Shear Wave Propagation Velocity Research Articles

Shear wave trajectory detection in ultra-fast M-mode images for liver fibrosis assessment: A deep learning-based line detection approach

Stiffness measurement using shear wave propagation velocity has been the most common non-invasive method for liver fibrosis assessment. The velocity is captured through a trace recorded by transient ultrasonographic elastography, with the slope indicating the velocity of the wave. However, due to various factors such as noise and shear wave attenuation, detecting shear wave trajectory on wave propagation maps is a challenging task. In this work, we made the first attempt to use deep learning methods for shear wave trajectory detection on wave propagation maps. Specifically, we adopted five deep learning models in this task and evaluated them by using a well-acknowledged metric based on EA-Angular-Score (EAA) and task-specific metric based on Young s-Score (Ys) in the line-detection field. Furthermore, we proposed an end-to-end framework based on a Transformer and Hough transform, named Transformer-enhanced Hough Transform (TEHT). It took a wave propagation map as input image and directly output the slope of the shear wave trajectory. The framework extracts multi-scale local features from wave propagation maps, employs a deformable attention mechanism for feature fusion, identifies the target line using the Hough transform’s voting mechanism, and calculates the contribution of each scale through channel attention. Wave propagation maps from 68 patients were utilized in this study, with manual annotation performed by a rater who was trained as a radiologist, serving as the reference value. The evaluation revealed that the SLNet model exhibited F-measure of EA and Ys values as 40.33 % and 40.72 %, respectively, while the TEHT model showed F-measure of EA and Ys values as 80.96 % and 98.00 %, respectively. TEHT yielded significantly better performance than other deep learning models. Moreover, TEHT demonstrated strong concordance with the gold standard, yielding R2 values of 0.967 and 0.968 for velocity and liver stiffness, respectively. The present study therefore suggests the application of the TEHT model for assessing liver fibrosis owing to its superiority among the five deep learning models.

Stability analysis of circular tunnels using spatiotemporal accelerations formulated considering heterogeneity of seismic wave propagation velocities

The space–time dependent horizontal and vertical seismic accelerations in a soil medium owing to the inhomogeneity in the shear and primary wave propagation velocities were analytically derived satisfying the boundary conditions on the ground surface and the base. The developed analytical formulations were applied to study the influence of wave velocity heterogeneity on the support pressure required for the circular tunnel stability placed in granular soils using the stress-based limit analysis in conjunction with finite elements. The support pressure was determined as the maximum normal stress exerted by the surrounding earth at its ultimate failure on the tunnel boundary. Further, the effect of frequency of seismic waves on the seismic accelerations, magnitude of tunnel support pressure and the variation of normal stress around the tunnel periphery has been presented in detail. The support pressure was found to be higher considering the heterogeneous wave velocity than the uniform one. A lower dimensionless frequency resulted in higher support pressures for a lower wave velocity ratio and higher power parameter of the power law used to model the wave velocity profile. Otherwise, for higher wave velocity ratio, the effect of power parameter diminishes, and the support pressure is higher for higher dimensionless frequency.

Characteristics of karst caves inferred from microtremor studies: A case study from Cerme Cave, Yogyakarta, Indonesia

A microtremor survey based on ground surface data acquisition was used to identify and characterize the karst area of Cerme Cave, Yogyakarta, Indonesia, from the entrance to the exit of the cave. The entrance and exit of the cave are used as tie-in points because the characteristics of the two locations can be directly observed. Parameters used in this study include ground vibration amplification, shear wave velocity, and Poisson’s ratio. The presence of cavities can be characterized by a relatively strong contrast between these physical parameters and their surroundings. The exit of the cave, which can be considered as a sinkhole, has a dominant frequency of 3.2 to 4.6 Hz, which is relatively higher than that of the surrounding area. At the entrance of Cerme Cave, which has a large cavity, a small ground vibration amplification was detected, less than 0.1. The entrance and exit of the cave also exhibit a low shear wave propagation velocity of less than 350 m/s. The presence of a subsurface fluvial channel in Cerme Cave can be characterized by a high Poisson’s ratio of 0.4–0.5, a gain value of less than 0.1, and a shear wave velocity of less than 350 m/s.

