Shear Wave Elastography Quantification of Blood Elasticity During Clotting

Deep venous thrombosis (DVT) affects millions of people worldwide. A fatal complication occurs when the thrombi detach and create a pulmonary embolism. The diagnosis and treatment of DVT depends on clot's age. The elasticity of thrombi is closely related to its age. Blood was collected from pigs and anticoagulated using ethylenediaminetetraacetic acid (EDTA). Coagulation was initiated using calcium ions. Supersonic shear wave imaging was used to generate shear waves using 100 μs tone bursts of 8 MHz. Tracking of the shear waves was done by ultrafast imaging. Postprocessing of the data was done using Matlab^®. Two-dimensional (2-D) maps of elasticity were obtained by calculating the speed of shear wave propagation. Elasticity varied with time from around 50 Pa at coagulation to 1600 Pa at 120 min after which the elasticity showed a natural decreased (17%) because of thrombolytic action of plasmin. Ejection of the serum from the clot showed a significant decrease in the elasticity of the clot next to the liquid pool (65% decrease), corresponding to the detachment of the clot from the beaker wall. The use of a thrombolytic agent (Urokinase) on the coagulated blood decreased the shear elasticity close to the point of injection, which varied with time and distance. Supersonic imaging proved to be useful mapping the 2-D clot's elasticity. It allowed the visualization of the heterogeneity of mechanical properties of thrombi and has potential use in predicting thrombi breakage as well as in monitoring thrombolytic therapy.     

An Artifact in Supersonic Shear Wave Elastography

Supersonic shear wave elastography is a novel ultrasound technology that allows objective evaluation of soft tissue stiffness. The purpose of this study is to report an artifact in supersonic shear wave elastography that may strongly affect the accuracy and quality of the measurement of soft tissue stiffness, and to step-by-step describe how the artifact was found and how it was verified by a series of experiments under different conditions. There were a total of three longitudinal band-like artifacts, 1.3 cm apart from each other on the entire image along the length of the SuperLinear SL15-4 transducer surface, with the middle one at the center of the image. When using supersonic shear wave elastography, users should be keenly aware of the possible occurrence of the artifact and avoid it by choosing the quantification measurement regions of interest (ROIs) away from the artifact regions.     

Computer-Aided Diagnosis Based on Quantitative Elastographic Features with Supersonic Shear Wave Imaging

Supersonic shear wave imaging (SSI) has recently been explored as a technique to evaluate tissue elasticity modulus and has become a valuable tool for tumor characterization. The purpose of this study was to develop a novel computer-aided diagnosis (CAD) system that can acquire quantitative elastographic information from color SSI elastography images automatically and objectively for the purpose of classifying benign and malignant breast tumors. Conventional ultrasonography (US) and SSI elastography images of 125 breast tumors (81 benign, 44 malignant), in 93 consecutive patients (mean age: 40 y, age range: 16–75 y), were obtained. After reconstruction of tissue elasticity data and automatic segmentation of each breast tumor, 10 quantitative elastographic features of the tumor and peri-tumoral areas, respectively (elasticity modulus mean, maximum and standard deviation, hardness degree and elasticity ratio), were computed and evaluated. A support vector machine (SVM) classifier was used for optimum classification via combination of these features. The B-mode Breast Imaging Reporting and Data System (BI-RADS) was used to compare gray-scale US and SSI elastography with respect to diagnostic performance. Histopathologic examination was used as the reference standard. Student's t-test, the Mann-Whitney U-test, the point biserial correlation coefficient and receiver operating characteristic curve analysis were performed for statistical analysis. As a result, the accuracy, sensitivity, specificity, positive predictive value and negative predictive value of benign/malignant classification were 95.2% (119/125), 90.9% (40/44), 97.5% (79/81), 95.2% (40/42) and 95.2% (79/83) for the CAD scheme, respectively, and 79.2% (99/125), 90.9% (40/44), 72.8% (59/81), 64.5% (40/62) and 93.7% (59/63) for BI-RADS assessment, respectively. The area under the receiver operating characteristic curve (A_z value) for the proposed CAD system using the combination of elastographic features was significantly higher than the A_z value for visual assessment by the radiologists using BI-RADS (0.97 vs. 0.91). The results indicate that SSI elastography could be used for computer-aided feature extraction, and the proposed CAD method could improve the diagnostic accuracy of classification of breast tumors to avoid unnecessary biopsy. Furthermore, elastographic features of the peri-tumoral area have the potential to provide critical information in differential diagnosis.     

