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PubMed Journals Articles About "Point Frequency Shift Method Shear Wave Attenuation Measurement" RSS

17:39 EST 14th November 2019 | BioPortfolio

Point Frequency Shift Method Shear Wave Attenuation Measurement PubMed articles on BioPortfolio. Our PubMed references draw on over 21 million records from the medical literature. Here you can see the latest Point Frequency Shift Method Shear Wave Attenuation Measurement articles that have been published worldwide.

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Showing "Point Frequency Shift Method Shear Wave Attenuation Measurement" PubMed Articles 1–25 of 25,000+

Two-Point Frequency Shift (2P-FS) Method for Shear Wave Attenuation Measurement.

Ultrasound shear wave elastography (SWE) is an increasingly used noninvasive modality for quantitative evaluation of tissue mechanical properties. SWE typically uses an acoustic radiation force to produce laterally propagating shear waves that are tracked in the spatial and temporal domains, in order to obtain the wave velocity. One of the ways to study the viscoelasticity is through studying the shear wave phase velocity dispersion curves. Shear wave attenuation can be also characterized in viscoelastic ti...


Assessment of corneal viscoelasticity using elastic wave optical coherence elastography.

The corneal viscoelasticity have great clinical significance, such as the early diagnosis of keratoconus. In this work, an analysis method which utilized the elastic wave velocity, frequency and energy attenuation to assess the corneal viscoelasticity is presented. Using phase-resolved optical coherence tomography, the spatial-temporal displacement map is derived. The phase velocity dispersion curve and center frequency are obtained by transforming the displacement map into the wavenumber-frequency domain t...

Validation of a New Point Shear-Wave Elastography Method for Noninvasive Assessment of Liver Fibrosis: A Prospective Multicenter Study.

To validate the diagnostic value of a new point shear-wave elastography method, S-shearwave elastography (S-SWE; Samsung Medison Co., Ltd.), in noninvasive assessment of liver fibrosis.


Analysis of velocity calculation methods of laser-induced surface acoustic wave.

The key to measuring residual stress by surface acoustic wave method is the accurate measurement of velocity. In this paper, the velocity of laser-induced broadband surface acoustic wave is studied, and three velocity calculation methods of surface acoustic wave, time domain method, phase method and wavelet method are compared. The calculation error of the time domain method under the condition of dispersion is analyzed. A recursive method for calculating phase difference is proposed to improve the efficien...

Spectral Quantification of Nonlinear Elasticity using Acousto-elasticity and Shear-Wave Dispersion.

Tissue biomechanical properties are known to be sensitive to pathological changes. Accordingly, various techniques have been developed to estimate tissue mechanical properties. Shear-wave elastography (SWE) measures shear-wave speed (SWS) in tissues, which can be related to shear modulus. Although viscosity or stress-strain non-linearity may act as confounder of SWE, their explicit characterization may also provide additional information about tissue composition as a contrast modality. Viscosity can be rela...

Bi-annular shear-horizontal wave MPT tailored to generate the SH1 mode in a plate.

The use of a specific wave mode is critical in ultrasonic non-destructive evaluations but it is difficult to generate a specific mode, especially a higher mode at a frequency where there exist multiple wave modes. Here, we propose a compact omnidirectional shear-horizontal wave MPT (magnetostrictive patch transducer) having two annular magnetostrictive patches for the generation of a nearly pure SH1 (second shear-horizontal) mode in a plate for frequencies above the first cutoff frequency. While a common wa...

Laser-speckle-contrast projection tomography for three-dimensional shear wave imaging.

Laser-speckle-contrast shear wave (LSC-SW) imaging is an optical method for tracking the propagation of a transient shear wave. With high spatial resolution and sensitivity in detecting displacements, this method is suitable for performing mechanical measurements in vitro. Here, we present a LSC-SW tomographic imaging system for visualizing the propagating shear wave wavefront in four dimensions [i.e., three-dimensional (3D) space plus time]. The volumetric elasticity distribution of a sample is constructed...

Fast Local Phase Velocity Based Imaging (LPVI): Shear Wave Particle Velocity and Displacement Motion Study.

