共聚焦图像数据的三维重建和显示

本文介绍利用激光扫描共聚焦显微镜获得的共聚焦图像的三维重建和显示方法,并以ＡＣＡＳ Ｕｌｔｉｎａ３１２激光扫描共聚焦显微镜系统为例,分析了ＳＰＦ算法、投影算法和深度阴影算法等共聚焦图像数据的三维重建和图像显示方法的特点。     

基于光学相干层析图像的离体牙三维重建

利用shear-warp算法对离体牙的光学相干层析图像进行三维重建,通过不透明度传递函数的合理设置及光照模型的引入实现牙齿内部组织结构的可视化,便于医生在早期龋齿诊断中定位病变.介绍了shear-warp算法的原理、用于龋齿检测的全光纤光学相干层析成像系统及其二维层析图,以及利用离体牙牙冠的二维层析图重建获得三维结构图.     

基于计算机三维图象技术的失语症病灶空间定位法

首次把计算机三维重建方法应用于失语症的研究中,主要有三方面的工作:(1)建立了一套精细程度较高的标准CT脑图,用三维重建方法建立了标准立体头颅,并用伪彩色显示不同的脑结构和语言区.(2)提出标准化应在三维空间内进行的观点,改进的标准化方法充分利用了CT所能提供的关于脑结构的信息,从而使病灶在每层标准CT脑图上的定位更加准确.(3)对两类临床表现不同但CT显示病灶位置相近的失语症病人共47例进行了研究.通过对标准化之后的病灶的统计处理,得到病灶的集中部位,并对其进行三维重建,在标准立体头颅中显示其空间位置的差别.     

利用共聚焦显微镜系统进行视觉显微结构的三维重建

本文介绍利用共聚焦激光扫描显微镜系统进行的三种动物视觉显微结构的三维重建.所重建的对象为鸽视顶盖的神经元,蜻蜒小眼的晶锥和蟾蜍两个视顶盖之间的纤维联接结构.通过对约60μm厚的样品的共聚焦激光扫描,得到了1和3μm厚的连续光学切面的图象.利用计算机对这些图象进行三维重建得到的模型富有实体感和体视感,特别是以荧光染料标记的样品其三维重建结果比预料的好.三维重建的结果首次展示了这三种视觉显微结构的三维形态,这对进一步研究视觉显微结构的定量形态学和结构功能关系有重要意义,特别是这种装置能研究活组织的三维构型.对该系统的原理和优良性能也作了介绍.     

鞘翅目形态结构的三维重建与功能之间关系探讨的有效方法评估

本文简要介绍了计算机三维重建技术在鞘翅目形态学研究中的应用,并对所涉及到的成像设备及相关技术做了简要的介绍和评估。同时,本文也对计算机三维重建技术的未来发展方向做了初步的展望。     

三维重建技术与生物陶瓷相结合在下颌骨连续性缺损个体化修复中的应用

目的探讨三维重建技术与生物陶瓷相结合,制作下颌骨连续性缺损的个体化修复假体的可能性。方法（1）应用三维重建技术获得下颌骨连续性缺损的三维重建模型;（2）完成下颌骨连续性缺损的个体化修复假体的生物陶瓷置换。结果应用三维重建技术,能够准确地获得与下颌骨连续性缺损相匹配的个体化生物陶瓷修复体。结论三维重建技术与生物陶瓷相结合可以完成下颌骨连续性缺损的个体化修复,这种技术可以满足下颌骨连续性缺损的外形和功能重建的需要。     

计算机三维重建华虻复眼性特异小网膜细胞结构

本文在计算机三维重建的基础上讨论了华虻复眼小网膜性特异结构与功能的关系,三维模型展示了中央小网膜细胞和部分外周小网膜细胞的空间构型及相互关系.在生物组织连续切片三维重建的对位技术方面,摸索了一套方法.保证了在Cromemco微机系统上实现对华虻复眼小网膜细胞的三维重建.证实了复眼光感受器性特化区R_7和R_8为并行排列的形式,并与非性特化区的R_7、R_8进行了比较.     

