Fractures play a crucial role in various fields such as hydrocarbon exploration,groundwater resources management,and earthquake research.The determination of fracture location and the estimation of parameters such as ...Fractures play a crucial role in various fields such as hydrocarbon exploration,groundwater resources management,and earthquake research.The determination of fracture location and the estimation of parameters such as fracture length and dip angle are the focus of geophysical work.In borehole observation system,the short distance between fractures and detectors leads to weak attenuation of elastic wave energy,and high-frequency source makes it easier to identify small-scale fractures.Compared to traditional monopole logging methods,dipole logging method has advantage of exciting pure shear waves sensitive to fractures,so its application is becoming increasingly widespread.However,since the reflected shear waves and scattered shear waves of fractures correspond to different fracture properties,how to distinguish and analyze these two kinds of waves is crucial for accurately characterizing the fracture parameters.To address this issue,numerical simulation of wave responses by a single fracture near a borehole in rock formation is performed,and the generation mechanism and characteristics of shear waves scattered by fractures are investigated.It is found that when the dip angle of the fracture surpasses a critical threshold,the S-wave will propagate to both endpoints of the fracture and generate scattered S-waves,resulting in two distinct scattered wave packets on the received waveform.When the polarization direction of the acoustic source is parallel to the strike of the fracture,the scattered SH-waves always have larger amplitude than the scattered SV-waves regardless of changing the fracture dip angle.Unlike SV-waves,the SH-waves scattered by the fracture do not have any mode conversion.Additionally,propagation of S-waves to a short length fracture can induce dipole mode vibration of the fracture within a wide frequency range.The phenomena of shear waves reflected and scattered by the fracture are further illustrated and verified by two field examples,thus showing the potential of scattered waves for fracture evaluation and characterization with borehole observation system.展开更多
BACKGROUND Thyroid dysfunction during pregnancy is an important disease affecting the health of mothers and children.Two-dimensional(2D)shear wave elastography(SWE)is the newest ultrasonic elastography technology and ...BACKGROUND Thyroid dysfunction during pregnancy is an important disease affecting the health of mothers and children.Two-dimensional(2D)shear wave elastography(SWE)is the newest ultrasonic elastography technology and its value in differentiating benign and malignant thyroid nodules has been widely recognized.However,the value of 2D SWE in evaluating and predicting thyroid function is unclear.AIM To explore prospectively the value of 2D SWE quantitative analysis for the evaluation of thyroid function in the first trimester.METHODS We included outpatients of reproductive age in the Department of Gynecology in Shanghai Changning Maternity and Infant Health Hospital between March 2023 and March 2024 who had conventional ultrasound examination and 2D SWE of the thyroid.They also underwent transvaginal ultrasound examination to confirm early intrauterine pregnancy and serum thyroid stimulating hormone(TSH)level was measured.The patients were divided into pregnant with normal TSH,pregnant with abnormal TSH,and nonpregnant with normal TSH.Conventional ultrasound and 2D SWE results were compared among the three groups.RESULTS A total of 108 patients were included in the study;57 in the pregnant with normal TSH group,18 in the pregnant with abnormal TSH group and 33 were in the nonpregnant with normal TSH group.Thyroid size,thyroid echotexture,2D SWE quantitative parameters including mean elasticity in the region of interest and maximal elasticity in the region of interest showed no significant differences among the three groups(P>0.05).CONCLUSION Conventional ultrasound and 2D SWE features could not reflect the level of serum TSH.展开更多
This study explores the significance of using two-dimensional shear wave elastography(2D-SWE)to assess liver stiffness(LS)and spleen area(SPA)for predicting post-hepatectomy liver failure(PHLF).By providing a non-inva...This study explores the significance of using two-dimensional shear wave elastography(2D-SWE)to assess liver stiffness(LS)and spleen area(SPA)for predicting post-hepatectomy liver failure(PHLF).By providing a non-invasive method to measure LS,which correlates with the degree of liver fibrosis,and SPA,an indicator of portal hypertension,2D-SWE offers a comprehensive evaluation of a patient’s hepatic status.These advancements are particularly crucial in hepatic surgery,where accurate preoperative assessments are essential for optimizing surgical outcomes and minimizing complications.This letter highlights the prac-tical implications of integrating 2D-SWE into clinical practice,emphasizing its potential to improve patient safety and surgical precision by enhancing the ability to predict PHLF and tailor surgical approaches accordingly.展开更多
BACKGROUND Integrating conventional ultrasound features with 2D shear wave elastography(2D-SWE)can potentially enhance preoperative hepatocellular carcinoma(HCC)predictions.AIM To develop a 2D-SWE-based predictive mod...BACKGROUND Integrating conventional ultrasound features with 2D shear wave elastography(2D-SWE)can potentially enhance preoperative hepatocellular carcinoma(HCC)predictions.AIM To develop a 2D-SWE-based predictive model for preoperative identification of HCC.METHODS A retrospective analysis of 884 patients who underwent liver resection and pathology evaluation from February 2021 to August 2023 was conducted at the Oriental Hepatobiliary Surgery Hospital.The patients were divided into the modeling group(n=720)and the control group(n=164).The study included conventional ultrasound,2D-SWE,and preoperative laboratory tests.Multiple logistic regression was used to identify independent predictive factors for RESULTS In the modeling group analysis,maximal elasticity(Emax)of tumors and their peripheries,platelet count,cirrhosis,and blood flow were independent risk indicators for malignancies.These factors yielded an area under the curve of 0.77(95%confidence interval:0.73-0.81)with 84%sensitivity and 61%specificity.The model demonstrated good calibration in both the construction and validation cohorts,as shown by the calibration graph and Hosmer-Lemeshow test(P=0.683 and P=0.658,respectively).Additionally,the mean elasticity(Emean)of the tumor periphery was identified as a risk factor for microvascular invasion(MVI)in malignant liver tumors(P=0.003).Patients receiving antiviral treatment differed significantly in platelet count(P=0.002),Emax of tumors(P=0.033),Emean of tumors(P=0.042),Emax at tumor periphery(P<0.001),and Emean at tumor periphery(P=0.003).CONCLUSION 2D-SWE’s hardness value serves as a valuable marker for enhancing the preoperative diagnosis of malignant liver lesions,correlating significantly with MVI and antiviral treatment efficacy.展开更多
BACKGROUND Real-time shear wave elastography(SWE)is a non-invasive imaging technique used to measure tissue stiffness by generating and tracking shear waves in real time.This advanced ultrasound-based method provides ...BACKGROUND Real-time shear wave elastography(SWE)is a non-invasive imaging technique used to measure tissue stiffness by generating and tracking shear waves in real time.This advanced ultrasound-based method provides quantitative information regarding tissue elasticity,offering valuable insights into the mechanical properties of biological tissues.However,the application of real-time SWE in the musculoskeletal system and sports medicine has not been extensively studied.AIM To explore the practical value of real-time SWE for assessing Achilles tendon hardness in older adults.METHODS A total of 60 participants were enrolled in the present study,and differences in the elastic moduli of the bilateral Achilles tendons were compared among the following categories:(1)Age:55-60,60-65,and 65-70-years-old;(2)Sex:Male and female;(3)Laterality:Left and right sides;(4)Tendon state:Relaxed and tense state;and(5)Tendon segment:Proximal,middle,and distal.RESULTS There were no significant differences in the elastic moduli of the bilateral Achilles tendons when comparing by age or sex(P>0.05).There were,however,significant differences when comparing by tendon side,state,or segment(P<0.05).CONCLUSION Real-time SWE plays a significant role compared to other examination methods in the evaluation of Achilles tendon hardness in older adults.展开更多
