超声弹性成像用于高强度聚焦超声损伤的检测

采用超声弹性成像的方法检测高强度聚焦超声在动物组织内产生的损伤.结果表明,聚焦超声的损伤在应变分布图(弹性图像)上表现为应变较小的区域,即损伤部位的弹性模量较周围组织的大,组织切片的损伤范围和大小也与应变分布图的结果一致.     

血管内超声弹性成像中的数据采集系统设计

基于射频信号处理的血管内超声弹性成像技术对于动脉粥样硬化易损斑块的识别具有重要意义。为验证超声弹性重建算法的准确性,设计了一种血管内超声射频信号采集系统,系统利用线同步信号为触发源,同步采集超声射频信号、心电和血压信号;引入基于单片机的控制模块,解决多块采集卡同步和超声射频信号帧间旋转不一致性矫正问题;将采集卡和控制模块等集成到同一控制平台下,实现各硬件块之间的协同工作;利用ini配置文件和MATLAB计算引擎调用技术,简化采集卡配置过程,实现采集结果的可视化。     

超声弹性成像的原理及理论分析

超声弹性成像能够获得常规的成像模态无法获取的组织弹性这种基本的信息，具有非常重要的临床价值。本文详细介绍了超声弹性成像的一般原理与改进，以及理论分析的方法。     

超声弹性成像技术研究现状

超声弹性成像(ultrasound elastography,UE)是以软组织的弹性参量为对象的一种新的成像技术,它弥补了传统超声成像技术不能提供生态学特性的不足,拓宽了超声图像在肿瘤探测及扩散疾病成像方面的应用,具有非常重要的临床应用价值。本文详细介绍了超声弹性成像技术的实现原理、研究现状以及常用的临床衡量指标,如对比度传输率、应变滤波器、时间延时等,并对其发展做出展望。     

超声弹性成像中应变滤波器的理论及其发展

弹性成像能够提供组织弹性这一基本的力学属性，具有很广阔的应用前景。应变滤波器是超声弹性成像的重要理论框架，可广泛应用于超声弹性成像效果的评估、分析和预测。本详细综述了应变滤波器的理论和发展，并对献中的一些笔误作了修正，对实现的一些细节作了说明。通过对应变滤波器的理解，可以加深对超声弹性成像效果的理解，并对采用合适的方法和参数以获得最佳的成像效果以指导。     

超声弹性成像的原理及理论分析

超声弹性成像能够获得常规的成像模态无法获取的组织弹性这种基本的信息 ,具有非常重要的临床价值。本文详细介绍了超声弹性成像的一般原理与改进 ,以及理论分析的方法     

超声弹性成像中应变滤波器的理论及其发展

弹性成像能够提供组织弹性这一基本的力学属性,具有很广阔的应用前景。应变滤波器是超声弹性成像的重要理论框架,可广泛应用于超声弹性成像效果的评估、分析和预测。本文详细综述了应变滤波器的理论和发展,并对文献中的一些笔误作了修正,对实现的一些细节作了说明。通过对应变滤波器的理解,可以加深对超声弹性成像效果的理解,并对采用合适的方法和参数以获得最佳的成像效果以指导。     

血管内超声弹性图的构建原理和临床应用研究

血管内超声技术的发展提供了评价血管和斑块断面信息的手段 ,但却不能准确反映粥样斑块的生物物理属性。血管内超声弹性图通过描述血管壁径向的应变情况 ,再现了管壁和斑块的生物弹性特征 ,可以分辨不稳定斑块、预测斑块破裂并能反映斑块成分 ;结果也较之单纯血管内超声显像更为客观。我们对该项技术的构建原理和临床应用研究现状进行了综述 ,并指出了该项技术目前存在的缺点和将来的发展方向。     

超声弹性成像在乳腺疾病诊断中的仿真分析

乳腺疾病是当今女性的常见病,由于超声检查简单易行,已成为乳腺疾病中良恶性肿块鉴别的常用方法.本研究借助于MATLAB软件下的PDE工具箱,利用有限元分析方法,结合弹性力学理论计算得到良恶性乳腺肿块在不同情况下的应变分布图.仿真结果表明,对于弹性模量较大的肿块,其x方向应变和切应变图像在鉴别诊断上都具有较高的临床应用价值,但是对于一些硬度较大的良性病变和一些硬度较小的恶性病变,其准确性不是很高,为后续研究提供了依据.     

