In vivo Quantification of Liver Stiffness in a Rat Model of Hepatic Fibrosis with Acoustic Radiation Force

Liver fibrosis is currently staged using needle biopsy, a highly invasive procedure with a number of disadvantages. Measurement of liver stiffness changes that accompany progression of the disease may provide a quantitative and noninvasive method to assess the health of the liver. The purpose of this study is to investigate the correlation between liver stiffness measured by radiation force induced shear waves and disease related changes in the liver. An additional aim is to present initial findings on the effects of liver viscosity on radiation force induced shear wave morphology. Liver fibrosis was induced in 10 rats using carbon tetrachloride (CCl₄), while five rats acted as controls. Liver stiffness was measured in vivo in all rats after a treatment period of 8 weeks using a modified Siemens SONOLINE Antares scanner (Siemens Medical Solutions USA, Ultrasound Division, Issaquah, WA, USA). The spatial coherence of radiation force induced shear waves propagating in the viscoelastic rat liver decreased significantly with propagation distance, compared with shear waves in an elastic phantom and a finite element model of a purely elastic medium. Animals were sacrificed after imaging and liver samples were taken for histopathologic analysis and collagen quantification using picrosirius red staining and hydroxyproline assay. At the end of the treatment period, five rats had healthy livers (stage F0), while six had severe fibrosis (F3) and the rest had light to moderate fibrosis (F1 and F2). The measured liver stiffness for the F0 group was 1.5 ± 0.1 kPa (mean ± 95% confidence interval) and for F3 livers was 1.8 ± 0.2kPa. In this study, liver stiffness was found to be linearly correlated with the amount of collagen in the liver measured by picrosirius red staining (r² = 0.43, p = 0.008). In addition, stiffness spatial heterogeneity was also linearly correlated with liver collagen content (r² = 0.58, p = 0.001) by picrosirius red staining. These results are consistent with those obtained by Salameh et al. (2007) and Yin et al. (2007b) using animal models of liver fibrosis and MR elastography. This suggests that stiffness measurement using acoustic radiation force can provide a quantitative assessment of the extent of fibrosis in the liver and can be potentially used for the diagnosis, management and study of liver fibrosis. (E-mail: michael.h.wang@duke.edu)     

Quantitative Viscoelasticity Mapping of Human Liver Using Supersonic Shear Imaging: Preliminary In Vivo Feasability Study

This paper demonstrates the feasibility of in vivo quantitative mapping of liver viscoelasticity using the concept of supersonic shear wave imaging. This technique is based on the combination of a radiation force induced in tissues by focused ultrasonic beams and a very high frame rate ultrasound imaging sequence capable of catching in real time the transient propagation of resulting shear waves. The local shear wave velocity is recovered using a dedicated time-of-flight estimation technique and enables the 2-D quantitative mapping of shear elasticity. This imaging modality is performed using a conventional ultrasound probe during a standard intercostal ultrasonographic examination. Three supersonic shear imaging (SSI) sequences are applied successively in the left, middle and right parts of the 2-D ultrasonographic image. Resulting shear elasticity images in the three regions are concatenated to provide the final image covering the entire region-of-interest. The ability of the SSI technique to provide a quantitative and local estimation of liver shear modulus with a millimetric resolution is proven in vivo on 15 healthy volunteers. Liver moduli extracted from in vivo data from healthy volunteers are consistent with those reported in the literature (Young's modulus ranging from 4 to 7.5 kPa). Moreover, liver stiffness estimation using the SSI mode is shown to be fast (less than one second), repeatable (5.7% standard deviation) and reproducible (6.7% standard deviation). This technique, used as a complementary tool for B-mode ultrasound, could complement morphologic information both for fibrosis staging and hepatic lesions imaging (E-mail: jl.gennisson@espci.fr).     

