基于工作流的医学图像三维可视化平台

针对当今医学影像领域的软件工具包普遍缺乏有效的算法集成机制和友好的用户图形界面的情况,采用Java2平台企业版（J2EE）的体系结构开发了一种基于工作流的医学图像三维可视化平台——POMI。在该平台上实现了一个切片数据重建及可视化模块,该模块以工作流机制集成了一系列算法和可视化工具。利用该模块完成了对虚拟中国人的部分切片数据分析、三维重建以及结果的可视化。基于POMI平台这种易于集成数据源和算法工具的高可扩展性结构,可以为医学影像技术领域的研究人员提供一个理想的集成分析平台。     

无线传感网3D-MCM封装结构的设计与实现

设计和实现了一种新型的三维多芯片组件(3D-MCM).采用融合了FCOB(flip-chip on board)、COB(chip on board)、BGA(ball grid array)等技术的三维封装(3D packaging)形式,通过倒装焊和引线键合等互连技术在高密度多层有机基板上实现了塑封BGA器件和裸芯片的混载集成.对器件结构的散热特性进行了数值模拟,并对热可靠性进行了评估.实现了电功能和热机械可靠性,达到设计要求并付诸应用.     

Super deep 3D images from a 3D omnifocus video camera

When using stereographic image pairs to create three-dimensional (3D) images, a deep depth of field in the original scene enhances the depth perception in the 3D image. The omnifocus video camera has no depth of field limitations and produces images that are in focus throughout. By installing an attachment on the omnifocus video camera, real-time super deep stereoscopic pairs of video images were obtained. The deeper depth of field creates a larger perspective image shift, which makes greater demands on the binocular fusion of human vision. A means of reducing the perspective shift without harming the depth of field was found.     

基于图像的启发式三维火焰重建算法

研究了火焰的重建,为改进现有稀疏视角输入下的层析成像算法的重建精度,提出了一种基于图像的启发式火焰重建方法。该重建方法通过迭代优化求解能量约束模型,实现对火焰三维温度场的重建。算法允许复杂的成像模型应用于重建过程中,使渲染过程更接近火焰真实成像过程,并对数据平滑性进行约束,以提高重建结果质量。算法在迭代过程中使用启发式规则引导温度场数据调整,使算法快速收敛,并通过使用图形处理器加速重建过程。使用模拟数据和真实捕获数据进行实验,结果表明,与现有方法相比,提出的方法有效提高了重建结果的精度及平滑性,验证了提出方法的有效性。     

3D scanning data processing and registration for the construction of urban scenes via image methods

The difficulty of the 3D registration mainly lies in the huge computation for a precise alignment, especially for large data of urban scenes. In this paper, we proposed an algorithm that converts this 3D problem into 2D case. The main idea is to map the point cloud onto the image. Then, SIFT algorithm is adopted to detect the key points of the images, and key points from two images corresponding to the two point clouds ready to be registered are matched to form several pairs. Next, the key point pairs construct an intrinsic link between the images. From the one-to-one correspondence between pixel and point, this relation can be converted back to 3D space, according to which a transform matrix can be consequently established. The resultant matrix aims at guiding the spatial transform to achieve an ideal 3D registration. Later experiments illustrate that it will obtain a preferable result in much less time.     

Topological elevation connection analysis for 3D line detection from dense airborne LIDAR data

This paper proposes a kernel-based strategy to analyze the distribution of local point clouds and detect 3D lines from dense airborne LIght Detection and Ranging (LIDAR) data. The proposed method, namely topological elevation connection (TEC) analysis, employs geometric criteria with an automatic procedure instead of threshold operation. The focused targets include flat roofs with parapets, step roofs, hipped roofs, and gable roofs. By comparing with reference data, the accuracy between the detected lines and reference data can reach within 0.2?m. Three-dimensional boundaries and structure lines are essential for building modeling and data registration. Many related works have focused on the collection of co-planar LIDAR points to calculate intersection lines with optimized thresholds. In addition, they did not focus on parapets because of the limitations of developed assumptions and the criteria used. It is crucial to analyze the local point distribution for the automation improvement of detection processes. The major objective is to automatically detect 3D lines using the TEC analysis instead of threshold selection. The interesting targets include building boundaries and a variety of rooftops. The core concept of TEC is that the local relief along the alignment must be smoother than the local relief across the alignment. All consecutive point clouds, which belong to one line, must be sufficient for progressive elevations along the alignment and the linear shape. In the validation, the detected results are compared with reference data. The comparisons indicate that the proposed scheme can reach a detection accuracy of 0.2 m and provide a higher degree of modeling automation for varied building types.     

