepatic fibrosis in patients with NAFLD. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  18. Visually assessed colour overlay features in shear-wave elastography for breast masses: quantification and diagnostic performance.

    Science.gov (United States)

    Gweon, Hye Mi; Youk, Ji Hyun; Son, Eun Ju; Kim, Jeong-Ah

    2013-03-01

    To determine whether colour overlay features can be quantified by the standard deviation (SD) of the elasticity measured in shear-wave elastography (SWE) and to evaluate the diagnostic performance for breast masses. One hundred thirty-three breast lesions in 119 consecutive women who underwent SWE before US-guided core needle biopsy or surgical excision were analysed. SWE colour overlay features were assessed using two different colour overlay pattern classifications. Quantitative SD of the elasticity value was measured with the region of interest including the whole breast lesion. For the four-colour overlay pattern, the area under the ROC curve (Az) was 0.947; with a cutoff point between pattern 2 and 3, sensitivity and specificity were 94.4 % and 81.4 %. According to the homogeneity of the elasticity, the Az was 0.887; with a cutoff point between reasonably homogeneous and heterogeneous, sensitivity and specificity were 86.1 % and 82.5 %. For the SD of the elasticity, the Az was 0.944; with a cutoff point of 12.1, sensitivity and specificity were 88.9 % and 89.7 %. The colour overlay features showed significant correlations with the quantitative SD of the elasticity (P colour overlay features and the SD of the elasticity in SWE showed excellent diagnostic performance and showed good correlations between them.

  19. In Vivo Evaluation of the Biomechanical Properties of Optic Nerve and Peripapillary Structures by Ultrasonic Shear Wave Elastography in Glaucoma.

    Science.gov (United States)

    Dikici, Atilla Suleyman; Mihmanli, Ismail; Kilic, Fahrettin; Ozkok, Ahmet; Kuyumcu, Gokhan; Sultan, Pinar; Samanci, Cesur; Halit Yilmaz, Mehmet; Rafiee, Babak; Tamcelik, Nevbahar; Isik Hasiloglu, Zehra; Kantarci, Fatih

    2016-04-01

    Primary open-angle glaucoma is a multifactorial serious disease characterized by progressive retinal ganglion cell death and loss of visual field. The purposes of this study were to investigate shear wave elastography (SWE) use in the evaluation of the optic nerve (ON) and peripapillary structures, and to compare the findings between glaucomatous and control eyes. A case-controlled study, including 21 patients with primary open-angle glaucoma and 21 age-matched control subjects, was carried out. All of the participants had comprehensive ophthalmological exams that included corneal biomechanical measurements with ocular response analyzer. In vivo evaluation of the biomechanical properties of the ON and peripapillary structures were performed with SWE in all participants. The Kolmogorov-Smirnov test was used to analyze the normal distribution of data. Differences of parameters in ophthalmologic data and stiffness values of patients with and without glaucoma were evaluated using the Mann-Whitney U test. There were no statistically significant differences between the glaucoma and control groups in terms of age (P > 0.05) and gender (P > 0.05). Corneal hysteresis was lower in the glaucoma group (P glaucoma group (P glaucoma patients for each measured region (P biomechanical properties of the ON and peripapillary structures in vivo with SWE in glaucoma. We observed stiffer ON and peripapillary tissue in glaucomatous eyes, indicating that SWE claims new perspectives in the evaluation of ON and peripapillary structures in glaucoma disease.

  20. Shear-Wave Elastography: Could it be Helpful for the Diagnosis of Non-Mass-Like Breast Lesions?

    Science.gov (United States)

    Wang, Zhi Li; Li, Ye; Wan, Wen Bo; Li, Nan; Tang, Jie

    2017-01-01

    The goal of this study was to analyze the diagnostic performance of shear wave elastography (SWE) in differentiation of benign and malignant non-mass-like (NML) breast lesions. Three hundred sixteen consecutive breast lesions in 305 patients who have been scheduled for ultrasound (US)-guided core needle biopsy or vacuum-assisted biopsy or surgical excision between January 2013 and August 2013 were initially included in this study. Finally, 63 patients with 67 lesions classified as NML lesions comprised our study population. The features of SWE and its diagnostic performance in NML lesions were analyzed. Among the 67 NML lesions, 33 were malignant and 34 were benign. The maximum elastic modulus, mean elastic modulus, minimum elastic modulus, elastic modulus ratio and stiff rim sign of the malignant lesions were all significantly higher than those of benign lesions (p modulus and stiff rim sign got significantly higher diagnostic specificity and positive predictive value (PPV) than conventional US (p breast lesions. The combination of conventional US and SWE could reduce unnecessary benign biopsies of NML lesions. Copyright © 2016. Published by Elsevier Inc.

  1. Quantitative analysis of peri-tumor tissue elasticity based on shear-wave elastography for breast tumor classification.

    Science.gov (United States)

    Xiao, Yang; Zeng, Jie; Qian, Ming; Zheng, Rongqin; Zheng, Hairong

    2013-01-01

    For shear-wave elastography (SWE) images, the most common site of tumor-associated stiffness is generally in the surrounding stroma rather than the tumor itself. The aim of this study is to assess the value of the peri-tumor tissue elasticity in the classification of breast tumors. SWE images of 106 breast tumors (65 benign, 41 malignant) were collected from 82 consecutive patients. By applying the image processing method, 5 elastographic features of the peri-tumor area (elasticity modulus mean, maximum, standard deviation, hardness degree and elasticity ratio) were computed to represent peri-tumor tissue elasticity. B-mode Breast Imaging Reporting and Data System (BI-RADS) were used for comparing the diagnostic performances between the grayscale US and color SWE images. Histopathologic results were used as the reference standard. The t-test, point biserial correlation coefficient and receiver operating characteristic (ROC) curve analysis were performed for statistical analysis. As a result, the Az values (area under ROC curve) were 0.92, 0.95, 0.94, 0.91, and 0.98 for the classifiers using the five elastographic features respectively, and 0.91 for BI-RADS assessment. The results showed that the peri-tumor tissue elasticity could provide valuable information for breast tumor classification.

  2. Shear-wave elastography in invasive ductal carcinoma: correlation between quantitative maximum elasticity value and detailed pathological findings.

    Science.gov (United States)

    Cho, Eun Yoon; Ko, Eun Sook; Han, Boo-Kyung; Kim, Rock Bum; Cho, Sooyoun; Choi, Ji Soo; Hahn, Soo Yeon

    2016-05-01

    Further information is needed regarding whether histopathological characteristics affect breast tumor elasticity. To determine whether maximum elasticity values vary according to tumor-stroma ratio, dominant stroma type, or presence of fibrosis in invasive breast cancer. This study included 71 patients with invasive ductal carcinoma not otherwise specified (IDC NOS) who underwent breast shear-wave elastography (SWE). Maximum elasticity (Emax) values were retrospectively correlated with pathological findings that included tumor-stroma ratio, dominant stroma type (collagen, fibroblast, lymphocyte), and fibrosis. Multiple linear regression analysis was performed to determine variables independently associated with Emax. High histologic grade was significantly correlated with higher Emax (P = 0.042). Estrogen receptor and progesterone receptor expression negatively correlated with high elasticity values (P = 0.013 and P = 0.03, respectively). Breast cancers that exhibited higher cellularity demonstrated a greater level of stiffness that was not statistically significant (ρ = 0.153; P = 0.193). While dominant stroma type and fibrosis did not affect Emax (P = 0.197 and P = 0.598, respectively), lesion size was significantly associated with Emax (ρ = 0.474, P < 0.001). On multivariate analysis, only lesion size was significantly associated with Emax (P < 0.001). The composition of tumors did not affect their Emax. © The Foundation Acta Radiologica 2015.

  3. Correlation between insulin resistance and breast elasticity heterogeneity measured by shear wave elastography in premenopausal women – a pilot study

    Science.gov (United States)

    Rzymski, Pawel; Wysocki, Piotr J.; Kycler, Witold; Opala, Tomasz

    2011-01-01

    Introduction Recent studies have demonstrated a strong correlation between obesity, insulin resistance, increased insulin and insulin-like growth factor levels and the risk of breast cancer. Our study was aimed at exploring correlations between glucose, insulin, insulin resistance, obesity and quantitatively estimated breast elasticity in healthy women. Material and methods The pilot study included 37 premenopausal women aged 22-45 years who underwent B-mode sonography and real-time shear wave elastography. Blood was collected for fasting insulin and glucose, and HOMA insulin resistance index was calculated. Results The mean elasticity of glandular and fatty tissue measured in both breasts was 12.5 ±3.5 kPa and 10.9 ±3.7 kPa respectively. Insulin levels did not correlate with glandular tissue elasticity (Rs=–0.23, p=0.15), but nearly correlated with fat tissue elasticity (Rs=–0.30, p=0.06), in outer quadrants significantly (Rs=–0.38, p=0.02). Interestingly, a strong correlation of insulin and insulin resistance with elasticity heterogeneity was found in fatty tissue (Rs=–0.59, pelasticity also correlated with body mass index. Conclusions Insulin levels and insulin resistance correlate with breast fat tissue heterogeneity, but their role in breast pathology remains unclear. PMID:22328885

  4. Correlation between insulin resistance and breast elasticity heterogeneity measured by shear wave elastography in premenopausal women - a pilot study.

    Science.gov (United States)

    Rzymski, Pawel; Wysocki, Piotr J; Kycler, Witold; Opala, Tomasz

    2011-12-31

    Recent studies have demonstrated a strong correlation between obesity, insulin resistance, increased insulin and insulin-like growth factor levels and the risk of breast cancer. Our study was aimed at exploring correlations between glucose, insulin, insulin resistance, obesity and quantitatively estimated breast elasticity in healthy women. The pilot study included 37 premenopausal women aged 22-45 years who underwent B-mode sonography and real-time shear wave elastography. Blood was collected for fasting insulin and glucose, and HOMA insulin resistance index was calculated. The mean elasticity of glandular and fatty tissue measured in both breasts was 12.5 ±3.5 kPa and 10.9 ±3.7 kPa respectively. Insulin levels did not correlate with glandular tissue elasticity (Rs=-0.23, p=0.15), but nearly correlated with fat tissue elasticity (Rs=-0.30, p=0.06), in outer quadrants significantly (Rs=-0.38, p=0.02). Interestingly, a strong correlation of insulin and insulin resistance with elasticity heterogeneity was found in fatty tissue (Rs=-0.59, pelasticity also correlated with body mass index. Insulin levels and insulin resistance correlate with breast fat tissue heterogeneity, but their role in breast pathology remains unclear.