Fast Shear Compounding Using Robust 2-D Shear Wave Speed Calculation and Multi-directional Filtering

A fast shear compounding method was developed in this study using only one shear wave push-detect cycle, such that the shear wave imaging frame rate is preserved and motion artifacts are minimized. The proposed method is composed of the following steps: 1. Applying a comb-push to produce multiple differently angled shear waves at different spatial locations simultaneously; 2. Decomposing the complex shear wave field into individual shear wave fields with differently oriented shear waves using a multi-directional filter; 3. Using a robust 2-D shear wave speed calculation to reconstruct 2-D shear elasticity maps from each filter direction; and 4. Compounding these 2-D maps from different directions into a final map. An inclusion phantom study showed that the fast shear compounding method could achieve comparable performance to conventional shear compounding without sacrificing the imaging frame rate. A multi-inclusion phantom experiment showed that the fast shear compounding method could provide a full field-of-view, 2-D and compounded shear elasticity map with three types of inclusions clearly resolved and stiffness measurements showing excellent agreement to the nominal values.     

Quantification of Liver Viscoelasticity with Acoustic Radiation Force: A Study of Hepatic Fibrosis in a Rat Model

Ultrasound elastography, based on shear wave propagation, enables the quantitative and non-invasive assessment of liver mechanical properties such as stiffness and has been found to be feasible for and useful in the diagnosis of hepatic fibrosis. Most ultrasound elastographic methods use a purely elastic model to describe liver mechanical properties. However, to describe tissue that is dispersive and to obtain an accurate measure of tissue elasticity, the viscoelasticity of the tissue should be examined. The objective of this study was to investigate the shear viscoelastic characteristics, as measured by ultrasound elastography, of liver fibrosis in a rat model and to evaluate the diagnostic accuracy of viscoelasticity for staging liver fibrosis. Liver fibrosis was induced in 37 rats using carbon tetrachloride (CCl₄); 6 rats served as controls. Liver viscoelasticity was measured in vitro using shear waves induced by acoustic radiation force. The measured mean values of liver elasticity and viscosity ranged from 0.84 to 3.45 kPa and from 1.12 to 2.06 Pa·s for fibrosis stages F0–F4, respectively. Spearman correlation coefficients indicated that stage of fibrosis was well correlated with elasticity (0.88) and moderately correlated with viscosity (0.66). The areas under receiver operating characteristic curves were 0.97 (≥F2), 0.91 (≥F3) and 1.00 (F4) for elasticity and 0.91 (≥F2), 0.79 (≥F3) and 0.74 (F4) for viscosity, respectively. The results confirmed that shear wave velocity was dispersive in frequency, suggesting a viscoelastic model to describe liver fibrosis. The study finds that although viscosity is not as good as elasticity for staging fibrosis, it is important to consider viscosity to make an accurate estimation of elasticity; it may also provide other mechanical insights into liver tissues.     

Normal Values of Liver Shear Wave Velocity in Healthy Children Assessed by Acoustic Radiation Force Impulse Imaging Using a Convex Probe and a Linear Probe

Acoustic radiation force impulse (ARFI) is an image-guided ultrasound elastography method that allows quantification of liver stiffness by measurement of shear wave velocity. One purpose of the work described in this article was to determine the normal liver stiffness values of healthy children using ARFI with two different probes, 4 C1 and 9 L4. Another purpose was to evaluate the effects of site of measurement, age, gender and body mass index on liver stiffness values. This prospective study included 60 healthy children (newborn to 14 y) divided into four age groups. One thousand two hundred ARFI measurements were performed, that is, 20 measurements per patient (5 measurements in each lobe, with each probe). Means, standard deviations (SD) and confidence intervals for velocity were calculated for each hepatic lobe and each probe in each age group and for the whole group. Mean shear wave velocity measured in the right lobe was 1.19 ± 0.04 m/s (SD = 0.13) with the 4 C1 transducer and 1.15 ± 0.04 m/s (SD = 0.15) with the 9 L4 transducer. Age had a small effect on shear wave measurements. Body mass index and sex had no significant effects on ARFI values, whereas site of measurement had a significant effect, with lower ARFI values in the right hepatic lobe. ARFI is a non-invasive technique that is feasible to perform in children with both the 4 C1 and 9 L4 probes. The aforementioned velocity values obtained in the right lobe may be used as reference values for normal liver stiffness in children.     

