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https://www.readbyqxmd.com/read/28097687/requirements-for-accurate-estimation-of-anisotropic-material-parameters-by-magnetic-resonance-elastography-a-computational-study
#1
D J Tweten, R J Okamoto, P V Bayly
PURPOSE: To establish the essential requirements for characterization of a transversely isotropic material by magnetic resonance elastography (MRE). THEORY AND METHODS: Three methods for characterizing nearly incompressible, transversely isotropic (ITI) materials were used to analyze data from closed-form expressions for traveling waves, finite-element (FE) simulations of waves in homogeneous ITI material, and FE simulations of waves in heterogeneous material. Key properties are the complex shear modulus μ2 , shear anisotropy ϕ=μ1/μ2-1, and tensile anisotropy ζ=E1/E2-1...
January 17, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28092636/an-analysis-of-intrinsic-variations-of-low-frequency-shear-wave-speed-in-a-stochastic-tissue-model-the-first-application-for-staging-liver-fibrosis
#2
Yu Wang, Min Wang, Jingfeng Jiang
Shear wave elastography is increasingly being used to non-invasively stage liver fibrosis by measuring shear wave speed (SWS). This study quantitatively investigates intrinsic variations among SWS measurements obtained from heterogeneous media such as fibrotic livers. More specifically, it aims to demonstrate that intrinsic variations in SWS measurements, in general, follow a non-Gaussian distribution and are related to the heterogeneous nature of the medium being measured. Using the principle of maximum entropy (ME), our primary objective is to derive a probability density function (PDF) of the SWS distribution in conjunction with a lossless stochastic tissue model...
February 7, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28092532/improved-shear-wave-group-velocity-estimation-method-based-on-spatiotemporal-peak-and-thresholding-motion-search
#3
Carolina Amador Carrascal, Shigao Chen, Armando Manduca, James F Greenleaf, Matthew Urban
Quantitative ultrasound elastography is increasingly being used in the assessment of chronic liver disease. Many studies have reported ranges of liver shear wave velocities values for healthy individuals and patients with different stages of liver fibrosis. Nonetheless, ongoing efforts exist to stabilize quantitative ultrasound elastography measurements by assessing factors that influence tissue shear wave velocity values, such as food intake, body mass index (BMI), ultrasound scanners, scanning protocols, ultrasound image quality, etc...
January 11, 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/28092508/ultrasonic-shear-wave-elasticity-imaging-sequencing-and-data-processing-using-a-verasonics-research-scanner
#4
Yufeng Deng, Ned C Rouze, Mark L Palmeri, Kathryn R Nightingale
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...
January 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/28090117/generation-of-shear-waves-by-laser-in-soft-media-in-the-ablative-and-thermoelastic-regimes
#5
Pol Grasland-Mongrain, Yuankang Lu, Frederic Lesage, Stefan Catheline, Guy Cloutier
This article describes the generation of elastic shear waves in a soft medium using a laser beam. Our experiments show two different regimes depending on laser energy. Physical modeling of the underlying phenomena reveals a thermoelastic regime caused by a local dilatation resulting from temperature increase, and an ablative regime caused by a partial vaporization of the medium by the laser. Computed theoretical displacements are close to experimental measurements. A numerical study based on the physical modeling gives propagation patterns comparable to those generated experimentally...
November 28, 2016: Applied Physics Letters
https://www.readbyqxmd.com/read/28087063/spatial-dependent-mechanical-properties-of-the-heel-pad-by-shear-wave-elastography
#6
Che-Yu Lin, Pei-Yu Chen, Yio-Wha Shau, Hao-Chih Tai, Chung-Li Wang
The heel pad plays an important role in gait, and its biomechanical behavior and functionality are determined by its specialized architecture and mechanical properties. The purpose of this study was to apply supersonic shear wave elastography, an ultrasound-based noninvasive modality that can quantitatively estimate the shear stiffness of the tissue, to investigate the spatial-dependent mechanical properties of the heel pad. Measurements were conducted in 40 heel pads of 20 normal participants aged between 20 and 30 years by shear wave elastography...
January 6, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/28081023/a-case-study-of-hemochromatosis-and-conflicting-point-shear-wave-measurements-in-the-assessment-of-liver-fibrosis
#7
Tal Cohen, Richard G Barr
There are multiple factors that affect the shear wave speed in the assessment of liver stiffness. In this case report, we present a case of hemochromatosis that has elevated liver stiffness suggestive of significant fibrosis or cirrhosis; however on liver biopsy, no fibrosis was identified. This article will discuss the possibility that liver iron deposition may affect SWE measurements of the liver, leading to inaccurate assessment of liver fibrosis. In these cases, a liver biopsy may be required for accurate liver assessment...
