Changes In Shear Wave Velocity Research Articles

Assessing the treatment response of lateral elbow tendinopathy using time-dependent ultrasonography, Doppler imaging, and elastography

ObjectiveTo investigate the structural alterations, neovascularity, and elasticity of tendons and the relationship between elasticity and the Patient Rated Tennis Elbow Evaluation score after undergoing US-guided fenestration or surgery in patients with chronic lateral elbow tendinopathy.MethodsParticipants from the per-protocol population of a randomized trial conducted between October 2016 and June 2020 were included. The surgery and fenestration groups included 24 (mean age, 50 ± 7 years [standard deviation], 10 men) and 29 (47 ± 8 years, 18 men) participants, respectively. Ultrasound exams were performed at baseline, 6 months, and 12 months. Statistical analyses included linear mixed effects and generalized equation estimation models.ResultsFenestration had no significant impact on tendon thickness (p = 0.46). Conversely, surgery significantly increased tendon thickness at 6 months (p < 0.0001) and remained elevated at 12 months (p = 0.04). Tendon echostructure exhibited a group effect (p = 0.03), indicating a higher proportion of pathological scores in the surgery group post-intervention compared to the fenestration group. Both groups showed a similar reduction in neovascularity from 6 to 12 months postintervention (p = 0.006). Shear-wave velocity increased in the fenestration group at 6 months (p = 0.04), while the surgery group experienced a nonsignificant decrease at 6 months, with some improvement at 12 months (p = 0.08). Changes in shear-wave velocity did not correlate with clinical outcome.ConclusionsFenestration and surgery reduced tendon neovascularity over time. Unlike surgery, fenestration did not impact tendon size while improving tendon echostructure and elasticity.Critical relevance statementFenestration and surgery equally alleviated symptoms and decreased tendon neovascularity in lateral elbow tendinopathy; however, fenestration did not alter tendon thickness and improved echostructure and shear-wave velocity, suggesting shear-wave velocity’s potential for quantitatively monitoring tendon elasticity during healing.Key PointsReliable markers for monitoring healing response and informing treatment protocols in elbow tendinopathy are lacking.Fenestration and surgery reduced tendon neovascularity, while fenestration improved tendon echostructure and shear-wave velocity.Shear-wave velocity may provide quantitative measures to monitor tendon elasticity in response to treatment.Graphical

The effects of internal erosion on granular soils used in transport embankments

The flooding of embankments used for rail and other infrastructure has the potential to cause lasting weakening of slopes via the movement of fine particles induced by seepage. In laboratory experiments, internal erosion was induced in granular soil samples, with properties consistent with those used to construct transportation embankments, to assess how particle migration through, and out of, samples caused shear wave velocity, strength, stiffness and permeability changes. Shear wave velocity changes, measured using horizontal bender elements, of up to 19 % were observed following fine particle removal of up to 1 % of initial sample mass. Shear wave velocity change was found to be an indicator for identifying the development of permeability change during seepage-induced particle migration. Median measured permeability changes were +5 % and −34 % for samples containing 15 % and 30 % fines, respectively. The largest directly observed permeability and shear wave velocity changes occurred during the initial stages of seepage. Negative correlation was observed between mass of material removed from samples and peak friction angle. Following seepage, soils displayed a dual stiffness behaviour. Stiffness and strength changes were attributed to redistribution of fine particles and opening of pore spaces. Our results have implications for the monitoring of earthworks affected by flooding and seepage as the associated redistribution of fine particles may lead to large changes in slope properties.