Assessment of the Cervix in Pregnant Women Using Shear Wave Elastography: A Feasibility Study

The quantitative assessment of the cervix is crucial for the estimation of pre-term delivery risk and the prediction of the success of labor induction. We conducted a cross-sectional study using shear wave elastography based on the supersonic shear imaging technique. The shear wave speed (SWS) of the lower anterior part of the cervix was quantified over an 8-mm region of interest in 157 pregnant women. Cervical SWS is slightly but significantly reduced in patients diagnosed with pre-term labor and in patients who actually delivered pre-term.     

Preliminary Results on the Feasibility of Using ARFI/SWEI to Assess Cutaneous Sclerotic Diseases

In this study, acoustic radiation force impulse (ARFI) and shear wave elasticity imaging (SWEI) were applied to the skin to investigate the feasibility of their use in assessing sclerotic skin diseases. Our motivation was to develop a non-invasive imaging technology with real-time feedback of sclerotic skin disease diagnosis. This paper shows representative results from an ongoing study, recruiting patients with and without sclerosis. The stiffness of the imaged site was evaluated using two metrics: mean ARFI displacement magnitude and bulk shear wave speed inside the region of interest (ROI). In a subject with localized graft versus host disease (GVHD), the mean ARFI displacement inside sclerotic skin was 61% lower (p < 0.01) and shear wave speed 128% higher (p < 0.005) compared to those in normal skin—indicating stiffer mechanical properties in the sclerotic skin. This trend persisted through disease types. We conclude ARFI and SWEI can successfully differentiate sclerotic lesions from normal dermis.     

Acoustic Radiation Force Impulse Imaging of Human Prostates Ex Vivo

It has been challenging for clinicians using current imaging modalities to visualize internal structures and detect lesions inside human prostates. Lack of contrast among prostatic tissues and high false positive or negative detection rates of prostate lesions have limited the use of current imaging modalities in the diagnosis of prostate cancer. In this study, acoustic radiation force impulse (ARFI) imaging is introduced to visualize the anatomical and abnormal structures in freshly excised human prostates. A modified Siemens Antares ultrasound scanner (Siemens Medical Solutions USA Inc., Malvern, PA) and a Siemens VF10-5 linear array were used to acquire ARFI images. The transducer was attached to a three-dimensional (3-D) translation stage, which was programmed to automate volumetric data acquisition. A depth dependent gain (DDG) method was developed and applied to 3-D ARFI datasets to compensate for the displacement gradients associated with spatially varying radiation force magnitudes as a function of depth. Nine human prostate specimens were collected and imaged immediately after surgical excision. Prostate anatomical structures such as seminal vesicles, ejaculatory ducts, peripheral zone, central zone, transition zone and verumontanum were visualized with high spatial resolution and in good agreement with McNeal's zonal anatomy. The characteristic appearance of prostate pathologies, such as prostate cancerous lesions, benign prostatic hyperplasia, calcified tissues and atrophy were identified in ARFI images based upon correlation with the corresponding histologic slides. This study demonstrates that ARFI imaging can be used to visualize internal structures and detecting suspicious lesions in the prostate and appears promising for image guidance of prostate biopsy. (E-mail:liang.zhai@duke.edu)     

Assessing Hepatic Fibrosis Using 2-D Shear Wave Elastography in Patients with Liver Tumors: A Prospective Single-Center Study

