Photoacoustic elastography based on laser-excited shear wave

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.

Shear wave splitting analysis of local earthquakes from dense arrays in Shimian,Sichuan

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.

Combining the age-male-albumin-bilirubin-platelets score and shear wave elastography stratifies carcinogenic risk in hepatitis C patients after viral clearance

BACKGROUND The treatment of hepatitis C with direct-acting antiviral agents(DAAs)produces a high rate of sustained virological response(SVR)with fewer adverse events than interferon(IFN)therapy with a similar effect in inhibiting carcinogenesis as IFN therapy.The age-male-albumin-bilirubin-platelets(aMAP)score is useful for stratifying the risk of hepatocellular carcinoma in chronic hepatitis patients,and the velocity of shear waves(Vs)measured by shear wave elastography has also been shown to be useful for diagnosing the level of fibrotic progression in hepatitis C and predicting carcinogenic risk.Combining these two may improve the prediction of carcinogenic risk.AIM To determine whether combining the aMAP score with Vs improves carcinogenic risk stratification in medium-to-high-risk hepatitis C patients.METHODS This retrospective,observational study involved hepatitis C patients treated with DAAs who achieved SVR.Vs was measured before treatment(baseline),at the end of treatment(EOT),and 12 wk(follow-up 12)and 24 wk(follow-up 24)after treatment.The patients were followed for at least six months after EOT to determine whether cancer developed.Multiple regression analysis was used to identify factors contributing to hepatic carcinogenesis.The diagnostic performances of clinical parameters for predicting the presence of hepatocellular carcinoma were evaluated using receiver-operating characteristic(ROC)curve analyses.RESULTS A total of 279 patients(mean age 65.9 years,118 males,161 females)were included in the analysis.Multiple regression analysis was performed with carcinogenesis as the target variable and alanine aminotransferase,platelets,α-fetoprotein,Vs,and the Fib-4 index as explanatory variables;only Vs was found to be significant(P=0.0296).The cut-off value for Vs for liver carcinogenesis calculated using the ROC curve was 1.53 m/s.Carcinoma developed in 2.0%(3/151)of those with Vs<1.53 m/s and in 10.5%(9/86)of those with Vs≥1.53 m/s.CONCLUSION In hepatitis C patients after SVR,combining the aMAP score and Vs to stratify the risk of carcinogenesis is more efficient than uniform surveillance of all patients.

Comparative analysis of conventional ultrasound and shear wave elastography features in primary breast diffuse large B-cell lymphoma

BACKGROUND Primary breast diffuse large B-cell lymphoma(PB-DLBCL)is a rare subtype of non-Hodgkin lymphoma that accounts for<3%of extranodal lymphomas and 1%of breast tumors.Its diagnosis and management are challenging because of its rarity,heterogeneity,and aggressive behavior.Conventional ultrasound(US)is the first-line imaging modality for breast lesions;however,it has limited specificity and accuracy for PB-DLBCL.Shear wave elastography(SWE)is a novel US technique that measures tissue stiffness and may reflect the histological characteristics and biological behavior of breast lesions.AIM To compare the conventional US and SWE features of PB-DLBCL and evaluate their diagnostic performance and prognostic value.METHODS We retrospectively reviewed the clinical data and US images of 32 patients with pathologically confirmed PB-DLBCL who underwent conventional US and SWE before treatment.We analyzed conventional US features(shape,margin,orientation,echo,posterior acoustic features,calcification,and vascularity)and SWE features(mean elasticity value,standard deviation,minimum elasticity value,maximum elasticity value,and lesion-to-fat ratio)of the PB-DLBCL lesions.Using receiver operating characteristic curve analysis,we determined the optimal cutoff values and diagnostic performance of conventional US and SWE features.We also performed a survival analysis to assess the prognostic value of conventional US and SWE features.RESULTS The results showed that the PB-DLBCL lesions were mostly irregular in shape(84.4%),microlobulated or spiculated in margins(75%),parallel in orientation(65.6%),hypoechoic in echo(87.5%),and had posterior acoustic enhancement(65.6%).Calcification was rare(6.3%)and vascularity was variable(31.3%avascular,37.5%hypovascular,and 31.3%hypervascular).The mean elasticity value of PB-DLBCL lesions was significantly higher than that of benign breast lesions(113.4±46.9 kPa vs 27.8±16.4 kPa,P<0.001).The optimal cutoff value of the mean elasticity for distinguishing PB-DLBCL from benign breast lesions was 54.5 kPa,with a sensitivity of 93.8%,specificity of 92.9%,positive predictive value of 93.8%,negative predictive value of 92.9%,and accuracy of 93.3%.The mean elasticity value was also significantly correlated with Ki-67 expression level(r=0.612,P<0.001),which is a marker of tumor proliferation and aggressiveness.Survival analysis showed that patients with higher mean elasticity values(>54.5 kPa)had worse overall survival(OS)and progression-free survival(PFS)than those with lower mean elasticity values(<54.5 kPa)(P=0.038 for OS and P=0.027 for PFS).CONCLUSION Conventional US and SWE provide useful information for diagnosing and forecasting PB-DLBCL.SWE excels in distinguishing PB-DLBCL from benign breast lesions,reflects tumor proliferation and aggressiveness,and improves disease management.

