超声弹性显微镜成像系统开发与应用的初步研究

传统的超声弹性成像技术一般使用1MHz～10MHz的超声波,这一频段超声波的空间分辨率在毫米量级,它不能满足对生物组织中微细结构(如皮肤层,关节软骨等)的研究。文中介绍一套新开发的超声弹性显微镜成像系统,并将其初步应用于对关节软骨和老鼠表皮的成像研究中。该系统由加压系统和背向散射超声显微镜系统两部分组成,其中超声探头频率为50MHz。通过对关节软骨和老鼠表皮的成像实验表明,该系统可以清晰的对生物组织中微细结构成像,研究它们的机械特性。     

超声水浸法高精度测量玻璃材料声速的研究

材料的声速与其杨氏模量和密度有关,通过测量材料的声速可以评价材料的特性。相关研究表明,超低膨胀玻璃的声速是评价其热膨胀系数的关键参数,通过测量声速可以实现对超低膨胀玻璃热膨胀系数的间接无损测量。针对市售的超声声速测量仪器存在系统复杂且不易集成化的问题,结合高精度的数据采集卡设计了超声信号采集显示软件,并基于超声水浸脉冲反射法搭建了高精度的声速测量系统,系统结构简单,操作方便且较易集成化。采用该测量系统对制备的超低膨胀玻璃样品的声速进行了测量,结果表明该系统具有较高的声速测量分辨率,声速分辨率可达为0.2 m.s^-1,为使用超声声速法高精度测量超低膨胀玻璃的热膨胀系数奠定了研究基础。     

关节臂式柔性三坐标测量系统的数学模型及误差分析

关节臂式柔性三坐标测量系统是一种新颖的基于旋转关节和转动臂的三坐标测量系统，以角度测量基准取代了长度测量基准，它具有量程大、体积小、重量轻及使用灵活等优点．首先基于Denavit-Hartenberg方法建立了关节臂式柔性三坐标测量系统的理想数学模型和误差模型，并通过几何作图法对模型进行了验证．根据系统的特点和通过对系统中实际存在的影响测量结果的各种误差因素进行了详细分析，为进一步研究系统的误差补偿提供了理论基础．     

关节臂激光扫描系统光条中心提取方法研究

在基于关节臂的线激光扫描系统中,光条中心的提取精度和所用时间直接影响到整个系统的测量精度和实时响应能力。本文在国内外现有算法基础上整合改进,利用迭代阈值法、改进 Sobel 算子和光条修补算法完成光条粗提取,取中心点附近10 pixels利用灰度重心法计算光条中心精确位置。实验证明,该算法在350 mm×350 mm测量范围内,系统测量误差优于40μm,一次提取时间28 ms,确保系统35 f/s扫描频率,满足实时在线测量要求。     

柔性关节空间机器人基于神经网络的自适应反演控制

讨论了载体位姿无控情况下,漂浮基柔性关节空间机器人的关节运动控制器设计问题。利用系统动量、动量矩守恒关系及拉格朗日法,建立了空间机器人的动力学模型。为实现系统关节运动控制目标,借助于神经网络函数逼近技术,提出了一种柔性关节空间机器人的自适应反演控制方案。所提控制方案无需预知系统各惯性参数的真实信息,且可避免对载体位置相关量进行实时地测量与反馈,因此较适于实际应用。数值仿真结果表明:上述控制方案可使系统各柔性关节的振动较小,并能够有效地控制空间机器人完成所期望的关节运动。     

三维超声地震模型实时成像系统

室内水槽实验是研究地质沉积过程及其演化规律的重要手段,高精度获取沉积过程中的地质体的变化是这类模拟实验非常关键的环节。文章介绍了新研制的三维超声地震模型实时成像系统的主要组成及关键技术。该系统用于模拟海上地震,可以在沉积实验后通过快速测量及对数据的实时偏移处理与成像可以获取变化的多层复杂地质模型动态图像,极大地提高了实验效率和成像精度。该系统具有良好的实时性、成像质量以及探测范围,在对研究地质沉积、海洋地质以及三维地震模型研究等方面有着广泛应用前景。     

光纤光栅肘关节角度测量方法

为解决现有关节角度测量装置的不足,提出一种基于多光纤布拉格光栅(fiber Bragg grating, FBG)的关节角度测量方法。该方法将多光纤光栅固定在套袖上,套袖戴在肘关节上,辅以自主设计的基于LabVIEW关节角度计算及数据处理的程序和可视化界面,实现对肘关节角度实时测量并输出可视化数据。该套袖具有柔性化程度高、不受电磁信号干扰、测量效率高、结构简单的优点。对所制作套袖进行测量实验,实验结果表明,该测量方法的误差约为2.88%,重复性误差在4%以下,具有实际的应用价值。     