Elastography can be used as a diagnostic method for quantitative characterization of tissue hardness information and thus,differential changes in pathophysiological states of tissues.In this study,we propose a new met...Elastography can be used as a diagnostic method for quantitative characterization of tissue hardness information and thus,differential changes in pathophysiological states of tissues.In this study,we propose a new method for shear wave elastography(SWE)based on laser-excited shear wave,called photoacoustic shear wave elastography(PASWE),which combines photoacoustic(PA)technology with ultrafast ultrasound imaging.By using a focused laser to excite shear waves and ultrafast ultrasonic imaging for detection,high-frequency excitation of shear waves and noncontact elastic imaging can be realized.The laser can stimulate the tissue with the light absorption characteristic to produce the thermal expansion,thus producing the shear wave.The frequency of shear wave induced by laser is higher and the frequency band is wider.By tracking the propagation of shear wave,Young’s modulus of tissue is reconstructed in the whole shear wave propagation region to further evaluate the elastic information of tissue.The feasibility of the method is verified by experiments.Compared with the experimental results of supersonic shear imaging(SSI),it is proved that the method can be used for quantitative elastic imaging of the phantoms.In addition,compared with the SSI method,this method can realize the noncontact excitation of the shear wave,and the frequency of the shear wave excited by the laser is higher than that of the acoustic radiation force(ARF),so the spatial resolution is higher.Compared to the traditional PA elastic imaging method,this method can obtain a larger imaging depth under the premise of ensuring the imaging resolution,and it has potential application value in the clinical diagnosis of diseases requiring noncontact quantitative elasticity.展开更多
Liquefaction assessment based on strain energy is significantly superior to conventional stress-based methods.The main purpose of the present study is to investigate the correlation between shear wave velocity and str...Liquefaction assessment based on strain energy is significantly superior to conventional stress-based methods.The main purpose of the present study is to investigate the correlation between shear wave velocity and strain energy capacity of silty sands.The dissipated energy until liquefaction occurs was calculated by analyzing the results of three series of comprehensive cyclic direct simple shear and triaxial tests on Ottawa F65,Nevada,and Firoozkuh sands with varying silt content by weight and relative densities.Additionally,the shear wave velocity of each series was obtained using bender element or resonant column tests.Consequently,for the first time,a liquefaction triggering criterion,relating to effective overburden normalized liquefaction capacity energy(WL=s’c)to effective overburden stresscorrected shear wave velocity(eVs1)has been introduced.The accuracy of the proposed criteria was evaluated using in situ data.The results confirm the ability of shear wave velocity as a distinguishing parameter for separating liquefied and non-liquefied soils when it is calculated against liquefaction capacity energy(WL=s’c).However,the proposed WL=s’c-Vs1 curve,similar to previously proposed cyclic resistance ratio(CRR)-Vs1 relationships,should be used conservatively for fields vulnerable to liquefaction-induced lateral spreading.展开更多
The horizontal-to-vertical spectral ratio(HVSR)method has been used to characterize site-effect parameters that are indispensable in seismic hazard and risk-reduction studies in urban areas and rapid land-use planning...The horizontal-to-vertical spectral ratio(HVSR)method has been used to characterize site-effect parameters that are indispensable in seismic hazard and risk-reduction studies in urban areas and rapid land-use planning.This method is widely used because it is the cheapest and simplest geophysical method for the acquisition and processing stages.In subsequent developments,the HVSR method has been widely used to determine elastic rock parameters,particularly shear wave velocity(v_(S)),through the HVSR curve inversion process.Furthermore,the v_(S)structural model can be used to delineate the presence of complex geological structures,particularly faults and sedimentary basins.Bandar Lampung is a city in Lampung Province with many fault structures and groundwater basins to the south.There are 83 HVSR measurement points around Bandar Lampung for delineating the presence of fault structures and groundwater basins.We produced the HVSR curve from the measurement results and then performed an inversion process using the particle swarm optimization algorithm to obtain v_(S)for the depth profile.Subsequently,from this profile,we produced a two-dimensional(2D)lateral and vertical model.The mean v_(S)value was calculated from all the measurement points,and we found stiff soil layers reaching depths of approximately 5 m,with a value of v_(S)<330 m/s.A bedrock layer with a velocity exceeding 1250 m/s was visible at a depth of 100 m.Based on the 2D model,the v_(S)structure shows that the city of Bandar Lampung is divided into two zones,with a NW-SE boundary.The north-middle-eastern part of the city consists of harder rocks.This harder rock is characterized by extremely high v_(S)values,starting from a depth of 50 m.In contrast,the south-middle-west exhibits a low-moderate v_(S)anomaly associated with groundwater basins SW of the city.From the 2D v_(S)structural model,fault structures can be found along the city,characterized by a contrast of v_(S)values from low to medium and from medium to high.展开更多
How the state of living muscles modulates the features of nonlinear elastic waves generated by external dynamic loads remains unclear because of the challenge of directly observing and modeling nonlinear elastic waves...How the state of living muscles modulates the features of nonlinear elastic waves generated by external dynamic loads remains unclear because of the challenge of directly observing and modeling nonlinear elastic waves in skeletal muscles in vivo,considering their active deformation behavior.Here,this important issue is addressed by combining experiments performed with an ultrafast ultrasound imaging system to track nonlinear shear waves(shear shock waves)in muscles in vivo and finite element analysis relying on a physically motivated constitutive model to study the effect of muscle activation level.Skeletal muscle was loaded with a deep muscle stimulator to generate shear shock waves(SSWs).The particle velocities,second and third harmonics,and group velocities of the SSWs in living muscles under both passive and active states were measured in vivo.Our experimental results reveal,for the first time,that muscle states have a pronounced effect on wave features;a low level of activation may facilitate the occurrence of both the second and third harmonics,whereas a high level of activation may inhibit the third harmonic.Finite element analysis was further carried out to quantitatively explore the effect of active muscle deformation behavior on the generation and propagation of SSWs.The simulation results at different muscle activation levels confirmed the experimental findings.The ability to reveal the effects of muscle state on the features of SSWs may be helpful in elucidating the unique dynamic deformation mechanism of living skeletal muscles,quantitatively characterizing diverse shock wave-based therapy instruments,and guiding the design of muscle-mimicking soft materials.展开更多