Viscoelastic and Anisotropic Mechanical Properties of in vivo Muscle Tissue Assessed by Supersonic Shear Imaging

The in vivo assessment of the biomechanical properties of the skeletal muscle is a complex issue because the muscle is an anisotropic, viscoelastic and dynamic medium. In this article, these mechanical properties are characterized for the brachialis muscle in vivo using a noninvasive ultrasound-based technique. This supersonic shear imaging technique combines an ultra-fast ultrasonic system and the remote generation of transient mechanical forces into tissue via the radiation force of focused ultrasonic beams. Such an ultrasonic radiation force is induced deep within the muscle by a conventional ultrasonic probe and the resulting shear waves are then imaged with the same probe (5 MHz) at an ultra-fast framerate (up to 5000 frames/s). Local tissue velocity maps are obtained with a conventional speckle tracking technique and provide a full movie of the shear wave propagation through the entire muscle. Shear wave group velocities are then estimated using a time of flight algorithm. This approach provides a complete set of quantitative and in vivo parameters describing the muscle’s mechanical properties as a function of active voluntary contraction as well as passive extension of healthy volunteers. Anisotropic properties are also estimated by tilting the probe head with respects to the main muscular fibers direction. Finally, the dispersion of the shear waves is studied for these different configurations and shear modulus and shear viscosity are quantitatively assessed assuming the viscoelastic Voigt’s model. (E-mail: jl.gennisson@espci.fr)     

Dispersion in Tissue-Mimicking Gels Measured with Shear Wave Elastography and Torsional Vibration Rheometry

Dispersion, or the frequency dependence of mechanical parameters, is a primary confounding factor in elastography comparisons. We present a study of dispersion in tissue-mimicking gels over a wide frequency band using a combination of ultrasound shear wave elastography (SWE), and a novel torsional vibration rheometry which allows independent mechanical measurement of SWE samples. Frequency-dependent complex shear modulus was measured in homogeneous gelatin hydrogels of two different bloom strengths while controlling for confounding factors such as temperature, water content and material aging. Furthermore, both techniques measured the same physical samples, thereby eliminating possible variation caused by batch-to-batch gel variation, sample geometry differences and boundary artifacts. The wide-band measurement, from 1 to 1800 Hz, captured a 30%–50% increase in the storage modulus and a nearly linear increase with frequency of the loss modulus. The magnitude of the variation suggests that accounting for dispersion is essential for meaningful comparisons between SWE implementations.     

Acoustic Radiation Force Impulse and Supersonic Shear Imaging Versus Transient Elastography for Liver Fibrosis Assessment

Our study compared three elastographic methods—transient elastography (TE), acoustic radiation force impulse (ARFI) imaging and supersonic shear imaging (SSI)—with respect to the feasibility of their use in liver fibrosis evaluation. We also compared the performance of ARFI imaging and SSI, with TE as the reference method. The study included 332 patients, with or without hepatopathies, in which liver stiffness was evaluated using TE, ARFI and SSI. Reliable measurements were defined as a median value of 10 (TE, ARFI imaging) or 5 (SSI) liver stiffness measurements with a success rate ≥60% and an interquartile range interval <30%. A significantly higher percentage of reliable measurements were obtained using ARFI than by using TE and SSI: 92.1% versus 72.2% (p < 0.0001) and 92.1% versus 71.3% (p < 0.0001). Higher body mass index and older age were significantly associated with inability to obtain reliable measurements of liver stiffness using TE and SSI. In 55.4% of patients, reliable liver stiffness measurements were obtained using all three elastographic methods, and ARFI imaging and TE were similarly accurate in diagnosing significant fibrosis and cirrhosis, with TE as the reference method.     