The Effect of Steatosis on Shear-Wave Velocity and Viscoelastic Properties Related to Liver Fibrosis Progression in Rat Models

ObjectiveHepatic fibrosis has recently been evaluated using ultrasonography or magnetic resonance elastography. Although the shear wave velocity (SWV) obtained using point shear wave elastography (pSWE) provides a valuable measure of fibrosis, underlying steatosis may affect its measurement. MethodsUsing hepatic fibrosis samples, this study evaluated the effect of steatosis on the shear wave velocity of pSWE (Vs) and viscoelastic properties (assessed by dynamic mechanical analysis) of rat liver. Fifty rats with various grades of steatosis and fibrosis underwent open abdominal in vivo Vs measurements using a commercial ultrasound scanner. The mechanical properties of hepatic tissue were also characterized under ex vivo conditions using dynamic mechanical analysis and the Zener model of viscoelasticity. ResultsFibrosis and steatosis progression influenced Vs and elasticity. The SWV computed using the Zener model and Vs showed a substantial correlation (r > 0.8). Fibrosis progression increased SWV. Steatosis was also related to SWV. Steatosis progression obscured the SWV change associated with fibrosis progression. ConclusionWe conclude that steatosis progression affects the evaluation of fibrosis progression. This finding could aid discrimination of non-alcoholic steatohepatitis from non-alcoholic fatty liver disease using SWV.

Longitudinal assessment of liver stiffness using ARFI technique does not support increased risk of fibrosis in rheumatoid arthritis patients on methotrexate.

To assess the liver stiffness in patients with rheumatoid arthritis treated with methotrexate monotherapy using non-invasive, ultrasound-based elastography (acoustic radiation force impulse (ARFI) imaging) in a longitudinal approach. In total, 23 MTX-naive patients were longitudinally assessed using acoustic radiation force impulse (ARFI) imaging. Baseline assessments were carried out between July 2018 and April 2019, and the follow-up evaluations took place after an average of 2.6years. The main outcome variable was the mean shear wave velocity as measured by the ARFI method. It was calculated from 10 valid ARFI measurements for each patient. Inferential statistical analyses (within-group comparisons) were performed using t-tests for dependent samples or suitable nonparametric procedures. The main finding was that observed ARFI shear wave velocities did not increase during the observation period. In fact, this parameter decreased over time from 1.07m/s (SD = 0.23) at baseline without MTX exposure to 0.97m/s (SD = 0.16) at follow-up after a mean of 2.6years (P = 0.013). Moreover, the magnitude of the change in shear wave velocity could not be predicted by indicators of inflammation or disease activity, BMI, age, sex or NSAR intake (corresponding regression analysis: corrected R2 = 0.344; P = 0.296). No increased risk of liver fibrosis was found in RA patients treated with MTX monotherapy during observation period.

Evaluation of the coefficient of lateral stress at rest of granular materials under repetitive loading conditions

Although the internal stress state of soils can be affected by repetitive loading, there are few studies evaluating the lateral stress (or K0) of soils under repetitive loading. This study investigates the changes in K0 and directional shear wave velocity (Vs) in samples of two granular materials with different particle shapes during repetitive loading. A modified oedometer cell equipped with bender elements and a diaphragm transducer was developed to measure the variations in the lateral stress and the shear wave velocity, under repetitive loading on the loading and unloading paths. The study produced the following results: (1) Repetitive loading on the loading path resulted in an increase in the K0 of test samples as a function of cyclic loading number (i), and (2) Repetitive loading on the unloading path resulted in a decrease in K0 according to i. The shear wave velocity ratio (i.e. Vs(HH)/Vs(VH), where the first and second letters in parentheses corresponds to the directions of wave propagation and particle motion, respectively, and V and H corresponds to the vertical and horizontal directions, respectively) according to i supports the experimental observations of this study. However, when the tested material was in lightly over-consolidated state, there was an increase in K0 during repetitive loading, indicating that it was the initial K0, rather than the loading path, which is responsible for the change in K0. The power model can capture the variation in the K0 of samples according to i. Notably, the K0 = 1 line acts as the boundary between the increase and decrease in K0 under repetitive loading.