Effect of inconsistency of irradiation conditions of acoustic radiation force caused by tissue structure on shear wave velocity evaluation

Previous studies have shown that shear wave elastography of liver tissue can be unstable due to factors such as uncertainties in the acoustic radiation force (ARF) irradiation due to the influence of tissues near the surface and the complexity of the liver’s structure and its physical properties. This study aims to verify the influence of near-surface tissues on ARF and the effect of tissue structure on shear wave propagation and shear wave velocity (SWV) evaluation using wave propagation simulations by the elastic finite-difference time domain method. It is found that the ARF becomes weakly focused on multiple locations due to refraction of longitudinal waves by near-surface tissues, and multiple shear waves of small amplitude are propagated. However, a macroscopic SWV assessment, as in clinical practice, reduces the influence of near-surface tissues because the microscopic assessment results are averaged over the near-surface tissues.

Factors other than fibrosis that increase measured shear wave velocity.

Shear wave elastography (SWE) is now becoming an indispensable diagnostic tool in the routine examination of liver diseases. In particular, accuracy is required for shear wave propagation velocity measurement, which is directly related to diagnostic accuracy. It is generally accepted that the liver shear wave propagation velocity reflects the degree of fibrosis, but there are still few reports on other factors that increase the shear wave propagation velocity. In this study, we reviewed such factors in the literature and examined their mechanisms. Current SWE measures propagation velocity based on the assumption that the medium has a homogeneous structure, uniform density, and is purely elastic. Otherwise, the measurement is subject to error. The other (confounding) factors that we routinely experience are primarily: (1) Conditions that appear to increase the viscous component; and (2) Conditions that appear to increase tissue density. Clinically, the former includes acute hepatitis, congested liver, biliary obstruction, etc, and the latter includes diffuse infiltration of malignant cells, various storage diseases, tissue necrosis, etc. In any case, it is important to evaluate SWE in the context of the entire clinical picture.

Evaluation of the Elasticity of the Pancreas Using Acoustic Radiation Force Impulse Elastography in Patients with Acute Pancreatitis: A Systematic Review and Meta-Analysis.

Acoustic radiation force impulse (ARFI) elastography has been used to diagnose acute pancreatitis (AP). The present study aimed to assess the effectiveness of ARFI elastography in the diagnosis of AP. Studies examining the efficacy of ARFI elastography in AP were selected by searching MEDLINE, EMBASE, CENTRAL, ICTRP, and ClinicalTrial.gov. until September 2021. Meta-analyses were performed using random effects models. The Grading of Recommendations, Assessment, Development, and Evaluation approach was used to assess the certainty of the evidence. Eight case-control studies (994 patients) were included in the meta-analysis. The ARFI-Virtual Touch Quantification value (or ARFI shear wave propagation velocity) of the AP patient group was 0.83 m/s higher (95% confidence interval [CI]: 0.36-1.3) than that in the control group (95% CI: 1.0-1.28). The sensitivity and specificity of ARFI elastography for diagnosing AP were 98.3% (95% CI: 92.6-96.6%) and 95.5% (95% CI: 87.5-98.5%), respectively. The results showed that physicians could use ARFI elastography to accurately diagnose patients with AP. Additional well-designed studies are necessary to validate the efficacy of ARFI elastography in patients with AP.

How well does shear wave elastography predict elevated filling pressures? a comparison to the current guideline algorithm

Abstract Funding Acknowledgements Type of funding sources: Public hospital(s). Main funding source(s): University Hospitals (Uz) Leuven Background The assessment of left ventricular diastolic function is complex, as there is no single invasive parameter that provides a direct measurement of myocardial compliance, myocardial relaxation, or – as a surrogate - LV filling pressure. A combination of several parameters is therefore used to estimate the diastolic function. Shear wave (SW) elastography is a novel method based on high frame rate echocardiography. SWs occur after mechanical excitation of the myocardium, e.g. after mitral valve closure (MVC), and their propagation velocity is directly related to myocardial stiffness (MS). The propagation velocity of SWs is directly related to myocardial stiffness and could be used for estimating left ventricular diastolic pressures. Purpose The aim of this study was to investigate if the MS at mid-diastole or end-diastole and the velocities of natural shear waves are related and, thus, could be used to estimate left ventricular end-diastolic pressures (LVEDP) as marker of diastolic function. Methods We prospectively enrolled 70 patients with a wide range of diastolic function, scheduled for heart catheterization so that LV mid diastolic filling pressures (LVMDP) and enddiastolic filling pressures (LVEDP) could be invasively measured (Panel B). Patients with dysfunction in the anteroseptal wall or regional myocardial abnormalities, as well as severe aortic stenosis, and a more than moderate mitral regurgitation were excluded. Echocardiography was performed immediately after catheterization. SW elastography in parasternal long axis views of the left ventricle (LV) was performed using an experimental scanner (HD-PULSE) at 1050 ± 220 frames per second. Tissue acceleration maps were extracted from an anatomical M-mode line along the midline of the LV septum. The SW propagation velocity at MVC was measured as the slope on the M-mode acceleration map (Panel A). Standard echocardiographic parameters of diastolic function were obtained with a high end ultrasound machine. The Algorithm for evaluating diastolic dysfunction as recommended by the European Association of Cardiovascular Imaging Guidelines 2016 was used for estimating LVMDP. Results SW Velocity correlated better with LVMDP (AUC = 0.8, Sensitivity = 0.84, Specificity= 0.80; =0.26; Panels C,E) than the Guideline approach (AUC = 0.67, Sensitivity = 0.33, Specificity = 1.00, Panel G). SWV showed the best results in predicting LVEDP (AUC = 0.94, Sensitivity = 0.92, Specificity = 0.89 and =0.56 (Panels D,F)). Conclusions Shear wave velocities, detected by high frame rate elastography, have a strong correlation with the end-diastolic filling pressure and allowed significantly better to differentiate normal from elevated filling pressure that current guideline recommended algorithms. This suggests a potential clinical value of the new method for the non-invasive assessment of diastolic function. Abstract Figure. Abstract Figure.