多视角三维重建技术在石制品研究中的应用

三维重建技术已广泛应用于考古发掘、研究、展示等各个领域。通过对石制品的三维重建,可以帮助我们获取更加精准的数据信息,一些过去只能估算的测量指标得以精准化,由此催生出许多新的研究方法。本文回顾了十几年来三维重建方法在石器分析研究中的实例,如石制品的表面积、体积测量,台面、砾石面/人工面、片疤的精确数值获取,以及三维空间中打击方向、角度的判定等等,有效推动了石制品的深入研究。不同的三维重建技术各有优劣,多视角三维重建技术不受设备、场地、人员技术要求的限制,能够快速、准确地建立石制品的三维模型,并且获取如面积、体积、角度等通常难以准确测量的数据信息,其生成的点云、数字高程模型、正射影像图等还可以导入其他软件拓展使用。该技术的诸多优点,使其可以成为旧石器考古发掘、研究的日常工具。     

CT三维重建技术在肺磨玻璃结节诊断中的研究进展

三维重建技术在肺磨玻璃结节(ground-glass opacity,GGO)鉴别诊断中具有重要作用,比传统的二维CT对于相关图像参数的测量更准确,更完整。近年来国内外学者对三维重建下GGO影像学变量包括结节平均直径、体积及CT值等在非典型腺瘤样增生(atypical adenomatous hyperplasia,AAH)、原位癌(adenocarcinoma in situ,AIS)、微浸润腺癌(minimally invasive adenocarcinoma,MIA)及ⅠA期浸润性腺癌(invasive adenocarcinoma,IAC)的鉴别诊断方面的研究越来越多样化。对作为早期肺癌病灶的GGO,三维重建测量可从其体积-倍增时间、CT值的峰度和偏度、平均CT值及CT值分布的方差等参数来进行术前良恶性评估。本文针对近年来国内外对三维重建处理技术在GGO诊断中的研究予以回顾和总结,旨在对GGO临床诊治予以提示。     

小鼠海马锥体细胞树突棘形态的电镜三维重建

大多数神经元的复杂三维结构是很难直接观察的。激光扫描共聚焦显微镜技术结合染料标记技术可以重建神经元的三维形态,但精细结构的识别需要电子显微镜。利用透射电子显微镜技术,可以得到连续超薄组织切片的高分辨率图像,结合计算机支持的三维重建技术就可进一步获得神经细胞精细结构的三维信息。通过电镜三维重建技术对未成熟和成熟小鼠海马锥体细胞树突棘的形态进行了观察和分析,并对其关键步骤的操作技巧进行了重点说明。实验结果为进一步利用成像技术研究树突棘的结构、功能和可塑性提供了重要信息。     

Unified 3-D structure and projection orientation refinement using quasi-Newton algorithm

We describe an algorithm for simultaneous refinement of a three-dimensional (3-D) density map and of the orientation parameters of two-dimensional (2-D) projections that are used to reconstruct this map. The application is in electron microscopy, where the 3-D structure of a protein has to be determined from a set of 2-D projections collected at random but initially unknown angles. The design of the algorithm is based on the assumption that initial low resolution approximation of the density map and reasonable guesses for orientation parameters are available. Thus, the algorithm is applicable in final stages of the structure refinement, when the quality of the results is of main concern. We define the objective function to be minimized in real space and solve the resulting nonlinear optimization problem using a Quasi-Newton algorithm. We calculate analytical derivatives with respect to density distribution and the finite difference approximations of derivatives with respect to orientation parameters. We demonstrate that calculation of derivatives is robust with respect to noise in the data. This is due to the fact that noise is annihilated by the back-projection operations. Our algorithm is distinguished from other orientation refinement methods (i) by the simultaneous update of the density map and orientation parameters resulting in a highly efficient computational scheme and (ii) by the high quality of the results produced by a direct minimization of the discrepancy between the 2-D data and the projected views of the reconstructed 3-D structure. We demonstrate the speed and accuracy of our method by using simulated data.     