Evaluating changes in shear wave velocity due to blast-induced liquefaction

Blast liquefaction tests were performed in Christchurch, New Zealand in an area that experienced extensive liquefaction during the 2010–2011 Canterbury Earthquake Sequence. To evaluate the changes in shear wave velocity (VS) of the soil profile in the vicinity of the blasting, multi-channel analysis of surface waves (MASW) testing was performed before the blast, immediately following the blast (within 0.5 h), 4 h post-blast, and 24 h post-blast. Three different array setups with varying lengths and number of geophones were analyzed to study the effect of array length on the ability of MASW to capture changes in VS within the blast area. Results of the study show that array length can have a significant effect on the measured changes in VS immediately following blasting due to averaging of the properties inside and outside of the area where blasting induced liquefaction developed; however, these changes decrease at 24 h. Full recovery of pre-blast VS was not observed for all layers at 24 h post-blast. This study provides data for measurements of VS rapidly following liquefaction, which are sparse in the literature.

High-resolution shallow crustal shear wave velocity structure of Anyuan mining area and its adjacent region in Jiangxi Province, China

High-resolution seismic image is critically important for mining minerals. In this study, we collected seismic data from a local dense seismic array consisting of 154 stations around the Anyuan mining area and its adjacent region of Pingxiang City, Jiangxi Province in South China, and applied the ambient noise tomography (ANT) method to image the shear wave velocity structure in the study area. Shallow crustal velocities at depths less than 3.3 km were determined by direct inversion of Rayleigh wave group velocity dispersion curves at the period range of 0.5–5.0 s. Overall, the S-wave velocity structure has a tight correlation with surface geological and tectonic features in the study area. The shear wave velocity structure in the shallow crust of the Anyuan Mine and its adjacent areas displayed distinct low-velocity anomalies, which can be attributed to the depression of sedimentary structures and coal mining activities in the Pingxiang-Leping region. The zones surrounding the Anyuan fault (AYF) and Wangkeng fault (WKF) zones exhibited low-velocity anomalies from the ground surface to ~ 3.3 km underground. And the low-velocity anomalies at depths less than 1.2 km could be related to the sedimentary environment of coal mine and the coal mining activities, while the low-velocity anomalies at depths below 1.2 km are caused by the presence of fracture medium, oil and gas in the fault zone. The shear wave velocity changes sharply across the AYF, and the characteristics of the velocity change interface indicate that the AYF is inclined toward the northwest, with its extension reaching depths of approximately 3 km underground.Graphical

Probing environmental and tectonic changes underneath Mexico City with the urban seismic field

Abstract. The sediments underneath Mexico City have unique mechanical properties that give rise to strong site effects. We investigated temporal changes in the seismic velocity at strong-motion and broadband seismic stations throughout Mexico City, including sites with different geologic characteristics ranging from city center locations situated on lacustrine clay to hillside locations on volcanic bedrock. We used autocorrelations of urban seismic noise, enhanced by waveform clustering, to extract subtle seismic velocity changes by coda wave interferometry. We observed and modeled seasonal, co- and post-seismic changes, as well as a long-term linear trend in seismic velocity. Seasonal variations can be explained by self-consistent models of thermoelastic and poroelastic changes in the subsurface shear wave velocity. Overall, sites on lacustrine clay-rich sediments appear to be more sensitive to seasonal surface temperature changes, whereas sites on alluvial and volcaniclastic sediments and on bedrock are sensitive to precipitation. The 2017 Mw 7.1 Puebla and 2020 Mw 7.4 Oaxaca earthquakes both caused a clear drop in seismic velocity, followed by a time-logarithmic recovery that may still be ongoing for the 2017 event at several sites or that may remain incomplete. The slope of the linear trend in seismic velocity is correlated with the downward vertical displacement of the ground measured by interferometric synthetic aperture radar, suggesting a causative relationship and supporting earlier studies on changes in the resonance frequency of sites in the Mexico City basin due to groundwater extraction. Our findings show how sensitively shallow seismic velocity and, in consequence, site effects react to environmental, tectonic and anthropogenic processes. They also demonstrate that urban strong-motion stations provide useful data for coda wave monitoring given sufficiently high-amplitude urban seismic noise.