Optimization design of conical reaction teeth of shear wave vibroseis vibration plate

The vibrator plate is the link between the vibroseis vehicle and the earth,as well as the core com-ponent of the vibrator vehicle.In this paper,the coupling effect between the vibrator plate and the earth is an-alyzed from two aspects of reaction tooth arrangement and reaction tooth conical angle,and three groups of experimental models are optimized and designed.The model construction and numerical analysis of the shear wave vibroseis vibrator plate are carried out with ANSYS software.The motion law between the vibration plate and the earth at work was studied,the strain energy of the three experimental models in operation,the maximum displacement of particle at the same position and other reference indices were compared and ana-lyzed,with 28 conical reaction teeth were arranged on both sides.The coupling effect between the vibration plate and the earth was best when the tooth angle was 60°.Compared with the toothless vibration plate,the energy efficiency is improved by about 20%,and the coupling effect between the vibrator plate and the earth is effectively enhanced.It is found that the coupling effect is enhanced through increasing the number of reac-tion teeth of the vibration plate by increasing the coupling area between the vibration plate and the earth.

Real-time Shear Wave Elastography Assessment of Muscle Elasticity in Patients with Renal Failure

Objective:To explore the value of real-time elastic shear wave in evaluating muscle elasticity in patients with renal failure.Methods:50 patients with chronic renal failure from January 2019 to December 2022 were randomly selected as the experimental group,and 50 healthy patients aged 21-61 during the same period were selected as the control group,and the basic information of the patients,including age,gender,body mass index,etc.,were collected.Besides,the Young's modulus of the two groups of patients were observed and analyzed.Results:The Young's modulus values of left and right gastrocnemius muscles in the experimental group were significantly lower than those in the control group(P<0.05),and there was no statistical difference between the left and right sides of the experimental group and the control group(P>0.05).Conclusion:Real-time shear wave elastography provides a non-invasive,real-time and effective tool for the assessment of muscle elasticity in patients with renal failure.Through further research and optimization,real-time shear wave elastography will play a greater role in the prevention and treatment of patients with renal failure,improving the quality of life and prognosis of patients.

Assessment of Calf Skeletal Muscle Stiffness in Diabetic Nephropathy Patients with Medial Tibial Stress Syndrome by Two-Dimensional Shear Wave Elastography

Objective:To explore the feasibility of two-dimensional shear wave elastography in evaluating calf skeletal muscle stiffness in diabetic nephropathy patients with medial tibial stress syndrome.Methods:A total of 48 diabetic nephropathy patients with medial tibial stress syndrome from January 2020 to December 2022 were included as the study group,and 48 patients with diabetic nephropathy during the same period were included as the control group.Both groups were detected by two-dimensional shear wave elastography with ultrasonic equipment,and Young‘s modulus of the tibialis anterior muscle,tibialis posterior muscle,and gastrocnemius muscle were observed and analyzed in the two groups.Results:The Young‘s modulus values of tibialis anterior muscle,tibialis posterior muscle,and gastrocnemius muscle in the study group were significantly lower than those in the control group(P<0.05).Conclusion:Two-dimensional shear wave elastography is feasible for the evaluation of calf skeletal muscle stiffness in diabetic nephropathy patients with medial tibial stress syndrome,and has high accuracy and repeatability.This technique can be used to diagnose,treat and monitor muscle lesions in patients with diabetic nephropathy,and can also be used to assess muscle fatigue and exercise capacity,which has broad application prospects.

