实时超声膨胀测量系统在关节软骨中的实验研究

关节软骨是覆盖关节表面的一层承载生物重量的组织。关节软骨在正常状态下，软骨蛋白多糖的弹性和胶原纤维的张力保持平衡。这种平衡的微小变化会引起关节软骨的退化。关节软骨特别是其表层区域的膨胀是和骨关节炎的退化相联系的，定量的测量关节软骨的膨胀可以表征骨关节炎的退化变化。本文的主要目的是介绍一种新的实时超声膨胀测量系统，并把该系统应用到关节软骨的研究中。该系统使用50MHz的超声来实时动态观测用胰岛素和0．15M生理盐水溶液分别浸泡处理的牛膝盖关节软骨的非均匀瞬时深度依赖膨胀行为。实验表明，实时超声检测的方法为关节软骨的退化研究提供了独特的工具。这项技术结合关节内窥镜检查，具有潜在的早期诊断体内关节退化的价值。     

实时超声弹性图像特征量化方法及其应用研究

0引言检测生物组织力学特性的超声弹性成像是近年来新兴的超声影像学技术,但目前的研究工作主要集中在如何构建弹性图像上,缺乏对弹性图像信息与临床诊断结果的前瞻性研究。五分法[1]及弹性比值[2-4]法是最常用的评估乳腺肿瘤方法,受诊断者主观影响较大,没有形成统一的标准,限制了超声弹性成像技术在临床上的广泛应用。构建科学、系统、有效的肿瘤弹性特征的量化和提取方法就显得尤其     

基于空耦换能器的碳纤维增强环氧树脂编织复合材料激光超声检测技术

激光超声技术具有无需耦合剂、快速及高分辨等特点,适用于各向异性碳纤维增强树脂编织复合材料的缺陷检测。运用有限元法分析了激励位置和编织结构对激光点源激发超声波信号的影响,获得了弹性波在材料内部的传播规律以及能量分布特征,并采用1 MHz空气耦合换能器搭建了一套小型化、低成本的非接触激光超声C扫描成像系统,开展了斜纹和缎纹碳纤维增强树脂编织复合材料的近表微结构和内部缺陷检测实验。结果表明,基于空气耦合换能器的激光超声成像可以高精度地再现碳纤维增强树脂编织复合材料的近表树脂囊、碳纤维束形状、取向、尺寸及其内部缺陷等空间分布特征,有望为航空复合材料提供一种原位的微结构表征和缺陷检测方法。      

多光谱光声层析技术在肿瘤学中的应用进展

多光谱光声层析技术是一种新兴的光声成像技术,兼具光声断层扫描和多光谱成像的优点。该成像技术需要利用内源性和外源性光声成像对比剂进行成像。成像时,激光发射器发射多个波长的激光束照射组织,组织发生热弹性膨胀并产生超声波,将超声换能器接收的光声信号进行后处理,分解光谱信息并重建图像。目前,多光谱光声层析技术已广泛用于多种肿瘤的研究。文章着重介绍光声成像对比剂和多光谱光声层析技术的发展近况以及在临床转化中取得的研究进展。     

浅谈电子显微摄影

电子显微镜诞生于六十多年前。它的放大倍率达几百倍至几十万倍 ,因此 ,具有比普通光学显微镜更大的分辨率 ,能看到普通光学显微镜无法看到的亚微结构和分子结构 ,它是医学、生物、化学、冶金及刑事侦察等科学领域进行分子学水平研究的重工具。现代电子显微镜不仅能观察形态 ,而且能进行微细区域元素分析。1　电子显微镜的结构和工作原理电子显微镜的结构与工作原理与普通光学显微镜基本相似。都有光源、透镜成像系统和观察与照相系统等。它们之间最根本区别在于电子显微镜是以电子束代替可见光成像 ,用电磁线圈取代了光学透镜系统。所观察…     

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。     

超声激发振动声成像实验系统的设计

根据超声激发振动声成像的基本原理,设计并构建一个能获得振动声图像的实验系统.该系统由高频信号部分、超声发射及传播部分、低频信号处理和计算机处理与控制等四部分构成.实验表明,该系统能获得生物仿体或软组织内刚性物体的振动声图像,为进行生物组织的振动声成像研究提供了基础;通过采用更高灵敏度的低频水听器和改善共焦换能器的分辨力...     