Influence of Body Mass on Running-Induced Changes in Mechanical Properties of Plantar Fascia.

Shiotani, H, Mizokuchi, T, Yamashita, R, Naito, M, and Kawakami, Y. Influence of body mass on running-induced changes in mechanical properties of plantar fascia. J Strength Cond Res 37(11): e588-e592, 2023-Body mass is a major risk factor for plantar fasciopathy; however, evidence explaining the process between risk factors and injury development is limited. Long-distance running induces transient and site-specific reduction in plantar fascia (PF) stiffness, reflecting mechanical fatigue and microscopic damage within the tissue. As greater mechanical loads can induce greater reduction in tissue stiffness, we hypothesized that the degree of running-induced change in PF stiffness is associated with body mass. Ten long-distance male runners (age: 21 - 23 years, body mass: 55.5 ± 4.2 kg; mean ± SD ) and 10 untrained men (age: 20 - 24 years, body mass: 58.4 ± 5.6 kg) ran for 10 km. Before and immediately after running, the shear wave velocity (SWV) of PF at the proximal site, which is an index of tissue stiffness, was measured using ultrasound shear wave elastography. Although the PF SWV significantly decreased after running in runners (-4.0%, p = 0.010) and untrained men (-21.9%, p < 0.001), runners exhibited smaller changes ( p < 0.001). The relative changes in SWV significantly correlated with body mass in both runners ( r = -0.691, p = 0.027) and untrained individuals ( r = -0.723, p = 0.018). These results indicate that a larger body mass is associated with a greater reduction in PF stiffness. Our findings provide in vivo evidence of the biomechanical basis for body mass as a risk factor for plantar fasciopathy. Furthermore, group differences suggest possible factors that reduce the fatigue responses, such as adaptation enhancing the resilience of PF and running mechanics.

Effect of parameters associated with soil-to-structure relative stiffness on seismic fragility curves of subway station

Seismic response and vulnerability of subway station underground structures are greatly influenced by kinematic soil-structure interaction, which is a function of soil properties and stiffness. Therefore, this paper investigates the influence of parameters associated with soil-to-structure relative stiffness (F) on the seismic fragility curves of underground structures. Incremental dynamic analysis method is conducted employing finite element analysis to establish the fragility curves of the station structure considering 44 earthquake records. The soil was simulated as a two-dimensional (2D) finite element domain and its nonlinear behavior is described employing the Davidenkov constitutive model. Appropriate plasticity models simulated the nonlinearity of concrete and reinforcing rebars. It was found that the failure probability of the structure decreases significantly as soil shear wave velocity increases, and the change of probability of structural failure was quantified for changes in shear wave velocity within the range 200 m/s to 600 m/s. It was also found that the failure probability of subway station in heterogeneous soil is significantly higher than that of a structure buried in homogeneous soil. On the other hand, the cross-section type of the structure has less influence on its seismic vulnerability. The seismic performance of the structure with higher F is relatively better, while there are special cases where some structures with high F that are more susceptible to failure under earthquake than structures with lower F. The findings can provide helpful guide for the performance-based seismic design of underground structures.

Passive muscle stiffness is correlated with the intramuscular adipose tissue in young individuals.