  5. Shear-wave elastography of invasive breast cancer: correlation between quantitative mean elasticity value and immunohistochemical profile.

    Science.gov (United States)

    Youk, Ji Hyun; Gweon, Hye Mi; Son, Eun Ju; Kim, Jeong-Ah; Jeong, Joon

    2013-02-01

    To compare the mean elasticity value, as measured by shear-wave elastography (SWE), with immunohistochemical profile of invasive breast cancer. This was an institutional review board-approved retrospective study, with a waiver of informed consent. A total of 166 invasive breast cancers in 152 women undergoing preoperative SWE and surgery were included. Quantitative mean elasticity values in kPa were measured for each lesion by using SWE. Medical records were reviewed to determine palpability, invasive size, lymphovascular invasion, histologic grade, and axillary lymph node status. Based on the immunohistochemical profiles, tumor subtypes were categorized as triple-negative (TN), luminal A and B, or human epidermal growth factor receptor 2-enriched cancer. The mean elasticity value was correlated with clinicopathological features using univariate regression models and multivariate linear regression analysis. Palpability (P elasticity value. For the immunohistochemical profiles and tumor subtypes, the estrogen receptor (P = 0.015), progesterone receptor (P = 0.002), Ki-67 (P = 0.009), and the TN (P = 0.009) tumor subtype were correlated with the mean elasticity value. Multivariate logistic regression analysis showed that the following variables were significantly associated with the mean elasticity value: palpable abnormality, histologic grade, and lymphovascular invasion. No immunohistochemical profile of the cancers was independently correlated with the mean elasticity value. For invasive breast cancers, clinicopathological features of poor prognosis showed higher mean elasticity values than those of good prognosis. However, the immunohistochemical profile showed no independent association with the mean elasticity value.

  6. Laboratory Measurement of Compressional and Shear Wave Speed in Polycrystalline sI and sII Gas Hydrates and Ice as Functions of Temperature and Pressure

    Science.gov (United States)

    Helgerud, M. B.; Waite, W. F.; Kirby, S. H.; Nur, A.

    2001-12-01

    We report on laboratory measurements of compressional and shear wave speeds in compacted, polycrystalline sI methane and sII methane-ethane hydrates and ice Ih. The hydrate samples were made from granulated ice warmed to 290 K in the presence of methane or methane-ethane gas at high pressure. The resulting porous gas hydrate samples were uniaxially compacted within the synthesis pressure vessel using a hydraulic ram with a moving piston and fixed end plug fitted with shear transducers. Once the samples were fully compacted, the temperature was cycled in steps from 258 to 288 K while the uniaxial pressure was held constant at 60 MPa. After temperature cycling was completed, the uniaxial pressure was varied between 30 and 90 MPa at 283, 273, 263 and 253 K. At the end of each experiment, the uniaxial pressure was slowly decreased to 1 atm at 253 K. Shear and compressional wave speed measurements were made throughout each experiment. For ice Ih, the sample was evacuated before compaction, the measurement temperature range was 253 to 268 K and the applied uniaxial pressure did not exceed 42 MPa. Analysis of the data produces several interesting observations. Among them are: 1) sI and sII gas hydrate resist compaction much more than ice. A pressure of 42 MPa fully compacted the ice sample at 268 K, but a pressure of 105 MPa had to be applied for several days (at temperatures of 253, 278 and 288 K) to fully compact the hydrate samples. 2) Wave speed increases at constant sample length strongly suggest grain to grain bonds form between adjacent ice or gas hydrate grains. The relative wave speed increases with time show this process is more efficient in ice samples, perhaps due to the higher mobility of water in ice's crystal lattice. 3) Within the pressure and temperature conditions studied, the wave speed based calculations of Poisson's ratio are 5 to 6% smaller in sI and sII gas hydrate than in ice. 4) Shear wave speed decreases with increasing uniaxial pressure in Ice

  7. Influence of coupling with shear horizontal surface acoustic wave on lateral propagation of Rayleigh surface acoustic wave on 128°YX-LiNbO3

    Science.gov (United States)

    Zhang, Benfeng; Han, Tao; Tang, Gongbin; Zhang, Qiaozhen; Omori, Tatsuya; Hashimoto, Ken-ya

    2017-07-01

    In this paper, we investigate the impact of the coupling with shear horizontal (SH) surface acoustic wave (SAW) on the propagation of Rayleigh SAW in periodic grating structures on 128°YX-LiNbO3. First, the frequency dispersion behavior with longitudinal and lateral wavenumbers of Rayleigh SAW is calculated using the finite element method (FEM) software COMSOL. It is shown that the coupling causes (1) the satellite stopband and (2) variation of the anisotropy factor. It is also shown these phenomena remain even when the electromechanical coupling factor of SH SAW is zero. Then, the extended thin plate model which can take coupling between two SAWs into account, is applied to simulate the result of FEM. Good agreement between these results indicated that the mechanical coupling is responsible for these two phenomena. Finally, including electrical excitation and detection, the model is applied to the infinitely long interdigital transducer (IDT) structure and the calculated result is compared with that obtained by the three-dimensional FEM. The excellent agreement of both results confirms the effectiveness of the extended thin plate model.

  8. Shear wave elastography using ultrasound: effects of anisotropy and stretch stress on a tissue phantom and in vivo reactive lymph nodes in the neck

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ha Young [Dept. of Radiology, University of Inha College of Medicine, Incheon (Korea, Republic of); Lee, Jeong Hyun; Shin, Ji Hoon; Kim, So Yeon; Shin, Hee Jung; Choi, Young Jun; Baek, Jung Hwa [Dept. of Radiology and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul (Korea, Republic of); Park, Jeong Seon [Dept. of Radiology, Hanyang University College of Medicine, Seoul (Korea, Republic of)

    2017-01-15

    The purpose of this study was to evaluate how the anisotropy and the static stretch stress of the cervical musculature influence the measured shear modulus in a tissue-mimicking phantom and in cervical lymph nodes in vivo by using shear wave elastography (SWE). SWE was performed on a phantom using a pig muscle and on the middle jugular cervical lymph nodes in six volunteers. Tissue elasticity was quantified using the shear modulus and a supersonic shear wave imaging technique. For the phantom study, first, the optimal depth for measurement was determined, and then, SWE was performed in parallel and perpendicular to the muscle fiber orientation with and without strain stress. For the in vivo study, SWE was performed on the cervical lymph nodes in parallel and perpendicular to the sternocleidomastoid muscle fiber direction with and without neck stretching. The mean values of the shear modulus (meanSM) were then analyzed. In the phantom study, the measured depth significantly influenced the meanSM with a sharp decrease at the depth of 1.5 cm (P<0.001). Strain stress increased the meanSM, irrespective of the muscle fiber orientation (P<0.001). In the in vivo study, the meanSM values obtained in parallel to the muscle fiber orientation were greater than those obtained perpendicular to the fiber orientation, irrespective of the stretch stress (P<0.001). However, meanSM was affected significantly by the stretch stress parallel to the muscle fiber orientation (P<0.001). The anisotropic nature of the cervical musculature and the applied stretch stress explain the variability of the SWE measurements and should be identified before applying Swee for the interpretation of the measured shear modulus values.

  9. Shear wave elastography using ultrasound: effects of anisotropy and stretch stress on a tissue phantom and reactive lymph nodes in the neck

    Directory of Open Access Journals (Sweden)

    Ha Young Lee

    2017-01-01

    Full Text Available Purpose The purpose of this study was to evaluate how the anisotropy and the static stretch stress of the cervical musculature influence the measured shear modulus in a tissue-mimicking phantom and in cervical lymph nodes in vivo by using shear wave elastography (SWE. Methods SWE was performed on a phantom using a pig muscle and on the middle jugular cervical lymph nodes in six volunteers. Tissue elasticity was quantified using the shear modulus and a supersonic shear wave imaging technique. For the phantom study, first, the optimal depth for measurement was determined, and then, SWE was performed in parallel and perpendicular to the muscle fiber orientation with and without strain stress. For the in vivo study, SWE was performed on the cervical lymph nodes in parallel and perpendicular to the sternocleidomastoid muscle fiber direction with and without neck stretching. The mean values of the shear modulus (meanSM were then analyzed. Results In the phantom study, the measured depth significantly influenced the meanSM with a sharp decrease at the depth of 1.5 cm (P<0.001. Strain stress increased the meanSM, irrespective of the muscle fiber orientation (P<0.001. In the in vivo study, the meanSM values obtained in parallel to the muscle fiber orientation were greater than those obtained perpendicular to the fiber orientation, irrespective of the stretch stress (P<0.001. However, meanSM was affected significantly by the stretch stress parallel to the muscle fiber orientation (P<0.001. Conclusion The anisotropic nature of the cervical musculature and the applied stretch stress explain the variability of the SWE measurements and should be identified before applying SWE for the interpretation of the measured shear modulus values.

  10. Estimation of Shear Wave Velocity from MASW and H/V Joint Inversion in a Noisy Area of Sao Paulo City, Brazil

    Science.gov (United States)

    Ullah, I.; Luiz Prado, R.

