基于凸包算法的三维表面重建中边缘轮廓提取

在三维表面重建过程中，边缘轮廓的提取起着关键的作用。为了对头部CT图片中的颅骨边缘进行有效地提取，提出利用平面凸包进行边缘轮廓提取的方法。利用该方法提取出头部CT图像中的颅骨边缘，并将其作为三维表面重建中的轮廓输人，取得了良好的效果。同时，将通过该方法得到的颅骨边缘应用于基于颅骨的三维面貌复原技术研究中，为面貌复原技术的发展提供了新的思路。     

一种新的处理非封闭图像表面的三维表面提取算法研究

对皮下组织表面 ,例如表皮·真皮组织交界面进行定性和定量的检测已经越来越成为医学、生物学等诸多学科中有关人体皮肤的课题中不可或缺的重要研究手段 在利用计算机自动检测皮下组织表面的过程中 ,涉及到的一个关键问题就是如何从图像中提取边界成分 动态边界模型 (snake)作为一种边界提取算法被广泛地应用于这类问题中 在这个算法的基础上 ,提出了可以从断层图像中将对象的三维表面提取出来的算法———动态开放表面模型 并应用此算法开发了一套皮下组织表面自动提取重建系统 通过对共焦点显微镜断层图像处理的实验 ,验证了本系统的实用性和可靠性     

一种全自动的三维肺实质分割算法

精确的肺实质三维分割是对肺部病变进行计算机辅助检测或诊断的必要步骤,但复杂的胸部组织结构使得肺实质的精确分割变得较为困难。提出了一种结合阈值分割、区域增长、改进波阵面法等多种方法的全自动的三维肺实质分割方法。该方法使用计算机视觉及图像分析小组/国际肺癌早期行动计划（Computer Vision and Image Analysis Group/International Early Lung Cancer Action Program,VIA/I-ELCAP）和肺部图像数据库联盟（Lung Image Database Consortium,LIDC）提供的数据进行实验,结果证明这个方法能快速、精确地得到肺实质。     

基于反求工程的牙颌模型的建立

目的:利用三维激光扫描仪扫描全牙列模型,对获得的数据进行处理,重构牙颌的三维图形。方法:将获得的三维点云数据进行处理,包括数据平滑、特征提取、数据分割、自由曲面建模等实现牙颌的三维重构。结论:得到牙颌的三维重建数字模型,牙颌模型的建立将极大地提高后期医生设计牙齿的质量与效率。     

电容层析成像系统三维图像重建的研究

探讨了电容层析成像(ECT)系统中利用二维断层图像进行三维表面重建并由三维图像求取两相流中离散相体积和观察其空间位置的方法。首先对二维断层图像序列进行轮廓抽取和细线化，然后进行轮廓匹配和轮廓插值并进行表面重建。初步的仿真结果表明，使用的三维重建算法简单、重建精度高、成像速率快。     

New technique of obtaining visually perceived positions of 3-D images using movements of users’ bodies

Three-dimensional (3-D) images are perceived as images that float in front of the screens of 3-D displays. Users should be able to interact with these images instantaneously and accurately in applications where their bodies actually seen by them interact with the images. However, conventional techniques using just binocular disparity are too slow and inaccurate. Therefore, we propose a new technique where the visually perceived positions of images are obtained from the body movements of users. The feasibility of this technique was evaluated in an experiment using the positions obtained from users as they reached out to touch the images. These positions were closer to the visually perceived positions of the images than those calculated from binocular disparity. These findings demonstrate the feasibility of the proposed technique for 3-D interactive applications.     

A novel feature-based tracking approach to the detection, localization, and 3-D reconstruction of internal defects in hardwood logs using computer tomography

A novel feature-based tracking approach based on the Kalman filter is proposed for the detection, localization, and 3-D reconstruction of internal defects in hardwood logs from cross-sectional computer tomography (CT) images. The defects are simultaneously detected, classified, localized, and reconstructed in 3-D space, making the proposed scheme computationally much more efficient than existing methods where the defects are detected and localized independently in individual CT image slices and the 3-D reconstruction of the defects accomplished via correspondence analysis across the various CT image slices. Robust techniques for defect detection and classification are proposed. Defect class-specific tracking schemes based on the Kalman filter, B-spline contour approximation, and Snakes contour fitting are designed which use the geometric parameters of the defect contours as the tracking variables. Experimental results on cross-sectional CT images of hardwood logs from select species such as white ash, hard maple, and red oak are presented.     

Affine-based registration of CT and MR modality images of human brain using multiresolution approaches: comparative study on genetic algorithm and particle swarm optimization

We present a non-linear 2-D/2-D affine registration technique for MR and CT modality images of section of human brain. Automatic registration is achieved by maximization of a similarity metric, which is the correlation function of two images. The proposed method has been implemented by choosing a realistic, practical transformation and optimization techniques. Correlation-based similarity metric should be maximal when two images are perfectly aligned. Since similarity metric is a non-convex function and contains many local optima, choice of search strategy for optimization is important in registration problem. Many optimization schemes are existing, most of which are local and require a starting point. In present study we have implemented genetic algorithm and particle swarm optimization technique to overcome this problem. A comparative study shows the superiority and robustness of swarm methodology over genetic approach.     