We investigated the relationship between intramuscular adipose tissue (IntraMAT) and muscle stiffness (passive and mechanical) and lengthening in young individuals, hypothesizing that (1) passive muscle stiffness is negatively correlated with the IntraMAT content, and (2) the IntraMAT content is negatively correlated with mechanical changes in muscle stiffness and fascicle length during passive dorsiflexion. Twenty men and women (20.3 ± 1.3years) participated in this study. Axial T1-weighted magnetic resonance imaging was performed at the thickest point of the medial gastrocnemius (MG) to measure the IntraMAT cross-sectional area (CSA) and muscle tissue CSA (units; cm2). The shear wave velocity (SWV) and fascicle length at the three ankle joint angles, namely 15° with plantarflexion (PF15), 0° with neutral position (NP), and 15° with dorsiflexion (DF15), were measured as parameters of muscle stiffness (unit; m/s) and lengthening (unit; cm) using ultrasound shear wave elastography and B-mode imaging. We further calculated the changes in SWV and fascicle length from PF15 to NP and from NP to DF15 as mechanical muscle stiffness and lengthening, respectively. There was a relationship between IntraMAT CSA and absolute SWV at DF15 (r = -0.47, P < 0.05). Further, a relationship was observed between IntraMAT CSA and change in SWV and fascicle length from NP to DF15 (r = -0.47 and r = 0.59, P < 0.05); whereas no relationship was observed between changes in fascicle length and muscle SWV (r = -0.23, P = 0.33). These results may indicate biomechanical and/or physiological associations between IntraMAT CSA and passive muscle stiffness.

Shear Wave Velocity to Evaluate the Effect of Botulinum Toxin on Post-Stroke Spasticity of the Lower Limb.

(1) Background: The evaluation of muscles with spasticity using ultrasound elastography has attracted attention recently, and the shear wave velocity (SWV) technique can measure the mechanical properties of tissues objectively and quantitatively. The purpose of this study was to evaluate the effect of using SWV to assess the effect of Botulinum toxin type A (BoNT-A) treatment in adult patients with post-stroke lower limb spasticity. (2) Methods: We assessed the modified Ashworth Scale, the modified Tardieu Scale, and SWV at rest and after stretching before and at 1 month after BoNT-A treatment in 10 adult participants with post-stroke lower limb spasticity. (3) Results: Significant changes in SWV of the ankle joint in maximum dorsiflexion to the extent possible (SWV stretched) were observed after BoNT-A treatment. SWV stretched was positively correlated with joint range of motion. Participants whose joint range of motion did not improve (i.e., gastrocnemius medialis muscle (GCM) extension distance did not change) had significantly more reductions in SWV stretched after BoNT-A treatment. (4) Conclusions: Our results suggest that the SWV measurements may serve as a quantitative assessment to determine the effect of the BoNT-A treatment in adult stroke patients. SWV measurements to assess GCM spasticity should consider the effects of tension, material properties and activation level of muscles. The challenge is to measure SWV with matching limb positions in patients without contractures.

Monitoring Seasonal Shear Wave Velocity Changes in the Top 6 m at Garner Valley in Southern California With Borehole Data

AbstractSubsurface structures play important roles in seismic ground motion, crustal hydrology, stability of the built environment, and more. Constraining temporal changes of subsurface shear wave velocity (VS) can provide useful information to all these topics and the growing field of hydrological monitoring with seismic velocity. Using borehole records at Garner Valley, CA, we estimate seasonal subsurface VS variations from impulse response functions (IRFs) of earthquake data (2005–2018) along with IRFs and cross‐correlation of cross‐hole experiment data (2015–2018). The inferred VS variations are up to ∼25% in the top 6 m and ∼10% at 2–5 m in depth. The VS variations correlate strongly with the water table depth changes, suggesting that the changes are mostly due to fluctuations of pore pressure in the shallow material. The shallow velocity changes alter the near‐surface conditions, can affect seismic hazard estimation, and may be improperly attributed to deeper processes without careful analysis.

Baseline Liver Elastography Does Not Predict Risks of Hepato-Toxicity to Reduced Dose Inotuzumab Therapy Combined with Minihcvd in B-Cell Acute Lymphoblastic Leukemia