基于VTK的医学图像三维可视化系统

医学图像的三维可视化可以通过可视化工具包（VTK）提供的API实现。VTK是医学图像可视化的开法工具包,它把可视化的算法封装起来,利用简单的代码生成所需图形。基于VTK的医学图像三维可视化系统阐述了如何借助VTKAPI读入二维医学图像序列、操作二维图像、重建三维图像以及进行三维图像可视化的全套方案,为临床医生的诊断、治疗提供了有益的途径。     

A statistical approach to computer processing of cryo-electron microscope images: virion classification and 3-D reconstruction

The scattering density of the virus is represented as a truncated weighted sum of orthonormal basis functions in spherical coordinates, where the angular dependence of each basis function has icosahedral symmetry. A statistical model of the image formation process is proposed and the maximum likelihood estimation method computed by an expectation-maximization algorithm is used to estimate the weights in the sum and thereby compute a 3-D reconstruction of the virus particle. If multiple types of virus particle are represented in the boxed images then multiple 3-D reconstructions are computed simultaneously without first requiring that the type of particle shown in each boxed image be determined. Examples of the procedure are described for viruses with known structure: (1). 3-D reconstruction of Flockhouse Virus from experimental images, (2). 3-D reconstruction of the capsid of Nudaurelia Omega Capensis Virus from synthetic images, and (3). 3-D reconstruction of both the capsid and the procapsid of Nudaurelia Omega Capensis Virus from a mixture of unclassified synthetic images.     

Automatic determination of anatomical coordinate systems for three-dimensional bone models of the isolated human knee

The combination of three-dimensional (3-D) models with dual fluoroscopy is increasingly popular for evaluating joint function in vivo. Applying these modalities to study knee motion with high accuracy requires reliable anatomical coordinate systems (ACSs) for the femur and tibia. Therefore, a robust method for creating ACSs from 3-D models of the femur and tibia is required. We present and evaluate an automated method for constructing ACSs for the distal femur and proximal tibia based solely on 3-D bone models. The algorithm requires no observer interactions and uses model cross-sectional area, center of mass, principal axes of inertia, and cylindrical surface fitting to construct the ACSs. The algorithm was applied to the femur and tibia of 10 (unpaired) human cadaveric knees. Due to the automated nature of the algorithm, the within specimen variability is zero for a given bone model. The algorithm’s repeatability was evaluated by calculating variability in ACS location and orientation across specimens. Differences in ACS location and orientation between specimens were low (<1.5 mm and <2.5°). Variability arose primarily from natural anatomical and morphological differences between specimens. The presented algorithm provides an alternative method for automatically determining subject-specific ACSs from the distal femur and proximal tibia.     

A microcomputer based system for three-dimensional reconstructions from tomographic or histologic sections

The reconstructions of three-dimensional (3-D) objects from serial two-dimensional (2-D) images can contribute to the understanding of many biologic structures, from organelles to organs and tissues. The 3-D reconstruction of sections can be divided into several major tasks: image acquisition, alignment of slices, internal object definition, object reconstruction and rotation of the completed image. A fast, versatile, interactive system was devised for the reconstruction of 3-D objects from serial 2-D images using a low-cost microcomputer, original programs and commercial software. The system allows reconstruction from any serial images, e.g., electron micrographs, histologic sections or computed tomograms. A photographic image or a microscopic field is acquired into the computer memory using a video digitizer. Slices are superimposed and aligned to each other using an operator-interactive program. A contour-(edge-) finding algorithm isolates an object of interest from the background image by "subtraction" of the image from an overlaid, slightly shifted identical image. Contours for each slice are input to a reconstruction procedure, which calculates the x, y and z coordinates of every point in a slice and the thickness and number of slices. It then calculates the illumination for every point using a given point source of light and an intensity-fading coefficient. Finally, the points are represented by cubes to provide dimension and reflective surfaces. A cube of appropriate shade and color represents in 2-D the equivalent of a 3-D object; this results in a very effective 3-D image. The reconstruction is rotated by recalculating the positions of every point defining the object and rebuilding the image.(ABSTRACT TRUNCATED AT 250 WORDS)     

A three-dimensional model of the human pulmonary acinus.

A three-dimensional (3-D) model of the human pulmonary acinus, a gas exchange unit, is constructed with a labyrinthine algorithm generating branching ducts that fill a given space completely. Branching down to the third respiratory bronchioles is generated with the proposed algorithm. A subacinus, a region supplied by the last respiratory bronchiole, is approximated to be a set of cubic cells with a side dimension of 0.5 mm. The labyrinthine algorithm is used to determine a pathway through all cells only once, except at branching points with the smallest path lengths. In choosing each step of a pathway, random variables are used. Resulting labyrinths have equal mean path lengths and equal surface areas of inner walls. An alveolus can be generated by attaching alveolar septa, 0.25 mm long and 0.1 mm wide, to the inner walls. Total alveolar surface area and numbers of alveolar ducts, alveolar sacs, and alveoli in our 3-D acinar model are in good accordance with those reported in the literature.     