Shear wave splitting(SWS)is regarded as the most effective geophysical method to delineate mantle flow fields by detecting seismic azimuthal anisotropy in the earth's upper mantle,especially in tectonically active...Shear wave splitting(SWS)is regarded as the most effective geophysical method to delineate mantle flow fields by detecting seismic azimuthal anisotropy in the earth's upper mantle,especially in tectonically active regions such as subduction zones.The Aleutian-Alaska subduction zone has a convergence rate of approximately 50 mm/yr,with a trench length reaching nearly 2800 km.Such a long subduction zone has led to intensive continental deformation and numerous strong earthquakes in southern and central Alaska,while northern Alaska is relatively inactive.The sharp contrast makes Alaska a favorable locale to investigate the impact of subduction on mantle dynamics.Moreover,the uniqueness of this subduction zone,including the unusual subducting type,varying slab geometry,and atypical magmatic activity and composition,has intrigued the curiosity of many geoscientists.To identify different sources of seismic anisotropy beneath the Alaska region and probe the influence of a geometrically varying subducting slab on mantle dynamics,extensive SWS analyses have been conducted in the past decades.However,the insufficient station and azimuthal coverage,especially in early studies,not only led to some conflicting results but also strongly limited the in-depth investigation of layered anisotropy and the estimation of anisotropy depth.With the completion of the Transportable Array project in Alaska,recent studies have revealed more detailed mantle structures and characteristics based on the dense station coverage and newly collected massive seismic data.In this study,we review significant regional-and continental-scale SWS studies in the Alaska region and conclude the mantle flow fields therein,to understand how a geometrically varying subducting slab alters the regional mantle dynamics.The summarized mantle flow mechanisms are believed to be conducive to the understanding of seismic anisotropy patterns in other subduction zones with a complicated tectonic setting.展开更多
Shear logs,also known as shear velocity logs,are used for various types of seismic analysis,such as determining the relationship between amplitude variation with offset(AVO)and interpreting multiple types of seismic d...Shear logs,also known as shear velocity logs,are used for various types of seismic analysis,such as determining the relationship between amplitude variation with offset(AVO)and interpreting multiple types of seismic data.This log is an important tool for analyzing the properties of rocks and interpreting seismic data to identify potential areas of oil and gas reserves.However,these logs are often not collected due to cost constraints or poor borehole conditions possibly leading to poor data quality,though there are various approaches in practice for estimating shear wave velocity.In this study,a detailed review of the recent advances in the various techniques used to measure shear wave(S-wave)velocity is carried out.These techniques include direct and indirect measurement,determination of empirical relationships between S-wave velocity and other parameters,machine learning,and rock physics models.Therefore,this study creates a collection of employed techniques,enhancing the existing knowledge of this significant topic and offering a progressive approach for practical implementation in the field.展开更多
Magnetic resonance imaging is the gold standard compared other clinical fin-dings.But shear wave elastography technique combined with endoscopic ultra-sound can evaluate the degree of fibrosis of fistula tissue in Cr...Magnetic resonance imaging is the gold standard compared other clinical fin-dings.But shear wave elastography technique combined with endoscopic ultra-sound can evaluate the degree of fibrosis of fistula tissue in Crohn’s disease patients.This topic is highly relevant to the current discourse,especially for It shows a certain degree of innovation and practicality and is worthy of study and popularization.展开更多
Using seismic data of the aftershocks sequence of the April 20, 2013 Lushan earthquake recorded by seismic temporary and permanent stations in the source region, with the visual inspection of particle motion diagrams,...Using seismic data of the aftershocks sequence of the April 20, 2013 Lushan earthquake recorded by seismic temporary and permanent stations in the source region, with the visual inspection of particle motion diagrams, this paper preliminarily contains the polarization directions of fast shear wave and the time-delays of split shear waves at every station, and analyzes the crustal anisotropic characteristics in the source region. In the study area, the polarization direc- tions at stations BAX, TQU, L 132, L 133, L 134, and L 135 are northeast, which is consistent with the strike of Dachuan- Shuangshi fault. There are two polarization directions at MDS and L131, which are northeast and southeast. The scatter of polarization directions suggests the complex stress field around these two stations where two faults intersect. For the normalized time-delays at every station, the range is 1.02-8.64 ms/km. The largest time-delay is from L134 which is closest to the mainshock, and the smallest one is from L133. The variations in time-delays show the decreasing at stations BAX, L134, and L135 because of the stress-relaxation after earthquake.展开更多
The Shimian area of Sichuan sits at the junction of the Bayan Har block.Sichuan-Yunnan rhombic block,and Yangtze block,where several faults intersect.This region features intense tectonic activity and frequent earthqu...The Shimian area of Sichuan sits at the junction of the Bayan Har block.Sichuan-Yunnan rhombic block,and Yangtze block,where several faults intersect.This region features intense tectonic activity and frequent earthquakes.In this study,we used local seismic waveform data recorded using dense arrays deployed in the Shimian area to obtain the shear wave splitting parameters at 55 seismic stations and thereby determine the crustal anisotropic characteristics of the region.We then analyzed the crustal stress pattern and tectonic setting and explored their relationship in the study area.Although some stations returned a polarization direction of NNW-SSE.a dominant polarization direction of NW-SE was obtained for the fast shear wave at most seismic stations in the study area.The polarization directions of the fast shear wave were highly consistent throughout the study-area.This orientation was in accordance with the direction of the regional principal compressive stress and parallel to the trend of the Xianshuihe and Daliangshan faults.The distribution of crustal anisotropy in this area was affected by the regional tectonic stress field and the fault structures.The mean delay time between fast and slow shear waves was 3.83 ms/km.slightly greater than the values obtained in other regions of Sichuan.This indicates that the crustal media in our study area had a high anisotropic strength and also reveals the influence of tectonic complexity resulting from the intersection of multiple faults on the strength of seismic anisotropy.展开更多