January 9, 2017: Ultrasound Quarterly
https://www.readbyqxmd.com/read/28081009/influence-of-wall-thickness-and-diameter-on-arterial-shear-wave-elastography-a-phantom-and-finite-element-study
#8
Elira Maksuti, Fabiano Bini, Stefano Fiorentini, Giulia Blasi, Matthew Urban, Franco Marinozzi, Matilda Larsson
Quantitative, non-invasive and local measurements of arterial mechanical properties could be highly beneficial for early diagnosis of cardiovascular disease and follow up of treatment. Arterial Shear Wave Elastography (SWE) and wave velocity dispersion analysis have previously been applied to measure arterial stiffness. Arterial wall thickness (h) and inner diameter (D) vary with age and pathology and may influence the shear wave propagation. Nevertheless, the effect of arterial geometry in SWE has not yet been systematically investigated...
January 12, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28081004/reverberant-shear-wave-fields-and-estimation-of-tissue-properties
#9
Kevin J Parker, Juvenal Ormachea, Fernando Zvietcovich, Benjamin Castaneda
The determination of shear wave speed is an important subject in the field of elastography, since elevated shear wave speeds can be directly linked to increased stiffness of tissues. MRI and ultrasound scanners are frequently used to detect shear waves and a variety of estimators are applied to calculate the underlying shear wave speed. The estimators can be relatively simple if plane wave behavior is assumed with a known direction of propagation. However, multiple reflections from organ boundaries and internal inhomogeneities and mode conversions can create a complicated field in time and space...
February 7, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28078847/real-time-shear-wave-elastrography-and-apri-index-for-evaluating-autoimmune-hepatitis-fibrosis
#10
L L Sun, G Dong, B Wang, Q Zheng, S Wang, R F Zhang
The objective of this study was to investigate the significance of real-time supersonic shear imaging (SSI) and serum biochemical index in evaluating the degree of autoimmune hepatitis fibrosis. Retrospective analysis was carried out to study 291 cases of patients with autoimmune hepatitis, and discuss the value of SSI application, APRI index and bilirubin on autoimmune hepatitis. The area under the receiver operating characteristic curve (AUROC) was taken for statistical analysis to determine its diagnostic accuracy...
October 2016: Journal of Biological Regulators and Homeostatic Agents
https://www.readbyqxmd.com/read/28077785/the-diagnostic-performance-of-shear-wave-speed-sws-imaging-for-thyroid-nodules-with-elasticity-modulus-and-sws-measurement
#11
Dan Wang, Ya-Ping He, Yi-Feng Zhang, Bo-Ji Liu, Chong-Ke Zhao, Hui-Jun Fu, Qing Wei, Hui-Xiong Xu
To evaluate the diagnostic performance of a new technique of shear wave speed (SWS) imaging for the diagnosis of thyroid nodule with elasticity modulus and SWS measurement. 322 thyroid nodules in 322 patients (216 benign nodules, 106 malignant nodules) were included in this study. All the nodules received conventional ultrasound (US) and SWS imaging (Aplio500, Toshiba Medical Systems, Japan) before fine-needle aspiration (FNA) and/or surgery. The values of E-max and E-mean with elastic modulus (61.27 ± 36...
January 6, 2017: Oncotarget
https://www.readbyqxmd.com/read/28076414/a-mri-compatible-combined-mechanical-loading-and-mr-elastography-setup-to-study-deformation-induced-skeletal-muscle-damage-in-rats
#12
Jules L Nelissen, Larry de Graaf, Willeke A Traa, Tom J L Schreurs, Kevin M Moerman, Aart J Nederveen, Ralph Sinkus, Cees W J Oomens, Klaas Nicolay, Gustav J Strijkers
Deformation of skeletal muscle in the proximity of bony structures may lead to deep tissue injury category of pressure ulcers. Changes in mechanical properties have been proposed as a risk factor in the development of deep tissue injury and may be useful as a diagnostic tool for early detection. MRE allows for the estimation of mechanical properties of soft tissue through analysis of shear wave data. The shear waves originate from vibrations induced by an external actuator placed on the tissue surface. In this study a combined Magnetic Resonance (MR) compatible indentation and MR Elastography (MRE) setup is presented to study mechanical properties associated with deep tissue injury in rats...
2017: PloS One
https://www.readbyqxmd.com/read/28075330/building-an-open-source-simulation-platform-of-acoustic-radiation-force-based-breast-elastography
#13
Yu Wang, Bo Peng, Jingfeng Jiang
Ultrasound-based elastography techniques including quasi-static strain elastography (SE), acoustic radiation force Impulse (ARFI) imaging, point shear wave elastography (pSWE) and supersonic shear imaging (SSI) have been used to differentiate breast tumors. The objective of this study is to extend a previously published virtual simulation platform of SE toward acoustic radiation force-based breast elastography. The proposed platform inherited four key components from the previously published virtual SE platform: an ultrasound simulator (Field II), a mesh generator (Tetgen), a finite element (FE) solver (FEBio) and a visualization and data processing package (VTK)...