Bone segmentation and 3D visualization of CT images for traumatic pelvic injuries

Pelvic bone segmentation is a vital step in analyzing pelvic CT images, which assists physicians with diagnostic decision making in cases of traumatic pelvic injuries. Due to the limited resolution of the original CT images and the complexity of pelvic structures and their possible fractures, automatic pelvic bone segmentation in multiple CT slices is very difficult. In this study, an automatic pelvic bone segmentation approach is proposed using the combination of anatomical knowledge and computational techniques. It is developed for solving the problem of accurate and efficient bone segmentation using multiple consecutive pelvic CT slices obtained from each patient. Our proposed segmentation method is able to handle variation of bone shapes between slices there by making it less susceptible to inter‐personal variability between different patients' data. Moreover, the designed training models are validated using a cross‐validation process to demonstrate the effectiveness. The algorithm's capability is tested on a set of 20 CT data sets. Successful segmentation results and quantitative evaluations are present to demonstrate the effectiveness and robustness of proposed algorithm, well suited for pelvic bone segmentation purposes.     

3D multiwavelet based block coding algorithm for compression of volumetric medical images

Three dimensional (3D) medical images possess some specific characteristics that should be utilized by an efficient compression scheme. In this article, one such compression scheme for volumetric 3D medical image data is presented. Two processes involved in this scheme are decorrelation and encoding. Decorrelation of the 3D data is realized through 3D multiwavelet transform with apt prefiltering so as to give good representation of the image which could be exploited by the encoder. Encoding is done through proposed Block Coding Algorithm, which is embedded, block based, and wavelet transform coding algorithm without maintaining any list structures. The idea behind this algorithm is to sort the 3D transform coefficients in to a 1D array with respect to declining thresholds and to use state table to keep track of the blocks and coefficients that has been coded. In the experiment conducted on various 3D magnetic resonance and computed tomography images of human brain with multiwavelets such as Geronimo–Hardin–Massopust, Chui‐Lian, and orthogonal symmetric/antisymmetric (SA4), efficiency of the proposed scheme was weighed against the state of art encoders such as 3D Set Partitioning in Hierarchical Trees, 2D Set Partitioned Embedded BloCK Coder, and No List SPIHT. Attributes used for performance measurements are peak signal to noise ratio, bit rate, and structural similarity index of reconstructed image with respect to original image. © 2014 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 24, 182–192, 2014     

3D boundary recovery by constrained Delaunay tetrahedralization

Three‐dimensional boundary recovery is a fundamental problem in mesh generation. In this paper, we propose a practical algorithm for solving this problem. Our algorithm is based on the construction of a constrained Delaunay tetrahedralization (CDT) for a set of constraints (segments and facets). The algorithm adds additional points (so‐called Steiner points) on segments only. The Steiner points are chosen in such a way that the resulting subsegments are Delaunay and their lengths are not unnecessarily short. It is theoretically guaranteed that the facets can be recovered without using Steiner points. The complexity of this algorithm is analyzed. The proposed algorithm has been implemented. Its performance is reported through various application examples. Copyright © 2010 John Wiley & Sons, Ltd.     