Background: Inotuzumab ozogamicin (InO) is an anti-CD22 antibody drug conjugate that is FDA approved for the treatment of relapsed/refractory B-cell acute lymphoblastic leukemia (B-cell ALL). Liver toxicity, particularly veno-occlusive disease (VOD) was the most important grade 3 toxicity in the Phase III INO-VATE study of InO, driven by the active cytotoxic agent calicheamicin conjugated to InO, especially in pts who underwent subsequent stem cell transplantation (SCT) (Kantarjian et. al, NEJM 2016). However proper assessment of liver function and fibrosis through elastographic measurements might predict the risks of subsequent liver toxicity with InO. Aim: We aimed to study the extent of liver toxicity, including VOD, in pts treated with InO and its correlation to baseline liver elastography. Methods: Pts with B-cell ALL treated with InO containing low intensity combination regimen [miniCVD-InO- blinatumomab-rituximab (previously published; Jabbour et. al. Cancer 2018)] as part of a clinical trial (NCT01371630) underwent baseline liver elastography and were prospectively monitored for any evidence of liver toxicity, including VOD. Elastography was done within 4 weeks prior to the first infusion of InO and liver stiffness was stratified based on the median shear wave velocity (SWV) using the acoustic radiation force impulse (ARFI) technique. Elastographic median SWV >1.7 m/s was considered as evidence of definite liver fibrosis. We captured the patient characteristics, history of known liver disorders, baseline liver function tests, total dose of InO administered and any subsequent liver toxicities including VOD. Any antecedent or subsequent history of SCT was noted; liver toxicity was graded according to the NCI CTCAE, v5. The dose of InO was capped at a cumulative maximum of 2.7mg/m2 of body surface area (administered in fractionated doses) and all pts received concurrent ursodiol prophylaxis with InO. Results: From Jan 2018- April 2022, 50 consecutive pts treated with the above regimen and with baseline elastography reports available as part of the research protocol were analyzed. The median age of the pts was 54.9 years (yrs) (range, 21.7-87.7 yrs) and only 1 pt had a known prior liver ailment of non-alcoholic fatty liver disease (NAFLD). Baseline characteristics are mentioned in Table 1. The median InO dose received by the pts were 1.5 mg/m2 (range, 0.9-2.7 mg/m2) and only 11 pts (22%) received the maximum cumulative InO dose of 2.7 mg/m2. A total of 11 pts (22%) had a baseline maximum SWV >1.7 m/s which radiologically corresponds to possible compensated advanced chronic liver disease (cACLD) and no pts had a SWV >2.1 m/s (corresponds to clinically significant portal hypertension; CSPH). All pts achieved CR/CRi as best response and 14 pts (28%) underwent consolidative SCT. Only one pt developed a VOD of the liver, diagnosed based on clinical and radiological findings, at D+60 post haploidentical-SCT with Flu/Mel140 conditioning and post-transplant cyclophosphamide. This pt had normal baseline liver elastography and had received a cumulative InO dose of 1.5 mg/m2. Another 5-pts (10%) had ≥ grade 3 liver toxicity (1 pt with hyperbilirubinemia and 4 pts with ALT elevation), all of whom had baseline SWV <1.7 m/s on elastography. On regression analysis using age, cumulative InO dose, baseline values of total bilirubin, ALT and INR, and SWV cutoffs as covariates, no factor significantly affected the risks of ≥ grade 3 liver toxicity. After adopting the use of reduced dose fractionated InO administration regimen, routine ursodiol prophylaxis and avoiding peri-transplant azole antifungal prophylaxis in InO exposed B-cell ALL pts at our center, the frequency of liver toxicites including VOD has significantly reduced compared to the 11% rate of VOD described in the INO-VATE study. With these improvisations reducing the overall frequency of InO induced liver toxicity, the positive predictive value of a pre-InO elastography to envisage the risks of subsequent VOD and other liver toxicity in these pts is highly limited. Conclusion: In a prospectively monitored group of pts of B-cell ALL treated with fractionated InO containing combination regimen, baseline liver elastography did not predict the risk of subsequent liver toxicity. Sequential liver elastographies to monitor dynamic changes in SWV needs to be analyzed in future studies to further assess its predictive role for InO induced liver toxicity. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Prolonged Sitting Causes Leg Discomfort in Middle Aged Adults: Evaluation of Shear Wave Velocity, Calf Circumference, and Discomfort Questionaries.