The characteristics of shear wave splitting in the source region of the April 20,2013 Lushan earthquake

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.

Shear Wave Elastography of Invasive Ductal Carcinoma:Correlations between Shear Wave Velocity and Histological Prognostic Factors

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.

Three dimensional shear wave velocity structure of crust and upper mantle in South China Sea and its adjacent regions by surface waveform inversion

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.

Shear wave velocity is a useful marker for managing nonalcoholic steatohepatitis

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.

Shear wave velocity-based liquefaction evaluation in the great Wenchuan earthquake: a preliminary case study

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.

Shear wave velocity-based evaluation and design of stone column improved ground for liquefaction mitigation

The evaluation and design of stone column improvement ground for liquefaction mitigation is a challenging issue for the state of practice. In this paper, a shear wave velocity-based approach is proposed based on the well-defined correlations of liquefaction resistance （CRR）-shear wave velocity （V）-void ratio （e） of sandy soils, and the values of parameters in this approach are recommended for preliminary design purpose when site specific values are not available. The detailed procedures of pre- and post-improvement liquefaction evaluations and stone column design are given. According to this approach, the required level of ground improvement will be met once the target V of soil is raised high enough （i.e., no less than the critical velocity） to resist the given earthquake loading according to the CRR-V relationship, and then this requirement is transferred to the control of target void ratio （i.e., the critical e） according to the V-e relationship. As this approach relies on the densification of the surrounding soil instead of the whole improved ground and is conservative by nature, specific considerations of the densification mechanism and effect are given, and the effects of drainage and reinforcement of stone columns are also discussed. A case study of a thermal power plant in Indonesia is introduced, where the effectiveness of stone column improved ground was evaluated by the proposed V-based method and compared with the SPT-based evaluation. This improved ground performed well and experienced no liquefaction during subsequent strong earthquakes.

Non-invasive assessment of liver fibrosis using twodimensional shear wave elastography in patients with autoimmune liver diseases

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.

Value of shear wave elastography with maximal elasticity in differentiating benign and malignant solid focal liver lesions

BACKGROUND It is important to differentiate benign and malignant focal liver lesions(FLLs)accurately.Despite the wide use and acceptance of shear wave elastography(SWE),its value for assessing the elasticity of FLLs and differentiating benign and malignant FLLs is still investigational.Previous studies of SWE for FLLs used mean elasticity as the parameter to reflect the stiffness of FLLs.Considering the inhomogeneity of tumor stiffness,maximal elasticity(Emax)might be the suitable parameter to reflect the stiffness of FLLs and to differentiate malignant FLLs from benign ones.AIM To explore the value of SWE with Emax in differential diagnosis of solid FLLs.METHODS We included 104 solid FLLs in 95 patients and 50 healthy volunteers.All the subjects were examined using conventional ultrasound(US)and virtual touch tissue quantification(VTQ)imaging.A diagnosis of benign or malignant FLL was made using conventional US.Ten VTQ values were acquired after 10 consecutive measurements for each FLL and each normal liver,and the largest value was recorded as Emax.RESULTS There were 56 cases of malignant FLLs and 48 cases of benign FLLs in this study.Emax of malignant FLLs(3.29±0.88 m/s)was significantly higher than that of benign FLLs(1.30±0.46 m/s,P<0.01)and that of livers in healthy volunteers(1.15±0.17 m/s,P<0.01).The cut-off point of Emax was 1.945,and the area under the curve was 0.978.The sensitivity and specificity of Emax were 92.9%and 91.7%,respectively,higher(but not significantly)than those of conventional US(80.4%for sensitivity and 81.3%for specificity).Combined diagnosis of conventional US and Emax using parallel testing improved the sensitivity to 100%with specificity of 75%.CONCLUSION SWE is a convenient and easy method to obtain accurate stiffness information of solid FLLs.Emax is useful for differential diagnosis of FLLs,especially in combination with conventional US.