Liver Stiffness Measurements by Means of Supersonic Shear Imaging in Patients Without Known Liver Pathology

We used supersonic shear imaging to determine the liver stiffness (LS) values of 82 patients without known liver pathology and studied the factors that influence these measurements. Five LS measurements were made in each subject, and the median value, expressed in kilopascals, was calculated. Reliable LS measurements were obtained in 84.5% of patients. Higher body mass index and older age were associated with failure to obtain reliable measurements. The mean value of LS measurements determined by SSI in our cohort of patients without known liver pathology was 6 ± 1.4 kPa. The mean LS measurements determined by SSI for men were significantly higher than those for women; body mass index did not significantly influence SSI measurements. Thus, 6 kPa is the mean SSI value in patients without known liver pathology, with higher values being obtained in men.     

彩超在诊断下肢深静脉血栓中的作用

目的探讨彩色多普勒血流显像（CDFI）在诊断下肢深静脉血栓（DVT）中的作用。方法对96例273条临床拟诊断下肢深静脉血栓形成的患者进行CDFI和静脉造影检查。结果273条静脉经造影证实均为DVT，CDFI检出262务，DVT经CDFI检查有特征性表现，可据此确诊DVT。结论CDFI在诊断DVT中有重要作用。     

下肢深静脉血栓彩色多普勒超声显像的探讨

目的：探讨彩色多普勒超声对下肢深静脉血栓的诊断价值。方法：对临床疑有下肢深静脉血栓形成患者78例,87条病肢,应用彩色多普勒超声检测及上行性静脉造影检查。结果：彩超共检出阳性患者74例,83条病肢。超声诊断敏感性为95．3％,准确性为97．6％;下肢深静脉各段均可形成血栓,以股静脉段患病率最高（30．9％）;左下肢患病例数明显多于右下肢,左、右之比为2．4：1（P＜0．001）。结论：急、慢性血栓彩色多普勒超声显像特点各异。彩色多普勒超声检测下肢深静脉血栓具有无创、安全、准确及可重复应用等优点。     

二维彩色多普勒血流显像在下肢深静脉血栓中的应用

目的为探讨二维彩色多普勒血流显像（２ＤＣＤＦＩ）在下肢深静脉血栓（ＤＶＴ）中的应用价值。方法３０例３０条下肢ＤＶＴ进行了２ＤＣＤＦＩ检查,均经静脉造影证实。结果ＤＶＴ超声表现为腔内血栓回声;探头加压静脉腔不可压闭或部分压闭;腔内缺乏彩色血流信号或出现充盈缺损;脉冲Ｄｏｐｐｌｅｒ示无血流或血流频谱不随呼吸而变化。超声诊断符合率为９６７％（２９／３０）。结论２ＤＣＤＦＩ是评价下肢ＤＶＴ一种有价值的实用方法     

Propagation Imaging in the Demonstration of Common Shear Wave Artifacts

In this article, we describe our experience with shear wave propagation imaging (SWPI) as an adjunct to 2‐dimensional (2D) shear wave elastography (SWE) in a cohort of patients being evaluated for diffuse liver disease. Two‐dimensional SWE has been extensively studied in previous publications; however, 2D SWE using propagation images has not been widely described in the literature to date. We observed that when certain artifacts occurred on the color elastograms, highly characteristic changes to shear wave propagation contours were seen, which can help clarify the cause of the artifacts. To our knowledge, the use of SWPI to explain the etiology of artifacts has never been published before. The artifacts described in this article include the capsule reverberation artifact, penetration limitation or dropout artifact, artifact due to blood vessels, shadowing artifact, tissue motion artifact, and near‐field distortion/precompression artifact. Hence, the purpose of this article is to show examples of common artifacts seen on 2D SWE as depicted on corresponding SWPI to demonstrate that both types of image displays are complementary to each other.     

彩色多普勒超声对下肢深静脉血栓的评价

目的探讨彩色多普勒对下肢深静脉血栓的诊断与疗效的评价.方法对16例拟诊下肢深静脉血栓的患者进行检查.测量患肢静脉管径、受累部位,观察声像图改变及彩色多普勒的血流特征.随访治疗前后变化.结果急性血栓患者静脉管径增宽,内有不规则的低回声.彩色多普勒超声显示完全阻塞者无血流通过,不完全阻塞者为充盈缺损,且血流缓慢.经溶栓治疗及肢体活动等治疗后,血流逐渐恢复.慢性血栓显示回声较高,治疗后范围缩小,需时较长.结论彩色多普勒超声评价下肢深静脉血栓有重复性好、可靠性高的优势.     