超声弹性成像技术评估先前剖宫产妇女的子宫瘢痕弹性程度

目的 以子宫周围完整肌层为参照,应用弹性成像技术评价定量评价剖宫产(CS)瘢痕弹性程度,并探讨剖宫产瘢痕弹性程度是否受既往剖宫产临床特征的影响.方法 将2017年1月至2020年12月于本院超声科就诊的怀孕37周的剖宫产史子宫瘢痕患者纳入研究,经阴道超声选择两个感兴趣区(ROI):子宫瘢痕(区1)和周围子宫肌层(区2)...     

超声弹性成像仿真的有限元分析

本文利用有限元分析的方法，用弹性力学的理论计算得到软组织在不同情况下的应变分布。这对于弹性成像的理论分析具有重要的辅助作用，可以研究软组织的不同状态和各种力学参数对弹性成像的影响，以及从理论上估计弹性成像的局限性。有限元分析的结果说明，弹性成像比较适于检测较硬的肿块，另外，还可能判断乳腺肿瘤的一些性质，这在临床上有很大的参考价值。     

The effect of vascular curvature on three-dimensional reconstruction of intravascular ultrasound images

Objective: To characterize the effect of vessel curvature on the geometric accuracy of conventional three-dimensional reconstruction (3DR) algorithms for intravascular ultrasound image data.Background: A common method of 3DR for intravascular ultrasound image data involves geometric reassembly and volumetric interpolation of a spatially related sequence of tomographic cross sections generated by an ultrasound catheter withdrawn at a constant rate through a vascular segment of interest. The resulting 3DR is displayed as a straight segment, with inherent vascular curvature neglected. Most vascular structures, however, are not straight but curved to some degree. For this reason, vascular curvature may influence the accuracy of computer-generated 3DR.Methods: We collected image data using three different intravascular ultrasound catheters (2.9 Fr, 4.3 Fr, 8.0 Fr) during a constant-rate pullback of 1 mm/sec through tubing of known diameter with imposed radii of curvature ranging from 2 to 10 cm. Image data were also collected from straight tubing. Image data were digitized at 1.0-mm intervals through a length of 25 mm. Two passes through each radius of curvature were performed with each intravascular ultrasound catheter. 3DR lumen volume for each radius of curvature was compared to that theoretically expected from a straight cylindrical segment. Differences between 3DR lumen volume of theoreticalversus curved (actual) tubes were quantified as absolute percentage error and categorized as a function of curvature. Tubing deformation error was quantified by quantitative coronary angiography (QCA).Results: Volumetric errors ranged from 1% to 35%, with an inverse relationship demonstrated between 3DR lumen volume and segmental radius of curvature. Higher curvatures (r<6.0 cm) induced greater lumen volume error when compared to lower curvatures (r>6.0 cm). This trend was exhibited for all three catheters and was shown to be independent of tubing deformation artifacts. QCA-determined percentage diameter stenosis indicated no deformation error as a function of curvature. Total volumetric error contributed by tubing deformation was estimated to be 0.05%.Conclusions: Catheter-dependent geometrical error arises in three-dimensionally reconstructed timed linear pullbacks of intravascular ultrasound images due in part to uniplanar vascular curvature. Three-dimensional reconstruction of timed linear pullbacks is robust for vessels with low radii of curvature; however, careful interpretation of three-dimensional reconstructions from timed linear pullbacks for higher radii of curvature is warranted. These data suggest that methods of spatially correct three-dimensional reconstruction of intravascularultrasound images should be considered when more pronounced vascular curvature is present.     

高重叠率下弹性成像应变估计值的小波去噪研究

目的 高的数据窗重叠率是提高弹性成像轴向分辨率的必要条件,但重叠率的增加会使位移估计的相关误差急剧增长,产生所谓的"蠕虫"噪声.本研究使用小波收缩法去除高重叠率下弹性图像蠕虫噪声.方法 对每一条轴向应变A-line先进行3级离散小波分解,然后根据4种自适应阈值之一使用软阈值函数对每一层小波高频系数进行量化,最后进行小波...     