Diagnostic accuracy of ultrasound shear wave elastography combined with superb microvascular imaging for breast tumors: A protocol for systematic review and meta-analysis.

Background:Shear wave elastography (SWE) is a new ultrasonic elastography technique for evaluating the hardness of living tissue by measuring the propagation velocity of shear wave in tissue, which is characterized by real-time, non-invasive and quantitative. The SWE technique can be used to diagnose the lesions of different tissues and organs, and the quantitative measurement of SWE is considered as more objective information about breast masses. Superb microvascular imaging (SMI) is a new noninvasive Doppler ultrasound imaging method, which can display blood flow information with high spatial resolution and high frame rate, while keeping the minimum low-speed blood flow components. Therefore, SMI can diagnose diseases closely related to angiogenesis at a relatively early stage. However, the results of these studies have been contradictory. The present meta-analysis aimed at determining the accuracy of SWE combined with SMI in the differential diagnosis between benign and malignant breast lesions.Methods:We will search PubMed, Web of Science, Cochrane Library, and Chinese biomedical databases from their inceptions to the April 18, 2021, without language restrictions. Two authors will independently carry out searching literature records, scanning titles and abstracts, full texts, collecting data, and assessing risk of bias. Review Manager 5.2 and Stata14. 0 software will be used for data analysis.Results:This systematic review will determine the accuracy of shear wave elastography combined with superb microvascular imaging in the differential diagnosis between benign and malignant breast tumors.Conclusion:Its findings will provide helpful evidence for the accuracy of shear wave elastography combined with superb microvascular imaging in the differential diagnosis between benign and malignant breast tumors.Systematic review registration:INPLASY202150075

Shear Wave Velocity Estimation Using the Real-Time Curve Tracing Method in Ultrasound Elastography

The estimation of shear wave velocity is very important in ultrasonic shear wave elasticity imaging (SWEI). Since the stability and accuracy of ultrasonic testing equipment have been greatly improved, in order to further improve the accuracy of shear wave velocity estimation and increase the quality of shear wave elasticity maps, we propose a novel real-time curve tracing (RTCT) technique to accurately reconstruct the motion trace of shear wave fronts. Based on the curve fitting of each frame shear wave, the propagation velocity of two-dimensional shear waves can be estimated. In this paper, shear wave velocity estimation and shear wave image reconstruction are implemented for homogeneous regions and stiff spherical inclusion regions with different elasticity, respectively. The experimental result shows that the proposed shear wave velocity estimation method based on the real-time curve tracing method has advantages in accuracy and anti-noise performance. Moreover, by eliminating artifacts of shear wave videos, the velocity map acquired can restore the shape of inclusions better. The real-time curve tracing method can provide a new idea for the estimation of shear wave velocity and elastic parameters.

Can shear wave imaging distinguish between diffuse interstitial and replacement myocardial fibrosis?