Shear-wave velocity is a key parameter for calibrating monitoring time-lapse 4D seismic data during CO2-EOR （Enhanced Oil Recovery） and CO2 sequestration. However, actual S-wave velocity data are lacking, especially...Shear-wave velocity is a key parameter for calibrating monitoring time-lapse 4D seismic data during CO2-EOR （Enhanced Oil Recovery） and CO2 sequestration. However, actual S-wave velocity data are lacking, especially in 4D data for CO2 sequestration because wells are closed after the CO2 injection and seismic monitoring is continued but no well log data are acquired. When CO2 is injected into a reservoir, the pressure and saturation of the reservoirs change as well as the elastic parameters of the reservoir rocks. We propose a method to predict the S-wave velocity in reservoirs at different pressures and porosities based on the Hertz-Mindlin and Gassmann equations. Because the coordination number is unknown in the Hertz Mindlin equation, we propose a new method to predict it. Thus, we use data at different CO2 injection stages in the Gao89 well block, Shengli Oilfield. First, the sand and mud beds are separated based on the structural characteristics of the thin sand beds and then the S-wave velocity as a function of reservoir pressure and porosity is calculated. Finally, synthetic seismic seismograms are generated based on the predicted P- and S-wave velocities at different stages of CO2 injection.展开更多
The correlations between shear wave velocity(SWV)calculated from virtual touch tissue imaging quantification(VTIQ)technique and histological prognostic factors of invasive ductal carcinoma was investigated.A total of ...The correlations between shear wave velocity(SWV)calculated from virtual touch tissue imaging quantification(VTIQ)technique and histological prognostic factors of invasive ductal carcinoma was investigated.A total of 76 breast tumors histologically confirmed as invasive ductal carcinomas were included in this study.SWV values were measured by VTIQ for each lesion preoperatively or prior to breast biopsy.The maximum values were recorded for statistical analysis.Medical records were reviewed to determine tumor size,histological grade,lymph node status and immunohistochemical results.Tumor subtypes were categorized as luminal A,luminal B,human epidermal growth factor receptor 2(HER2)positive and triple negative.The correlations between SWV and histological prognostic factors were analyzed.It was found that tumor size showed positive association with SWV(r=0.465,P<0.001).Larger tumors had significantly higher SWV than smaller ones(P=0.001).Histological grade 1 tumors had significantly lower SWV values than those with higher histological grade(P=0.015).The Ki67 expression,tumor subtypes and lymph node status showed no statistically significant correlations with SWV,although triple negative tumors and lymph node-positive tumors showed higher SWV values.It was concluded that tumor size was significantly associated with SWV.Higher histological grade was associated with increased SWV.There was no statistically significant correlations between SWV and other histological prognostic factors.展开更多
We assembled approximately 328 seismic records. The data set was from 4 digitally recording long-period and broadband stations of CDSN. We carried out the inversion based on the partitioned waveform inversion (PWI). I...We assembled approximately 328 seismic records. The data set was from 4 digitally recording long-period and broadband stations of CDSN. We carried out the inversion based on the partitioned waveform inversion (PWI). It partitions the large-scale optimization problem into a number of independent small-scale problems. We adopted surface waveform inversion with an equal block (2((2() discretization in order to acquire the images of shear velocity structure at different depths (from surface to 430 km) in the crust and upper-mantle. The resolution of all these anomalies has been established with (check-board( resolution tests. These results show significant difference in velocity, lithosphere and asthenosphere structure between South China Sea and its adjacent regions.展开更多
AIM:To investigate whether a noninvasive measurement of tissue strain has a potential usefulness for management of nonalcoholic steatohepatitis(NASH).METHODS:In total 26 patients,23 NASHs and 3 normal controls were en...AIM:To investigate whether a noninvasive measurement of tissue strain has a potential usefulness for management of nonalcoholic steatohepatitis(NASH).METHODS:In total 26 patients,23 NASHs and 3 normal controls were enrolled in this study.NASH was staged based on Brunt criterion.At a region of interest(ROI),a shear wave was evoked by implementing an acoustic radiation force impulse(ARFI),and the propagation velocity was quantif ied.RESULTS:Shear wave velocity(SWV) could be reproducibly quantified at all ROIs in all subjects except for 4 NASH cases,in which a reliable SWV value was not calculated at several ROIs.An average SWV of 1.34 ± 0.26 m/s in fibrous stage 0-1 was significantly slower than 2.20 ± 0.74 m/s and 2.90 ± 1.01 m/s in stages 3 and 4,respectively,but was not significantly different from 1.79 ± 0.78 m/s in stage 2.When a cutoff value was set at 1.47 m/s,receiver operating characteristic analysis showed significance to dissociate stages 3 and 4 from stage 0-1(P=0.0092) with sensitivity,specificity and area under curve of 100%,75% and 94.2%,respectively.In addition,the correlation between SWV and hyaluronic acid was significant(P<0.0001),while a tendency toward negative correlation was observed with serum albumin(P=0.053).CONCLUSION:The clinical implementation of ARFI provides noninvasive repeated evaluations of liver stiffness at an arbitrary position,which has the potential to shed new light on NASH management.展开更多
The great Wenchuan earthquake （Ms= 8.0） in 2008 caused severe damage in the western part of the Chengdu Plain. Soil liquefaction was one of the major causes of damage in the plain areas, and proper evaluation of liq...The great Wenchuan earthquake （Ms= 8.0） in 2008 caused severe damage in the western part of the Chengdu Plain. Soil liquefaction was one of the major causes of damage in the plain areas, and proper evaluation of liquefaction potential is important in the definition of the seismic hazard facing a given region and post-earthquake reconstruction. In this paper, a simplified procedure is proposed for liquefaction assessment of sandy deposits using shear wave velocity （V）, and soil liquefaction from the Banqiao School site was preliminarily investigated after the earthquake. Boreholes were made at the site and shear wave velocities were measured both by SASW and down-hole methods. Based on the in-situ soil information and V profiles, the liquefaction potential of this site was evaluated. The results are reasonably consistent with the actual field behavior observed after the earthquake, indicating that the proposed procedure is effective. The possible effects of gravel and fines contents on liquefaction of sandy soils were also briefly discussed.展开更多
AIM To determine the diagnostic accuracy of two-dimensional shear wave elastography(2D-SWE) for the noninvasive assessment of liver fibrosis in patients with autoimmune liver diseases(AILD) using liver biopsy as the r...AIM To determine the diagnostic accuracy of two-dimensional shear wave elastography(2D-SWE) for the noninvasive assessment of liver fibrosis in patients with autoimmune liver diseases(AILD) using liver biopsy as the reference standard.METHODS Patients with AILD who underwent liver biopsy and 2D-SWE were consecutively enrolled. Receiver operating characteristic(ROC) curves were constructed to assess the overall accuracy and to identify optimal cut-off values.RESULTS The characteristics of the diagnostic performance were determined for 114 patients with AILD. The areas under the ROC curves for significant fibrosis, severe fibrosis, and cirrhosis were 0.85, 0.85, and 0.86, respectively, and the optimal cut-off values associated with significant fibrosis(≥ F2), severe fibrosis(≥ F3), and cirrhosis(F4) were 9.7 k Pa, 13.2 k Pa and 16.3 k Pa, respectively. 2D-SWE showed sensitivity values of 81.7% for significant fibrosis, 83.0% for severe fibrosis,and 87.0% for cirrhosis, and the respective specificity values were 81.3%, 74.6%, and 80.2%. The overall concordance rate of the liver stiffness measurements obtained using 2D-SWE vs fibrosis stages was 53.5%.CONCLUSION2D-SWE showed promising diagnostic performance for assessing liver fibrosis stages and exhibited high cut-off values in patients with AILD. Low overall concordance rate was observed in the liver stiffness measurements obtained using 2D-SWE vs fibrosis stages.展开更多
基金supported by Scientific Research and Technology Development Project of CNPC(2024ZG38,2024ZG42)the CNPC Innovation Fund(2022DQ02-0307).