Flying triangulation--an optical 3D sensor for the motion-robust acquisition of complex objects

Three-dimensional (3D) shape acquisition is difficult if an all-around measurement of an object is desired or if a relative motion between object and sensor is unavoidable. An optical sensor principle is presented-we call it "flying triangulation"-that enables a motion-robust acquisition of 3D surface topography. It combines a simple handheld sensor with sophisticated registration algorithms. An easy acquisition of complex objects is possible-just by freely hand-guiding the sensor around the object. Real-time feedback of the sequential measurement results enables a comfortable handling for the user. No tracking is necessary. In contrast to most other eligible sensors, the presented sensor generates 3D data from each single camera image.     

Nonintrusive coupling of 3D and 2D laminated composite models based on finite element 3D recovery

In order to simulate the mechanical behavior of large structures assembled from thin composite panels, we propose a coupling technique, which substitutes local 3D models for the global plate model in the critical zones where plate modeling is inadequate. The transition from 3D to 2D is based on stress and displacement distributions associated with Saint‐Venant problems, which are precalculated automatically for a simple 3D cell. The hybrid plate/3D model is obtained after convergence of a series of iterations between a global plate model of the structure and localized 3D models of the critical zones. This technique is nonintrusive because the global calculations can be carried out using commercial software. Evaluation tests show that convergence is fast and that the resulting hybrid model is very close to a full 3D model. Copyright © 2014 John Wiley & Sons, Ltd.     

Generation and quality improvement of 3D models from silhouettes of 2D images

The shape-from-silhouette (SFS) method has been widely used in 3D shape reconstruction. It uses silhouettes of a series of 2D images captured from multiple viewpoints of an object to generate a 3D model that describes the visual hull of the object. The SFS method faces an inherent problem that virtual features appear all over the model. In addition, concavities on the object may wrongly be modeled as convex shapes because they are invisible on image silhouettes. The purpose of this study is to propose a method to generate a 3D model from silhouettes of multiple images and propose a quality improvement method to overcome the above-mentioned problems. The 3D modeling method focuses on accurate evaluation of 3D points intersected by all polyhedra from different views and the removal of poor meshes on triangulation. The quality improvement method is essentially an iterative procedure, which for smoothing the model and eliminating virtual features and artifacts, while preserving the consistency of all silhouettes. The proposed method is to be used for product presentations in e-commerce, in which the 3D model must be covered with color texture of an object. Several examples are presented to illustrate the capability of the proposed method.     

基于自适应BM3D的侧扫声纳图像散斑降噪

侧扫声纳(SSS)是一种利用声波的水下传播特性完成水下探测的电子设备。因为侧扫声纳利用回波强度成像,所以不可避免地引入散斑噪声。本文针对散斑噪声,提出了基于自适应三维块匹配滤波(BM3D)的侧扫声纳图像散斑降噪方法。该算法首先对SSS图像进行幂变换和对数变换,采用小波变换估计整体图像噪声,同时用局部噪声估计结果更新BM3D算法的参数。然后本文算法比较全局估计和局部估计的结果,选择最合适的参数解决噪声分布不均匀的问题。实验结果表明,本文改进的BM3D算法能有效地降低SSS图像中的散斑噪声,获得良好的视觉效果。本文算法的等效视数至少提高了6.83%,散斑抑制指数低于传统方法,散斑抑制和平均保存指数至少减少了3.30%。该方法主要用于声纳图像降噪,对于超声、雷达或OCT图像等受散斑噪声污染的信号也有一定的实用价值。     

Simulated radiance profiles for automating the interpretation of airborne passive multi-spectral infrared images

Methodology is developed for simulating the radiance profiles acquired from airborne passive multispectral infrared imaging measurements of ground sources of volatile organic compounds (VOCs). The simulation model allows the superposition of pure-component laboratory spectra of VOCs onto spectral backgrounds that simulate those acquired during field measurements conducted with a downward-looking infrared line scanner mounted on an aircraft flying at an altitude of 2000-3000 ft (approximately 600-900 m). Wavelength selectivity in the line scanner is accomplished through the use of a multichannel Hg:Cd:Te detector with up to 16 integrated optical filters. These filters allow the detection of absorption and emission signatures of VOCs superimposed on the upwelling infrared background radiance within the instrumental field of view (FOV). By combining simulated radiance profiles containing analyte signatures with field-collected background signatures, supervised pattern recognition methods can be employed to train automated classifiers for use in detecting the signatures of VOCs during field measurements. The targeted application for this methodology is the use of the imaging system to detect releases of VOCs during emergency response scenarios. In the work described here, the simulation model is combined with piecewise linear discriminant analysis to build automated classifiers for detecting ethanol and methanol. Field data collected during controlled releases of ethanol, as well as during a methanol release from an industrial facility, are used to evaluate the methodology.     