Abstract Funding Acknowledgements Type of funding sources: None. Background Diffuse interstitial or myocardial replacement fibrosis are common features of a large variety of cardiomyopathies. These alterations contribute to functional changes, particularly to an increased myocardial stiffness (MS). Histological examination is the gold standard for myocardial fibrosis quantification, however, it requires endomyocardial biopsy which is invasive and not without risks. Cardiac magnetic resonance (CMR) can characterize the extent of both diffuse and replacement fibrosis and may have prognostic value in various cardiomyopathies. Echocardiographic shear wave (SW) elastography is an emerging approach for measuring MS in vivo. SWs occur after mechanical excitation of the myocardium, e.g. after mitral valve closure (MVC), and their propagation velocity is directly related to MS, thus providing an opportunity to assess stiffness at end-diastole. Purpose The aim was to investigate if velocities of natural SW can distinguish between interstitial and replacement fibrosis. Methods We prospectively enrolled 47 patients (22 patients after heart transplant [54.2 ± 15.8 years, 82.6% male] and 25 patients with established hypertrophic cardiomyopathy [54.0 ± 13.5 years, 80.0% male]) undergoing CMR during their check-up. We performed SW elastography in parasternal long axis views of the LV using a fully programmable experimental scanner (HD-PULSE) equipped with a clinical phased array transducer (Samsung Medison P2-5AC) at 1100 ± 250 frames per second. Tissue acceleration maps were extracted from an anatomical M-mode line along the midline of the LV septum. The SW propagation velocity at MVC was measured as the slope in the M-mode image. All patients underwent T1 mapping as well as late gadolinium enhancement (LGE) cardiac magnetic resonance at 1.5 T to assess the presence of diffuse or replacement fibrosis (Figure A). Therefore, patients were divided in three groups: no fibrosis, diffuse fibrosis and replacement fibrosis. Results Mechanical SW’s were observed in 46 subjects starting immediately after MVC and propagating from the LV base to the apex. SW propagation velocity at MVC correlated well with native myocardial T1 values (r = 0.65, p < 0.0001) and differed significantly among groups (p < 0.0001), with a significant post-test between any pair of groups (Figure B). SW velocities below a cut-off of 6.01 m/s showed the highest accuracy to identify patients without any type of fibrosis (sensitivity 88 %, specificity 89%, area under the curve = 0.93) (Figure C). A cut-off of 8.11 m/s could distinguish replacement fibrosis from diffuse fibrosis with a sensitivity and specificity of 59% and 92 %, respectively (area under the curve = 0.80) (Figure D). Conclusions Shear wave velocities after mitral valve closure can distinguish between normal and pathological myocardium and can detect differences between diffuse and replacement fibrosis. Abstract Figure.

Shear wave elastography: can we discover elevated diastolic filling pressures?

Abstract Funding Acknowledgements Type of funding sources: Public hospital(s). Main funding source(s): University Hospitals (Uz) Leuven Background The assessment of the left ventricular diastolic function is complex, as there is no single invasive parameter that provides a direct measurement of myocardial relaxation, myocardial compliance, or – as a surrogate - LV filling pressure. Estimation of diastolic function is therefore based on the combination of several parameters. Shear wave (SW) elastography is a novel method based on high frame rate echocardiography. SWs occur after mechanical excitation of the myocardium, e.g. after mitral valve closure (MVC), and their propagation velocity is directly related to myocardial stiffness (MS). Purpose The aim of this study was to investigate if velocities of natural shear waves are related to MS at end-diastole (ED) and, thus, could be used to estimate left ventricular end-diastolic pressures (LVEDP) as marker of diastolic function. Methods So far, we have prospectively enrolled 42 patients with a wide range of diastolic function, scheduled for heart catheterization so that LV filling pressures could be invasively measured. Patients with severe aortic stenosis, mitral stenosis of any degree and a more than moderate mitral regurgitation, as well as regional myocardial abnormalities or dysfunction in the anteroseptal wall were excluded. Echocardiography was performed immediately after catheterization. SW elastography in parasternal long axis views of the left ventricle (LV) was performed using an experimental scanner (HD-PULSE) at 1100 ± 250 frames per second. Tissue acceleration maps were extracted from an anatomical M-mode line along the midline of the LV septum. The SW propagation velocity at MVC was measured as the slope on the M-mode acceleration map (Figure A). Standard echocardiographic parameters of diastolic function were obtained with a high end ultrasound machine. Results SW velocities at ED correlated well with the invasively measured LVEDP (r = 0.74, p < 0.001, Figure B). In comparison, classical echocardiographic parameters correlated only weakly with LVEDP (E/A: r = 0.398, p = 0.02, Figure C; E/E’: r = 0.204, p = 0.247, Figure D). For the detection of an elevated LVEDP above 15 mmHg, a cut off value for the SW velocity at MVC of 4.395 m/s (Figure A) was associated with a sensitivity of 91.3% and a specificity of 90.9%. Conclusions End-diastolic shear wave velocities, measured by high frame rate shear wave elastography, showed a significant correlation with the end-diastolic filling pressure of the LV and allowed to differentiate normal from elevated filling pressure which indicates a potential clinical value of the new method for a non-invasive and direct assessment of LV diastolic function. More patients will be included to confirm these findings. Abstract Figure.