关节活动度的照相测量方法

文章提出人体关节活动度的照相测量方法,即在被测关节的固定臂和活动臂上分别贴两个圆形标志点,用数码相机拍摄标志点连线在关节旋转前后的两个定义位置,通过数学方法计算标志点连线之间的角度在旋转前后的变化,得出该关节的关节活动度.照相测量法相对于传统的量角器测量法来说,减少了测量误差、缩短了测量时间,是一种精确、有效、经济的新方法.     

关节臂式三坐标测量系统整车扫描方案优化

柔性关节臂式三坐标测量系统是仿照人体手臂关节结构,由多根杆件通过旋转关节链接组成的,它以角度基准取代长度基准,具有体积小、重量轻、便于携带和使用灵活等优点,因此被广泛应用在汽车逆向工程中。该文研究了关节臂式三坐标测量系统的工作原理和方法,并对其优缺点进行阐述,提出了一种整车外形扫描的工作方法,利用最小二乘法迭代原理编译程序,使多块点云高精度无缝拼接。     

可降解水凝胶作为关节软骨修复材料的研究进展

可降解水凝胶因其良好的生物相容性和生物降解性被广泛用于关节软骨的修复和再生。本文以可降解水凝胶在软骨组织工程中的三类应用策略为主线,概述了用于原位成型可注射水凝胶的蛋白多糖类材料及纳米复合类材料;系统总结了传统工艺制造组织工程支架的优缺点及多种工艺结合的制备方法;重点归纳了近年来3D打印组织工程支架从纯软骨到骨/软骨一体化、从单层到多层的研究进展;最后分析了可降解水凝胶作为关节软骨支架材料在微观定向结构和生物活性功能化方面的局限性,并作出展望：未来开展多材料、多尺度、多诱导的高仿生梯度支架是关节软骨组织工程的一个重要研究方向。     

Ultrasound evaluation of mechanical injury of bovine knee articular cartilage under arthroscopic control

A local cartilage injury can trigger development of posttraumatic osteoarthritis (OA). Surgical methods have been developed for repairing cartilage injuries. Objective and sensitive methods are needed for planning an optimal surgery as well as for monitoring the surgical outcome. In this laboratory study, the feasibility of an arthroscopic ultrasound technique for diagnosing cartilage injuries was investigated. In bovine knees (n = 7) articular cartilage in the central patella and femoral sulcus was mechanically degraded with a steel brush modified for use under arthroscopic control. Subsequently, mechanically degraded and intact adjacent tissue was imaged with a high frequency (40 MHz) intravascular ultrasound device operated under arthroscopic guidance. After opening the knee joint, mechanical indentation measurements were also conducted with an arthroscopic device at each predefined anatomical site. Finally, cylindrical osteochondral samples were extracted from the measurement sites and prepared for histological analysis. Quantitative parameters, i.e., reflection coefficient (R), integrated reflection coefficient (IRC), apparent integrated backscattering (AIB), and ultrasound roughness index (URI) were calculated from the ultrasound signals. The reproducibilities (sCV %) of the measurements of ultrasound parameters were variable (3.7% to 26.1%). Reflection and roughness parameters were significantly different between mechanically degraded and adjacent intact tissue (p < 0.05). Surface fibrillation of mechanically degraded tissue could be visualized in ultrasound images. Furthermore, R and IRC correlated significantly with the indentation stiffness. The present results are encouraging; however, further technical development of the arthroscopic ultrasound technique is needed for evaluation of the integrity of human articular cartilage in vivo.     