    2015-12-01

    The parameters shear wave velocity and soft sediment thickness are very important for the site investigation. Shear wave velocities are usually obtained from the dispersion curve analysis of surface wave (MASW), which are obtained by active or passive seismic array. Dispersion curve provides a reliable velocity estimate at frequencies above the fundamental resonant frequency of the site (Hobiger et al, 2009), however dispersion curve analysis does not provide information about the deeper layers,. The information of deeper layer can be included from H/V spectral ratio analysis, which provides a very good estimate of fundamental frequency of site. A joint inversion analysis of dispersion and H/V curves have been made, the dispersion curve has been obtained by active source (MASW) while H/V ratios are obtained from seismic ambient noise recording through single 3 component broadband seismometer. H/V curve inversion are linked with Rayleigh wave ellipticty curve, however Bonnefoy-Claudet (2008) have shown that both Rayleigh and Love waves contribute to the H/V spectrum, so it is necessary to accurately extract Rayleigh wave ellipticity from single station recording. We have utilized two techniques to retrieve Rayliegh wave ellipticty from our noise recording. One is random decrement technique, RayDec (Hobiger et al, 2009) and second, time frequency analysis (Neries project, 2010). This Rayleigh wave ellipticty from H/V recording and dispersion curve from MASW have been jointly inverted. The inversion has been carried out using neighborhood algorithm introduced to geophysics by Sambridge (1999). Shear wave velocity profile have been compared with borehole result (at same location), which showed a very promising correlation, especially within zone of high velocity contrast and depth of bedrock.References 1. Bonnefoy-Claudet, (2008), Effects of Love waves on microtremor H/V ratio, Bull. Seismol.Soc 2. Hobiger, (2009), Single station determination of Rayleigh wave

  11. Shear-wave reflection imaging using a MEMS-based 3C landstreamer and a vertical impact source - an esker study in SW Finland

    Science.gov (United States)

    Brodic, Bojan; Malehmir, Alireza; Maries, Georgiana; Ahokangas, Elina; Mäkinen, Joni; Pasanen, Antti

    2017-04-01

    Higher resolution of S-wave seismic data compared to the P-wave ones are attractive for the researches working with the seismic methods. This is particularly true for near-surface applications due to significantly lower shear-wave velocities of unconsolidated sediments. Shear-wave imaging, however, poses certain restrictions on both source and receiver selections and also processing strategies. With three component (3C) seismic receivers becoming more affordable and used, shear-wave imaging from vertical sources is attracting more attention for near-surface applications. Theoretically, a vertical impact source will always excite both P- and S-waves although the excited S-waves are radially polarized (SV). There is an exchange of seismic energy between the vertical and radial component of the seismic wavefield. Additionally, it is theoretically accepted that there is no energy conversion or exchange from vertical into the transverse (or SH) component of the seismic wavefield, and the SH-waves can only be generated using SH sources. With the objectives of imaging esker structure (glacial sediments), water table and depth to bedrock, we conducted a seismic survey in Virttaankangas, in southwestern Finland. A bobcat-mounted vertical drop hammer (500 kg) was used as the seismic source. To obtain better source coupling, a 75×75×1.5 cm steel plate was mounted at the bottom of the hammer casing and all the hits made on this plate after placing it firmly on the ground at every shot point. For the data recording, we used a state-of-the-art comprising of 100 units, 240 m-long, 3C MEMS (micro electro-mechanical system) based seismic landstreamer developed at Uppsala University. Although the focus of the study was on the vertical component data, careful inspection of the transverse (SH) component of the raw data revealed clear shear wave reflections (normal moveout velocities ranging from 280-350 m/s at 50 m depth) on several shot gathers. This indicated potential for their

  12. Liver Stiffness According to Data of Shear Wave Elastography in Patients with Diabetes Mellitus Type 2 and Nonalcoholic Fatty Liver Disease Depending on Activity of NAFLD

    Directory of Open Access Journals (Sweden)

    O.B. Dynnyk

    2014-09-01

    Full Text Available Shear wave elastography is one of the most promising non-invasive methods for diagnosis of fibrosis and steatosis in chronic diffuse liver diseases, which can be used as an alternative to biopsy. Given its widespread introduction into clinical practice, the groups of scientists from around the world pay more attention to the study of factors that can affect the measurement and its diagnostic efficacy. Our research devoted to the study of liver parenchyma stiffness changes measured by shear wave elastography/elastometry in patients with nonalcoholic fatty liver disease, according to univariate correlation and multiple linear regression analysis data, showed that independent determinants associated with increasing of liver parenchyma stiffness were degree of insulin resistance, obesity and transaminase activity.

  13. Lateral field excitation (LFE) of thickness shear mode (TSM) acoustic waves in thin film bulk acoustic resonators (FBAR) as a potential biosensor.

    Science.gov (United States)

    Dickherber, Anthony; Corso, Christopher D; Hunt, William

    2006-01-01

    Lateral field excitation (LFE) of a thin film bulk acoustic resonator (FBAR) is an ideal platform for biomedical sensors. A thickness shear mode (TSM) acoustic wave in a piezoelectric thin film is desirable for probing liquid samples because of the poor coupling of shear waves into the liquid. The resonator becomes an effective sensor by coating the surface with a bio- or chemi-specific layer. Perturbations of the surface can be detected by monitoring the resonance condition. Furthermore, FBARs can be easily fabricated to operate at higher frequencies, yielding greater sensitivity. An array of sensors offers the possibility of redundancy, allowing for statistical decision making as well as immediate corroboration of results. Array structures also offer the possibility of signature detection, by monitoring multiple targets in a sample simultaneously. This technology has immediate application to cancer and infectious disease diagnostics and also could serve as a tool for general proteomic research.

  14. Simultaneous multi-band valley-protected topological edge states of shear vertical wave in two-dimensional phononic crystals with veins

    OpenAIRE

    Huo, Shao-yong; Chen, Jiu-jiu; Huang, Hong-bo; Huang, Guo-Liang

    2017-01-01

    The introduction of the concept of valley pseudospin to phononic crystals has made a remarkable topologically protected interface transport of sound, which opens a novel research area referred to as valley Hall topological insulators. Here, we demonstrate the simultaneous multi-band edge states of shear vertical waves in two-dimensional phononic crystals with veins. The multi-band edge states are topologically valley-protected and are obtained by simultaneously gapping multiple Dirac points a...

  15. Differentiating benign from malignant solid breast masses: value of shear wave elastography according to lesion stiffness combined with greyscale ultrasound according to BI-RADS classification

    OpenAIRE

    Evans, A; Whelehan, P; Thomson, K; Brauer, K; Jordan, L; Purdie, C; McLean, D; Baker, L; Vinnicombe, S; Thompson, A.

    2012-01-01

    Background: The aim of this study was to assess the performance of shear wave elastography combined with BI-RADS classification of greyscale ultrasound images for benign/malignant differentiation in a large group of patients. Methods: One hundred and seventy-five consecutive patients with solid breast masses on routine ultrasonography undergoing percutaneous biopsy had the greyscale findings classified according to the American College of Radiology BI-RADS. The mean elasticity values from fou...

  16. Shear Wave Velocity and Site Amplification Factors for 25 Strong-Motion Instrument Stations Affected by the M5.8 Mineral, Virginia, Earthquake of August 23, 2011

    Science.gov (United States)

    Kayen, Robert E.; Carkin, Brad A.; Corbett, Skye C.; Zangwill, Aliza; Estevez, Ivan; Lai, Lena

    2015-01-01

    Vertical one-dimensional shear wave velocity (Vs) profiles are presented for 25 strong-motion instrument sites along the Mid-Atlantic eastern seaboard, Piedmont region, and Appalachian region, which surround the epicenter of the M5.8 Mineral, Virginia, Earthquake of August 23, 2011. Testing was performed at sites in Pennsylvania, Maryland, West Virginia, Virginia, the District of Columbia, North Carolina, and Tennessee. The purpose of the study is to determine the detailed site velocity profile, the average velocity in the upper 30 meters of the profile (VS,30), the average velocity for the entire profile (VS,Z), and the National Earthquake Hazards Reduction Program (NEHRP) site classification. The Vs profiles are estimated using a non-invasive continuous-sine-wave method for gathering the dispersion characteristics of surface waves. A large trailer-mounted active source was used to shake the ground during the testing and produce the surface waves. Shear wave velocity profiles were inverted from the averaged dispersion curves using three independent methods for comparison, and the root-mean square combined coefficient of variation (COV) of the dispersion and inversion calculations are estimated for each site.

  17. Crack Features and Shear-Wave Splitting Associated with Fracture Extension during Hydraulic Stimulation of the Geothermal Reservoir in Soultz-sous-Forêts

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    Adelinet M.

    2016-05-01

    Full Text Available The recent tomography results obtained within the scope of the Enhanced Geothermal System (EGS European Soultz project led us to revisit the meso-fracturing properties of Soultz test site. In this paper, we develop a novel approach coupling effective medium modeling and shear-wave splitting to characterize the evolution of crack properties throughout the hydraulic stimulation process. The stimulation experiment performed in 2000 consisted of 3 successive injection steps spanning over 6 days. An accurate 4-D tomographic image was first carried out based upon the travel-times measured for the induced seismicity [Calò M., Dorbath C., Cornet F.H., Cuenot N. (2011 Large-scale aseismic motion identified through 4-D P-wave tomography, Geophys. J. Int. 186, 1295-1314]. The current study shows how to take advantage of the resulting compressional wave (Calò et al., 2011 and shear-wave velocity models. These are given as input data to an anisotropic effective medium model and converted into crack properties. In short, the effective medium model aims to estimate the impact of cracks on velocities. It refers to a crack-free matrix and 2 families of penny-shaped cracks with orientations in agreement with the main observed geological features: North-South strike and dip of 65°East and 65°West [Genter A., Traineau H. (1996 Analysis of macroscopic fractures in granite in the HDR geothermal well EPS-1, Soultz-sous-Forêts, France, J. Vol. Geoth. Res. 72, 121-141], respectively. The resulting output data are the spatial distributions of crack features (lengths and apertures within the 3-D geological formation. We point out that a flow rate increase results in a crack shortening in the area imaged by both compressional and shear waves, especially in the upper part of the reservoir. Conversely, the crack length, estimated during continuous injection rate phases, is higher than during the increasing injection rate phases. A possible explanation for this is that

  18. Comparison of Virtual Touch Tissue Imaging & Quantification (VTIQ) and Toshiba shear wave elastography (T-SWE) in diagnosis of thyroid nodules: Initial experience.