硅橡胶膜细胞载体的应力分析及生物相容性

目的 报道一种自制的硅橡胶膜细胞载体,通过三维有限元方法计算其表面应变分布情况,并作细胞生物相容性分析,对材料进行全面评价,为细胞的应力刺激实验提供理论依据。方法 将硅橡胶材料制作成0.1 cm厚的透明薄膜,结合硅橡胶材料的泊松比以及弹性模量,应用三维有限元分析软件对数据进行处理,模拟硅橡胶受到牵张应变后产生的形变;通过MTT方法比较细胞在硅橡胶和标准培养板上的生长情况,并采取体外皮下包埋实验验证硅橡胶材料是否具有生物学毒性。结果 在对材料加载0.5%~20%的过程中,有效应变范围集中在硅橡胶膜的中心区域,约占总面积的90%;同时,硅橡胶材料虽然在生物相容性方面与标准培养板存在一定差异,但其本身无生物学毒性。结论 这种自制的硅橡胶细胞载体表面应力分布良好,生物相容性尚可满足细胞培养,但表面需进一步改善,可满足细胞的牵张应变实验。     

Use of a Rayleigh damping model in elastography

A Rayleigh damping model applied to magnetic resonance elastography incorporates attenuation behavior proportionally related to both elastic and inertial forces, and allows two damping parameters to be extracted from an MRI motion dataset. Under time-harmonic conditions, the model can be implemented by the use of complex shear modulus and density, whereas viscoelastic damping models commonly used in elastography consist of only a complex shear modulus, and model only a single damping effect. Simulation studies reveal that the differences between damped elastic behavior resulting from a purely complex shear modulus (CSM damping) and from a purely complex density (CD damping) become larger as the overall level of damping present (indicated by the damping ratio) increases. A plot of results generated from the finite element (FE) model indicate the relative motion differences estimated for a range of damping ratios and CSM/CD damping combinations increase with damping ratio, and can be up to 15% at a damping ratio of 50% and therefore using the correct model for a Rayleigh damped material becomes increasingly important as damping levels increase. Resonance-related effects cause values from this plot to vary by as much as 3% as parameters such as wave speed, frequency, and problem size are altered. These motion differences can be compared to expected noise levels to estimate the parameter resolution achievable by a reconstruction algorithm. An optimization-based global property reconstruction algorithm was developed, and used for testing Rayleigh damping parameter reconstructions with gaussian noise added to the simulated motion input data. The coherent motion errors resulting from altering the combination of the two damping parameters are large enough to allow accurate determination of both of the Rayleigh damping parameters with incoherent noise levels comparable to MR measurements. The accuracy achieved by the global reconstructions was significantly better than would be predicted by examining the motion differences for differing CSM/CD damping combinations, which is likely to be due to the low ratio between number of reconstructed parameters and number of noisy measurements.     

Mechanics of porcine coronary arteriesex vivo employing impedance planimetry: A new intravascular technique

Our objective was to evaluate methodological aspects of impedance planimetry, a new balloon catheter-based technique, for the investigation of coronary artery mechanical wall properties. We used a four ring-electrode electrical impedance measuring system that was located inside a balloon. Two of the electrodes were used for excitation and connected to a generator producing a constant alternating current of 250 mA at 5 kHz. The other two electrodes for detection were placed midway between the excitation electrodes. The balloon was distended with electrically conducting fluid through an infusion channel. The vessel cross-sectional area (CSA) was measured according to the field gradient principle by measuring the impedance of the fluid inside the balloon. Impedance planimetry was applied in the three major branches of the coronary arteries of seven extracted porcine hearts to assess luminal CSAs in response to internal pressurization. The biomechanical wall properties were evaluated by computing the strain [(r−r ₀)·r ₀ ⁻¹, wherer is the vessels inner radius computed as (CSA · π⁻¹)^? andr ₀ is the radius of the vessel at a minimal distension pressure], the tension [(r·dP), wheredP is the transmural pressure difference], and the pressure elastic modulus (ΔP·r·Δr ⁻¹). We found thatin vitro testing demonstrated that impedance planimetry was accurate and reproducible. The technique has controllable sources of crror. Measurements were performed with consecutively increasing pressures in the range 1–25 kPa (8–188 mmHg, 0.01–0.25 atm). The CSAs increased nonlinearly and were significantly larger in the left anterior descendent coronary artery (LAD) (1 kPa, mean 5.0 mm²; 25 kPa, mean 21.8 mm²) than in both the left circumflex (Cx) (4.5–16.0 mm²) and the right coronary artery (RCA) (2.8–15.6 mm²) (analysis of variance,P<0.001 for both). The circumferential wall tension-strain relation showed exponential behavior. For a given strain, tension values for LAD were significantly lower than those of Cx (P<0.01). The pressure elastic modulus-strain relation also was exponential, and values for Cx were significantly lower than values for LAD (P<0.001) and RCA (P<0.05). Impedance planimetry was applied to the study of coronary artery biomechanicsex vivo. The LAD had the largest CSA, and the Cx was the least compliant. Methodological aspects of anin vivo introduction of the method require additional evaluation.     