The purpose of this study was to investigate the diagnostic performance of 2-D shear wave elastography (2-D-SWE) in evaluations of liver stiffness in patients with liver tumors before resection. A total of 121 consecutive patients with hepatocellular carcinoma (HCC) (n = 93), intra-hepatic cholangiocarcinoma (n = 6), mixed hepatocellular carcinoma and intra-hepatic cholangiocarcinoma (n = 6), liver metastases (n = 10) and benign tumors (n = 6) were prospectively enrolled in this study from June 2015 to March 2016. Three valid 2-D-SWE measurements for each patient and median liver stiffness values were calculated. Fibrosis staging was evaluated according to the METAVIR scoring system. A receiver operating characteristic curve analysis was used to assess diagnostic performance. In this study, we found that median liver stiffness values were significantly higher in patients with primary liver tumors than in those with liver metastases and benign tumors (11.80 kPa vs. 5.85 kPa, p < 0.001). In addition, liver stiffness, assessed using 2-D-SWE, was highly correlated with pathologically confirmed liver fibrosis stage. Liver fibrosis stage and liver stiffness values were analyzed using Spearman's correlation (0.708, p < 0.001). The median liver stiffness values were as follows: F1, 6.7 kPa; F2, 6.33 kPa; F3, 9.2 kPa; F4, 13.7 kPa. The area under the receiver operating characteristic curves of the liver stiffness values that predicted significant fibrosis (≥F2), severe fibrosis (≥F3) and cirrhosis (=F4) were 83.5%, 91.6% and 88.1%, respectively. According to the Youden index, the optimal cutoff values for predicting significant fibrosis (≥F2), severe fibrosis (≥F3) and cirrhosis (=F4) were 7.05 kPa (sensitivity = 74.6%, specificity = 100.0%), 9.45 kPa (sensitivity = 78.8%, specificity = 100.0%) and 11.1 kPa (sensitivity = 83.1%, specificity = 89.3%), respectively. We conclude that 2-D-SWE is a useful, accurate and non-invasive method for evaluating hepatic fibrosis in patients with liver tumors adapted to hepatectomy (ClinicalTrials.gov ID: NCT02958592).     

Value of Shear Wave Elastography in the Diagnosis of Gouty and Non-Gouty Arthritis

Our aim was to analyze the diagnostic performance of shear wave elastography (SWE) in the diagnosis of gouty arthritis (GA) and non-gouty arthritis (non-GA). Thirty-nine patients in the GA group and 55 patients in the non-GA group were included in the study. Based on the echo intensity of the joint lesions, the GA group was subdivided into hypo-echoic GA, slightly hyper-echoic GA and hyper-echoic GA subgroups. Quantitative SWE features were evaluated and receiver operating characteristic analysis was performed. On the basis of the study, the elastic modulus (E_max), mean elastic modulus (E_mean), minimum elastic modulus (E_min) and elastic modulus standard deviation (E_SD) were significantly higher in the GA group than in the non-GA group and were highest in the hyper-echoic GA subgroup (p < 0.01 for all). E_min, E_mean and E_max were significantly higher in the hyper-echoic GA subgroup than in the hypo-echoic GA subgroup and non-GA group (p < 0.001 for all), and E_SD was significantly higher in the hyper-echoic GA subgroup than in the non-GA group (p = 0.001). E_min, E_mean, E_max and E_SD were higher in the hypo-echoic GA subgroup than in the non-GA group, and the differences were significant (p < 0.001 for all). Based on the hypo-echoic GA subgroup and non-GA group, areas under the receiver operating characteristic curves for the prediction of GA were 0.749 for E_min, 0.877 for E_mean, 0.896 for E_max and 0.886 for E_SD, with optimal cutoff values of 29.40 kPa for E_min, 45.35 kPa for E_mean, 67.54 kPa for E_max and 7.85 kPa for E_SD. Our results indicate that SWE can differentially diagnose GA and non-GA, especially when the ultrasound manifestations are not typical.     

Measurement of Liver Stiffness Using Shear Wave Elastography in a Rat Model: Factors Impacting Stiffness Measurement with Multiple- and Single-Tracking-Location Techniques

