数字聚焦超声反射CT成像初步研究

对于单元发，阵接收的模型，采用反射回波的包络作为投影，按滤波后投影算法（ＦＢＰ法）进行重建，得到物体内某一截面的重建像，然后调整接收阵的位置，获取多层截面的投影并重建成像，运用体绘制法（ＶｏｌｕｍｅＲｅｎｄｅｒｉｎｇＩｍａｇｉｎｇ）绘制了三维像，图像效果不好，分辨率不高，针对这一问题，文中应用了电子延迟方法处理接收信号，即对接收阵各阵元接收到的回波号依照散射点相对接收中阵的空间位置关系进行一定时间     

螺旋CT胆道成像技术及质量保证

本文简明扼要地阐述了螺旋CT胆道成像技术的原理和实际应用方法，以及保证影像质量和提高诊断效率的具体措施和经验。     

超声反射CT在水下物体成像中的应用

本文重点介绍了沿平面扫描成像，提出了修正扫描起始点位置以及换能器孔径影响的一种方法，得到较好的实验结果。     

板状材料激光超声CT成像的研究

1引言激光超声技术[1]是指由一束激光来检测另一束激光激发超声的技术,其较传统用压电换能器的超声检测有以下优点:高的空间和时间分辨率,高的灵敏度,非常适合在线非接触检测。目前激光超声检测技术不仅是声传播基础研究的重要实验手段,而     

医学超声成像的模拟研究

简述医学超声成像模拟研究的主要方法,探讨其研究意义和应用前景。将现有的超声成像模拟算法分为基于线性假设和基于非线性假设的两大类,介绍每类中代表方法的基本原理,并讨论两类方法的差异,其中基于数值方法求解超声波动方程的模拟算法更符合实际超声成像过程,为更好地理解超声图像中的各种现象、寻求组织特性和图像特征间的匹配关系提供了有效的研究工具。     

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。     

基于GPU的超声弹性成像并行实现研究

为了提高超声弹性成像计算速度,提出使用GPU硬件加速基于互相关技术和相位零估计的弹性成像技术。先描述这两种弹性成像技术的实现细节及特点,然后分析这两种技术的计算密集操作部分的并行化计算可能性,最后通过GPU程序开发工具ArrayFire实现了基于GPU的互相关和相位零估计的超声弹性成像技术。通过模拟和扫描仿真人体组织的弹性成像体模获得的压缩前后数据帧对基于GPU的超声弹性成像方法进行测试与验证。实验结果表明,基于GPU的方法可以大幅提高弹性图计算速度,在处理单帧弹性图条件下,与基于互相关方法比较,加速比达到42,而基于相位零估计的方法在提高数据吞吐量的情况下加速比可达到65。     

甲状腺肿块的超声、CT与病理对照观察

目的:研究超声与CT对甲状腺肿块的诊断的准确率。方法:我院2012年8月-2013年9月经手术病理证实为甲状腺肿块患者的病例为53例,其中恶性病例11例。对所有病例的术前超声与CT表现进行分析。结果:在显示甲状腺肿块的边缘方面,超声更为清晰(P0.05),在显示囊变坏死与钙化等状况时,两者相似,没有统计学意义(P0.05)。结论:在显示甲状腺肿块方面,超声与CT均能良好的表现出来,将二者结合使用可以有效的提升诊断的准确率。     

螺旋CT泌尿系统成像的扫描技术探讨及临床应用

本文阐述了应用螺旋ＣＴ成像技术于泌尿器官的研究，包括贤脏，膀胱，输尿道等。结果表明这种新技术对于精确诊断这些器官的病变能提供可靠的影像数据而不会对病人产生创伤。     

生物声学成像中声速不均匀性解决方法的研究进展

对于以超声波为载体的生物医学声学成像(如超声、光声和磁声成像等)技术,为了简化问题,常在假设待测组织内声速恒定的前提下,重建组织内的声阻抗、光吸收分布、光学特性参数分布或者电导率分布等。但是,实际生物组织内部的声速是存在差异的(最大可达10%),因而在此假设前提下重建出的图像通常是不准确的。在介绍声速不均匀性对声学图像重建影响的基础上,对超声、光声和磁声成像中解决声速不均匀问题的主要方法,特别是光声层析成像中重建组织内声速分布的主要方法进行总结和归纳,讨论各自的优点和不足,并展望未来的可能发展方向。     