January 11, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28073534/turbulence-increases-the-risk-of-microcystin-exposure-in-a-eutrophic-lake-lake-taihu-during-cyanobacterial-bloom-periods
#14
Jian Zhou, Boqiang Qin, Xiaoxia Han, Lin Zhu
Toxic cyanobacterial harmful algal blooms (CyanoHABs) have posed serious water use and public health threats because of the toxins they produce, such as the microcystins (MCs). The direct physical effects of turbulence on MCs, however, have not yet been addressed and is still poorly elucidated. In this study, a 6-day mesocosm experiment was carried out to evaluate the effects of wind wave turbulence on the competition of toxic Microcystis and MCs production in highly eutrophicated and turbulent Lake Taihu, China...
May 2016: Harmful Algae
https://www.readbyqxmd.com/read/28069229/rapid-formation-of-ni3sn4-joints-for-die-attachment-of-sic-based-high-temperature-power-devices-using-ultrasound-induced-transient-liquid-phase-bonding-process
#15
Z L Li, H J Dong, X G Song, H Y Zhao, J C Feng, J H Liu, H Tian, S J Wang
High melting point Ni3Sn4 joints for the die attachment of SiC-based high temperature power devices was successfully achieved using an ultrasound-induced transient liquid phase (TLP) bonding process within a remarkably short bonding time of 8s. The formed intermetallic joints, which are completely composed of the refined equiaxial Ni3Sn4 grains with the average diameter of 2μm, perform the average shear strength of 26.7MPa. The sonochemical effects of ultrasonic waves dominate the mechanism and kinetics of the rapid formation of Ni3Sn4 joints...
May 2017: Ultrasonics Sonochemistry
https://www.readbyqxmd.com/read/28065540/cardiac-shear-wave-velocity-detection-in-the-porcine-heart
#16
Hendrik J Vos, Bas M van Dalen, Ilkka Heinonen, Johan G Bosch, Oana Sorop, Dirk J Duncker, Antonius F W van der Steen, Nico de Jong
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...
January 5, 2017: Ultrasound in Medicine & Biology
https://www.readbyqxmd.com/read/28065370/a-new-qualitative-pattern-classification-of-shear-wave-elastograghy-for-solid-breast-mass-evaluation
#17
Rui Cong, Jing Li, Song Guo
OBJECTIVES: 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. METHODS: 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...
February 2017: European Journal of Radiology
https://www.readbyqxmd.com/read/28063644/are-transient-and-shear-wave-elastography-useful-tools-in-gaucher-disease
#18
Muriel Webb, Ari Zimran, Tama Dinur, Oren Shibolet, Stella Levit, David M Steinberg, Ophira Salomon
Up to now, there are no reliable biochemical markers or imaging that could reveal early tissue damage in Gaucher disease. Therefore, we addressed whether elastography technique can serve as a tool for evaluating patients with Gaucher disease. The study included 42 patients with Gaucher disease type I and 33 patients with liver cirrhosis as well as 22 healthy volunteers. Ultrasound and Doppler examination was performed on each participant prior to apply transient and 2D shear wave elastography. In Gaucher disease the median stiffness of the spleen as assessed by transient elastography (TE) and shear wave elastography (SWE) was 35KPa and 22KPa respectively in contrast to the median stiffness of healthy controls (16...
December 23, 2016: Blood Cells, Molecules & Diseases
https://www.readbyqxmd.com/read/28062178/testicular-shear-wave-elastography-in-normal-and-infertile-men-a-prospective-study-on-601-patients
#19
Laurence Rocher, Aline Criton, Jean-Luc Gennisson, Vincent Izard, Sophie Ferlicot, Mickael Tanter, Gerard Benoit, Marie France Bellin, Jean-Michel Correas
Our aim in the study described here was to prospectively establish the feasibility of using and reproducibility of testicular shear-wave elastography in the assessment of testicular stiffness in 62 normal patients and 539 infertile men with obstructive azoospermia (OA), non-Klinefelter syndrome non-obstructive azoospermia (non-KS NOA), Klinefelter syndrome NOA (KS NOA), oligoasthenoteratozoospermia (OAT) or a left varicocele. The feasibility rate was 96.9%, with an intra-class correlation coefficient of 0.85 (95% confidence interval: 0...
January 3, 2017: Ultrasound in Medicine & Biology
https://www.readbyqxmd.com/read/28057657/measuring-shear-wave-speed-with-point-shear-wave-elastography-and-mr-elastography-a-phantom-study
#20
Riwa Kishimoto, Mikio Suga, Atsuhisa Koyama, Tokuhiko Omatsu, Yasuhiko Tachibana, Daniel K Ebner, Takayuki Obata
OBJECTIVES: To compare shear-wave speed (SWS) measured by ultrasound-based point shear-wave elastography (pSWE) and MR elastography (MRE) on phantoms with a known shear modulus, and to assess method validity and variability. METHODS: 5 homogeneous phantoms of different stiffnesses were made. Shear modulus was measured by a rheometer, and this value was used as the standard. 10 SWS measurements were obtained at 4 different depths with 1.0-4.5 MHz convex (4C1) and 4...
January 5, 2017: BMJ Open
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