SNR Weighting for Shear Wave Speed Reconstruction in Tomoelastography

2020 ◽  
Vol 34 (1) ◽  
Author(s):  
Cemre Ariyurek ◽  
Bilal Tasdelen ◽  
Yusuf Ziya Ider ◽  
Ergin Atalar
Keyword(s):  
Shear Wave ◽  
Wave Speed ◽  
Shear Wave Speed

scholarly journals Spatial variations in Achilles tendon shear wave speed

2014 ◽  
Vol 47 (11) ◽  
pp. 2685-2692 ◽  
Author(s):  
Ryan J. DeWall ◽  
Laura C. Slane ◽  
Kenneth S. Lee ◽  
Darryl G. Thelen
Keyword(s):  
Achilles Tendon ◽  
Shear Wave ◽  
Wave Speed ◽  
Spatial Variations ◽  
Shear Wave Speed

Measured temperature and pressure dependence of Vp and Vs in compacted, polycrystalline sI methane and sII methane–ethane hydrate

2003 ◽  
Vol 81 (1-2) ◽  
pp. 47-53 ◽  
Author(s):  
M B Helgerud ◽  
W F Waite ◽  
S H Kirby ◽  
A Nur
Keyword(s):  
High Pressure ◽  
Shear Wave ◽  
Pressure Dependence ◽  
Gas Hydrate ◽  
Pressure Vessel ◽  
Wave Speed ◽  
Measured Temperature ◽  
Shear Wave Speed ◽  
Temperature And Pressure ◽  
Fixed End

We report on compressional- and shear-wave-speed measurements made on compacted polycrystalline sI methane and sII methane–ethane hydrate. The gas hydrate samples are synthesized directly in the measurement apparatus by warming granulated ice to 17°C in the presence of a clathrate-forming gas at high pressure (methane for sI, 90.2% methane, 9.8% ethane for sII). Porosity is eliminated after hydrate synthesis by compacting the sample in the synthesis pressure vessel between a hydraulic ram and a fixed end-plug, both containing shear-wave transducers. Wave-speed measurements are made between –20 and 15°C and 0 to 105 MPa applied piston pressure. PACS No.: 61.60Lj

Diagnosis of liver fibrosis based on quantification of factors associated with shear wave speed

Choonpa Igaku ◽  
2021 ◽  
Author(s):  
Hiroko IIJIMA ◽  
Toshifumi TADA ◽  
Hiroyuki HACHIYA ◽  
Takashi NISHIMURA ◽  
Junko NISHIMURA ◽  
...  
Keyword(s):  
Liver Fibrosis ◽  
Shear Wave ◽  
Wave Speed ◽  
Shear Wave Speed ◽  
Factors Associated

scholarly journals A soft cervix, categorized by shear-wave elastography, in women with short or with normal cervical length at 18–24 weeks is associated with a higher prevalence of spontaneous preterm delivery

2018 ◽  
Vol 46 (5) ◽  
pp. 489-501 ◽  
Author(s):  
Edgar Hernandez-Andrade ◽  
Eli Maymon ◽  
Suchaya Luewan ◽  
Gaurav Bhatti ◽  
Mohammad Mehrmohammadi ◽  
...  
Keyword(s):  
Cohort Study ◽  
Preterm Delivery ◽  
Shear Wave ◽  
Wave Speed ◽  
Shear Wave Elastography ◽  
Cervical Length ◽  
Singleton Pregnancy ◽  
Short Cervix ◽  
Shear Wave Speed ◽  
Spontaneous Preterm Delivery

AbstractObjective:To determine whether a soft cervix identified by shear-wave elastography between 18 and 24 weeks of gestation is associated with increased frequency of spontaneous preterm delivery (sPTD).Materials and methods:This prospective cohort study included 628 consecutive women with a singleton pregnancy. Cervical length (mm) and softness [shear-wave speed: (SWS) meters per second (m/s)] of the internal cervical os were measured at 18–24 weeks of gestation. Frequency of sPTD <37 (sPTD<37) and <34 (sPTD<34) weeks of gestation was compared among women with and without a short (≤25 mm) and/or a soft cervix (SWS <25thpercentile).Results:There were 31/628 (4.9%) sPTD<37 and 12/628 (1.9%) sPTD<34 deliveries. The combination of a soft and a short cervix increased the risk of sPTD<37 by 18-fold [relative risk (RR) 18.0 (95% confidence interval [CI], 7.7–43.9); P<0.0001] and the risk of sPTD<34 by 120-fold [RR 120.0 (95% CI 12.3–1009.9); P<0.0001] compared to women with normal cervical length. A soft-only cervix increased the risk of sPTD<37 by 4.5-fold [RR 4.5 (95% CI 2.1–9.8); P=0.0002] and of sPTD<34 by 21-fold [RR 21.0 (95% CI 2.6–169.3); P=0.0003] compared to a non-soft cervix.Conclusions:A soft cervix at 18–24 weeks of gestation increases the risk of sPTD <37 and <34 weeks of gestation independently of cervical length.