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    He, Ya-Ping; Xu, Hui-Xiong; Li, Xiao-Long; Li, Dan-Dan; Bo, Xiao-Wan; Zhao, Chong-Ke; Liu, Bo-Ji; Wang, Dan; Xu, Hui-Xiong

    2017-01-01

    The aim of this study was to compare the diagnostic performance of two different 2D shear wave speed imaging techniques of Virtual Touch Tissue Imaging & Quantification (VTIQ) and Toshiba shear wave elastography (T-SWE) in predicting malignant thyroid nodules (TNs). 75 TNs in 75 patients which were subject to both VTIQ and T-SWE examinations were enrolled and analyzed. Shear wave speed (SWS) values on VTIQ and T-SWE were computed (SWS_max, min, mean and median). Area under the receiver operating characteristic (AUROC) curve was obtained to assess the diagnostic performance. The AUROC for VTIQ was the highest with SWS_min whereas for T-SWE was SWS_max (0.774 versus 0.851; p > 0.05). The AUROC, sensitivity and negative predictive value (NPV) corresponding to SWS_max for VTIQ were significantly lower than those for T-SWE (0.717 versus 0.851, 61.5% versus 92.3% and 78.7% versus 94.3%; all p  0.05). In general, VTIQ is equal to T-SWE for diagnosis of TNs. In the clinical practice, the selection of SWS_max should be avoided in VTIQ whereas should be selected in T-SWE.

  19. Monitoring of cornea elastic properties changes during UV-A/riboflavin-induced corneal collagen cross-linking using supersonic shear wave imaging: a pilot study.

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    Nguyen, Thu-Mai; Aubry, Jean-François; Touboul, David; Fink, Mathias; Gennisson, Jean-Luc; Bercoff, Jeremy; Tanter, Mickael

    2012-08-31

    Keratoconus disease or post-LASIK corneal ectasia are increasingly treated using UV-A/riboflavin-induced corneal collagen cross-linking (CXL). However, this treatment suffers from a lack of techniques to provide an assessment in real-time of the CXL effects. Here, we investigated the potential interest of corneal elasticity as a biomarker of the efficacy of this treatment. For this purpose, supersonic shear wave imaging (SSI) was performed both ex vivo and in vivo on porcine eyes before and after CXL. Based on ultrasonic scanners providing ultrafast frame rates (~30 kHz), the SSI technique generates and tracks the propagation of shear waves in tissues. It provides two- and three-dimensional (2-D and 3-D) quantitative maps of the corneal elasticity. After CXL, quantitative maps of corneal stiffness clearly depicted the cross-linked area with a typical 200-μm lateral resolution. The CXL resulted in a 56% ± 15% increase of the shear wave speed for corneas treated in vivo (n = 4). The in vivo CXL experiments performed on pigs demonstrated that the quantitative estimation of local stiffness and the 2-D elastic maps of the corneal surface provide an efficient way to monitor the local efficacy of corneal cross-linking.

  20. Comparison of shear-wave slowness profiles at 10 strong-motion sites from noninvasive SASW measurements and measurements made in boreholes

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    Brown, L.T.; Boore, D.M.; Stokoe, K.H.

    2002-01-01

    The spectral-analysis-of-surface-waves (SASW) method is a relatively new in situ method for determining shear-wave slownesses. All measurements are made on the ground surface, making it much less costly than methods that require boreholes. The SASW method uses a number of active sources (ranging from a commercial Vibroseis truck to a small handheld hammer for the study conducted here) and different receiver spacings to map a curve of apparent phase velocity versus frequency. With the simplifying assumption that the phase velocities correspond to fundamental mode surface waves, forward modeling yields an estimate of the sub-surface shear-wave slownesses. To establish the reliability of this indirect technique, we conducted a blind evaluation of the SASW method. SASW testing was performed at 10 strong-motion stations at which borehole seismic measurements were previously or subsequently made; if previously made, the borehole results were not used for the interpretation of the SASW data, and vice-versa. Comparisons of the shear-wave slownesses from the SASW and borehole measurements are generally very good. The differences in predicted ground-motion amplifications are less than about 15% for most frequencies. In addition, both methods gave the same NEHRP site classification for seven of the sites. For the other three sites the average velocities from the downhole measurements were only 5-13 m/sec larger than the velocity defining the class C/D boundary. This study demonstrates that in many situations the SASW method can provide subsurface information suitable for site response predictions.

  1. Comparison of strain and shear-wave ultrasounic elastography in predicting the pathological response to neoadjuvant chemotherapy in breast cancers.

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    Ma, Yan; Zhang, Shuo; Li, Jing; Li, Jianyi; Kang, Ye; Ren, Weidong

    2017-06-01

    To compare the diagnostic performances of strain elastography (SE) and shear-wave elastography (SWE) for predicting response to neoadjuvant chemotherapy (NACT) in patients with breast cancer. This prospective study recruited 71 eligible patients from June 2014 to May 2016. All patients provided written informed consent. Tumour stiffness was assessed by the SE strain ratio (R), SWE maximum elasticity (Emax) and SWE mean elasticity (Emean). Ultrasonic elastography (UE) assessments were performed at each NACT cycle (t1 - t6). For the purpose of predicting, the relative changes in elastographic parameters after the first and second NACT cycles were considered as the variables [Δ(t1) and Δ(t2)]. The area under the receiver operating characteristics (AUC) curve was compared. ΔEmean(t2) and R2 displayed the best diagnostic performances within their own modalities (AUC = 0.93 and 0.90 for predicting favourable response to NACT; AUC = 0.92 and 0.78 for predicting NACT resistance, respectively). There were no significant differences in AUCs for ΔEmean(t2) and some UE parameters (P > 0.05). By contrast, ΔEmean(t2) was significantly superior to all other SE parameters for predicting resistance (P < 0.05). SE and SWE exhibited similar performances for predicting favourable NACT responses; SWE was better than SE for predicting NACT resistance. • Elastography parameters after the second NACT cycle showed the best diagnostic performances. • SWE and SE yielded similar diagnostic performances in predicting favourable responses. • SWE performed better than SE in predicting the pathological resistance to NACT. • Discrepant results may be due to the breast thickness and lesion depth.

  2. Quantitative Shear-Wave Elastography of the Liver in Preterm Neonates with Intra-Uterine Growth Restriction.

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    Marianne Alison

    Full Text Available The feasibility and reproducibility of liver stiffness measurements using Supersonic Shear-wave Imaging (SSI in preterm neonate have not been reported. Our aim was to determine if liver stiffness differs between intra-uterine growth restriction (IUGR and appropriate for gestational age (AGA preterm infants with/without cholestasis. We measured liver stiffness (in kPa in 45 AGA and 18 IUGR preterm infants, and assessed reproducibility in 26 preterms using Intraclass Correlation Coefficients (ICC and Bland-Altman tests. Liver stiffness values were compared between AGA and IUGR with and without cholestasis and correlated with birth weight. Measurements showed high reproducibility (ICC = 0.94-0.98 for intra-operator, 0.86 for inter-operator with good agreement (95% limits: -1.24 to 1.24 kPa. During the first postnatal week, liver stiffness was higher in IUGR (7.50 ±1.53 kPa than in AGA infants (5.11 ±0.80 kPa, p<0.001. After day 8, liver stiffness remained unchanged in AGA but increased progressively in IUGR infants (15.57 ±6.49 kPa after day 21. Liver stiffness was higher in IUGR neonates with cholestasis (19.35 ± 9.80 kPa than without cholestasis (7.72 ± 1.27 kPa, p<0.001. In conclusion, quantitative liver SSI in preterms is feasible and reproducible. IUGR preterms who will develop cholestasis present high liver stiffness even at birth, before biological cholestasis occurs.

  3. A seismological evidence for the northwestward movement of Africa with respect to Iberia from shear-wave splitting

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    Mohamed K. Salah

    2012-09-01

    Full Text Available Seismic anisotropy and its main features along the convergent boundary between Africa and Iberia are detected through the analysis of teleseismic shear-wave splitting. Waveform data generated by 95 teleseismic events recorded at 17 broadband stations deployed in the western Mediterranean region are used in the present study. Although the station coverage is not uniform in the Iberian Peninsula and northwest Africa, significant variations in the fast polarization directions and delay times are observed at stations located at different tectonic domains. Fast polarization directions are oriented predominantly NW-SE at most stations which are close to the plate boundary and in central Iberia; being consistent with the absolute plate motion in the region. In the northern part of the Iberian Peninsula, fast velocity directions are oriented nearly E–W; coincident with previous results. Few stations located slightly north of the plate boundary and to the southeast of Iberia show E–W to NE-SW fast velocity directions, which may be related to the Alpine Orogeny and the extension direction in Iberia. Delay times vary significantly between 0.2 and 1.9 s for individual measurements, reflecting a highly anisotropic structure beneath the recording stations. The relative motion between Africa and Iberia represents the main reason for the observed NW-SE orientations of the fast velocity directions. However, different causes of anisotropy have also to be considered to explain the wide range of the splitting pattern observed in the western Mediterranean region. Many geophysical observations such as the low Pn velocity, lower lithospheric Q values, higher heat flow and the presence of high conductive features support the mantle flow in the western Mediterranean, which may contribute and even modify the splitting pattern beneath the studied region.

  4. Value of real-time shear wave elastography in evaluating classification of liver fibrosis: a Meta-analysis

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    WU Yue

    2017-09-01

    Full Text Available ObjectiveTo investigate the diagnostic value of real-time shear wave elastography (SWE technique in evaluating classification of liver fibrosis. MethodsPubMed, CNKI, CBM, VIP, and Wanfang Data were searched for Chinese and English articles on SWE for evaluating classification of liver fibrosis published from January 2010 to December 2016, and these articles were screened and evaluated. Meta-disc 1.4 software was used for the meta-analysis of the data in the articles included. ResultsA total of 11 English articles were included, with 1560 cases in total. In the ≥F2 group, SWE had a pooled sensitivity of 0.85 (95% confidence interval [CI]:0.82-0.87, a specificity of 0.79 (95%CI:0.76-0.82, and a diagnostic odds ratio (DOR of 30.81 (95%CI: 16.55-57.34. In the ≥F3 group, SWE had a pooled sensitivity of 0.87 (95%CI:0.84-0.91, a specificity of 0.84 (95%CI:0.82-0.87, and a DOR of 41.45 (95%CI:18.25-94.45. In the F4 group, SWE had a pooled sensitivity of 0.88 (95%CI:0.83-0.91, a specificity of 0.91 (95%CI:0.89-092, and a DOR of 67.18 (95%CI:30.03-150.31. The areas under the receiver operating characteristic curve for these three groups were 0.914 7, 0.922 3, and 0.952 0, respectively. ConclusionSWE has a high diagnostic value in evaluating the classification of liver fibrosis and can be used to determine liver fibrosis stage in clinical practice.