Fast and precise noninvasive evaluation of tissue mechanical properties is of high importance in ultrasound shear wave elastography. In this study we present an updated, faster version of the local phase velocity based imaging (LPVI) method used to create images of local phase velocity in soft tissues. The updated LPVI implementation uses one-dimensional Fourier transforms in spatial dimensions separately in comparison to its original implementation. A directional filter is applied upon the shear wave field...

Prospective comparison of transient, point shear wave, and magnetic resonance elastography for staging liver fibrosis.

To perform head-to-head comparisons of the feasibility and diagnostic performance of transient elastography (TE), point shear-wave elastography (pSWE), and magnetic resonance elastography (MRE).

Clutter Filter Wave Imaging.

The elastic properties of human tissue can be evaluated through the study of mechanical wave propagation captured using high-frame rate ultrasound imaging. Methods such as block-matching or phase-based motion estimation have been used to estimate the displacement induced by the mechanical waves. In this paper, a new method for detecting mechanical wave propagation without motion estimation is presented, where the motion of interest is accentuated by an appropriate clutter filter. Thus, the mechanical wave p...

Experimental and field investigations on seismic response of joints and beddings in rocks.

Based on experimental and in-situ tests, the propagation and attenuation rules of seismic wave in the intact and jointed rocks subjected to conventional triaxial loading condition were investigated, especially the influencing effects of joints and beddings on the attenuation. Meanwhile, the frequency-spectrum evolutions during the process of attenuation were analysed in detail. To verify the outcomes obtained from the laboratory, the attenuation characteristics of seismic wave generated by blasting in under...

Measurement of velocity and attenuation of ultrasonic guided wave for real-time estimation of cure-dependent anisotropic viscoelastic properties of carbon fiber-reinforced plastics.

An ultrasonic guided wave-based cure monitoring technique is developed to estimate cure-dependent anisotropic viscoelastic properties of carbon fiber reinforced plastics (CFRPs). The guided wave propagating in the transverse direction of a CFRP was measured during a cure process and the energy velocity and attenuation were obtained by signal processing. A micromechanics model and transfer matrix method were used to express the energy velocity and attenuation as functions of only the complex Young's modulus ...

Location specific temperature compensation of guided wave signals in structural health monitoring.

In guided wave structural health monitoring, defects are typically detected by identifying high residuals obtained via the baseline subtraction method, where an earlier measurement is subtracted from the 'current' signal. Unfortunately, varying environmental and operational conditions, such as temperature, also produce signal changes and hence, potentially, high residuals. While the majority of the temperature compensation methods that have been developed target the changed wave speed induced by varying tem...

Placental elasticity assessment by point shear wave elastography in pregnancies with intrauterine growth restriction.

Background Placental elasticity varies in different diseases. Our objective was to evaluate placental elasticity using point shear wave elastography (pSWE) in pregnancies with intrauterine growth restriction (IUGR). Methods A total of 66 pregnant women with IUGR and 81 healthy pregnant women were enrolled. Placental elasticity was measured using the transabdominal pSWE method. Ten measurements were made, and the mean was accepted as the mean placental elasticity value in each case. The results for IUGR preg...

Comparison of ultrasonic attenuation within two- and three-dimensional polycrystalline media.

An analytical approach to develop explicit formulas of attenuation coefficient in both 2D and 3D cases is proposed. It results in a better understanding of the grain scattering mechanisms within a polycrystalline material and the grain size effects on the attenuation of an ultrasonic wave. It is based on the Stanke and Kino's model and uses the Born approximation. An explicit formula is deduced for untextured polycrystals with equiaxed grains of cubic symmetry and allows a rigorous comparison of the attenua...

Usefulness of noninvasive shear wave elastography for the assessment of hepatic fibrosis in dogs with hepatic disease.

Two-dimensional shear wave elastography (2D-SWE) can noninvasively evaluate hepatic elastic modulus as shear wave velocity (SWV). Additionally, it may predict the presence of clinical relevant hepatic fibrosis (≥F2) in dogs with hepatic disease.

Cascaded rotational Doppler effect.