Accounting for nonlinear soil properties in the computational method of seismic microzoning

The paper notes that in recent years, attention to the study of nonlinear phenomena in engineering seismology has sharply increased. The problem of accounting for nonlinear phenomena can be solved using instrumental and computational studies, as well as collaterally. In the latter case, the possible level of soil nonlinearity is estimated using the instrumental method, then the possible features of soil movements are calculated numerically. An algorithm for taking into account the nonlinearity of soils when calculating vibrations of the soil strata under intense seismic influences is proposed. The algorithm was developed on the basis of the known empirical relationships between the soil types and their indicators. The number of plasticity was chosen as an indicator of the soil type. Additionally, the necessary criteria and refinements have been introduced to correctly take into account the normal stress and calculate the deformation. The value of the shear wave propagation velocity in the soil, closely related to the physical state of the soil, is considered as a modulated indicator. The way of using the proposed algorithm for the method developed on the basis of the multiple-reflected waves theory and the method developed on the FEM basis is shown.

The behaviour of natural shear waves under different loading conditions

Abstract Background Shear wave imaging (SWI) is a novel ultrasound technique based on the detection of transverse waves traveling through the myocardium using high frame rate echocardiography. These waves can be naturally induced e.g. by mitral valve closure (MVC). Their propagation velocity is dependent on the stiffness of the myocardium. Previous studies have shown the potential of SWI for the non-invasive assessment of myocardial stiffness. So far, the influence of loading on shear wave propagation velocities has not been extensively investigated. Purpose The aim of this study was to explore how loading changes affect shear wave propagation velocities after MVC. Methods Until now, 5 pigs (weight: 33.5±6.9 kg) were included. Echocardiographic images and left ventricular pressure recordings were simultaneously acquired during acute loading alterations: 1) preload was reduced by balloon occlusion of the vena cava inferior, 2) afterload was increased by balloon occlusion of the descending aorta and 3) preload was increased by intra-venous administration of 500 ml of saline. Left ventricular parasternal long-axis views were acquired with an experimental high frame rate ultrasound scanner (average frame rate: 1247±179 Hz). Shear waves were visualized on tissue acceleration maps by drawing an M-mode line along the interventricular septum. Shear wave propagation velocities after MVC were calculated by measuring the slope of the wave front on the acceleration maps (Figure A). Results The changes in left ventricular end-diastolic pressures (LV EDP) between baseline and each intervention are shown in Figure B. Preload reduction resulted in significantly reduced LV EDP (p<0.01). The shear wave propagation velocities after MVC dropped with preload reduction and increased significantly by increasing afterload as well as preload (both p<0.05) (Figure C). There was a good positive correlation between the change in LV EDP and the change in shear wave velocities (r=0.83; p<0.001) (Figure D). Conclusion The shear wave propagation velocity after MVC was significantly influenced by alterations in left ventricular loading conditions and changes in these velocities were related to changes in LV EDP. These results indicate that shear wave measurements at MVC might be a potential novel parameter for the estimation of left ventricular filling pressures. More pigs will be included in the future to further confirm these findings. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): Fonds Wetenschappelijk Onderzoek - Vlaanderen

Shear wave elastography: can we estimate filing pressures?