组织精细结构的光学高分辨数据获取与图像重建

光学弱相干层析成像(OCT)技术可以对生物组织高分辨率无损成像。依据获得的样品光学截面数据,再通过三维重建,可以得到生物组织精细结构的再现。在生物组织结构再现的研究中,对于目前常用的生物组织切削照相、X-ray、超声这些方法,OCT作为一种无损高分辨率的3D光学显微技术是一种很好的补充。     

测量生物组织声衰减的声辐射压力法装置研制

引言 超声波在生物组织媒质中传播时将产生反射、折射、透射、衍射、散射、衰减和非线性等现象,提取和分析这些互作用的信息可以了解生物组织的自身特性。这是现代生物医学超声工程学基础研究的重要内容[1]。研究和测定这些生物组织超声特性参量,一方面为设计超声诊断显象仪、超声治疗仪、超声加热治癌机、超声手术刀等提供设计参数;另一方面也为发展定性定量的超声诊断和治疗提供鉴别判据。因此对于开发新设备和新的医疗方法均有重要意义[2]。 声衰减是声波在生物媒质中传播时的总的声能量损失,与生物组织结构和特性密切相关。国际上已采用…     

软模板法制备高频超声换能器用1-3复合压电材料

医用高频超声成像技术广泛应用于皮肤、眼睛及血管壁等人体组织的精细结构成像。1-3复合压电材料因具有较高的机电耦合系数而成为高频超声换能器的核心材料。传统的机械切割-填充、等离子蚀刻等1-3复合材料制备方法成本高、效率低, 难以实现工业化制备。本研究提出一种新的基于软模板的高频复合材料制备方法, 在获得高机电耦合系数的同时, 实现高性能1-3复合压电材料的低成本制备。研究采用微米孔径的软模板实现PZT粉的浆料填充, 通过热压烧结获得均匀竖立的PZT陶瓷微柱阵列, 进而制备出PZT/环氧1-3复合材料。对复合材料进行系统的机电性能测试, 并利用不同方法对复合材料的微结构及其均匀性进行表征。结果表明, 软模板法可使压电微柱具有完整的相结构和较高的成分均匀性, 能够实现较高的胚体压缩率, 提高陶瓷微柱的致密度, 同时形成了微柱阵列且微柱直径可控制在70 μm。软模板法有利于在提高复合材料超声频率(30~50 MHz)的同时获得64%的高机电耦合系数, 为医用高频超声成像以及超声生物显微镜等应用提供了一种高效的1-3复合压电材料工业化制备方法。     

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.     

A 100-200 MHz ultrasound biomicroscope

The development of higher frequency ultrasound imaging systems affords a unique opportunity to visualize living tissue at the microscopic level. This work was undertaken to assess the potential of ultrasound imaging in vivo using the 100-200 MHz range. Spherically focused lithium niobate transducers were fabricated. The properties of a 200 MHz center frequency device are described in detail. This transducer showed good sensitivity with an insertion loss of 18 dB at 200 MHz. Resolution of 14 /spl mu/m in the lateral direction and 12 /spl mu/m in the axial direction was achieved with f/1.14 focusing. A linear mechanical scan system and a scan converter were used to generate B-scan images at a frame rate up to 12 frames per second. System performance in B-mode imaging is limited by frequency dependent attenuation in tissues. An alternative technique, zone-focus image collection, was investigated to extend depth of field. Images of coronary arteries, the eye, and skin are presented along with some preliminary correlations with histology. These results demonstrate the feasibility of ultrasound biomicroscopy In the 100-200 MHz range. Further development of ultrasound backscatter imaging at frequencies up to and above 200 MHz will contribute valuable information about tissue microstructure.     

High frequency ultrasound imaging with optical arrays

Dynamically focused and steered high frequency ultrasound imaging systems require arrays with fine element spacing, wide bandwidths, and large apertures. However, these characteristics are difficult to achieve at frequencies greater than 30 MHz using conventional array construction methods. Optical schemes offer a solution. Focused laser beams incident on a suitable surface can generate and detect acoustic radiation. Precisely controlling the position and size of the beams defines points of transmission and detection, making it possible for pulse-echo image formation by synthetic aperture methods. An optical detection array was built, relying on a conventional piezoelectric transducer as an ultrasound source. The detection system, with near optimal resolution over a wide depth of field, demonstrates the potential for high frequency array implementation using optical techniques. A possible application is in pathology, where 2-D or 3-D fine resolution pulse-echo imaging can be performed in situ without the need for biopsies.     

High-frequency ultrasound annular array imaging. Part II: digital beamformer design and imaging

This is the second part of a two-paper series reporting a recent effort in the development of a high-frequency annular array ultrasound imaging system. In this paper an imaging system composed of a six-element, 43 MHz annular array transducer, a six-channel analog front-end, a field programmable gate array (FPGA)-based beamformer, and a digital signal processor (DSP) microprocessor-based scan converter will be described. A computer is used as the interface for image display. The beamformer that applies delays to the echoes for each channel is implemented with the strategy of combining the coarse and fine delays. The coarse delays that are integer multiples of the clock periods are achieved by using a first-in-first-out (FIFO) structure, and the fine delays are obtained with a fractional delay (FD) filter. Using this principle, dynamic receiving focusing is achieved. The image from a wire phantom obtained with the imaging system was compared to that from a prototype ultrasonic backscatter microscope with a 45 MHz single-element transducer. The improved lateral resolution and depth of field from the wire phantom image were observed. Images from an excised rabbit eye sample also were obtained, and fine anatomical structures were discerned.     