文摘Fractures play a crucial role in various fields such as hydrocarbon exploration,groundwater resources management,and earthquake research.The determination of fracture location and the estimation of parameters such as fracture length and dip angle are the focus of geophysical work.In borehole observation system,the short distance between fractures and detectors leads to weak attenuation of elastic wave energy,and high-frequency source makes it easier to identify small-scale fractures.Compared to traditional monopole logging methods,dipole logging method has advantage of exciting pure shear waves sensitive to fractures,so its application is becoming increasingly widespread.However,since the reflected shear waves and scattered shear waves of fractures correspond to different fracture properties,how to distinguish and analyze these two kinds of waves is crucial for accurately characterizing the fracture parameters.To address this issue,numerical simulation of wave responses by a single fracture near a borehole in rock formation is performed,and the generation mechanism and characteristics of shear waves scattered by fractures are investigated.It is found that when the dip angle of the fracture surpasses a critical threshold,the S-wave will propagate to both endpoints of the fracture and generate scattered S-waves,resulting in two distinct scattered wave packets on the received waveform.When the polarization direction of the acoustic source is parallel to the strike of the fracture,the scattered SH-waves always have larger amplitude than the scattered SV-waves regardless of changing the fracture dip angle.Unlike SV-waves,the SH-waves scattered by the fracture do not have any mode conversion.Additionally,propagation of S-waves to a short length fracture can induce dipole mode vibration of the fracture within a wide frequency range.The phenomena of shear waves reflected and scattered by the fracture are further illustrated and verified by two field examples,thus showing the potential of scattered waves for fracture evaluation and characterization with borehole observation system.
基金Supported by the Natural Science Foundation of Shanghai,No.22ZR1458200Medical Ph.D Innovative Talent Base Project of Changning District,No.RCJD2021B09+1 种基金Key Specialty of Changning District,No.20231004Shanghai Changning Maternity and Infant Health Hospital Start-Up Project,No.2020Y-14.
文摘BACKGROUND Thyroid dysfunction during pregnancy is an important disease affecting the health of mothers and children.Two-dimensional(2D)shear wave elastography(SWE)is the newest ultrasonic elastography technology and its value in differentiating benign and malignant thyroid nodules has been widely recognized.However,the value of 2D SWE in evaluating and predicting thyroid function is unclear.AIM To explore prospectively the value of 2D SWE quantitative analysis for the evaluation of thyroid function in the first trimester.METHODS We included outpatients of reproductive age in the Department of Gynecology in Shanghai Changning Maternity and Infant Health Hospital between March 2023 and March 2024 who had conventional ultrasound examination and 2D SWE of the thyroid.They also underwent transvaginal ultrasound examination to confirm early intrauterine pregnancy and serum thyroid stimulating hormone(TSH)level was measured.The patients were divided into pregnant with normal TSH,pregnant with abnormal TSH,and nonpregnant with normal TSH.Conventional ultrasound and 2D SWE results were compared among the three groups.RESULTS A total of 108 patients were included in the study;57 in the pregnant with normal TSH group,18 in the pregnant with abnormal TSH group and 33 were in the nonpregnant with normal TSH group.Thyroid size,thyroid echotexture,2D SWE quantitative parameters including mean elasticity in the region of interest and maximal elasticity in the region of interest showed no significant differences among the three groups(P>0.05).CONCLUSION Conventional ultrasound and 2D SWE features could not reflect the level of serum TSH.
基金Supported by Guangdong Medical Science and Technology Research Fund Project,No.A2024475.
文摘This study explores the significance of using two-dimensional shear wave elastography(2D-SWE)to assess liver stiffness(LS)and spleen area(SPA)for predicting post-hepatectomy liver failure(PHLF).By providing a non-invasive method to measure LS,which correlates with the degree of liver fibrosis,and SPA,an indicator of portal hypertension,2D-SWE offers a comprehensive evaluation of a patient’s hepatic status.These advancements are particularly crucial in hepatic surgery,where accurate preoperative assessments are essential for optimizing surgical outcomes and minimizing complications.This letter highlights the prac-tical implications of integrating 2D-SWE into clinical practice,emphasizing its potential to improve patient safety and surgical precision by enhancing the ability to predict PHLF and tailor surgical approaches accordingly.
基金Supported by the National Natural Science Foundation of China Youth Training Project,No.2021GZR003and Medical-engineering Interdisciplinary Research Youth Training Project,No.2022YGJC001.
文摘BACKGROUND Integrating conventional ultrasound features with 2D shear wave elastography(2D-SWE)can potentially enhance preoperative hepatocellular carcinoma(HCC)predictions.AIM To develop a 2D-SWE-based predictive model for preoperative identification of HCC.METHODS A retrospective analysis of 884 patients who underwent liver resection and pathology evaluation from February 2021 to August 2023 was conducted at the Oriental Hepatobiliary Surgery Hospital.The patients were divided into the modeling group(n=720)and the control group(n=164).The study included conventional ultrasound,2D-SWE,and preoperative laboratory tests.Multiple logistic regression was used to identify independent predictive factors for RESULTS In the modeling group analysis,maximal elasticity(Emax)of tumors and their peripheries,platelet count,cirrhosis,and blood flow were independent risk indicators for malignancies.These factors yielded an area under the curve of 0.77(95%confidence interval:0.73-0.81)with 84%sensitivity and 61%specificity.The model demonstrated good calibration in both the construction and validation cohorts,as shown by the calibration graph and Hosmer-Lemeshow test(P=0.683 and P=0.658,respectively).Additionally,the mean elasticity(Emean)of the tumor periphery was identified as a risk factor for microvascular invasion(MVI)in malignant liver tumors(P=0.003).Patients receiving antiviral treatment differed significantly in platelet count(P=0.002),Emax of tumors(P=0.033),Emean of tumors(P=0.042),Emax at tumor periphery(P<0.001),and Emean at tumor periphery(P=0.003).CONCLUSION 2D-SWE’s hardness value serves as a valuable marker for enhancing the preoperative diagnosis of malignant liver lesions,correlating significantly with MVI and antiviral treatment efficacy.