The clinical use of elastography for monitoring fibrosis progression is challenged by the subtle changes in liver stiffness associated with early-stage fibrosis and the comparatively large variance in stiffness estimates provided by elastography. Single-tracking-location (STL) shear wave elasticity imaging (SWEI) is an ultrasound elastography technique previously found to provide improved estimate precision compared with multiple-tracking-location (MTL) SWEI. Because of the improved precision, it is reasonable to expect that STL-SWEI would provide improved ability to differentiate liver fibrosis stage compared with MTL-SWEI. However, this expectation has not been previously challenged rigorously. In this work, the performance of STL- and MTL-SWEI in the setting of a rat model of liver fibrosis is characterized, and the advantages of STL-SWEI in staging fibrosis are explored. The purpose of this study was to determine what advantages, if any, arise from using STL-SWEI instead of MTL-SWEI in the characterization of fibrotic liver. Thus, the ability of STL-SWEI to differentiate livers at various METAVIR fibrosis scores, for ex vivo postmortem measurements, is explored. In addition, we examined the effect of the common confounding factor of fluid versus solid boundary conditions in SWEI experiments. Sprague-Dawley rats were treated with carbon tetrachloride over several weeks to produce liver disease of varying severity. STL and MTL stiffness measurements were performed ex vivo and compared with the METAVIR scores from histological analysis and the duration of treatment. A strong association was observed between liver stiffness and weeks of treatment with the liver toxin carbon tetrachloride. Direct comparison of STL- and MTL-SWEI measurements revealed no significant difference in ability to differentiate fibrosis stages based on SWEI mean values. However, image interquartile range was greatly improved in the case of STL-SWEI, compared with MTL-SWEI, at small beam spacing.     

Shear Wave Velocity Measurements for Differential Diagnosis of Solid Breast Masses: A Comparison between Virtual Touch Quantification and Virtual Touch IQ

This study compared the diagnostic performance of two shear wave speed measurement techniques in 81 patients with 83 solid breast lesions. Virtual Touch Quantification, which provides single-point shear wave speed measurement capability (SP-SWS), was compared with Virtual Touch IQ, a new 2-D shear wave imaging technique with multi-point shear wave speed measurement capability (2D-SWS). With SP-SWS, shear wave velocity was measured within the lesion (“internal” value) and the marginal areas (“marginal” value). With 2D-SWS, the highest velocity was measured. The marginal values obtained with the SP-SWS and 2D-SWS methods were significantly higher for malignant lesions and benign lesions, respectively (p < 0.0001). Sensitivity, specificity and accuracy were 86% (36/42), 90% (37/41) and 88% (73/83), respectively, for SP-SWS, and 88% (37/42), 93% (38/41) and 90% (75/83), respectively, for 2D-SWS. It is concluded that 2D-SWS is a useful diagnostic tool for differentiating malignant from benign solid breast masses.     

Evaluation of Non-alcoholic Fatty Liver Disease Using Acoustic Radiation Force Impulse Imaging Elastography in Rat Models

The aim of this study is to evaluate the utility of acoustic radiation force impulse (ARFI) elastography for assessing hepatic fibrosis stage and non-alcoholic fatty liver disease (NAFLD) severity, as well as the relationship among hepatic histologic changes using shear wave velocity (SWV). Animal models with various degrees of NAFLD were established in 110 rats. The right liver lobe was processed and embedded in a fabricated gelatin solution (porcine skin). Liver mechanics were measured using SWV induced by acoustic radiation force. Among the histologic findings, liver elasticity could be used to differentiate normal rats from rats with simple steatosis (SS) as well as distinguish SS from non-alcoholic steatohepatitis (NASH), with areas under the receiver operating characteristic curves (AUROC) of 0.963 (95% confidence interval = 0.871–0.973) and 0.882 (95% confidence interval = 0.807–0.956), respectively. For NAFLD rats, the diagnostic performance of ARFI elastography in predicting significant fibrosis (F ≥ 2) had an AUROC of 0.963. For evaluating steatosis severity, we found a progressive increase in ARFI velocity proportional to steatotic severity in NAFLD rat models, but we observed no significant differences for steatotic severity after excluding the rats with fibrosis. ARFI elastography may be used to differentiate among degrees of severity of NAFLD and hepatic fibrotic stages in NAFLD rat models.     