Abstract Background The assessment of the left ventricular diastolic function is complex, as there is no single non-invasive parameter that provides a direct measurement of myocardial relaxation, myocardial compliance, or – as a surrogate - LV filling pressure. Estimation of diastolic function is therefore based on the combination of many parameters. Shear wave (SW) elastography (SWE) is a novel method based on high frame rate echocardiography. SWs occur after mechanical excitation of the myocardium, e.g. after mitral valve closure (MVC), and their propagation velocity is directly related to myocardial stiffness (MS). Purpose The aim of this study was to investigate if velocities of natural shear waves are related to MS at end diastole (ED) and, thus, could be used to estimate left ventricular end-diastolic pressures (LVEDP) as marker of diastolic function. Methods So far, we have prospectively enrolled 30 patients with a wide range of diastolic function, scheduled for heart catheterization so that LV filling pressures could be invasively measured. Patients with severe aortic stenosis, mitral stenosis of any degree and a more than moderate mitral regurgitation, as well as regional myocardial abnormalities or dysfunction in the anteroseptal wall were excluded. Echocardiography was performed immediately after catheterization. SW elastography in parasternal long axis views of the left ventricle (LV) was performed using an experimental scanner (HD-PULSE) at 1100±250 frames per second. Tissue acceleration maps were extracted from an anatomical M-mode line along the midline of the LV septum. The SW propagation velocity at MVC was measured as the slope on the M-mode acceleration map (Figure A). Results SW velocities at ED correlated very well with the invasively measured LVEDP (r=0.815, p<0.001, Figure B). In comparison, classical echocardiographic parameters correlated only weakly or not with LVEDP (E/A: r=0.528, p=0.036, Figure C; E/e': r=−0.169, p=0,531, Figure D) with LVEDP. For the detection of an elevated LVEDP above 15 mmHg, a cut off value for the SW velocity at MVC of 3.75 m/s was associated with a Sensitivity of 92.9% and a Specificity of 83.3%. Conclusions End-diastolic shear wave velocities, measured by high frame rate shear wave elastography, showed a significant correlation with the end-diastolic filling pressure of the LV indicating a potential clinical value of the new method for a non-invasive and direct assessment of LV diastolic function. More patients will be included to confirm these findings. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): Fonds Wetenschappelijk Onderzoek Flanderen (Research Foundation Flanders)

Shear wave elastography by high frame rate echocardiography can detect diffuse myocardial fibrosis after heart transplantation

Abstract Background Myocardial fibrosis is fundamental in the development of cardiac failure, regardless of ethiology. In both animal models and humans it has been shown that diffuse myocardial fibrosis (DMF) contributes to functional impairment, especially to increased passive myocardial stiffness, which is an important pathophysiological determinant of left ventricular diastolic dysfunction. Histological examination is the gold standard for myocardial fibrosis quantification, however, it requires endomyocardial biopsies which are invasive and not without risk. Echocardiographic shear wave (SW) elastography, based on high frame rate imaging, is an emerging approach for measuring myocardial stiffness in vivo. Natural SWs occur after mechanical excitation of the myocardium, e.g. after mitral valve closure (MVC) and their propagation velocity is directly related to myocardial stiffness, thus providing an opportunity to assess myocardial stiffness at end-diastole. Purpose The aim was to investigate if propagation velocities of natural SWs can be used to detect diffuse myocardial fibrosis in a cohort of heart transplant recipients. Methods We prospectively enrolled 22 patients (10.3±6.3 years after HTx) that underwent CMR during their annual check-up. We performed SW elastography in parasternal long axis views of the left ventricle using a fully programmable experimental scanner (HD-PULSE) equipped with a clinical phased array transducer (Samsung Medison P2–5AC) at 1100±250 frames per second. The SW propagation velocities at MVC were measured in the basal LV septum. Native T1 and extracellular volume (ECV) were measured at the same segment to evaluate DMF. A cut-off value for native T1 of 1040 ms and for ECV of 29% was used to define DMF in our cohort. Results We found good correlations between SW velocities and both myocardial T1 (r=0.80, p<0.0001, Figure A) and ECV (r=0.64, p=0.003, Figure B) measured with CMR. Further, we derived reference thresholds of natural SW velocities to identify DMF in HTx patients. The optimal cut-off value of SW velocity to identify patients with nativT1>1040 ms was 4.84 m/s (AUC 0.81, sensitivity 82%, specificity 82%, Figure C). To identify patients with ECV>0.29 the cut-off value of SW velocity was 4.74 m/s (AUC 0.74, sensitivity 73%, specificity 78%, Figure D). Conclusions End-diastolic shear wave propagation velocities, as measure of myocardial stiffness, showed a good correlation with CMR defined diffuse myocardial injury. Values higher than 4.74 m/s could identify diffuse myocardial injury in HTX patients with a good sensitivity and good specificity. These findings thus suggest that shear wave elastography has the potential to become a valuable non-invasive method for the detection of diffuse myocardial fibrosis. Funding Acknowledgement Type of funding source: None

Management of the dynamic properties of a base modified by deep soil mixing technology