彩色多普勒超声在下肢深静脉血栓形成诊断中的价值

目的 探讨彩色多普勒血流显像（ＣＤＦＩ）在下肢深静脉血栓形成（ＤＶＴ）诊断中的价值。方法 对８９例拟诊下肢ＤＶＴ患者在７１２条下肢静脉进行ＣＤＦＩ和静脉造影检查。结果 ＣＤＦＩ检出并经静脉造影证实的ＣＶＴ静脉共６４３例。ＣＤＦＩ的主要优点是：①节约时间,易于快速找至静脉;②对鉴别完全或不完全阻塞性血栓有一定帮助;③便于检查髂静脉血栓,尤其血栓髂总静脉蔓延时。ＣＤＦＩ和静脉造影在判断有无ＤＶＴ方面,     

彩色多普勒血流显像诊断下肢静脉病变的价值

目的　评价彩色多普勒血流显像 (CDFI)检测临床下肢静脉病变的应用价值。方法　对临床下肢静脉病变 90例 10 7条下肢静脉进行CDFI检查。结果　CDFI可迅速清晰地显示下肢静脉的解剖图像 ,其中检出 61例 64条下肢静脉有血栓形成 (急性血栓 3 1例 ,慢性血栓 3 0例 ) ,8例 9条深静脉瓣功能不全 ,3 1例 3 4条为下肢静脉曲张。结论　下肢深静脉血栓形成有一定的声像特征 ,CDFI检出敏感性高 ,可对血栓作出位置、范围和管腔阻塞程度的判断 ,是帮助临床选择治疗方案和客观评价药物疗效的重要方法。判断有无深静脉瓣功能不全 ,可为临床手术和治疗提供可靠依据     

Acoustic Waves in Medical Imaging and Diagnostics

Up until about two decades ago acoustic imaging and ultrasound imaging were synonymous. The term ultrasonography, or its abbreviated version sonography, meant an imaging modality based on the use of ultrasonic compressional bulk waves. Beginning in the 1990s, there started to emerge numerous acoustic imaging modalities based on the use of a different mode of acoustic wave: shear waves. Imaging with these waves was shown to provide very useful and very different information about the biological tissue being examined. We discuss the physical basis for the differences between these two basic modes of acoustic waves used in medical imaging and analyze the advantages associated with shear acoustic imaging. A comprehensive analysis of the range of acoustic wavelengths, velocities and frequencies that have been used in different imaging applications is presented. We discuss the potential for future shear wave imaging applications.     

下肢深静脉血栓形成相关因素分析及护理干预

目的:对下肢深静脉血栓形成的相关因素进行分析,并提出护理干预措施。方法:对96例下肢深静脉血栓形成的相关因素分别进行单因素分析,并进行统计学处理。结果:骨科相关性疾病、剖宫产术、胸腹大手术与下肢深静脉血栓形成有显著统计学意义(P<0.05)。结论:对下肢深静脉血栓的高危因素应进行有针对性的护理干预,以降低下肢深静脉血栓形成发生率及致残率。     

Supersonic Shear Wave Imaging of the Spleen for Staging of Liver Fibrosis in Rats

The goal of the work described here was to explore the cause of spleen stiffness (SS) in hepatic fibrogenesis and evaluate the value of SS in liver fibrosis (LF) staging. LF was induced with carbon tetrachloride (CCl₄) in rats (n = 40). Supersonic shear wave imaging and contrast-enhanced ultrasound were performed to determine liver stiffness (LS), SS and splenic hemodynamics. SS, LS and free portal pressure exhibited moderate correlations with fibrosis stage (r = 0.744–0.835, p < 0.001). Time–intensity curves of contrast-enhanced ultrasound for the spleen were presented as decreasing peak intensity and slope of decrease, and increasing time to peak. Splenic sinus dilation and congestion were observed on histopathologic analysis. The area under the receiver operating characteristic curve of SS was higher than that of LS for differentiating LF stages 0–2 from stages 3–4 (Z = 2.293, p = 0.02). SS is a reliable diagnostic marker for the assessment of LF in the CCl₄ model, especially for severe fibrosis. Elevated portal pressure is the cause of increasing SS.