Value of Acoustic Radiation Force Impulse Imaging Elastography for Non-invasive Evaluation of Patients with Nonalcoholic Fatty Liver Disease

The goals of the work described here were to evaluate the clinical utility of acoustic radiation force impulse (ARFI) elastography in differentiating non-alcoholic fatty liver disease (NAFLD) histologic subtypes and to determine if ARFI elastography measurements correlate with the severity of liver fibrosis. We compared ARFI elastography measurements with clinical, biologic and histologic features (simple steatosis or steatohepatitis) in 64 patients with histologically proven NAFLD. ARFI elastography is suitable for distinguishing patients with non-alcoholic steatohepatitis from those with simple steatosis, with an area under the receiver operating characteristic curve (AUROC) of 0.867 (95% confidence interval = 0.782–0.953). There was a highly significant correlation (r = 0.843) between ARFI elastography measurements and fibrosis (p < 0.001). In patients with non-alcoholic steatohepatitis, the diagnostic performance of ARFI elastography in predicting significant fibrosis (F ≥ 2) had an AUROC of 0.944. ARFI elastography better predicted F = 4 fibrosis (AUROC = 0.984). In conclusion, ARFI elastography is a promising method for differentiating patients with non-alcoholic steatohepatitis from patients with simple steatosis and can also predict significant fibrosis in these patients.     

Shear Wave Elastography for Assessment of Steatohepatitis and Hepatic Fibrosis in Rat Models of Non-Alcoholic Fatty Liver Disease

The purpose of this study was to evaluate shear wave elastography (SWE) as a method for determining the severity of non-alcoholic fatty liver disease (NAFLD) and the stage of hepatic fibrosis, as well as the major determinants of liver elasticity among the various histologic and biomolecular changes associated with NAFLD. Rat NAFLD models with various degrees of NAFLD severity were created and imaged using SWE. The explanted livers were subjected to histopathologic evaluation and RNA expression analysis. Among the histologic and biomolecular findings, the fibrosis stage and the collagen RNA level were significant independent factors associated with liver elasticity (p < 0.001). Liver elasticity was effective in detecting non-alcoholic steatohepatitis (NASH) and in determining fibrosis stage, and the corresponding areas under the receiver operating characteristic curves were 0.963 and 0.927–0.997, respectively. In conclusion, SWE is a potential non-invasive method for the detection of NASH and staging of hepatic fibrosis in patients with NAFLD.     

Acoustic Structure Quantification Versus Point Shear Wave Speed Measurement for the Assessment of Liver Fibrosis in Viral Hepatitis B

This study was conducted to evaluate the value of acoustic structure quantification (ASQ) technology versus that of point shear wave speed measurement (PSWSM) imaging technology for the assessment of liver fibrosis stage. A total of 104 patients with chronic hepatitis B (CHB) and 30 healthy control patients underwent ASQ and PSWSM examinations. Seven quantitative parameters were obtained from ASQ, and a principal component analysis was used to establish the integrative indicators. A quantitative parameter, known as the shear wave speed (SWS, m/s), was obtained from the PSWSM. The METAVIR scores for the assessment of pathologic liver fibrosis were used as a benchmark. Liver fibrosis stages exhibited a good correlation with the integrative indicators and SWS (r?=?0.682, p?<0.001; r?=?0.651, p?<0.001). The areas under the receiver operating characteristic curves for ASQ and PSWSM were 0.705 and 0.854 for mild liver fibrosis (F?≥?1, p?=?0.045), 0.813 and 0.743 for significant liver fibrosis (F?≥?2, p?=?0.115), 0.839 and 0.857 for severe liver fibrosis (F?≥?3, p?=?0.417) and 0.874 and 0.971 for liver cirrhosis (F?=?4, p?=?0.016), respectively. In conclusion, both ASQ and PSWSM were promising ultrasonic methods for assessing liver fibrosis in patients with CHB; however, PSWSM was more valuable for identifying mild liver fibrosis (F?≥?1) and cirrhosis (F?=?4) than ASQ, and the combination of PSWSM and ASQ improved the accuracy of diagnosing severe liver fibrosis (F?≥?3).     