Evaluation of internal and shell stiffness in the differential diagnosis of breast non-mass lesions by shear wave elastography

BACKGROUND The diagnostic specificity of conventional ultrasound for breast non-mass lesions(NMLs)is low at approximately 21%-43%.Shear wave elastography(SWE)can distinguish benign from malignant lesions by evaluating the internal and peripheral stiffness.SWE has good reproducibility and high diagnostic efficacy.However,there are very few independent studies on the diagnostic value of SWE in breast NMLs.AIM To determine the value of SWE in the differential diagnosis of breast NMLs.METHODS This study enrolled a total of 118 patients with breast NMLs who underwent SWE examinations in the Beijing Shijitan Hospital Affiliated to Capital Medical University and The Second Hospital of Shandong University from January 2019 to January 2020.The internal elastic parameters of the lesions were recorded,including maximum(Emax),mean(Emean)and minimum elastic values and the standard deviation.The following peripheral parameters were noted:Presence of a“stiff rim”sign;Emax,and Emean elasticity values within 1 mm,1.5 mm,2 mm,2.5 mm and 3 mm from the edge of NMLs.The receiver operating characteristic curve of each parameter was drawn,and the areas under the curve were calculated.RESULTS Emax,Emean and elastic values,and the standard deviation of the internal elastic values in malignant NMLs were significantly higher than those in benign NMLs(P<0.05).The percentage with the“stiff rim”sign in malignant NMLs was significantly higher than that in the benign group(P<0.05),and Emax and Emean at the shell of 1 mm,1.5 mm,2 mm,2.5 mm and 3 mm in the malignant group were all higher than those in the benign group(P<0.05).Of the surrounding elasticity values,Emax of the shell at 2.5 mm in malignant NMLs had maximum areas under the curve of 0.900,and the corresponding sensitivity and specificity were 94.57%and 85.86%,respectively.CONCLUSION The“stiff rim”sign and multiple quantitative elastic values within and around the lesion had good diagnostic performance in the differential diagnosis of breast NMLs.Emax in peripheral tissue had better diagnostic efficiency than other parameters.

A Modified Monte Carlo Model of Speckle Tracking of Shear Wave Induced by Acoustic Radiation Force for Acousto-Optic Elasticity Imaging

A modified Monte Carlo model of speckle tracking of shear wave propagation in scattering media is proposed. The established Monte Carlo model mainly concerns the variations of optical electric field and speckle. The two- dimensional intensity distribution and the time evolution of speckles in different probe locations are obtained. The fluctuation of speckle intensity tracks the acoustic-radiation-force shear wave propagation, and especially the reduction of speckle intensity implies attenuation of shear wave. Then, the shear wave velocity is estimated quantitatively on the basis of the time-to-peak algorithm and linear regression processing. The results reveal that a smaller sampling interval yields higher estimation precision and the shear wave velocity is estimated more efficiently by using speckle intensity difference than by using speckle contrast difference according to the estimation error. Hence, the shear wave velocity is estimated to be 2.25 m/s with relatively high accuracy for the estimation error reaches the minimum （0.071）.

Stress-dependent shear wave splitting and permeability in fractured porous rock

It is well known that shear wave propagates slower across than parallel to a fracture, and as a result, a travelling shear wave splits into two directions when it encounters a fracture. Shear wave splitting and permeability of porous rock core samples having single fracture were experimentally investigated using a high-pressure triaxial cell, which can measure seismic shear wave velocities in two directions mutually perpendicular to the sample axis in addition to the longitudinal compressive wave velocity. A single fracture was created in the samples using a modified Brazilian split test device, where the cylindrical sample edges were loaded on two diametrically opposite lines by sharp guillotines along the sample length. Based on tilt tests and fracture surface profilometry, the method of artificially induced tensile fracture in the sample was found to create repeatable fracture surfaces and morphologies. Seismic velocities of the fractured samples were determined under different levels of stress confinement and fracture shear displacement or mismatch. The effective confining stress was varied from 0.5 MPa to55 MPa, while the fractures were mismatched by 0 mm, 0.45 mm and 1 mm. The degree of matching of the fracture surfaces in the core samples was evaluated using the joint matching coefficient(JMC). Shear wave splitting, as measured by the difference in the magnitudes of shear wave velocities parallel(V_(S1))and perpendicular(V_(S2)) to the fracture, is found to be insensitive to the degree of mismatching of the fracture joint surfaces at 2 MPa, and decreased and approached zero as the effective stress was increased.Simple models for the stress-and JMC-dependent shear wave splitting and fractured rock permeability were developed based on the experimental observations. The effects of the joint wall compressive strength(JCS), JMC and stress on the stress dependency of joint aperture were discussed in terms of hydro-mechanical response. Finally, a useful relationship between fractured rock permeability and shear wave splitting was found after normalization by using JMC.