Conversion of building properties is performed primarily to reduce the compressibility of the base and increase strength. However, in addition to changing the static properties of soils, it is necessary to take into account changes in dynamic properties, such as dynamic shear modulus, damping coefficient, velocity of elastic shear and longitudinal waves. Thus, it is possible to control the dynamic properties of the base by converting the construction properties of soils. In this paper, we consider the change in the velocity of shear waves in a base transformed by the technology of deep soil mixing (DSM). In the work, the influence of additional vertical stresses on the dynamic properties of the bases transformed using deep soil mixing technology was evaluated. As a parameter that allowed us to evaluate the dynamic properties, the propagation velocity of elastic shear waves was chosen. Shear wave velocity was estimated based on the results of triaxial tests using the method of low-amplitude torsional vibrations in a resonant column. The research results showed that at small values of axial strains, there is no significant increase in the velocity of shear waves, an increase in the speed of shear waves by two times with an increase in stress by 0.6 MPa.

Differentiation of hypertensive heart disease and hypertrophic cardiomyopathy with myocardial stiffness measurements: a shear wave imaging study using ultra-high frame rate echocardiography

Abstract Background Recently, cardiac shear wave (SW) elastography, based on high frame rate (HFR) echocardiography, has been proposed as new non-invasive technique for assessing myocardial stiffness. As myocardial stiffness increases with increasing wall stress, differences in measured operating myocardial stiffness do not necessarily reflect differences in intrinsic myocardial properties, but can also be caused by mere changes in loading or chamber geometry. This complicates myocardial stiffness interpretation for different types of pathologic hypertrophy. Purpose To explore the relationship between myocardial stiffness and underlying pathological substrates for cardiac hypertrophy. Methods We included 20 patients with hypertension (HT) and myocardial remodelling (59±14 years, 75% male), 20 patients with hypertrophic cardiomyopathy (HCM) (59±16 years, 60% male) and 20 healthy controls (56±14 years, 75% male). Left ventricular (LV) parasternal long axis views were acquired with an experimental HFR scanner at 1293±362 frames per seconds. Propagation velocity of SW occurring after mitral valve closure in the interventricular septum (IVS) served as measure of operating myocardial stiffness (Figure A). To compare myocardial stiffness among hearts with differing loading conditions and chamber geometry, SW velocities were normalized to end-diastolic wall stress, estimated at IVS from regional wall thickness, longitudinal and circumferential regional radii of curvature, and non-invasively estimated LV end-diastolic pressure (EDP). Results SW velocities differed significantly between groups (p<0.001). The controls had the lowest SW velocities (4.02±0.97 m/s), whereas values between HT and HCM group were comparable (6.46±0.99 m/s vs. 7.00±2.10 m/s; p=0.738). Considering end-diastolic wall stress, HCM patients had the same SW velocity at lower wall stress compared to HT (Figure B), indicating higher myocardial stiffness in the HCM group. SW velocities normalized for wall stress indicated significantly different myocardial stiffness among all groups (p<0.001) (Figure C). In a multiple linear regression model, the underlying pathological substrate independently influenced SW velocity (beta 1.37, 95% CI (0.78–1.96); p<0.001), while wall stress did not significantly affect its value (p=0.479). Conclusions Our study demonstrated that SW elastography can detect differences in myocardial stiffness in hypertensive heart and hypertrophic cardiomyopathy. Additionally, our results suggest that SW velocity is dominated by underlying myocardial tissue properties. We hypothesize that differential changes in cardiomyocytes and/or the extracellular matrix contribute to the differential myocardial stiffening in different pathologic entities of LV hypertrophy. Thus, SW elastography could provide useful novel diagnostic information in the evaluation of LV hypertrophy. Figure A, B, C Funding Acknowledgement Type of funding source: None

Studies of the shear wave velocity in soil cement under the anisotropic stress state