High frequency coded imaging system with RF

Coded transmission is an approach to solve the inherent compromise between penetration and resolution required in ultrasound imaging. Our goal was to examine the applicability of the coded excitation to HF (20-35 MHz) ultrasound imaging. A novel real-time imaging system for research and evaluation of the coded transmission was developed. The digital programmable coder- digitizer module based on the field programmable gate array (FPGA) chip supports arbitrary waveform coded transmission and RF echo sampling up to 200 megasamples per second, as well as real-time streaming of digitized RF data via a high-speed USB interface to the PC. All RF and image data processing were implemented in the software. A novel balanced software architecture supports real-time processing and display at rates up to 30 frames/sec. The system was used to acquire quantitative data for sine burst and 16-bit Golay code excitation at 20 MHz fundamental frequency. SNR gain close to 14 dB was obtained. The example of the skin scan clearly shows the extended penetration and improved contrast when a 35-MHz Golay code is used. The system presented is a practical and low-cost implementation of a coded excitation technique in HF ultrasound imaging that can be used as a research tool as well as to be introduced into production.     

Limited-angle spatial compound imaging of skin with high-frequency ultrasound (20 MHz)

In dermatology, high-frequency ultrasound (HFUS) is used for high-resolution skin imaging. The conventional B-scan type approach is to perform lateral scans perpendicular to the direction of sound propagation. Ultrasound spatial compounding enables improvement of the image contrast, suppression of speckle and noise, and reduction of imaging artifacts in comparison with conventional B-mode imaging, but it has not yet found its way into HFUS skin imaging applications. In this paper, the potential of HFUS spatial compounding for skin imaging is systematically evaluated. A new HFUS system with a sophisticated scanner for limited-angle (up to +/-40 degrees) spatial compound imaging was developed and implemented. Echo signals are acquired using a 20 MHz spherically focused single-element transducer with an axial and lateral resolution of 69 mum and 165 mum, respectively, in the focus. A calibration scheme for the estimation of unknown system parameters and precise image reconstruction has been developed. The implemented system has been evaluated using measurements of geometrically well-defined structures, speckle phantoms, and in vivo measurements. The results show the advantage of the proposed spatial compound skin imaging concept compared with conventional B-mode imaging in terms of image contrast, isotropy, and independence from the orientation of surfaces.     

A single FPGA-based portable ultrasound imaging system for point-of-care applications

We present a cost-effective portable ultrasound system based on a single field-programmable gate array (FPGA) for point-of-care applications. In the portable ultrasound system developed, all the ultrasound signal and image processing modules, including an effective 32-channel receive beamformer with pseudo-dynamic focusing, are embedded in an FPGA chip. For overall system control, a mobile processor running Linux at 667 MHz is used. The scan-converted ultrasound image data from the FPGA are directly transferred to the system controller via external direct memory access without a video processing unit. The potable ultrasound system developed can provide real-time B-mode imaging with a maximum frame rate of 30, and it has a battery life of approximately 1.5 h. These results indicate that the single FPGA-based portable ultrasound system developed is able to meet the processing requirements in medical ultrasound imaging while providing improved flexibility for adapting to emerging POC applications.     

Intravascular ultrasound tissue harmonic imaging in vivo

Tissue harmonic imaging (THI) has been shown to increase image quality of medical ultrasound in the frequency range from 2 to 10 MHz and might, therefore, also be used to improve image quality in intravascular ultrasound (IVUS). In this study we constructed a prototype IVUS system that could operate in both fundamental frequency and second harmonic imaging modes. This system uses a conventional, continuously rotating, single-element IVUS catheter and was operated in fundamental 20 MHz, fundamental 40 MHz, and harmonic 40 MHz modes (transmit 20 MHz, receive 40 MHz). Hydrophone beam characterization measurements demonstrated the build-up of a second harmonic signal as a function of increasing pressure. Imaging experiments were conducted in both a tissue-mimicking phantom and in an atherosclerotic animal model in vivo. Acquisitions of fundamental 20 and 40 MHz and second harmonic acquisitions resulted in cross sections of the phantom and a rabbit aorta. The harmonic results of the imaging experiments showed the feasibility of intravascular THI with a conventional IVUS catheter both in a phantom and in vivo. The harmonic acquisitions also showed the potential of THI to reduce image artifacts compared to fundamental imaging.     

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.