基金Supported by Sichuan Orthopaedic Hospital Research Project,No.2019MS02.
文摘BACKGROUND Real-time shear wave elastography(SWE)is a non-invasive imaging technique used to measure tissue stiffness by generating and tracking shear waves in real time.This advanced ultrasound-based method provides quantitative information regarding tissue elasticity,offering valuable insights into the mechanical properties of biological tissues.However,the application of real-time SWE in the musculoskeletal system and sports medicine has not been extensively studied.AIM To explore the practical value of real-time SWE for assessing Achilles tendon hardness in older adults.METHODS A total of 60 participants were enrolled in the present study,and differences in the elastic moduli of the bilateral Achilles tendons were compared among the following categories:(1)Age:55-60,60-65,and 65-70-years-old;(2)Sex:Male and female;(3)Laterality:Left and right sides;(4)Tendon state:Relaxed and tense state;and(5)Tendon segment:Proximal,middle,and distal.RESULTS There were no significant differences in the elastic moduli of the bilateral Achilles tendons when comparing by age or sex(P>0.05).There were,however,significant differences when comparing by tendon side,state,or segment(P<0.05).CONCLUSION Real-time SWE plays a significant role compared to other examination methods in the evaluation of Achilles tendon hardness in older adults.
基金supported by the National Key R&D Program of China(Grant No.2022YFC2402400)the National Natural Science Foundation of China(Grant No.62275062)and Guangdong Provincial Key Laboratory of Biomedical Optical Imaging Technology(Grant No.2020B121201010-4).
文摘Elastography can be used as a diagnostic method for quantitative characterization of tissue hardness information and thus,differential changes in pathophysiological states of tissues.In this study,we propose a new method for shear wave elastography(SWE)based on laser-excited shear wave,called photoacoustic shear wave elastography(PASWE),which combines photoacoustic(PA)technology with ultrafast ultrasound imaging.By using a focused laser to excite shear waves and ultrafast ultrasonic imaging for detection,high-frequency excitation of shear waves and noncontact elastic imaging can be realized.The laser can stimulate the tissue with the light absorption characteristic to produce the thermal expansion,thus producing the shear wave.The frequency of shear wave induced by laser is higher and the frequency band is wider.By tracking the propagation of shear wave,Young’s modulus of tissue is reconstructed in the whole shear wave propagation region to further evaluate the elastic information of tissue.The feasibility of the method is verified by experiments.Compared with the experimental results of supersonic shear imaging(SSI),it is proved that the method can be used for quantitative elastic imaging of the phantoms.In addition,compared with the SSI method,this method can realize the noncontact excitation of the shear wave,and the frequency of the shear wave excited by the laser is higher than that of the acoustic radiation force(ARF),so the spatial resolution is higher.Compared to the traditional PA elastic imaging method,this method can obtain a larger imaging depth under the premise of ensuring the imaging resolution,and it has potential application value in the clinical diagnosis of diseases requiring noncontact quantitative elasticity.
文摘Liquefaction assessment based on strain energy is significantly superior to conventional stress-based methods.The main purpose of the present study is to investigate the correlation between shear wave velocity and strain energy capacity of silty sands.The dissipated energy until liquefaction occurs was calculated by analyzing the results of three series of comprehensive cyclic direct simple shear and triaxial tests on Ottawa F65,Nevada,and Firoozkuh sands with varying silt content by weight and relative densities.Additionally,the shear wave velocity of each series was obtained using bender element or resonant column tests.Consequently,for the first time,a liquefaction triggering criterion,relating to effective overburden normalized liquefaction capacity energy(WL=s’c)to effective overburden stresscorrected shear wave velocity(eVs1)has been introduced.The accuracy of the proposed criteria was evaluated using in situ data.The results confirm the ability of shear wave velocity as a distinguishing parameter for separating liquefied and non-liquefied soils when it is calculated against liquefaction capacity energy(WL=s’c).However,the proposed WL=s’c-Vs1 curve,similar to previously proposed cyclic resistance ratio(CRR)-Vs1 relationships,should be used conservatively for fields vulnerable to liquefaction-induced lateral spreading.
文摘The horizontal-to-vertical spectral ratio(HVSR)method has been used to characterize site-effect parameters that are indispensable in seismic hazard and risk-reduction studies in urban areas and rapid land-use planning.This method is widely used because it is the cheapest and simplest geophysical method for the acquisition and processing stages.In subsequent developments,the HVSR method has been widely used to determine elastic rock parameters,particularly shear wave velocity(v_(S)),through the HVSR curve inversion process.Furthermore,the v_(S)structural model can be used to delineate the presence of complex geological structures,particularly faults and sedimentary basins.Bandar Lampung is a city in Lampung Province with many fault structures and groundwater basins to the south.There are 83 HVSR measurement points around Bandar Lampung for delineating the presence of fault structures and groundwater basins.We produced the HVSR curve from the measurement results and then performed an inversion process using the particle swarm optimization algorithm to obtain v_(S)for the depth profile.Subsequently,from this profile,we produced a two-dimensional(2D)lateral and vertical model.The mean v_(S)value was calculated from all the measurement points,and we found stiff soil layers reaching depths of approximately 5 m,with a value of v_(S)<330 m/s.A bedrock layer with a velocity exceeding 1250 m/s was visible at a depth of 100 m.Based on the 2D model,the v_(S)structure shows that the city of Bandar Lampung is divided into two zones,with a NW-SE boundary.The north-middle-eastern part of the city consists of harder rocks.This harder rock is characterized by extremely high v_(S)values,starting from a depth of 50 m.In contrast,the south-middle-west exhibits a low-moderate v_(S)anomaly associated with groundwater basins SW of the city.From the 2D v_(S)structural model,fault structures can be found along the city,characterized by a contrast of v_(S)values from low to medium and from medium to high.