Introduction: Prolonged sitting causes leg discomfort. We evaluated shear wave velocity (SWV) of leg muscles, leg circumference, and leg discomfort associated with 2 h sitting. Methods: Twenty-one middle-aged men and 19 middle-aged women participated in the study. SWV and leg circumference was measured just after sitting, 60 min, 120 min, and after 3 min of leg raising. Leg discomfort was assessed before sitting and 120 min. Results: SWV was significantly greater in men than women and increased over time, and decreased with leg raising. The percentage increase in lower leg circumference was significantly greater in women than in men, and it increased over time. Leg discomfort significantly increased after 120 min in both men and women. Discussions: Because SWV is proportional to an increase in intramuscular compartment pressure in the lower leg, intramuscular compartment pressure increased over time with sitting and decreased with leg raising. Considering the changes in SWV and leg circumference, it was inferred that prolonged sitting causes an increase in intramuscular compartment pressure and intravascular blood volume, as well as an increase in water content in the leg subcutaneous tissue. Leg discomfort was estimated to be due to increased intra-leg fluid. Brief leg raising may resolve leg edema and discomfort.

Evaluation of change in tumor stiffness measured by acoustic radiation force impulse imaging for early prediction of response to neoadjuvant chemotherapy in breast cancer.

In this study, the role of change in tumor stiffness between pre- and post-two cycles of neoadjuvant chemotherapy (NACT) measured by Acoustic Radiation Force Impulse (ARFI) imaging for predicting the response to NACT in breast cancer was analyzed. Fifty-two adult women with biopsy-proven locally advanced breast cancer and early-stage breast cancer who received NACT followed by either modified radical mastectomy or breast conservation surgery were included in the study. Tumor stiffness represented by shear wave velocity (SWV) in meter per second by ARFI imaging was measured before and after two cycles of NACT. Participants were categorized into responders and nonresponders based on pathological response assessment from the postoperative specimen. The association of change in tumor stiffness between pre- and post-two cycles of NACT with final pathological response status was assessed. The mean change in SWV before and after completion of two cycles of NACT was 0.42 ± 0.16 and 0.17 ± 0.11 m/s in responders and nonresponders, respectively, and this difference was proven to be statistically significant (p < 0.001) suggesting that tumors that exhibit a larger reduction in tumor stiffness, respond better. An SWV reduction cut-off of 0.295 m/s between baseline and post-two cycles of NACT was also arrived at, which can discriminate between responders and nonresponders with a sensitivity and specificity of 88% and 83%, respectively. Difference in tumor stiffness measured by ARFI imaging before and after two cycles of chemotherapy can be used as a reliable early predictor of response to chemotherapy in breast cancer.

Dynamic Properties of Calcareous Sands from Urban Areas of Abu Dhabi

Abu Dhabi (ABD) has recently developed its national building code that mandates dynamic analysis of large structures to seismic loadings. Large strain dynamic properties such as shear modulus (G) and damping ratio (D) of local undisturbed calcareous sands are not available. Designers are compelled to choose degradation models from studies on calcareous sands of other regions that are usually reconstituted. This research presents for the first time large strain dynamic properties of calcareous sands of urban ABD. Undisturbed samples are collected from different areas of urban ABD and are tested in cyclic triaxial (CT) devices fitted with bender elements (BE). The dynamic properties as functions of confinement are curve fitted with power models, whereas their variation with shear strain level is curve fitted with hyperbolic models. The results are compared with findings of previous studies on calcareous and silica sands. The results indicate that dynamic properties of all samples degrade with shear strain at almost the same rate irrespective of their spatial distribution. The proposed degradation models can therefore be used in dynamic analyses. The results from this study show smaller rates of degradation in dynamic properties compared to other studies on similar sands. The change in low-strain shear wave velocity (Vs) with confinement is significant among the tested samples; therefore, a site-specific evaluation of Vs is recommended. The dynamic properties of calcareous sands of ABD and previous studies however exhibit larger degradation with shear strain and a smaller increase in confinement compared to silica sands.