Holographic digital Fourier microscopy for selective imaging of biological tissue

We present an application of digital Fourier holography for selective imaging of scatterers with different sizes in turbid media such as biological tissues. A combination of Fourier holography and high‐resolution digital recording, digital Fourier microscopy (DFM) permits crucial flexibility in applying filtering to highlight scatterers of interest in the tissue. The high‐resolution digital hologram is a result of the collation of Fourier holographic frames to form a large‐size composite hologram. It is expected that DFM has an improved signal‐to‐noise ratio as compared to conventional direct digital imaging, e.g., phase microscopy, as applied to imaging of small‐size objects. The demonstration of the Fourier filtering capacity of DFM using a biological phantom represents the main focus of this article. © 2005 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 14, 253–258, 2004; Published online inWiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.20031     

An experimental investigation of a method to obtain isoclinic data from isochromatic data

If the photoelastic model has a line of symmetry and is made from a stress frozen sheet, then it is shown how the isoclinics can be obtained from isochromatic measurements only. The accuracy is investigated with experimental examples. The method should have applications in transient problems and where the sandwich method is used.     

Dynamic responses of a three‐dimensional framework due to a moving carriage hoisting a swinging object

The literature regarding the three‐dimensional responses of a structure due to moving loads(s) is rare and that due to the moving swinging object has not been found yet. The purpose of this paper is to provide some information in this area, where the axial (x?), vertical (?) and horizontal (z?) dynamic responses of the three‐dimensional framework of a tyred overhead crane under the action of a moving trolley (m_T) hoisting a swinging object (m_sw) were calculated using the finite element method and the direct integration method. Instead of the conventional moving force problem where only the vertical (?) inertia effect of the moving trolley was considered, the three‐dimensional inertial effects due to the masses of both the moving trolley and the swinging object have been considered in this paper. To this end, an equivalent moving mass matrix has been presented and which is dependent on both the instantaneous swinging angle of the hoisted object (m_sw) and the instantaneous position of the moving trolley so that the contribution of the moving mass on the overall mass matrix of the entire structure itself is easily tackled. Finally, the title problem was solved by calculating the forced vibration responses of the three‐dimensional framework with time‐dependent overall mass and damping matrices and subjected to an equivalent moving force. Some factors pertinent to the title problem, such as the magnitude, velocity and acceleration of the moving trolley and the swinging angles of the hoisted object, were studied. Numerical results reveal that, in addition to the conventional dynamic responses in the vertical (?) direction, the other two components in the axial (x?) and horizontal (z?) directions for a three‐dimensional structure are also significant. Copyright © 2004 John Wiley & Sons, Ltd.     

Application of Fourier transform infrared spectroscopic imaging to the study of effects of age and dietary l-arginine on aortic lesion composition in cholesterol-fed rabbits

Diet-induced atherosclerotic lesions in the descending thoracic segment of rabbit aorta were analysed ex vivo by micro-attenuated total reflection (ATR)–Fourier transform infrared (FTIR) spectroscopic imaging. The distribution and chemical character of lipid deposits within the arterial wall near intercostal branch ostia were assessed in histological sections from immature and mature rabbits fed cholesterol with or without l-arginine supplements. Previous studies have shown that both these properties change with age in cholesterol-fed rabbits, putatively owing to changes in the synthesis of nitric oxide (NO) from l-arginine. Immature animals developed lesions at the downstream margin of the branch ostium, whereas lipid deposition was observed at the lateral margins in mature animals. Dietary l-arginine supplements had beneficial effects in mature rabbit aorta, with overall disappearance of the plaques; on the other hand, they caused only a slight decrease of the lipid load in lesions at the downstream margin of the ostium in immature rabbits. ATR–FTIR imaging enabled differences in the lipid to protein density ratio of atherosclerotic lesions caused by age and diet to be visualized. Lipid deposits in immature rabbits showed higher relative absorbance values of their characteristic spectral bands compared with those in immature l-arginine-fed rabbits and mature rabbits. The multivariate methods of principal component analysis (PCA) and factor analysis (FA) were employed, and relevant chemical and structural information were obtained. Two distinct protein constituents of the intima–media layer at different locations of the wall were identified using the method of FA. This approach provides a valuable means of investigating the structure and chemistry of complex heterogeneous systems. It has potential for in vivo diagnosis of pathology.     