Probing articular cartilage damage and disease by quantitative magnetic resonance imaging

Osteoarthritis (OA) is a debilitating disease that reflects a complex interplay of biochemical, biomechanical, metabolic and genetic factors, which are often triggered by injury, and mediated by inflammation, catabolic cytokines and enzymes. An unmet clinical need is the lack of reliable methods that are able to probe the pathogenesis of early OA when disease-rectifying therapies may be most effective. Non-invasive quantitative magnetic resonance imaging (qMRI) techniques have shown potential for characterizing the structural, biochemical and mechanical changes that occur with cartilage degeneration. In this paper, we review the background in articular cartilage and OA as it pertains to conventional MRI and qMRI techniques. We then discuss how conventional MRI and qMRI techniques are used in clinical and research environments to evaluate biochemical and mechanical changes associated with degeneration. Some qMRI techniques allow for the use of relaxometry values as indirect biomarkers for cartilage components. Direct characterization of mechanical behaviour of cartilage is possible via other specialized qMRI techniques. The combination of these qMRI techniques has the potential to fully characterize the biochemical and biomechanical states that represent the initial changes associated with cartilage degeneration. Additionally, knowledge of in vivo cartilage biochemistry and mechanical behaviour in healthy subjects and across a spectrum of osteoarthritic patients could lead to improvements in the detection, management and treatment of OA.     

Fourier transform infrared spectral analysis of degenerative cartilage: an infrared fiber optic probe and imaging study

A preliminary investigation into the diagnostic potential of an infrared fiber optic probe (IFOP) for evaluating degenerative human articular cartilage is described. Twelve arthritic human tibial plateaus obtained during arthroplasty were analyzed using the IFOP. Infrared spectra were obtained from IFOP contact with articular surface sites visually graded normal or degraded (Collins Scale grade 1 and grade 3, respectively). Comparisons of infrared spectral parameters (peak heights and areas) were made to elucidate spectral indicators of surface degeneration. IFOP spectral analysis revealed subtle but consistent changes between grades 1 and 3 sites. Infrared absorbance bands arising from type II collagen were observed to change with degradation. More degraded tissues exhibited increased amide II (1590-1480 cm(-1))/1338 cm(-1) area ratio (p=0.034) and decreased 1238/1227 cm(-1) peak ratio (p = 0.017); similar changes were seen with Fourier transform infrared imaging spectroscopy (FT-IRIS) analysis. Grades 1 and 3 cartilage showed consistent spectral differences in the amide II, III, and 1338 cm(-1) regions that are likely related to type II collagen degradation that accompanies cartilage degeneration. These results suggest that it may be possible to monitor subtle changes related to early cartilage degeneration, allowing for IFOP use during arthroscopy for in situ determination of cartilage integrity.     

Estimation of fixed charge density and diffusivity profiles in cartilage using contrast enhanced computer tomography

Contrast enhanced computer tomography (CT) imaging of articular cartilage has been proposed for diagnostics of cartilage degeneration, that is, osteoarthritis. Previous studies also indicate that acute cartilage damage can be detected by measuring diffusion of contrast agent into cartilage using CT. However, currently, there is no reliable method to measure spatial diffusion rates within cartilage tissue, and only average bulk values have been reported. In this paper, we develop a method to determine depthwise diffusivity of contrast agents in cartilage tissue using contrast enhanced CT. The triphasic mechano‐electrochemical theory of cartilage is modified to include diffusion of contrast agents. By applying statistical inversion theory and Bayesian approximation error approach, the method allows us to estimate a fixed charge density distribution in the cartilage tissue, an important determinant for mechanical competence of articular cartilage. The method is tested by using a one‐dimensional simulation study. Preliminary tests with experimental data on diffusion of anionic iodine contrast agent in bovine articular cartilage indicate that the method can provide realistic estimates for depth dependent fixed charge density. Thereby, the present study can improve our understanding on the feasibility of contrast enhanced CT for cartilage diagnostics. Copyright © 2014 John Wiley & Sons, Ltd.     

Altered swelling and ion fluxes in articular cartilage as a biomarker in osteoarthritis and joint immobilization: a computational analysis

In healthy cartilage, mechano-electrochemical phenomena act together to maintain tissue homeostasis. Osteoarthritis (OA) and degenerative diseases disrupt this biological equilibrium by causing structural deterioration and subsequent dysfunction of the tissue. Swelling and ion flux alteration as well as abnormal ion distribution are proposed as primary indicators of tissue degradation. In this paper, we present an extension of a previous three-dimensional computational model of the cartilage behaviour developed by the authors to simulate the contribution of the main tissue components in its behaviour. The model considers the mechano-electrochemical events as concurrent phenomena in a three-dimensional environment. This model has been extended here to include the effect of repulsion of negative charges attached to proteoglycans. Moreover, we have studied the fluctuation of these charges owning to proteoglycan variations in healthy and pathological articular cartilage. In this sense, standard patterns of healthy and degraded tissue behaviour can be obtained which could be a helpful diagnostic tool. By introducing measured properties of unhealthy cartilage into the computational model, the severity of tissue degeneration can be predicted avoiding complex tissue extraction and subsequent in vitro analysis. In this work, the model has been applied to monitor and analyse cartilage behaviour at different stages of OA and in both short (four, six and eight weeks) and long-term (11 weeks) fully immobilized joints. Simulation results showed marked differences in the corresponding swelling phenomena, in outgoing cation fluxes and in cation distributions. Furthermore, long-term immobilized patients display similar swelling as well as fluxes and distribution of cations to patients in the early stages of OA, thus, preventive treatments are highly recommended to avoid tissue deterioration.     