  5. Liver shear-wave velocity and serum fibrosis markers to diagnose hepatic fibrosis in patients with chronic viral hepatitis B

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    Liu, Jian Xue; Ji, Yong Hao; Zhao Junzhi; Zhang, Yao Ren; Dun, Guo Liang; Ning, Bo [Dept. of Ultrasonography, Baoji Central Hospital, Baoji (China); Ai, Hong [Dept. of Ultrasonography, The First Affiliated Hospital of Medical College, Xi' an Jiaotong University, Xi' an (China)

    2016-06-15

    To compare several noninvasive indices of fibrosis in chronic viral hepatitis B, including liver shear-wave velocity (SWV), hyaluronic acid (HA), collagen type IV (CIV), procollagen type III (PCIII), and laminin (LN). Acoustic radiation force impulse (ARFI) was performed in 157 patients with chronic viral hepatitis B and in 30 healthy volunteers to measure hepatic SWV (m/s) in a prospective study. Serum markers were acquired on the morning of the same day of the ARFI evaluation. Receiver operating characteristic (ROC) analysis was performed to evaluate and compare the accuracies of SWV and serum markers using METAVIR scoring from liver biopsy as a reference standard. The most accurate test for diagnosing fibrosis F ≥ 1 was SWV with the area under the ROC curve (AUC) of 0.913, followed by LN (0.744), HA (0.701), CIV (0.690), and PCIII (0.524). The best test for diagnosing F ≥ 2 was SWV (AUC of 0.851), followed by CIV (0.671), HA (0.668), LN (0.562), and PCIII (0.550). The best test for diagnosing F ≥ 3 was SWV (0.854), followed by CIV (0.693), HA (0.675), PCIII (0.591), and LN (0.548). The best test for diagnosing F = 4 was SWV (0.965), followed by CIV (0.804), PCIII (0.752), HA (0.744), and LN (0.662). SWV combined with HA and CIV did not improve diagnostic accuracy (AUC = 0.931 for F ≥ 1, 0.863 for F ≥ 2, 0.855 for F ≥ 3, 0.960 for F = 4). The performance of SWV in diagnosing liver fibrosis is superior to that of serum markers. However, the combination of SWV, HA, and CIV does not increase the accuracy of diagnosing liver fibrosis and cirrhosis.

  6. Comparison of diagnostic value of conventional ultrasonography and shear wave elastography in the prediction of thyroid lesions malignancy.

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    Ewelina Szczepanek-Parulska

    Full Text Available INTRODUCTION: Thyroid nodular disease (TND is a very common disorder. However, since the rate of malignancy is reported to be 3-10%, only a minority of patients require aggressive surgical treatment. As a result, there is a need for diagnostic tools which would allow for a reliable differentiation between benign and malignant nodules. Although a number of conventional ultrasonographic (US features are proved to be markers of malignancy, Shear Wave Elastography (SWE is considered to be an improvement of conventional US. The aim of this study was to compare conventional US markers and SWE diagnostic values in the differentiation of benign and malignant thyroid nodules. MATERIALS AND METHODS: All patients referred for thyroidectomy, irrespective of the indications, underwent a US thyroid examination prospectively. Patients with TND were included into the study. Results of the US and SWE examinations were compared with post-surgical histopathology. RESULTS: One hundred and twenty two patients with 393 thyroid nodules were included into the study. Twenty two patients were diagnosed with cancer. SWE turned out to be a predictor of malignancy superior to any other conventional US markers (OR=54.5 using qualitative scales and 40.8 using quantitative data on maximal stiffness with a threshold of 50 kPa. CONCLUSIONS: Although most conventional US markers of malignancy prove to be significant, none of them are characterized by both high sensitivity and specificity. SWE seems to be an important step forward, allowing for a more reliable distinction of benign and malignant thyroid nodules. Our study, assessing SWE properties on the highest number of thyroid lesions at the time of publication, confirms the high diagnostic value of this technique. It also indicates that a quantitative evaluation of thyroid lesions is not superior to simpler qualitative methods.

  7. Ultrasound point shear wave elastography assessment of liver and spleen stiffness: effect of training on repeatability of measurements.

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    Ferraioli, Giovanna; Tinelli, Carmine; Lissandrin, Raffaella; Zicchetti, Mabel; Bernuzzi, Stefano; Salvaneschi, Laura; Filice, Carlo

    2014-06-01

    To evaluate reproducibility of measurements of spleen stiffness (SS) and liver stiffness (LS) at several sites by using point shear wave elastography (pSWE) and to investigate any training effect. Healthy volunteers were consecutively enrolled. Measurements of SS and LS were performed by an expert (observer 1) and a novice (observer 2) at three different sites of liver and spleen. To assess the effect of training the study was conducted in two periods (period 1 and period 2). Concordance correlation coefficient was used to assess intra-observer and inter-observer reproducibility. A total of 92 subjects (67 men and 25 women) were enrolled in the study. Both intra-observer and inter-observer agreement were higher for the liver than for the spleen. Overall, the highest intra-observer and inter-observer agreement were obtained for the assessment of LS through intercostal space, and for measurements at this site there was a significantly better performance of observer 2 after the training period. For both observers, training improved the repeatability of SS measurements at all sites. A good intra-observer agreement was obtained only for measurements at the spleen lower pole. The results of this study show that a learning curve in pSWE acquisition should be taken into account both for SS and LS measurements. Reproducibility of SS measurements depends on the expertise of the operator. To achieve good reproducibility between measurements a training period is required. A learning curve in pSWE acquisition should be taken into account. SS measurements are less reproducible than LS measurements.

  8. Quantitative comparison of transient elastography (TE), shear wave elastography (SWE) and liver biopsy results of patients with chronic liver disease.

    Science.gov (United States)

    Kim, Hyun-Jin; Lee, Hae-Kag; Cho, Jae-Hwan; Yang, Han-Jun

    2015-08-01

    [Purpose] The purpose of this study was to carry out a comparitive analysis of hepatic fibrosis results of the liver hardness of patients with chronic liver disease as measured by elastography (TE), shear wave elastography (SWE), and liver biopsy. [Subjects and Methods] This study was a retrospective analysis of 304 patients who underwent SWE and TE before and after liver biopsy, taken from among patients who had been checked for liver fibrosis by liver biopsy between August 2013 and August 2014. We used receiver operating characteristic (ROC) curve to prove the diagnostic significance of liver stiffness, and then analyzed the sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of SWE and TE, as well as the kappa index through cross-analysis of SWE, TE, and liver biopsy. [Results] For liver hardness, the sensitivity of SWE was 84.39%, the specificity of SWE was 97.92%, the accuracy of SWE was 87.33%, the positive predictive value of SWE was 99.32%, and the negative predictive value of SWE was 63.51%. The sensitivity of TE was 94.80%, the specificity of TE was 77.08%, the accuracy of TE was 90.95%, the positive predictive value of TE was 93.97%, and the negative predictive value of TE was 80.43%. [Conclusion] It is our opinion that SWE and TE are non-invasive methods that are more effective than the invasive methods used for diagnosing liver hardness. Invasive methods cover only a section of liver tissue, and are more likely to cause side effects during biopsy.

  9. Quantification of elastic heterogeneity using contourlet-based texture analysis in shear-wave elastography for breast tumor classification.

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    Zhang, Qi; Xiao, Yang; Chen, Shuai; Wang, Congzhi; Zheng, Hairong

    2015-02-01

    Ultrasound shear-wave elastography (SWE) has become a valuable tool for diagnosis of breast tumors. The purpose of this study was to quantify the elastic heterogeneity of breast tumors in SWE by using contourlet-based texture features and evaluating their diagnostic performance for classification of benign and malignant breast tumors, with pathologic results as the gold standard. A total of 161 breast tumors in 125 women who underwent B-mode and SWE ultrasonography before biopsy were included. Five quantitative texture features in SWE images were extracted from the directional subbands after the contourlet transform, including the mean (Tmean), maximum (Tmax), median (Tmed), third quartile (Tqt), and standard deviation (Tsd) of the subbands. Diagnostic performance of the texture features and the classic features was compared using the area under the receiver operating characteristic curve (AUC) and the leave-one-out cross validation with Fisher classifier. The feature Tmean achieved the highest AUC (0.968) among all features and it yielded a sensitivity of 89.1%, a specificity of 94.3% and an accuracy of 92.5% for differentiation between benign and malignant tumors via the leave-one-out cross validation. Compared with the best classic feature, i.e., the maximum elasticity, Tmean improved the AUC, sensitivity, specificity and accuracy by 3.5%, 12.7%, 2.8% and 6.2%, respectively. The Tmed, Tqt and Tsd were also superior to the classic features in terms of the AUC and accuracy. The results demonstrated that the contourlet-based texture features captured the tumor's elastic heterogeneity and improved diagnostic performance contrasted with the classic features. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  10. A Machine-Learning Algorithm Toward Color Analysis for Chronic Liver Disease Classification, Employing Ultrasound Shear Wave Elastography.

    Science.gov (United States)

    Gatos, Ilias; Tsantis, Stavros; Spiliopoulos, Stavros; Karnabatidis, Dimitris; Theotokas, Ioannis; Zoumpoulis, Pavlos; Loupas, Thanasis; Hazle, John D; Kagadis, George C

    2017-09-01

    The purpose of the present study was to employ a computer-aided diagnosis system that classifies chronic liver disease (CLD) using ultrasound shear wave elastography (SWE) imaging, with a stiffness value-clustering and machine-learning algorithm. A clinical data set of 126 patients (56 healthy controls, 70 with CLD) was analyzed. First, an RGB-to-stiffness inverse mapping technique was employed. A five-cluster segmentation was then performed associating corresponding different-color regions with certain stiffness value ranges acquired from the SWE manufacturer-provided color bar. Subsequently, 35 features (7 for each cluster), indicative of physical characteristics existing within the SWE image, were extracted. A stepwise regression analysis toward feature reduction was used to derive a reduced feature subset that was fed into the support vector machine classification algorithm to classify CLD from healthy cases. The highest accuracy in classification of healthy to CLD subject discrimination from the support vector machine model was 87.3% with sensitivity and specificity values of 93.5% and 81.2%, respectively. Receiver operating characteristic curve analysis gave an area under the curve value of 0.87 (confidence interval: 0.77-0.92). A machine-learning algorithm that quantifies color information in terms of stiffness values from SWE images and discriminates CLD from healthy cases is introduced. New objective parameters and criteria for CLD diagnosis employing SWE images provided by the present study can be considered an important step toward color-based interpretation, and could assist radiologists' diagnostic performance on a daily basis after being installed in a PC and employed retrospectively, immediately after the examination. Copyright © 2017 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  11. A new computer aided diagnosis system for evaluation of chronic liver disease with ultrasound shear wave elastography imaging.