A novel active contour model for fully automated segmentation of intravascular ultrasound images: in vivo validation in human coronary arteries

The detection of lumen and media-adventitia borders in intravascular ultrasound (IVUS) images constitutes a necessary step for the quantitative assessment of atherosclerotic lesions. To date, most of the segmentation methods reported are either manual, or semi-automated, requiring user interaction at some extent, which increases the analysis time and detection errors. In this work, a fully automated approach for lumen and media-adventitia border detection is presented based on an active contour model, the initialization of which is performed via an analysis mechanism that takes advantage of the inherent morphologic characteristics of IVUS images. The in vivo validation of the proposed model in human coronary arteries revealed that it is a feasible approach, enabling accurate and rapid segmentation of multiple IVUS images.     

基于超声压痕技术的兔眼角膜生物力学特性

目的利用超声压痕技术探索兔眼角膜的生物力学特性。方法选取7月龄新西兰白兔眼球7只,制作完整角膜试样并固定于人工前房上。用微量注射泵给人工前房注水改变前房内的压力,并用压力传感器测量;在不同前房压力状态下,利用超声压痕设备在角膜顶点位置进行压痕实验,获得力-位移曲线。研究角膜力学参数(弹性模量、滞回量等)与前房压力的关系。结果由角膜压痕实验所得的力-位移曲线呈现非线性特点。前房内压力越大,角膜的力-位移曲线越陡峭。兔眼角膜的弹性模量随前房压力升高而增大,在前房压力为7～45 mm Hg(1 mm Hg=0. 133 k Pa)范围内,其数值范围为0. 30～1. 55 MPa。随前房压力增大,角膜滞回量呈现线性上升趋势。结论基于超声压痕技术获得的兔眼角膜弹性模量随前房压力呈线性增大,滞回量等角膜黏性特性参数与前房压力也相关。     

Segmental aortic wall stiffness from intravascular ultrasound at normal and subnormal aortic pressure in pigs

Segmental aortic wall stiffness was calculated from intravascular ultrasound images and intravascular pressures in six pigs at normal and subnormal aortic pressures (21 sequences of pressures and areas before and after boli of intravenous nitroglycerin). The wall stiffness was expressed as the pressure–strain elastic modulus (E_p). The E_p was calculated from the formula: E_p=ΔPRΔR^-1 (P, pressure; R, radius) in two different ways. First from maximal and minimal values of pressure and area. Second as the slope of linear regression line of ΔPR as a function of ΔR from 29 simultaneous recorded pressures and images. The average E_p value for all sequences in the different segments was 0.58 ± 0.55 10⁵ Pa (Method 1) and 0.50 ± 0.40 10⁵ Pa (Method 2). E_p increased with the distance from the heart at normal aortic pressures. At subnormal aortic pressures after intravenous nitroglycerin this relationship was not so evident. At subnormal aortic pressures the calculated E_p values were significantly reduced in the lower half of the abdominal aorta. The phase lag, i. e. hysteresis, between pressure and diameter was demonstrated. Our study shows the applicability of intravascular ultrasound as a tool to evaluate arterial wall stiffness.