Neutron laminography—a novel approach to three-dimensional imaging of flat objects with neutrons

Computed tomography (CT) is a three-dimensional (3D) imaging method which, for compact or prolate (i.e. rather isotropically extended around the rotation axis) specimens, can yield artefact-free reconstructed cross-sections. Laterally extended specimens like plate-like objects, however, are much less amenable to CT since reliable projection data cannot be acquired from angles where the plate is oriented parallel to the irradiation direction.To overcome this drawback, computed laminography (CL) was introduced recently to imaging set-ups at synchrotron storage rings. Here, we report on the first implementation of computed laminography with neutron radiation, showing measurements that were performed at the ANTARES neutron imaging facility at the FRM II research reactor of Technische Universität München. In general, neutrons are highly interesting probes for imaging since they provide a sensitivity to chemical elements very different from X-rays, yielding complementary information about the specimens investigated. Like for X-ray laminography, we avoid the projection directions where the beam is parallel to the long extensions of the specimen. We accomplish this by tilting of the rotation axis with respect to the transmitted-beam to an angle smaller than 90° (which would be the limiting case of CT) and roughly aligning the specimen's surface normal parallel to this rotation axis. The principles of neutron laminography are introduced and first test experiments are described.     

Advanced neutron imaging methods with a potential to benefit from pulsed sources

During the last decade neutron imaging has seen significant improvements in instrumentation, detection and spatial resolution. Additionally, a variety of new applications and methods have been explored. As a consequence of an outstanding development nowadays various techniques of neutron imaging go far beyond a two- and three-dimensional mapping of the attenuation coefficients for a broad range of samples. Neutron imaging has become sensitive to neutron scattering in the small angle scattering range as well as with respect to Bragg scattering. Corresponding methods potentially provide spatially resolved and volumetric data revealing microstructural inhomogeneities, texture variations, crystalline phase distributions and even strains in bulk samples. Other techniques allow for the detection of refractive index distribution through phase sensitive measurements and the utilization of polarized neutrons enables radiographic and tomographic investigations of magnetic fields and properties as well as electrical currents within massive samples. All these advanced methods utilize or depend on wavelength dependent signals, and are hence suited to profit significantly from pulsed neutron sources as will be discussed.     

X-ray computed tomography imaging of a tumor with high sensitivity using gold nanoparticles conjugated to a cancer-specific antibody via polyethylene glycol chains on their surface

Contrast agents are often used to enhance the contrast of X-ray computed tomography (CT) imaging of tumors to improve diagnostic accuracy. However, because the iodine-based contrast agents currently used in hospitals are of low molecular weight, the agent is rapidly excreted from the kidney or moves to extravascular tissues through the capillary vessels, depending on its concentration gradient. This leads to nonspecific enhancement of contrast images for tissues. Here, we created gold (Au) nanoparticles as a new contrast agent to specifically image tumors with CT using an enhanced permeability and retention (EPR) effect. Au has a higher X-ray absorption coefficient than does iodine. Au nanoparticles were supported with polyethylene glycol (PEG) chains on their surface to increase the blood retention and were conjugated with a cancer-specific antibody via terminal PEG chains. The developed Au nanoparticles were injected into tumor-bearing mice, and the distribution of Au was examined with CT imaging, transmission electron microscopy, and elemental analysis using inductively coupled plasma optical emission spectrometry. The results show that specific localization of the developed Au nanoparticles in the tumor is affected by a slight difference in particle size and enhanced by the conjugation of a specific antibody against the tumor.     

Finite element analyses of wave propagations due to a high‐speed train across bridges

The finite element mesh of the unbounded wave problem often contains a large number of degrees of freedom. Moreover, the wave reflection along the mesh boundary cannot be avoided if only the traditional time‐domain finite element method (FEM) is used. Thus, the main purpose of this study is to overcome those drawbacks and discuss how to use the three‐dimensional FEM to simulate the soil vibration due to a moving high‐speed train across bridges. A number of finite element analyses (FEA) including the isolation schemes of in‐filled and open trenches were performed. The appropriate mesh dimension in the direction of the railroad is suggested and validated. Moreover, the 3‐node wheel element for simulating the moving train and the least‐squares method for finding foundation properties are proposed. Since the finite element mesh contains a large number of degrees of freedom, the conjugated gradient method with the SSOR preconditioning scheme is recommended. In conclusion, this study indicates that the difficulty of the FEA for unbounded problems can be overcome efficiently even by using a personal computer. Copyright © 2002 John Wiley & Sons, Ltd.