Bias-heating recovery of MWCNT gas sensor

A sensor was made using Au/Cr electrodes on a glass substrate and a thin carbon multiwall nanotube film printed between them. A bias-heating method was used completely to desorb gas molecules and restore its initial conductance. The temperature of the thin carbon nanotube film varied depending on the magnitude of the voltage used, and this relationship was investigated. After being used to detect NO₂, the sensor returned to its initial conductance. This method enables complete recovery without additional processing steps, such as the fabrication of heat structure and ambient heating.     

Optical fiber-based laser remote sensor for airborne measurement of wind velocity and turbulence

We discuss an optical fiber-based continuous-wave coherent laser system for measuring the wind speed in undisturbed air ahead of an aircraft. The operational principles of the instrument are described, and estimates of performance are presented. The instrument is demonstrated as a single line of sight, and data from the inaugural test flight of August 2010 is presented. The system was successfully operated under various atmospheric conditions, including cloud and clear air up to 12?km (40,300?ft).     

CVD growth of fingerprint-like patterned 3D graphene film for an ultrasensitive pressure sensor

Nano Research - With the rapid development of wearable devices, flexible pressure sensors with high sensitivity and wide workable range are highly desired. In nature, there are many well-adapted...     

Virtual image correlation of magnetic resonance images for 3D geometric modelling of pelvic organs

Numerical simulation of pelvic system could lead to a better understanding of common pathology through objective and reliable analyses of pelvic mobility according to mechanical principles. In clinical context, patient‐specific simulation has the potential for a proper patient‐personalised cure. For this purpose, a simulable 3D geometrical model, well suited to patient anatomy, is required. However, the geometric modelling of pelvic system from medical images (MRI) is a complex operator‐dependent and time‐consuming process, not adapted to patient‐specific applications. This paper is addressing this challenging computational problem. The objective is to develop a technique, providing a smooth, consistent, and readily usable 3D geometrical model, seamlessly from image to simulation. In this paper, we use a generic topologically‐simplified B‐Spline model to represent pelvic organs. The presented paper develops a Virtual Image Correlation method to find the best correlation between the geometry and the image. The final reconstructed geometrical model is to be compatible with meshing and finite element simulation. Then, a variety of tests are performed to prove the concept, through both prototypical and pelvic models. Finally, since the pelvic system is complex, including structures hardly identifiable in MRI, some feasible solutions to introduce more complex pelvic models are also discussed.     

大规模3DGIS场景的多通道渲染算法研究

为了由多个计算机节点协同完成大规模三维地理信息系统(3DGIS)场景的渲染和显示,提出了一种基于分布式计算机体系结构的多通道渲染算法(3DGIS multi-channelrendering algorithm,GMCR)。三维地理信息系统同其他类似算法相比,该算法作了两项改进:(1)采用视锥组合计算方法将大规模三维场景分割为若干子场景并分配给不同计算机节点处理,可以保证场景拼接处的空间连续性和不变形性;(2)采用消息机制协调计算机节点的渲染处理与显示步调,以控制子场景的状态同步和显示同步。该算法简单易行、效果突出,利用多台低端设备实现了大规模3D场景渲染与显示,可以完成高端设备不能够实现的超大规模3D场景。以3DGIS城市交通系统演示环境实验为例,验证了该算法的可行性,结果表明GMCR方法可以支持多达185个计算机节点进行超大规模的3DGIS场景渲染。