Introduction. Deep soil mixing, that alters construction properties of foundations, allows to construct buildings and structures on the sites that have loose soils. As a rule, adverse geotechnical conditions are accompanied by dynamic forces that affect designed buildings and structures. The objective of these studies is to predict changes in mechanical properties of soils that follow the alteration of structural properties of a foundation. Soil cement is the focus of this study. Materials and methods. The findings of special laboratory tests of soil cement samples using the method of low amplitude torsional vibrations inside a resonant column in the anisotropic triaxial compression mode allowed to assess the effect of the supplementary vertical load on the velocity of shear elastic wave propagation. The co-authors present a description of the research method and provide an overview of the equipment used to conduct special laboratory tests. Tests were performed on undisturbed soil cement samples that had a natural water content. The anisotropic stress state of soil cement samples exposed to triaxial tests in the resonant column was caused by special behaviour features of the foundation. Results. In this study, laboratory tests had two stages. At the first stage, the effect of the vertical stress on the velocity of shear wave propagation was assessed. Correlation dependences between the shear wave velocity and the ratio of vertical and lateral stresses were obtained. At the second stage, shear wave propagation velocity values were identified at various combinations of lateral σ3 and vertical σ1 stresses. The results of the second stage are designated for the assessment of the effect of the anisotropic stress state and the projection of shear wave velocities at the stress levels anticipated on the site that will accommodate designed heavy structures. Conclusions. The findings allow to assess the effect of lateral and vertical stresses on changes of shear wave velocities in the triaxial compression mode. It was identified that at equal values of lateral stresses σ3, a 7-fold vertical stress σ1 increase leads to a 15 % increase in the shear wave velocity in soil cement Vs. At the same time, an increase in the ratio of vertical to lateral stresses σ1/σ3 by a factor of 15 causes an 11 % increase in the shear wave velocity. It is noted that the smaller the initial value of lateral stress σ3, the higher the rise in the shear wave velocity Vs in the course of testing. Correlation dependencies, presented in this study, can be used to assess the effect of the anisotropic state as the first approximation (for preliminary calculations) in the design of heavy structures on soil cement foundations.

The Value of Real-Time Shear Wave Elastography before and after Rehabilitation of Upper Limb Spasm in Stroke Patients.

Objective Our goal was to evaluate the efficacy of muscle spasm before and after rehabilitation by comparing shear wave propagation velocity (SWV) and Young's modulus (YM) in the normal and spastic biceps brachii in stroke patients. Methods A study of 60 stroke patients with upper limb spasm was performed; these patients were admitted from April 2018 to September 2019. The modified Ashworth scale (MAS) scores of the spastic biceps brachii before and after rehabilitation treatment were compared. SWV and YM on the spastic and normal biceps brachii before rehabilitation treatment, SWV and YM on the spastic and normal biceps brachii after rehabilitation treatment, and SWV and YM on the spastic biceps brachii before and after rehabilitation treatment were compared. Whether SWV and YM on the spastic biceps brachii are related to MAS was compared. Results There was a statistically significant difference in SWV and YM between the normal and spastic biceps brachii before (P < 0.01) and after (P < 0.05) the rehabilitation treatment. There was no statistically significant difference in SWV and YM in the normal biceps brachii before and after the rehabilitation treatment (P > 0.05). There was a statistically significant difference in SWV and YM in the spastic biceps brachii before and after the rehabilitation treatment (P < 0.01). SWV and FM of the spastic biceps brachii are correlated with MAS before and after rehabilitation treatment, and the correlation coefficient for SWV was 0.563 and 0.605 for YM (P < 0.05). Conclusion SWE can be used as a means of assessment before and after rehabilitation treatment.

The Influence of Heat Treatment on the Propagation Velocity of Shear Waves in Steel Bars

В статье обсуждаются вопросы возможности оценки изменения скорости ультразвуковой волны в прутках из стали 45 при разных видах термической обработки. Диаметр прутков 14 мм, длина рабочей части 20 см. Для структуроскопии использован электромагнитно-акустический способ ввода и приема поперечных волн осевой поляризации на основе проходного преобразователя. Измерения скорости волн проведены методом многократных отражений по сечению прутка. Термическую обработку кроме состояния поставки выполнили на 8 образцах прутков по следующим режимам: отжиг при 850 °С, нормализация при 850 °С, закалка от 850 °С в масле, отпуск при 200, 400, 450, 500, 600 °С. Представлены результаты изменения скорости поперечной волны в прутках при всех режимах термической обработки. Для повышения точности определения скорости поперечных волн измерены диаметры прутков с шагом 1 см по всей длине. Скорость поперечной волны в прутках после отжига составила 3240 м/с, а после закалки 3170 м/с. Состояние поставки и после нормализации показывает одинаковую скорость поперечной волны 3230 м/с. Полученные экспериментальные данные свидетельствуют, что отжиг увеличивает скорость распространения поперечной волны в прутке на 70 м/с относительно закалки без отпуска. С увеличением температуры отпуска наблюдается рост скорости распространения поперечной волны относительно закаленного состояния, достигающий увеличения на 65 м/c до 3235 м/с при температуре 600 °С.