Sensitivity of the Shear Wave Speed-Stress Relationship to Soft Tissue Material Properties and Fiber Alignment

2021 ◽  
Author(s):  
Jonathon Blank ◽  
Darryl Thelen ◽  
Matthew S. Allen ◽  
Joshua Roth
Keyword(s):  
Wave Propagation ◽  
Shear Modulus ◽  
Shear Wave ◽  
Wave Speed ◽  
Axial Stress ◽  
Beam Model ◽  
Fiber Alignment ◽  
Wave Speeds ◽  
Shear Wave Speed ◽  
Constitutive Properties

The use of shear wave propagation to noninvasively gauge material properties and loading in tendons and ligaments is a growing area of interest in biomechanics. Prior models and experiments suggest that shear wave speed primarily depends on the apparent shear modulus (i.e., shear modulus accounting for contributions from all constituents) at low loads, and then increases with axial stress when axially loaded. However, differences in the magnitudes of shear wave speeds between ligaments and tendons, which have different substructures, suggest that the tissue’s composition and fiber alignment may also affect shear wave propagation. Accordingly, the objectives of this study were to (1) characterize changes in the apparent shear modulus induced by variations in constitutive properties and fiber alignment, and (2) determine the sensitivity of the shear wave speed-stress relationship to variations in constitutive properties and fiber alignment. To enable systematic variations of both constitutive properties and fiber alignment, we developed a finite element model that represented an isotropic ground matrix with an embedded fiber distribution. Using this model, we performed dynamic simulations of shear wave propagation at axial strains from 0% to 10%. We characterized the shear wave speed-stress relationship using a simple linear regression between shear wave speed squared and axial stress, which is based on an analytical relationship derived from a tensioned beam model. We found that predicted shear wave speeds were both in-range with shear wave speeds in previous in vivo and ex vivo studies, and strongly correlated with the axial stress (R2 = 0.99). The slope of the squared shear wave speed-axial stress relationship was highly sensitive to changes in tissue density. Both the intercept of this relationship and the apparent shear modulus were sensitive to both the shear modulus of the ground matrix and the stiffness of the fibers’ toe-region when the fibers were less well-aligned to the loading direction. We also determined that the tensioned beam model overpredicted the axial tissue stress with increasing load when the model had less well-aligned fibers. This indicates that the shear wave speed increases likely in response to a load-dependent increase in the apparent shear modulus. Our findings suggest that researchers may need to consider both the material and structural properties (i.e., fiber alignment) of tendon and ligament when measuring shear wave speeds in pathological tissues or tissues with less well-aligned fibers.

Lithospheric structure of the North American Craton constrained by full waveform inversion

2021 ◽  
Author(s):  
Tong Zhou ◽  
Min Chen ◽  
Ziyi Xi ◽  
Jiaqi Li
Keyword(s):  
Shear Wave ◽  
Wave Speed ◽  
Waveform Inversion ◽  
Continental Lithosphere ◽  
Shear Wave Speed ◽  
The North ◽  
Full Waveform ◽  
Radial Anisotropy ◽  
North American Craton ◽  
Superior Craton

&lt;p&gt;Cratonic lithosphere is believed to be rigid and less deformed during a long period of time. However, the detailed structure of Cratons may bring information of the complex formation and assemblage process of the continental lithosphere. Here, we present the seismic radial anisotropic structure of the North American Craton (NAC) constrained by a regional full-waveform inversion (FWI) with 465,422 high-quality frequency-dependent travel time misfit measurements with the shortest period of 15 s from both the body wave and surface wave recordings of 5,120 stations and 160 earthquakes located in the contiguous U.S and surrounding regions. Started from an initial model constructed by combining US.2016 and Crust1.0 in the crust and S40RTS (isotropic) in the mantle, we are able to have the optimized crustal structure in terms of initial waveform similarity and get rid of existing features from other radially anisotropic mantle models.&lt;/p&gt;&lt;p&gt;Our new model reveals the NAC lithosphere with about +2% voigt shear wave speed anomaly and an average thickness of 200&amp;#8211;250 km beneath the Superior Craton, and becomes thinner towards the eastern, the southern, and the southwestern margins with a thickness decreased to 100&amp;#8211;150 km. The radial anisotropy manifests a layer of higher horizontal shear wave speed V&lt;sub&gt;SH&amp;#160;&lt;/sub&gt;(&amp;#958;=V&lt;sub&gt;SH&lt;/sub&gt;&lt;sup&gt;2&lt;/sup&gt;/V&lt;sub&gt;SV&lt;/sub&gt;&lt;sup&gt;2&lt;/sup&gt;&gt;1) beneath the core of Superior Craton down to around 160 km, where the higher vertical shear wave speed V&lt;sub&gt;SV &lt;/sub&gt;(&amp;#958;&lt;1) is observed beneath 160 km. Such radial anisotropy layering is also observed in the margin of continental lithosphere but with shallower depth. The radial anisotropic layer matches the receiver function results of mid-lithosphere discontinuities of the Craton cores, and the lithosphere conductivity result.&amp;#160;The radial anisotropy layering observation confirms the two-layered lithosphere structure of the NAC, where the upper layer likely represents the original radial anisotropy fabric related to the cooling of the craton core, while the lower layer might be related to the tectonic processes more recently, e.g., accretion .&amp;#160;The lithospheric thinning beneath the NAC margins indicates the deformation of the lithosphere and is likely controlled by the large-scale mantle convection, therefore relates to the further modification process of the NAC.&lt;/p&gt;

A feasibility study for noninvasive measurement of shear wave speed in live zebrafish

Ultrasonics ◽  
2020 ◽  
Vol 107 ◽  
pp. 106170
Author(s):  
Xiaoming Zhang ◽  
Alex X. Zhang ◽  
Boran Zhou ◽  
Xiaolei Xu
Keyword(s):  
Shear Wave ◽  
Feasibility Study ◽  
Wave Speed ◽  
Noninvasive Measurement ◽  
Shear Wave Speed

Bayesian Shear Wave Speed Reconstruction with an On-Axis ARFI Prior

2019 ◽  
Author(s):  
Derek Y. Chan ◽  
Ned C. Rouze ◽  
Mark L. Palmeri ◽  
Kathryn R. Nightingale
Keyword(s):  
Shear Wave ◽  
Wave Speed ◽  
Shear Wave Speed
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