Effects of Particle Shape on the Shear Wave Velocity and Shear Modulus of 3D Printed Sand Analogs

Isolating the effects of individual particle properties (e.g. shape, size, mineralogy, surface roughness) on the mechanical behavior of naturally occurring coarse-grained soils is a significant challenge in experimental studies. This challenge can be addressed by recent advances in 3D printing technology which enable generation of artificial sand-sized particles with independent control over particle size and shape. In this study, bender element tests are conducted to examine the isolated effects of particle shape on the shear wave velocity and shear modulus of 3D printed sand analogs. The experimental results show that the shear wave velocity and shear modulus of the 3D printed sand specimens exhibit a relationship with mean effective stress that is in agreement to that reported for natural sands. The specimens composed of 3D printed sands with greater particle roundness and sphericity exhibit greater shear wave velocity and shear modulus for a given void ratio, relative density, and mean effective stress. The changes in shear wave velocity can be captured in terms of differences in individual particle shape parameters such as roundness and sphericity as well as combined particle shape parameters such as regularity. Regression analysis is used to develop relationships between shear wave velocity and particle shape parameters and void ratio, which are shown to be in agreement with previously-published relationships and to reliably predict the shear wave velocity of natural sands. The results presented herein highlight the usefulness of testing 3D printed soils to identify functional trends and dependencies between soil response parameters and intrinsic properties. However, this requires verification of the results against published trends and assessment of the possible effects of the differences in constituent material between the 3D printed and the natural soils.

A Series Solution for 2D Scattering of Cylindrical SH-Waves by Surrounding Loose Rock Zone of Underground Tunnel Lining

This paper presents a closed-form series solution of cylindrical SH-wave scattering by the surrounding loose rock zone of underground tunnel lining in a uniform half-space based on the wave function expansion method and the mirror image method. The correctness of the series solution is verified through residual convergence and comparison with the published results. The influence of the frequency of the incident cylindrical SH-wave, the distance between the wave source and the lining, the lining buried depth, and the properties of the surrounding loose rock zone on the dynamic stress concentration of the tunnel lining is investigated. The results show that the incident wave with high frequency always makes the dynamic stress concentration of the tunnel lining obvious. With the increase of the distance between the wave source and the tunnel lining, the stress around the tunnel lining decreases, but the dynamic stress concentration factor around the tunnel lining does not decrease significantly but occasionally increases. The ground surface has a great influence on the stress concentration of the tunnel lining. The amplitude of the stress concentration factor of tunnel lining is highly related to the shear wave velocity of the surrounding loose rock zone. When the property of the surrounding rock (shear wave velocity) changes more, the amplitude of the stress concentration factor is larger, that is, the stress concentration is more significant.

Changes in placental elastography in the third trimester - Analysis using a linear mixed effect model.

Research into the role of ultrasound elastography to assess compromised placental tissue is ongoing. There is particular interest in evaluating its potential in the investigation of changes associated with uteroplacental dysfunction. To date, there is limited data on how different maternal and fetal considerations, such as advancing gestational age, amniotic fluid Index (AFI) and maternal body mass index (BMI) may influence shear wave velocity (SWV) measurements. This study aimed to evaluate longitudinal changes in SWV throughout gestation and model these changes with other developing fetal and maternal physiological and biological characteristics. The study utilised 238 singleton pregnancies and collected longitudinal data at repeated intervals in the 3rd trimester representing 629 individual data points. Linear mixed model regression analysis was used to identify significant predictors for SWV. From a total of ten variables selected for modelling, only gestational age, AFI, BMI, and sample depth were found to be significant predictors of placental SWV, and gestational age and AFI were found to have only a minimal impact on SWV. Sophisticated statistical modelling demonstrates that many of the expected maternal and fetal changes in the 3rd trimester have no or minimal impact on placental SWV. Understanding which factors influence placental SWV is essential to ascertain the technique's utility in managing pregnancies complicated by placental dysfunction in the future.