Application of Shear Wave Elastography and Contrast-Enhanced Ultrasound in Transrectal Prostate Biopsy

Objective To explore the clinical value of ultrasound shear wave elastography(SWE)and contrast-enhanced ultrasound(CEUS)in transrectal prostate biopsy.Methods A total of 54 patients(average age:67.79±12.01 years)in the experimental group underwent transrectal prostate biopsy under the guidance of SWE,while 46 patients(average age:69.22±11.54 years)in the control group underwent transrectal prostate biopsy guided by CEUS.Results There were a total of 451 needles,with an average of 8.35±1.67 needles per patient in the experimental group,and a total of 462 needles,with an average of 10.04±1.33 needles per patient in the control group.The difference in puncture times between the two groups was statistically significant(P<0.05).There was no significant difference in the positive detection rate,sensitivity or specificity between the two groups(P>0.05),but there was a significant difference in the diagnostic accuracy between the two groups(P<0.05).The E_(mean)and E_(max)of prostate cancer were significantly higher in the experimental group than in benign prostatic hyperplasia(P<0.05).The receiver operating characteristic curve(ROC)analysis showed that the area under the ROC curve(AUC)of E_(mean)was 0.752(S.E.=0.072,95%CI=0.611-0.894,P=0.007),and the best cutoff value was 47.005 kPa.Conclusion In summary,both SWE-and CEUS-guided transrectal prostate biopsy can help find the focus and guide the puncture,and improve the positive detection rate.

Role of shear wave elastography in the evaluation of the treatment and prognosis of supraspinatus tendinitis

BACKGROUND Supraspinatus tendinitis recurs easily after treatment.One of the main reasons is the lack of objective tools for the efficacy evaluation.Shear wave elastography(SWE)can quantitatively analyze the tissue elasticity of region of interest by measuring the Young’s modulus(YM)value.AIM To explore the role of SWE in the efficacy and prognostic evaluation of supraspinatus tendinitis.METHODS Eighty-seven patients with supraspinatus tendinitis treated in Jiading District Central Hospital Affiliated Shanghai University of Medicine and Health Sciences were recruited.Another 30 healthy volunteers were enrolled as the control group.The visual analogue scale(VAS)and Constant-Murley Score(CMS)were recorded before treatment.All participants were scanned by SWE scan,and the YM value of the region of interest were recorded.Spearman correlation analysis was performed on YM values with VAS and CMS.Univariate repeated measures analysis of variance was used to calculate the changing trend of VAS,CMS and SWE under different treatment courses.After treatment,the patients were further grouped based on who achieved significantly effective and curative treatment.The patients in the continued treatment group continued to receive treatment according to the YM value,and the remaining patients who stopped receiving treatment were included in the stopped treatment group.All patients were followed up for 1 year,and the difference in recurrence rates between the continued treatment group and the stopped treatment group were compared.RESULTS The SWE images of supraspinatus muscle in healthy volunteers were mainly blue,while those of patients with supraspinatus tendinitis showed regional red and green areas.The average YM value of the supraspinatus muscle in healthy volunteers was 26.12±4.03 kPa.The average YM value of patients with supraspinatus muscle was greater than that of healthy volunteers(average YM=60.61±11.53 kPa,t=26.344,P<0.001).The YM value was positively correlated with VAS(r=0.564,P<0.001)and negatively correlated with CMS(r=-0.411,P<0.001).The changes of VAS and CMS were the most obvious in course 1 and then decreased gradually.The degree of change in YM values was similar in different courses.After a 1-year follow-up,the cumulative relapse-free rate in the continued treatment group was 91.43%,which was significantly higher than that in the stopped treatment group(64.71%,X2=7.379,P=0.007).CONCLUSION SWE can objectively indicate the severity of supraspinatus tendinitis.Using the YM value as a criterion for curative effect may reduce the recurrence rate.