剪切波速度提高肌筋膜疼痛综合征患者疗效的价值初探

目的 探索剪切波速度（shear wave velocity, SWV）提高肌筋膜疼痛综合征（myofascial pain syndrome, MPS）患者治疗疗效的价值。方法 选择我院收治的MPS患者80例并定义为MPS组,同期选择健康志愿者80例作为对照组。采用视觉模拟评分(visual analogue scale, VAS)、疼痛评定指数(values of pain rating index, PRI)、现时疼痛强度 (present pain intensity, PPI)评估患者疼痛程度。使用声辐射力脉冲（acoustic radiation force impulse, ARFI）弹性成像观察斜方肌组织弹性并记录SWV值。MPS患者均接受6个疗程的常规治疗,之后将疗效达到显效及以上的患者根据患者自愿原则进行分组,继续以SWV作为疗效观察指标并进行治疗的定义为继续治疗组,不继续治疗的患者定义为停止治疗组。所有患者进行为期1年的随访,比较继续治疗组与停止治疗组治疗后复发率的差异。结果 治疗过程中患者VAS值和SWV值均呈下降趋势,其差异有统计学意义（FVAS=3.649,PVAS=0.000;FVAS=2.631,PVAS=0.018）。MPS患者整体治疗的显效率为78.8%。治疗后MPS患者的VAS 、PRI、PPI均显著低于治疗前,差异均具有统计学意义（均P＜0.05）。MPS组治疗后平均SWV（2.63±1.09 m/）显著低于治疗前（4.35±1.56 m/s）,差异具有统计学意义（t=8.084,P=0.000）。继续治疗组累计无复发率（93.33%）显著高于停止治疗组（61.29%）,Logrank检验差异有统计学意义（X2=8.760,P=0.003）。结论 ARFI的SWV值可以客观反应MPS患者病情的严重程度,利用SWV值作为疗效的判定标准可能可以获得更好的疗效。     

The Mechanical Properties of Ex Vivo Bovine and Porcine Crystalline Lenses: Age-Related Changes and Location-Dependent Variations

The mechanical properties of ex vivo animal lenses from three groups were evaluated: old bovine (25–30 mo old, n = 4), young bovine (6 mo old, n = 4) and young porcine (6 mo old, n = 4) eye globes. We measured the dynamics of laser-induced microbubbles created at different locations within the crystalline lenses. An impulsive acoustic radiation force was applied to the microbubble, and the microbubble displacements were measured using a custom-built high pulse repetition frequency ultrasound system. Based on the measured dynamics of the microbubbles, Young's moduli of bovine and porcine lens tissue in the vicinity of the microbubbles were reconstructed. Age-related changes and location-dependent variations in the Young's modulus of the lenses were observed. Near the center, the old bovine lenses had a Young's modulus approximately fivefold higher than that of young bovine and porcine lenses. The gradient of Young's modulus with respect to radial distance was observed in the lenses from three groups.     

Influence of Probe Pressure on Ultrasound-Based Shear Wave Elastography of the Liver Using Comb-Push 2-D Technology

It has been postulated that in the liver, applying increased probe pressure during ultrasound-based shear wave elastography (SWE) might lead to a false increase in the SWE result. We aimed to determine the influence of increased intercostal probe pressure when performing SWE of the liver. We also investigated the number of measurements required to achieve technically successful and reliable SWE examinations. This prospective, clinical study included 112 patients and 2240 SWE measurements of the liver. We applied probe pressure intercostally, to reduce the skin-to-liver capsule distance (SCD), which could stabilize the SWE signal and thus increase the number of technically successful measurements. We performed 10 measurements with maximum probe pressure and 10 with normal pressure in each patient. Thus, two analysis groups were compared for differences. Compared with normal pressure, maximum probe pressure significantly reduced the SCD (p < 0.001) and significantly increased the number of technically successful measurements from 981 to 1098, respectively (p < 0.001). The SWE results with normal and maximum probe pressure were 5.96 kPa (interquartile range: 2.41) and 5.45 kPa (interquartile range: 1.96), respectively (p < 0.001). In obese patients, a large SCD poses a diagnostic challenge for ultrasound SWE. We found that maximum intercostal probe pressure could reduce the SCD and increase the number of technically successful measurements, without falsely increasing the SWE result. Only three measurements were required to achieve technically successful and reliable SWE examinations.