    Science.gov (United States)

    Gatos, Ilias; Tsantis, Stavros; Spiliopoulos, Stavros; Karnabatidis, Dimitris; Theotokas, Ioannis; Zoumpoulis, Pavlos; Loupas, Thanasis; Hazle, John D; Kagadis, George C

    2016-03-01

    Classify chronic liver disease (CLD) from ultrasound shear-wave elastography (SWE) imaging by means of a computer aided diagnosis (CAD) system. The proposed algorithm employs an inverse mapping technique (red-green-blue to stiffness) to quantify 85 SWE images (54 healthy and 31 with CLD). Texture analysis is then applied involving the automatic calculation of 330 first and second order textural features from every transformed stiffness value map to determine functional features that characterize liver elasticity and describe liver condition for all available stages. Consequently, a stepwise regression analysis feature selection procedure is utilized toward a reduced feature subset that is fed into the support vector machines (SVMs) classification algorithm in the design of the CAD system. With regard to the mapping procedure accuracy, the stiffness map values had an average difference of 0.01 ± 0.001 kPa compared to the quantification results derived from the color-box provided by the built-in software of the ultrasound system. Highest classification accuracy from the SVM model was 87.0% with sensitivity and specificity values of 83.3% and 89.1%, respectively. Receiver operating characteristic curves analysis gave an area under the curve value of 0.85 with [0.77-0.89] confidence interval. The proposed CAD system employing color to stiffness mapping and classification algorithms offered superior results, comparing the already published clinical studies. It could prove to be of value to physicians improving the diagnostic accuracy of CLD and can be employed as a second opinion tool for avoiding unnecessary invasive procedures.

  12. Shear wave velocity measurements using acoustic radiation force impulse in young children with normal kidneys versus hydronephrotic kidneys

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    Shon, Beom Seok; Kim, Myung Joon; Han, Sang Won; Im, Young Jae; Lee, Mi Jung [Severance Children' s Hospital, Yonsei University College of Medicine, Seoul (Korea, Republic of)

    2014-04-15

    To measure shear wave velocities (SWVs) by acoustic radiation force impulse (ARFI) ultrasound elastography in normal kidneys and in hydronephrotic kidneys in young children and to compare SWVs between the hydronephrosis grades. This study was approved by an institutional review board, and informed consent was obtained from the parents of all the children included. Children under the age of 24 months were prospectively enrolled. Hydronephrosis grade was evaluated on ultrasonography, and three valid ARFI measurements were attempted using a high-frequency transducer for both kidneys. Hydronephrosis was graded from 0 to 4, and high-grade hydronephrosis was defined as grades 3 and 4. Fifty-one children underwent ARFI measurements, and three valid measurements for both kidneys were obtained in 96% (49/51) of the patients. Nineteen children (38.8%) had no hydronephrosis. Twenty-three children (46.9%) had unilateral hydronephrosis, and seven children (14.3%) had bilateral hydronephrosis. Seven children had ureteropelvic junction obstruction (UPJO). Median SWVs in kidneys with high-grade hydronephrosis (2.02 m/sec) were higher than those in normal kidneys (1.75 m/sec; P=0.027). However, the presence of UPJO did not influence the median SWVs in hydronephrotic kidneys (P=0.362). Obtaining ARFI measurements of the kidney is feasible in young children with median SWVs of 1.75 m/sec in normal kidneys. Median SWVs increased in high-grade hydronephrotic kidneys but were not different between hydronephrotic kidneys with and without UPJO.

  13. Quantified Mechanical Properties of the Deltoid Muscle Using the Shear Wave Elastography: Potential Implications for Reverse Shoulder Arthroplasty.

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    Taku Hatta

    Full Text Available The deltoid muscle plays a critical role in the biomechanics of shoulders undergoing reverse shoulder arthroplasty (RSA. However, both pre- and postoperative assessment of the deltoid muscle quality still remains challenging. The purposes of this study were to establish a novel methodology of shear wave elastography (SWE to quantify the mechanical properties of the deltoid muscle, and to investigate the reliability of this technique using cadaveric shoulders for the purpose of RSA. Eight fresh-frozen cadaveric shoulders were obtained. The deltoid muscles were divided into 5 segments (A1, A2, M, P1 and P2 according to the muscle fiber orientation and SWE values were measured for each segment. Intra- and inter-observer reliability was evaluated using intraclass correlation coefficient (ICC. To measure the response of muscle tension during RSA, the humeral shaft was osteotomized and subsequently elongated by an external fixator (intact to 15 mm elongation. SWE of the deltoid muscle was measured under each stretch condition. Intra- and inter-observer reliability of SWE measurements for all regions showed 0.761-0.963 and 0.718-0.947 for ICC(2,1. Especially, SWE measurements for segments A2 and M presented satisfactory repeatability. Elongated deltoid muscles by the external fixator showed a progressive increase in passive stiffness for all muscular segments. Especially, SWE outcomes of segments A2 and M reliably showed an exponential growth upon stretching (R2 = 0.558 and 0.593. Segmental measurements using SWE could be reliably and feasibly used to quantitatively assess the mechanical properties of the deltoid muscle, especially in the anterior and middle portions. This novel technique based on the anatomical features may provide helpful information of the deltoid muscle properties during treatment of RSA.

  14. Determination of the Elasticity of Breast Tissue during the Menstrual Cycle Using Real-Time Shear Wave Elastography.

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    Li, Xiang; Wang, Jian-Nan; Fan, Zhi-Ying; Kang, Shu; Liu, Yan-Jun; Zhang, Yi-Xia; Wang, Xue-Mei

    2015-12-01

    We examined breast tissue elasticity during the menstrual cycle using real-time shear wave elastography (RT-SWE), a recent technique developed for soft tissue imaging. Written informed consent for RT-SWE was obtained from all eligible patients, who were healthy women aged between 19 and 52 y. Young's moduli of the breast tissue in the early follicular, late phase and luteal phase were compared. There were no significant differences in the mean, maximum and minimum elasticity values (Emean, Emax and Emin) and standard deviation (ESD). RT-SWE of glandular tissue revealed that ESD was increased in the early follicular phase compared with the luteal phase. Means ± SD of Emin, Emax and Emean in glandular tissue were 5.174 ± 2.138, 8.308 ± 3.166 and 6.593 ± 2.510, respectively, and in adipose tissue, 3.589 ± 2.083, 6.733 ± 3.522 and 4.857 ± 2.564, respectively. There were no significant differences in stiffness between glandular and adipose tissues throughout the menstrual cycle, but glandular tissue stiffness was lower in the luteal phase than in the early follicular phase. On the basis of these observations in normal healthy women, we believe we have obtained sufficient information to establish the baseline changes in human breast elasticity during the menstrual cycle. In the future, we intend to compare the elasticity values of healthy breast tissue with those of breast tissue affected by various pathologies. Our results reveal the significant potential of RT-SWE in the rapid and non-invasive clinical diagnosis of breast diseases, such as breast cancers. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  15. Shear-wave elastography and immunohistochemical profiles in invasive breast cancer: evaluation of maximum and mean elasticity values.

    Science.gov (United States)

    Ganau, Sergi; Andreu, Francisco Javier; Escribano, Fernanda; Martín, Amaya; Tortajada, Lidia; Villajos, Maite; Baré, Marisa; Teixidó, Milagros; Ribé, Judit; Sentís, Melcior

    2015-04-01

    To evaluate the correlations of maximum stiffness (Emax) and mean stiffness (Emean) of invasive carcinomas on shear-wave elastography (SWE) with St. Gallen consensus tumor phenotypes. We used an ultrasound system with SWE capabilities to prospectively study 190 women with 216 histologically confirmed invasive breast cancers. We obtained one elastogram for each lesion. We correlated Emax and Emean with tumor size, histologic type and grade, estrogen and progesterone receptors, HER2 expression, the Ki67 proliferation index, and the five St. Gallen molecular subtypes: luminal A, luminal B without HER2 overexpression (luminal B HER2-), luminal B with HER2 overexpression (luminal B HER2+), HER2, and triple negative. Lesions larger than 20 mm had significantly higher Emax (148.04 kPa) and Emean (118.32 kPa) (P=0.005) than smaller lesions. We found no statistically significant correlations between elasticity parameters and histologic type and grade or molecular subtypes, although tumors with HER2 overexpression regardless whether they expressed hormone receptors (luminal B HER2+ and HER2 phenotypes) and triple-negative tumors had lower Emax and Emean than the others. We assessed the B-mode ultrasound findings of the lesions with some of the Emax or Emean values less than or equal to 80 kPa; only four of these had ultrasound findings suggestive of a benign lesion (two with luminal A phenotype and two with HER2 phenotype). We were unable to demonstrate statistically significant differences among the subtypes of invasive tumors, although there appears to be a trend toward lower Emax and Emean in the aggressive phenotypes. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  16. Diagnostic performance of qualitative shear-wave elastography according to different color map opacities for breast masses

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hana; Youk, Ji Hyun, E-mail: jhyouk@yuhs.ac; Gweon, Hye Mi; Kim, Jeong-Ah; Son, Eun Ju

    2013-08-15

    Purpose: To compare the diagnostic performance of qualitative shear-wave elastography (SWE) according to three different color map opacities for breast masses Materials and methods: 101 patients aged 21–77 years with 113 breast masses underwent B-mode US and SWE under three different color map opacities (50%, 19% and 100%) before biopsy or surgery. Following SWE features were reviewed: visual pattern classification (pattern 1–4), color homogeneity (E{sub homo}) and six-point color score of maximum elasticity (E{sub col}). Combined with B-mode US and SWE, the likelihood of malignancy (LOM) was also scored. The area under the curve (AUC) was obtained by ROC curve analysis to assess the diagnostic performance under each color opacity. Results: A visual color pattern, E{sub homo}, E{sub col} and LOM scoring were significantly different between benign and malignant lesions under all color opacities (P < 0.001). For 50% opacity, AUCs of visual color pattern, E{sub col}, E{sub homo} and LOM scoring were 0.902, 0.951, 0.835 and 0.975. But, for each SWE feature, there was no significant difference in the AUC among three different color opacities. For all color opacities, visual color pattern and E{sub col} showed significantly higher AUC than E{sub homo}. In addition, a combined set of B-mode US and SWE showed significantly higher AUC than SWE alone for color patterns, E{sub homo}, but no significant difference was found in E{sub col}. Conclusion: Qualitative SWE was useful to differentiate benign from malignant breast lesion under all color opacities. The difference in color map opacity did not significantly influence diagnostic performance of SWE.