Effects of ultrasound frequency, temporal sampling frequency, and spatial sampling step on the quantitative ultrasound parameters of articular cartilage

Quantitative ultrasound imaging may provide a technique for diagnosing initial signs of osteoarthritis (OA), such as surface fibrillation of articular cartilage. Because subchondral sclerosis and osteophyte formation occur in OA as well, ultrasonic analysis of subchondral bone could yield useful diagnostic information. In this study, we investigated whether low-frequency (5 MHz) ultrasound, typically used in bone diagnostics, would be feasible for evaluating the integrity of the surface of the cartilage. The reflection parameters in the time and frequency domains, the ultrasound roughness index, and the wavelet-based parameters were evaluated using ultrasound transducers operating at 5, 10, and 50 MHz frequencies. The effects of variable size of spatial sampling steps and of temporal sampling frequencies were also investigated. Custom-made phantoms and cartilage samples with various surface characteristics were analyzed. The reflection parameters detected the surface degradation with all ultrasound frequencies. The roughness of the surface could only be evaluated reliably with the 50 MHz-focused transducer. In conclusion, simultaneous analysis of the reflection parameters of the cartilage and the subchondral bone is feasible at low (5 MHz) ultrasound frequencies. However, reliable evaluation of the microtopography of the cartilage requires use of a higher ultrasound frequency.     

Measurement of acoustic output parameters from medical ultrasound devices with an RF power meter system

Current national and international standards for the measurement of acoustic output parameters of diagnostic medical ultrasound devices rely for their strict implementation on the ability to measure pulse intensity integral or pressure squared integral. A relatively inexpensive measurement system that utilizes a calibrated hydrophone in conjunction with a thermal RMS device is described. It is shown that this system can be used to locate maximum pulse average parameters in static beam devices and true maximum temporal average parameters in complex real-time diagnostic systems. The advantages of the system are discussed and measurement uncertainties are assessed.     

结构不对称条件下测速发电机的卡尔曼测速算法

针对基于测速发电机、光电编码器等测速传感器的传统测速系统存在低速测量性能,实时性,对结构不对称、电磁扰动等的抗干扰性等都较差的问题,提出了一种高精度宽范围实时滤波测速方法。以爪极永磁式交流测速电机为例,详细分析了其机械结构特性和工作原理,并在结构不对称条件下建立了爪极永磁式交流测速电机测速模型,提出了一种面向工程应用、计算量小的交互双模自适应降阶无迹卡尔曼滤波算法来实时估计永磁转子转速。该算法同时运行降阶和全阶交互双模自适应算法,当采用降阶估计值保障系统实时性时,在计算耗时较长的全阶算法运行完成一次后修正一次降阶估计值,提高测速精度。仿真结果表明,提出的测速算法对于结构不对称扰动具有良好的鲁棒性,能够适用于宽范围条件下的转速高精度实时跟踪,具有一定的工程指导意义。     

Engineering cartilage tissue interfaces using a natural glycosaminoglycan hydrogel matrix — An in vitro study

Hydrogels are suitable matrices for cartilage tissue engineering on account of their resemblance to native extracellular matrix of articular cartilage and also considering its ease of application, they can be delivered to the defect site in a minimally invasive manner. In this study, we evaluate the suitability of a fast gelling natural biopolymer hydrogel matrix for articular cartilage tissue engineering. A hydrogel based on two natural polymers, chitosan and hyaluronic acid derivative was prepared and physicochemically characterized. Chondrocytes were then encapsulated within the hydrogel and cultured over a period of one month. Cartilage regeneration was assessed by histological, biochemical and gene expression studies. Chondrocytes maintained typical round morphology throughout the course of this investigation, indicating preservation of their phenotype with sufficient production of extracellular matrix and expression of typical chondrogenic markers Collagen type 2 and aggrecan. The results suggest that the natural polymer hydrogel matrix can be used as an efficient matrix for articular cartilage tissue engineering.