We propose and substantiate experimentally the cascaded rotational Doppler effect for interactions of spinning objects with light carrying spin angular momentum. Based on mirror symmetry for electromagnetic interactions, we reveal that the frequency shift can be doubled through cascading two rotational Doppler processes that are mirror-imaged to each other. This effect is further experimentally verified with a rotating half-wave plate, and the mirror-imaging process is achieved by reflecting the frequency-s...

A tunable bidirectional SH wave transducer based on antiparallel thickness-shear (d) piezoelectric strips.

Guided wave based defects inspection is very promising in the field of structural health monitoring (SHM) and nondestructive testing (NDT) due to its less dissipation and thus long distance coverage. In comparison with the widely used Lamb waves, shear horizontal (SH) waves are relatively simple but less investigated probably due to the traditional notion that SH waves were usually excited by electromagnetic acoustic transducers (EMAT). In this work, we proposed a tunable method to excite single-mode bidire...

A high-resolution structural health monitoring system based on SH wave piezoelectric transducers phased array.

Guided wave based structural health monitoring (SHM) has been regarded as an effective tool to detect the early damage in large structures and thus avoid possible catastrophic failure. In recent years, Lamb wave phased array SHM technology had been intensively investigated while the inherent multi-mode and dispersive characteristic of Lamb waves limits its further applications. In comparison, the fundamental shear horizontal (SH) wave is non-dispersive with uncoupled displacements and thus more promising fo...

Fully Automatic Liver Attenuation Estimation combing CNN Segmentation and Morphological Operations.

Manually tracing regions of interest (ROIs) within the liver is the de facto standard method for measuring liver attenuation on computed tomography (CT) in diagnosing nonalcoholic fatty liver disease (NAFLD). However, manual tracing is resource intensive. To address these limitations and to expand the availability of a quantitative CT measure of hepatic steatosis, we propose the automatic liver attenuation ROI-based measurement (ALARM) method for automated liver attenuation estimation.

Intraocular Pressure-Dependent Corneal Elasticity Measurement Using High-Frequency Ultrasound.

Measurement of corneal biomechanical properties can aid in predicting corneal responses to diseases and surgeries. For delineation of spatially resolved distribution of corneal elasticity, high-resolution elastography system is required. In this study, we demonstrate a high-resolution elastography system using high-frequency ultrasound for ex-vivo measurement of intraocular pressure (IOP)-dependent corneal wave speed. Tone bursts of 500 Hz vibrations were generated on the corneal surface using an electromag...

Liver stiffness does not affect ultrasound-guided attenuation coefficient measurement in the evaluation of hepatic steatosis.

Recently, a new method has been developed to diagnose hepatic steatosis with attenuation coefficients based on the ultrasound-guided attenuation parameter (UGAP). We investigated whether fibrosis identified by hepatic stiffness measurements based on magnetic resonance elastography (MRE) affects attenuation coefficient measurement using UGAP for the evaluation of hepatic steatosis.

Liver Stiffness Assessed by Ultrasound Shear Wave Elastography from General Electric Accurately Predicts Clinically Significant Portal Hypertension in Patients with Advanced Chronic Liver Disease.

 Clinically significant portal hypertension (CSPH) is responsible for most of the complications in patients with cirrhosis. Liver stiffness (LS) measurement by vibration-controlled transient elastography (VCTE) is currently used to evaluate CSPH. Bi-dimensional shear wave elastography from General Electric (2D-SWE.GE) has not yet been validated for the diagnosis of PHT. Our aims were to test whether 2D-SWE.GE-LS is able to evaluate CSPH, to determine the reliability criteria of the method and to compare i...

Developing and using fast shear wave elastography to quantify physiologically-relevant tendon forces.

Direct quantification of physiologically-relevant tendon forces can be used in a wide range of clinical applications. However, tendon forces have usually been estimated either indirectly by computational models or invasively using force transducers, and direct non-invasive measurement of forces remains a big challenge. The aim of this study was to investigate the feasibility of using Shear Wave Elastography (SWE) for quantifying human tendon forces at physiological levels. An experimental protocol was devel...

Change in Shear Elastic Modulus of Thigh Muscle by Changing Muscle Length Using Ultrasound Shear Wave Elastography in Beagle Dogs.

 This study investigated the relationship between the change in the shear elastic modulus and the change in muscle length using ultrasound shear wave elastography.


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