  17. Diagnostic performances of shear wave elastography: which parameter to use in differential diagnosis of solid breast masses?

    Science.gov (United States)

    Lee, Eun Jung; Jung, Hae Kyoung; Ko, Kyung Hee; Lee, Jong Tae; Yoon, Jung Hyun

    2013-07-01

    To evaluate which shear wave elastography (SWE) parameter proves most accurate in the differential diagnosis of solid breast masses. One hundred and fifty-six breast lesions in 139 consecutive women (mean age: 43.54 ± 9.94 years, range 21-88 years), who had been scheduled for ultrasound-guided breast biopsy, were included. Conventional ultrasound and SWE were performed in all women before biopsy procedures. Ultrasound BI-RADS final assessment and SWE parameters were recorded. Diagnostic performance of each SWE parameter was calculated and compared with those obtained when applying cut-off values of previously published data. Performance of conventional ultrasound and ultrasound combined with each parameter was also compared. Of the 156 breast masses, 120 (76.9 %) were benign and 36 (23.1 %) malignant. Maximum stiffness (Emax) with a cut-off of 82.3 kPa had the highest area under the receiver operating characteristics curve (Az) value compared with other SWE parameters, 0.860 (sensitivity 88.9 %, specificity 77.5 %, accuracy 80.1 %). Az values of conventional ultrasound combined with each SWE parameter showed lower (but not significantly) values than with conventional ultrasound alone. Maximum stiffness (82.3 kPa) provided the best diagnostic performance. However the overall diagnostic performance of ultrasound plus SWE was not significantly better than that of conventional ultrasound alone. • SWE offers new information over and above conventional breast ultrasound • Various SWE parameters were explored regarding distinction between benign and malignant lesions • An elasticity of 82.3 kPa appears optimal in differentiating solid breast masses • However, ultrasound plus SWE was not significantly better than conventional ultrasound alone.

  18. Role of shear-wave elastography (SWE) in complex cystic and solid breast lesions in comparison with conventional ultrasound

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Bo Eun; Chung, Jin, E-mail: aqua0724@ewha.ac.kr; Cha, Eun-Suk; Lee, Jee Eun; Kim, Jeoung Hyun

    2015-07-15

    Highlights: • Complex cystic lesions have a broad spectrum of malignancy rate. • SWE is useful to evaluate cystic breast lesions. • Cutoff value of Emax was 108.5 kPa, for predicting malignancy. • Using this cutoff value, sensitivity of 86.7% and specificity of 97.3%. • SWE could reduce unnecessary biopsies in complex cystic and solid breast lesions. - Abstract: Objective: To evaluate the additional role of shear-wave elastography (SWE) in differential diagnosis of complex cystic and solid breast lesions. Materials and methods: From January 2013 to November 2013, 140 complex cystic and solid breast lesions from 139 consecutive patients were performed ultrasound and SWE prior to biopsy. BI-RADS ultrasound final assessment and SWE parameters were recorded for each lesion. Histopathologic diagnosis was used as the reference standard. Results: Among the 140 lesions, 30 lesions (21.4%) were malignant. The mean maximum elasticity (Emax) of malignant lesions (184.3 kPa) was significantly higher than that of benign lesions (45.5 kPa) (P < 0.001). Homogeneity of elasticity and color pattern were significantly different from malignancy and benign lesions (P < 0.05). Emax with cutoff value at 108.5 kPa showed Az value of 0.968 (95% CI, 0.932–0.985) with sensitivity of 86.7% and specificity of 97.3%. Using this cutoff value, false-positive rate was 2.7% and false-negative rate was 13.3%. By applying an Emax value of 108.5 kPa or less as a criterion for downgrading BI-RADS category 4a lesions to category 3 lesions, 103/123 (83.7%) lesions could be downgraded to category 3 lesions. Conclusion: Additional use of SWE could reduce unnecessary benign biopsies in complex cystic and solid breast lesions.

  19. Application of Refraction Microtremor (ReMi) technique for determination of 1-D shear wave velocity in a landslide area

    Science.gov (United States)

    Coccia, S.; Del Gaudio, V.; Venisti, N.; Wasowski, J.

    2010-06-01

    The application of the Refraction Microtremor (ReMi) method on slopes affected by or prone to landsliding is complicated by the presence of lateral lithological heterogeneities and irregular topography, which may hinder the extension of the geophone array to the minimum lengths (100-200 m) usually adopted in standard applications of this technique. We focus on deriving one-dimensional shear-wave velocity (Vs) vertical profiles from the analysis of microtremor recordings carried out in the municipality of Caramanico Terme (central Italy) where the seismic response has been monitored with a local accelerometer network since 2002. The stability of the ReMi data acquisitions and the reliability of the results in irregular landslide terrain were tested by using ReMi campaigns in three different periods and different acquisition parameters (seismograph channel number, geophone frequency and spacing). We also investigated the possible presence of directional variations in soil properties by carrying out noise recordings along L-shaped arrays. The influence of changing environmental conditions and of different acquisition parameters was tested by comparing the data obtained from different campaigns, using the same acquisition parameters, with the data from simultaneous acquisitions using different parameters. The tests showed that stable results can be obtained under different acquisition conditions provided that i) the ratio between the coherent and incoherent part of ambient noise is sufficiently high and ii) spatial aliasing does not contaminate the signal in the p (slowness)- f (frequency) matrix near the picking area: the latter condition can be satisfied by selecting geophone frequency and spacing appropriate for the site characteristics and for the investigation purpose. The differences in Vs measured in two orthogonal directions did not exceed 10-20 % and their analysis suggests that these directional variations are most likely due to anisotropy in noise source

  20. Low-level vertical wind shear effects on the gravity wave breaking over an isolated two-dimensional orography

    Directory of Open Access Journals (Sweden)

    Xu-Wei Bao

    2012-02-01

    Full Text Available Flow regimes of dry, stratified flow passing over an isolated two-dimensional (2-D orography mainly concentrate at two stagnation points. One occurs on the upslope of the orography owing to flow blocking; another is related to gravity wave breaking (GWB over the leeside. Smith (1979 put forward a hypothesis that the occurring of GWB is suppressed when the low-level vertical wind shear (VWS exceeds some value. In the present study, a theoretical solution in a two-layer linear model of orographic flow with a VWS over a bell-shaped 2-D orography is developed to investigate the effect of VWS on GWB's occurring over a range of surface Froude number Fr0=U0/Nh (U0 is surface wind speed, h is orography height and N is stability parameter, over which the GWB occurs first and the upstream flow blocking is excluded. Based on previous simulations and experiments, the range of surface Froude number selected is 0.6 ≤ Fr0≤2.0. Based on this solution, the conditions of surface wind speed (U0 and one-to-one matching critical VWS (Δuc for GWB's occurring are discussed. Over the selected range of Fr0, GWB's occurring will be suppressed if the VWS (Δu is larger than Δuc at given U0. Moreover, there is a maximum value of Δuc over the selected range of Fr0, which is labelled as Δumax, and its matching surface wind speed by U0m. Once the Δu is larger than Δumax, the flow will pass over the orography without GWB's occurring. That means, over the selected range of Fr0, the flow regime of 2-D orographic flow related to GWB occurring primarily will be absent when Δu > Δumax, regardless of the value for U0. In addition, the vertical profile of atmospheric stability and height of VWS could result in different features of mountain wave, which leads to different Δuc and Δumax for the GWB's occurring. The possible inaccuracy of estimated Δuc in the present linear model is also discussed.

  1. Modeling, design, packing and experimental analysis of liquid-phase shear-horizontal surface acoustic wave sensors

    Science.gov (United States)

    Pollard, Thomas B

    Recent advances in microbiology, computational capabilities, and microelectromechanical-system fabrication techniques permit modeling, design, and fabrication of low-cost, miniature, sensitive and selective liquid-phase sensors and lab-on-a-chip systems. Such devices are expected to replace expensive, time-consuming, and bulky laboratory-based testing equipment. Potential applications for devices include: fluid characterization for material science and industry; chemical analysis in medicine and pharmacology; study of biological processes; food analysis; chemical kinetics analysis; and environmental monitoring. When combined with liquid-phase packaging, sensors based on surface-acoustic-wave (SAW) technology are considered strong candidates. For this reason such devices are focused on in this work; emphasis placed on device modeling and packaging for liquid-phase operation. Regarding modeling, topics considered include mode excitation efficiency of transducers; mode sensitivity based on guiding structure materials/geometries; and use of new piezoelectric materials. On packaging, topics considered include package interfacing with SAW devices, and minimization of packaging effects on device performance. In this work novel numerical models are theoretically developed and implemented to study propagation and transduction characteristics of sensor designs using wave/constitutive equations, Green's functions, and boundary/finite element methods. Using developed simulation tools that consider finite-thickness of all device electrodes, transduction efficiency for SAW transducers with neighboring uniform or periodic guiding electrodes is reported for the first time. Results indicate finite electrode thickness strongly affects efficiency. Using dense electrodes, efficiency is shown to approach 92% and 100% for uniform and periodic electrode guiding, respectively; yielding improved sensor detection limits. A numerical sensitivity analysis is presented targeting viscosity

  2. Sensitivity Tests Between Vs30 and Detailed Shear Wave Profiles Using 1D and 3D Site Response Analysis, Las Vegas Valley

    Science.gov (United States)