基金supported by the National Students Training Program for Innovation(Grant No.202210007029)。
文摘How the state of living muscles modulates the features of nonlinear elastic waves generated by external dynamic loads remains unclear because of the challenge of directly observing and modeling nonlinear elastic waves in skeletal muscles in vivo,considering their active deformation behavior.Here,this important issue is addressed by combining experiments performed with an ultrafast ultrasound imaging system to track nonlinear shear waves(shear shock waves)in muscles in vivo and finite element analysis relying on a physically motivated constitutive model to study the effect of muscle activation level.Skeletal muscle was loaded with a deep muscle stimulator to generate shear shock waves(SSWs).The particle velocities,second and third harmonics,and group velocities of the SSWs in living muscles under both passive and active states were measured in vivo.Our experimental results reveal,for the first time,that muscle states have a pronounced effect on wave features;a low level of activation may facilitate the occurrence of both the second and third harmonics,whereas a high level of activation may inhibit the third harmonic.Finite element analysis was further carried out to quantitatively explore the effect of active muscle deformation behavior on the generation and propagation of SSWs.The simulation results at different muscle activation levels confirmed the experimental findings.The ability to reveal the effects of muscle state on the features of SSWs may be helpful in elucidating the unique dynamic deformation mechanism of living skeletal muscles,quantitatively characterizing diverse shock wave-based therapy instruments,and guiding the design of muscle-mimicking soft materials.
基金supported by the Outstanding Youth Project of Natural Science Foundation of Heilongjiang(YQ2023D006).
文摘Shear wave splitting(SWS)is regarded as the most effective geophysical method to delineate mantle flow fields by detecting seismic azimuthal anisotropy in the earth's upper mantle,especially in tectonically active regions such as subduction zones.The Aleutian-Alaska subduction zone has a convergence rate of approximately 50 mm/yr,with a trench length reaching nearly 2800 km.Such a long subduction zone has led to intensive continental deformation and numerous strong earthquakes in southern and central Alaska,while northern Alaska is relatively inactive.The sharp contrast makes Alaska a favorable locale to investigate the impact of subduction on mantle dynamics.Moreover,the uniqueness of this subduction zone,including the unusual subducting type,varying slab geometry,and atypical magmatic activity and composition,has intrigued the curiosity of many geoscientists.To identify different sources of seismic anisotropy beneath the Alaska region and probe the influence of a geometrically varying subducting slab on mantle dynamics,extensive SWS analyses have been conducted in the past decades.However,the insufficient station and azimuthal coverage,especially in early studies,not only led to some conflicting results but also strongly limited the in-depth investigation of layered anisotropy and the estimation of anisotropy depth.With the completion of the Transportable Array project in Alaska,recent studies have revealed more detailed mantle structures and characteristics based on the dense station coverage and newly collected massive seismic data.In this study,we review significant regional-and continental-scale SWS studies in the Alaska region and conclude the mantle flow fields therein,to understand how a geometrically varying subducting slab alters the regional mantle dynamics.The summarized mantle flow mechanisms are believed to be conducive to the understanding of seismic anisotropy patterns in other subduction zones with a complicated tectonic setting.
文摘Shear logs,also known as shear velocity logs,are used for various types of seismic analysis,such as determining the relationship between amplitude variation with offset(AVO)and interpreting multiple types of seismic data.This log is an important tool for analyzing the properties of rocks and interpreting seismic data to identify potential areas of oil and gas reserves.However,these logs are often not collected due to cost constraints or poor borehole conditions possibly leading to poor data quality,though there are various approaches in practice for estimating shear wave velocity.In this study,a detailed review of the recent advances in the various techniques used to measure shear wave(S-wave)velocity is carried out.These techniques include direct and indirect measurement,determination of empirical relationships between S-wave velocity and other parameters,machine learning,and rock physics models.Therefore,this study creates a collection of employed techniques,enhancing the existing knowledge of this significant topic and offering a progressive approach for practical implementation in the field.
文摘Magnetic resonance imaging is the gold standard compared other clinical fin-dings.But shear wave elastography technique combined with endoscopic ultra-sound can evaluate the degree of fibrosis of fistula tissue in Crohn’s disease patients.This topic is highly relevant to the current discourse,especially for It shows a certain degree of innovation and practicality and is worthy of study and popularization.
基金supported by Research Project in Earthquake Science(Nos.201308018 and No.201108002) National Natural Science Foundation of China(No.40904012)
文摘Using seismic data of the aftershocks sequence of the April 20, 2013 Lushan earthquake recorded by seismic temporary and permanent stations in the source region, with the visual inspection of particle motion diagrams, this paper preliminarily contains the polarization directions of fast shear wave and the time-delays of split shear waves at every station, and analyzes the crustal anisotropic characteristics in the source region. In the study area, the polarization direc- tions at stations BAX, TQU, L 132, L 133, L 134, and L 135 are northeast, which is consistent with the strike of Dachuan- Shuangshi fault. There are two polarization directions at MDS and L131, which are northeast and southeast. The scatter of polarization directions suggests the complex stress field around these two stations where two faults intersect. For the normalized time-delays at every station, the range is 1.02-8.64 ms/km. The largest time-delay is from L134 which is closest to the mainshock, and the smallest one is from L133. The variations in time-delays show the decreasing at stations BAX, L134, and L135 because of the stress-relaxation after earthquake.
基金This work is jointly supported by the National Natural Science Foundation of China(No.41904057)the National Key Research and Development Program of China(No.2018YFC1503402).
文摘The Shimian area of Sichuan sits at the junction of the Bayan Har block.Sichuan-Yunnan rhombic block,and Yangtze block,where several faults intersect.This region features intense tectonic activity and frequent earthquakes.In this study,we used local seismic waveform data recorded using dense arrays deployed in the Shimian area to obtain the shear wave splitting parameters at 55 seismic stations and thereby determine the crustal anisotropic characteristics of the region.We then analyzed the crustal stress pattern and tectonic setting and explored their relationship in the study area.Although some stations returned a polarization direction of NNW-SSE.a dominant polarization direction of NW-SE was obtained for the fast shear wave at most seismic stations in the study area.The polarization directions of the fast shear wave were highly consistent throughout the study-area.This orientation was in accordance with the direction of the regional principal compressive stress and parallel to the trend of the Xianshuihe and Daliangshan faults.The distribution of crustal anisotropy in this area was affected by the regional tectonic stress field and the fault structures.The mean delay time between fast and slow shear waves was 3.83 ms/km.slightly greater than the values obtained in other regions of Sichuan.This indicates that the crustal media in our study area had a high anisotropic strength and also reveals the influence of tectonic complexity resulting from the intersection of multiple faults on the strength of seismic anisotropy.
基金supported by the National High Techology Research and Development Program(No.2012AA050103)
文摘Shear-wave velocity is a key parameter for calibrating monitoring time-lapse 4D seismic data during CO2-EOR （Enhanced Oil Recovery） and CO2 sequestration. However, actual S-wave velocity data are lacking, especially in 4D data for CO2 sequestration because wells are closed after the CO2 injection and seismic monitoring is continued but no well log data are acquired. When CO2 is injected into a reservoir, the pressure and saturation of the reservoirs change as well as the elastic parameters of the reservoir rocks. We propose a method to predict the S-wave velocity in reservoirs at different pressures and porosities based on the Hertz-Mindlin and Gassmann equations. Because the coordination number is unknown in the Hertz Mindlin equation, we propose a new method to predict it. Thus, we use data at different CO2 injection stages in the Gao89 well block, Shengli Oilfield. First, the sand and mud beds are separated based on the structural characteristics of the thin sand beds and then the S-wave velocity as a function of reservoir pressure and porosity is calculated. Finally, synthetic seismic seismograms are generated based on the predicted P- and S-wave velocities at different stages of CO2 injection.