新疆阿魏特征显微结构的三维原位无损研究

利用新型第三代高亮度同步辐射光源相衬成像技术,可实现弱吸收(主要含碳、氢、氧和氮等元素)物质材料特征结构的无损三维鉴定。以具有极高药用价值的新疆地产药材——阿魏(Ferula)为研究对象,采用同步辐射高分辨X射线相衬显微CT技术,并结合相位恢复算法,有效解析和评价了新疆阿魏(F.sinkiangensis)的三维特征结构,极大提高了对药材类生物样品的显微结构和密度的分辨能力,从而为新疆阿魏的特征分辨、品质鉴定和真伪识别提供了一种直观可靠的三维可视化新手段。     

Accelerated Optical Projection Tomography Applied to In Vivo Imaging of Zebrafish

Optical projection tomography (OPT) provides a non-invasive 3-D imaging modality that can be applied to longitudinal studies of live disease models, including in zebrafish. Current limitations include the requirement of a minimum number of angular projections for reconstruction of reasonable OPT images using filtered back projection (FBP), which is typically several hundred, leading to acquisition times of several minutes. It is highly desirable to decrease the number of required angular projections to decrease both the total acquisition time and the light dose to the sample. This is particularly important to enable longitudinal studies, which involve measurements of the same fish at different time points. In this work, we demonstrate that the use of an iterative algorithm to reconstruct sparsely sampled OPT data sets can provide useful 3-D images with 50 or fewer projections, thereby significantly decreasing the minimum acquisition time and light dose while maintaining image quality. A transgenic zebrafish embryo with fluorescent labelling of the vasculature was imaged to acquire densely sampled (800 projections) and under-sampled data sets of transmitted and fluorescence projection images. The under-sampled OPT data sets were reconstructed using an iterative total variation-based image reconstruction algorithm and compared against FBP reconstructions of the densely sampled data sets. To illustrate the potential for quantitative analysis following rapid OPT data acquisition, a Hessian-based method was applied to automatically segment the reconstructed images to select the vasculature network. Results showed that 3-D images of the zebrafish embryo and its vasculature of sufficient visual quality for quantitative analysis can be reconstructed using the iterative algorithm from only 32 projections—achieving up to 28 times improvement in imaging speed and leading to total acquisition times of a few seconds.     

A genetic algorithm based molecular modeling technique for RNA stem-loop structures.

A new modeling technique for arriving at the three dimensional (3-D) structure of an RNA stem-loop has been developed based on a conformational search by a genetic algorithm and the following refinement by energy minimization. The genetic algorithm simultaneously optimizes a population of conformations in the predefined conformational space and generates 3-D models of RNA. The fitness function to be optimized by the algorithm has been defined to reflect the satisfaction of known conformational constraints. In addition to a term for distance constraints, the fitness function contains a term to constrain each local conformation near to a prepared template conformation. The technique has been applied to the two loops of tRNA, the anticodon loop and the T-loop, and has found good models with small root mean square deviations from the crystal structure. Slightly different models have also been found for the anticodon loop. The analysis of a collection of alternative models obtained has revealed statistical features of local variations at each base position.     

An ab initio algorithm for low-resolution 3-D reconstructions from cryoelectron microscopy images

A statistical method for determining low-resolution 3-D reconstructions of virus particles from cryoelectron microscope images by an ab initio algorithm is described. The method begins with a novel linear reconstruction method that generates a spherically symmetric reconstruction, which is followed by a nonlinear reconstruction method implementing an expectation-maximization procedure using the spherically symmetric reconstruction as an initial condition and resulting in a reconstruction with icosahedral symmetry. An important characteristic of the complete method is that very little need be known about the particle before the reconstruction is computed, in particular, only the type of symmetry and inner and outer radii. The method is demonstrated on synthetic cowpea mosaic virus data, and its robustness to 5% errors in the contrast transfer function, 5% errors in the location of the center of the particles in the images, and 5% distortion in the 3-D structure from which the images are derived is demonstrated numerically.