    West, Loyd Travis

    Site characterization is an essential aspect of hazard analysis and the time-averaged shear-wave velocity to 30 m depth "Vs30" for site-class has become a critical parameter in site-specific and probabilistic hazard analysis. Yet, the general applicability of Vs30 can be ambiguous and much debate and research surround its application. In 2007, in part to mitigate the uncertainty associated with the use of Vs30 in Las Vegas Valley, the Clark County Building Department (CCBD) in collaboration with the Nevada System of Higher Education (NSHE) embarked on an endeavor to map Vs30 using a geophysical methods approach for a site-class microzonation map of over 500 square miles (1500 km2) in southern Nevada. The resulting dataset, described by Pancha et al. (2017), contains over 10,700 1D shear-wave-velocity-depth profiles (SWVP) that constitute a rich database of 3D shear-wave velocity structure that is both laterally and vertical heterogenous. This study capitalizes on the uniquely detailed and spatially dense CCBD database to carry out sensitivity tests on the detailed shear-wave-velocity-profiles and the Vs30 utilizing 1D and 3D site-response approaches. Sensitivity tests are derived from the 1D oscillator response of a single-degree-of-freedom-oscillator and from 3D finite-difference deterministic simulations up to 15 Hz frequency using similar model parameters. Results demonstrate that the detailed SWVP are amplifying ground motions by roughly 50% over the simple Vs30 models, above 4.6 Hz frequency. Numerical simulations also depict significant lateral resonance, focusing, and scattering from seismic energy attributed to the 3D small-scale heterogeneities of the shear-wave-velocity profiles that result in a 70% increase in peak ground velocity. Additionally, PGV ratio maps clearly establish that the increased amplification from the detailed SWVPs is consistent throughout the model space. As a corollary, this study demonstrates the use of finite-differencing numerical

  3. Kinetic Simulations of the Interruption of Large-Amplitude Shear-Alfvén Waves in a High-β Plasma

    Science.gov (United States)

    Squire, J.; Kunz, M. W.; Quataert, E.; Schekochihin, A. A.

    2017-10-01

    Using two-dimensional hybrid-kinetic simulations, we explore the nonlinear "interruption" of standing and traveling shear-Alfvén waves in collisionless plasmas. Interruption involves a self-generated pressure anisotropy removing the restoring force of a linearly polarized Alfvénic perturbation, and occurs for wave amplitudes δ B⊥/B0≳β-1 /2 (where β is the ratio of thermal to magnetic pressure). We use highly elongated domains to obtain maximal scale separation between the wave and the ion gyroscale. For standing waves above the amplitude limit, we find that the large-scale magnetic field of the wave decays rapidly. The dynamics are strongly affected by the excitation of oblique firehose modes, which transition into long-lived parallel fluctuations at the ion gyroscale and cause significant particle scattering. Traveling waves are damped more slowly, but are also influenced by small-scale parallel fluctuations created by the decay of firehose modes. Our results demonstrate that collisionless plasmas cannot support linearly polarized Alfvén waves above δ B⊥/B0˜β-1 /2. They also provide a vivid illustration of two key aspects of low-collisionality plasma dynamics: (i) the importance of velocity-space instabilities in regulating plasma dynamics at high β , and (ii) how nonlinear collisionless processes can transfer mechanical energy directly from the largest scales into thermal energy and microscale fluctuations, without the need for a scale-by-scale turbulent cascade.

  4. Rheology over five orders of magnitude in model hydrogels: agreement between strain-controlled rheometry, transient elastography, and supersonic shear wave imaging.

    Science.gov (United States)

    Gennisson, Jean-Luc; Marcellan, Alba; Dizeux, Alexandre; Tanter, Mickaël

    2014-06-01

    Shear wave elastography helps physicians to characterize pathologies by assessing biomechanical properties of soft tissues. Compared with classical rheology, these techniques allow the quantification of the mechanical properties of tissues in the frequency range of hundreds of hertz. In this paper, ultrasound elastographic measurements and classical rheology are compared over a frequency range spanning five orders of magnitude [0.01 to 1200 Hz] to characterize model gels at multiple scales. Hybrid hydrogels were specially synthesized to get a fine tuning of the material dissipative response. Strain-controlled rheology (SCR) experiments were performed to get the elastic moduli G" and loss moduli G" from 0.01 Hz to 10 Hz and were confirmed by tensile tests. Transient elastography (TE from 50 to 400 Hz) and supersonic shear imaging (SSI from 200 to 1200 Hz) were used to characterize polymers at high frequency. Two different hydrogels were tested in the ultrasound setup with different concentration of scatterers. From low-frequency measurements, elastic moduli were extrapolated at high frequency and a very good correlation was obtained between SCR and TE and between SCR and SSI (r = 0.92 and r = 0.95, respectively). This paper demonstrates the capability of shear wave elastography to accurately image rheological properties of soft tissues, to differentiate soft elastic domains from viscous ones. It also gives new insights into soft material science because it provides a rheological tool in a high-frequency domain complementary to conventional rheometry.

  5. Review article "Remarks on factors influencing shear wave velocities and their role in evaluating susceptibilities to earthquake-triggered slope instability: case study for the Campania area (Italy"

    Directory of Open Access Journals (Sweden)

    V. Paoletti

    2012-07-01

    Full Text Available Shear wave velocities have a fundamental role in connection with the mitigation of seismic hazards, as their low values are the main causes of site amplification phenomena and can significantly influence the susceptibility of a territory to seismic-induced landslides. The shear wave velocity (Vs and modulus (G of each lithological unit are influenced by factors such as the degree of fracturing and faulting, the porosity, the clay amount and the precipitation, with the latter two influencing the unit water content. In this paper we discuss how these factors can affect the Vs values and report the results of different analyses that quantify the reduction in the rock Vs and shear modulus values connected to the presence of clay and water. We also show that significant results in assessing seismic-induced slope failure susceptibility for land planning targets could be achieved through a careful evaluation, based only on literature studies, of the geo-lithological and geo-seismic features of the study area.

  6. Effects of Acoustic Waves on Stick—Slip Behavior in Sheared Granular Media With Implications to Dynamic Earthquake Triggering and Slow Slip

    Science.gov (United States)

    Johnson, Paul; Marone, Chris; Knuth, Matt; Kaproth, Bryan; Carpenter, Brett; Behringer, Bob; Guyer, Robert; Le Bas, Pierre-Yves; Griffa, Michele; Carmeliet, Jan

    2010-05-01

    To better understand the physics of dynamic triggering and the influence of dynamic stressing on earthquake recurrence, we are conducting laboratory studies of stick—slip in granular media with and without applied acoustic waves. In our 3-D experiments, glass beads are used to simulate granular fault zone wear material, sheared in a double-direct configuration under constant normal stress, while subject to transient or continuous perturbations by acoustic waves. We find that the horizontal stress applied plays a crucial role in the response of the glass beads to applied waves. Under smaller normal stress (2MPa), and subject to wave amplitudes of >10-6 strain, we observe induced slow (silent) slip and tremor. Under moderate normal stress (4 MPa) and subject to >10-6 strain amplitude we observe both instantaneous and delayed triggering. Waves also cause significant disruption in the recurrence rate. The effects of waves are observed for many major-event cycles after wave excitation ceases, indicating a strain memory of waves in the granular material. Under slightly larger horizontal stress (5MPa), if strain amplitudes exceed 10-6, we observe instantaneous triggering followed by slow dynamics—the shear modulus recovers linearly with the-logarithm-of-time back to equilibrium. Slow dynamics is a classical elastic nonlinear (anelastic) behavior observed in acoustical experiments with rock samples in the lab as well as in Earth. Wave-induced disruption of periodic stick—slip is linked to failure of granular force chains. In 2-D experiments we are applying photoelastic discs in stick—slip measurements in order to visualize the evolution of the force chain network. Photoelastic measurements provide insight into failure, and in particular small adjustments in the force chains network that presage failure. A phenomenological model similar to Knopoff-Burridge shows the same general behaviors as well. In a companion paper, we show model results emplying a DEM approach

  7. Improved Dead Sea sinkhole site characterization at Ghor Al Haditha, Jordan, based on repeated shear wave reflection seismic profiling

    Science.gov (United States)

    Polom, Ulrich; Alrshdan, Hussam; Al-Halbouni, Djamil; Sawarieh, Ali; Dahm, Torsten; Krawczyk, CharLotte M.

    2016-04-01

    In October 2014 a high-resolution shallow shear wave reflection seismic survey was carried out at the Dead Sea sinkhole site Ghor Al Haditha, Jordan. It extended a survey undertaken in 2013, also in order to gather time-lapse profiles. In the framework of the DEad SEa Research Venue (DESERVE), a virtual institute of the Helmholtz Association and international partners, this investigation is part of a cross-disciplinary and cooperative international project of the Helmholtz Centers KIT, GFZ, and UFZ. At the investigation site, characterized by alluvial fan deposits, ongoing subsidence and sinkhole processes in the subsurface create massive reshaping of farming areas, including the destruction of housings, industrial sites, and infrastructure. The sinkhole hazard at the Dead Sea is significant, since similar processes are observed at several coastal segments of the Dead Sea. The new survey (in total 2.1 profile km) was targeted to improve the knowledge about the subsurface structures and to confine the results of the initial survey (1.8 km profile km), with respect to the presence or non-presence of a massive salt layer proposed at nearly 40 m depth. This salt layer is the central part of a widely established process hypothesis to generate shallow cavities by salt subrosion, which subsequently collapse to sinkholes at the surface. Results of the initial survey carried out in 2013 highlighted a new process hypothesis of subsurface mass transport by Dead Sea mud mobilization enclosed in the alluvial fan, so that an extended survey was undertaken in 2014. This, indeed, confirmed that there are no reflection seismic signal responses that would be expected to occur in the presence of a massive salt layer. Since evaluation of both hypothesis by new drilling could not be carried out due to safety reasons and permissions, it remained unclear which hypothesis is valid for the investigation site. However, we combined the 2013 and 2014 reflection seismic profiles and the

  8. Shear-wave elastography of the breast: value of a quality measure and comparison with strain elastography.

    Science.gov (United States)

    Barr, Richard G; Zhang, Zheng

    2015-04-01

    To determine whether addition of quality measure (QM) of shear-wave (SW) velocity (Vs) estimation can increase SW elastography sensitivity for breast cancer. With written informed consent, this institutional review board