基金grants from the Fundamental Research Funds for the Central Universities(No.2172015YGYL019)the Fundamental Research Funds for the Central Universities(No.2015LC021)+1 种基金National Natural Science Foundation of China(No.81000616)Hubei Key Laboratory of Molecular Imaging Research Funds(No.02.03.2015-149).
文摘The correlations between shear wave velocity(SWV)calculated from virtual touch tissue imaging quantification(VTIQ)technique and histological prognostic factors of invasive ductal carcinoma was investigated.A total of 76 breast tumors histologically confirmed as invasive ductal carcinomas were included in this study.SWV values were measured by VTIQ for each lesion preoperatively or prior to breast biopsy.The maximum values were recorded for statistical analysis.Medical records were reviewed to determine tumor size,histological grade,lymph node status and immunohistochemical results.Tumor subtypes were categorized as luminal A,luminal B,human epidermal growth factor receptor 2(HER2)positive and triple negative.The correlations between SWV and histological prognostic factors were analyzed.It was found that tumor size showed positive association with SWV(r=0.465,P<0.001).Larger tumors had significantly higher SWV than smaller ones(P=0.001).Histological grade 1 tumors had significantly lower SWV values than those with higher histological grade(P=0.015).The Ki67 expression,tumor subtypes and lymph node status showed no statistically significant correlations with SWV,although triple negative tumors and lymph node-positive tumors showed higher SWV values.It was concluded that tumor size was significantly associated with SWV.Higher histological grade was associated with increased SWV.There was no statistically significant correlations between SWV and other histological prognostic factors.
基金State Natural Scientific Foundation (49734150) and National High Performance Computation Foundation.
文摘We assembled approximately 328 seismic records. The data set was from 4 digitally recording long-period and broadband stations of CDSN. We carried out the inversion based on the partitioned waveform inversion (PWI). It partitions the large-scale optimization problem into a number of independent small-scale problems. We adopted surface waveform inversion with an equal block (2((2() discretization in order to acquire the images of shear velocity structure at different depths (from surface to 430 km) in the crust and upper-mantle. The resolution of all these anomalies has been established with (check-board( resolution tests. These results show significant difference in velocity, lithosphere and asthenosphere structure between South China Sea and its adjacent regions.
文摘AIM:To investigate whether a noninvasive measurement of tissue strain has a potential usefulness for management of nonalcoholic steatohepatitis(NASH).METHODS:In total 26 patients,23 NASHs and 3 normal controls were enrolled in this study.NASH was staged based on Brunt criterion.At a region of interest(ROI),a shear wave was evoked by implementing an acoustic radiation force impulse(ARFI),and the propagation velocity was quantif ied.RESULTS:Shear wave velocity(SWV) could be reproducibly quantified at all ROIs in all subjects except for 4 NASH cases,in which a reliable SWV value was not calculated at several ROIs.An average SWV of 1.34 ± 0.26 m/s in fibrous stage 0-1 was significantly slower than 2.20 ± 0.74 m/s and 2.90 ± 1.01 m/s in stages 3 and 4,respectively,but was not significantly different from 1.79 ± 0.78 m/s in stage 2.When a cutoff value was set at 1.47 m/s,receiver operating characteristic analysis showed significance to dissociate stages 3 and 4 from stage 0-1(P=0.0092) with sensitivity,specificity and area under curve of 100%,75% and 94.2%,respectively.In addition,the correlation between SWV and hyaluronic acid was significant(P<0.0001),while a tendency toward negative correlation was observed with serum albumin(P=0.053).CONCLUSION:The clinical implementation of ARFI provides noninvasive repeated evaluations of liver stiffness at an arbitrary position,which has the potential to shed new light on NASH management.
基金National Basic Research Program of China (973 Project) Under Grant No. 2007CB714203the Foundation for Seismological Researches, China Earthquake Administration Under Grant No. 200808022+1 种基金the China Postdoctoral Science Foundation Under Grant No. 20080430219, No. 20081476the National Natural Science Foundation of China Under Grant No. 50708095
文摘The great Wenchuan earthquake （Ms= 8.0） in 2008 caused severe damage in the western part of the Chengdu Plain. Soil liquefaction was one of the major causes of damage in the plain areas, and proper evaluation of liquefaction potential is important in the definition of the seismic hazard facing a given region and post-earthquake reconstruction. In this paper, a simplified procedure is proposed for liquefaction assessment of sandy deposits using shear wave velocity （V）, and soil liquefaction from the Banqiao School site was preliminarily investigated after the earthquake. Boreholes were made at the site and shear wave velocities were measured both by SASW and down-hole methods. Based on the in-situ soil information and V profiles, the liquefaction potential of this site was evaluated. The results are reasonably consistent with the actual field behavior observed after the earthquake, indicating that the proposed procedure is effective. The possible effects of gravel and fines contents on liquefaction of sandy soils were also briefly discussed.
文摘AIM To determine the diagnostic accuracy of two-dimensional shear wave elastography(2D-SWE) for the noninvasive assessment of liver fibrosis in patients with autoimmune liver diseases(AILD) using liver biopsy as the reference standard.METHODS Patients with AILD who underwent liver biopsy and 2D-SWE were consecutively enrolled. Receiver operating characteristic(ROC) curves were constructed to assess the overall accuracy and to identify optimal cut-off values.RESULTS The characteristics of the diagnostic performance were determined for 114 patients with AILD. The areas under the ROC curves for significant fibrosis, severe fibrosis, and cirrhosis were 0.85, 0.85, and 0.86, respectively, and the optimal cut-off values associated with significant fibrosis(≥ F2), severe fibrosis(≥ F3), and cirrhosis(F4) were 9.7 k Pa, 13.2 k Pa and 16.3 k Pa, respectively. 2D-SWE showed sensitivity values of 81.7% for significant fibrosis, 83.0% for severe fibrosis,and 87.0% for cirrhosis, and the respective specificity values were 81.3%, 74.6%, and 80.2%. The overall concordance rate of the liver stiffness measurements obtained using 2D-SWE vs fibrosis stages was 53.5%.CONCLUSION2D-SWE showed promising diagnostic performance for assessing liver fibrosis stages and exhibited high cut-off values in patients with AILD. Low overall concordance rate was observed in the liver stiffness measurements obtained using 2D-SWE vs fibrosis stages.