基于霍特林变换的三维医学图像快速配准算法

提出了一种新的基于霍特林变换的三维医学图像快速配准算法,这是将数据压缩技术用于图像配准的一种创新性尝试。传统的基于灰度的方法需要考虑整个三维数据的灰度信息,计算复杂度大,无法满足临床需要。论文将Otus算法与互信息量技术相结合提出了一种新的图像分割算法,用于提取待配准物体,从而得到物体的向量表示;然后通过霍特林变换的平移和旋转性质完成配准。实验结果表明此方法能准确,快速地处理图像刚性配准问题,特别适用于三维医学图像的配准。     

Image Processing for Planetary Limb/Terminator Extraction

A novel image segmentation technique for extracting limbs and terminators of planetary bodies is proposed. Conventional edge-based histogramming approaches are employed to trace object boundaries. The limb and terminator bifurcation is achieved by locating the harmonized segment in the two equations representing the 2-D parametrized boundary curve. This technique is quite efficient and robust. Although only spherical (near-spherical) planetary bodies in full view are addressed in detail, the proposed methodology can be extended to accommodate partially viewed and/or arbitrary-shaped objects; formulations for these cases are also given. Real planetary images from Voyager 1 and 2 serve as representative test cases to verify the proposed methodology.     

A Hough transform for detecting the location and orientation ofthree-dimensional surfaces via color encoded spots

Video-rate three-dimensional (3-D) acquisition is desirable, in particular for capturing the mouth's shape when modeling the vocal tract. In a new structured light technique, scenes are illuminated by an array of circular spots which are color encoded to resolve spatial ambiguity. The position and shape of the imaged spots depend on the location and orientation of the illuminated 3-D surface. We present a novel 3-D Hough transform (HT) to detect 3-D surface location and orientation via the imaged spots, with voting constraints applied to maximize potential accuracy. This new technique is demonstrated to successfully extract the 3-D data for a moving face from images acquired at video-rate.     

Comprehensive Cardiovascular Image Analysis Using MR and CT at Siemens Corporate Research

At Siemens Corporate Research we have created a set of tools for the analysis of MR and CT cardiovascular images in the applications Argus, Vessel View, and Proteus. Argus is designed to assess cardiovascular function by reporting measures of morphology and tissue health using a 2-D approach. Vessel View, a 3-D application, is capable of quantifying vascular integrity and provides tools for segmenting vessels. Lastly, Proteus has functionality for registering 3-D cardiac data sets (e.g., MR and CT). Taken together, these applications allow for a comprehensive analysis of MR and CT cardiovascular studies. Throughout this paper we will illustrate the capabilities of our tools via their application to an actual clinical case. Our contribution lies in combining several computer vision technologies and applying them to practical, real world problems.     

二维图像特征点自主提取算法研究

采用概率论理论,对二维图像进行灰度统计分析,采用计算标准差方法,对图像特征点区域定位并提取特征点.该方法提取特征点,仅需对抽样象素区域进行灰度标准差分析,避免了提取图像特征点,根据被处理图像的一些先验信息,利用试探方法确定阈值的局限性.通过分别对具有弱纹理及包含复杂背景的多物体自然二维图像的特征提取,证实了所提方法的有效性和可靠性,可满足机器视觉系统中自主、实时识别与提取二维图像特征点要求.     

序列剖面图像的三维重建和显示

本文提出了一种新的序列剖面图像三维重建和显示方法,即双目视差法。     

3-D modeling of remote dynamic situations employing mobile stereocameras

We propose a technique for 3-D modeling of objects in remote dynamic situations employing mobile stereocameras. Since the proposed technique allows independent movement of the cameras employed, 3-D modeling under various environments, such as remote places, can be realized. Our technique has an advantage over others in that camera calibration is not prerequisite to the 3-D modeling before taking images. A 3-D modeling system is described that captures images of remote objects, transfers the images by analog airwaves, and recovers the 3-D shape of the object from the images. It is expected that this technique will improve the efficiency of image information transfer. In the experiment performed, a human walking in a remote place was modeled successfully in 3-D in a laboratory by image transfer. This work was presented in part at the 11th International Symposium on Artificial Life and Robotics, Oita, Japan, January 23–25, 2006     

虚拟手术系统技术现状

虚拟手术是近年来在国际上发展迅速的一个领域。通过利用虚拟现实技术,医生们可以模拟在由患者的CT或MRI数据所构建的病灶处三维图像上进行手术操作,对于确定病灶位置,制定最佳手术方案和保证手术成功都具有十分重要的意义。该文分别对虚拟手术技术中的图像分割技术、人体器官三维重建技术以及软组织变形技术等几个主要方面研究做出了介绍,并分析了其技术需求及技术关键相关问题,为进一步进行虚拟手术系统的研究工作打下了一定基础。     

Fingerprint recognition using mel-frequency cepstral coefficients

This paper presents a new fingerprint recognition method based on mel-frequency cepstral coefficients (MFCCs). In this method, cepstral features are extracted from a group of fingerprint images, which are transformed first to 1-D signals by lexicographic ordering. MFCCs and polynomial shape coefficients are extracted from these 1-D signals or their transforms to generate a database of features, which can be used to train a neural network. The fingerprint recognition can be performed by extracting features from any new fingerprint image with the same method used in the training phase. These features are tested with the neural network. The different domains are tested and compared for efficient feature extraction from the lexicographically ordered 1-D signals. Experimental results show the success of the proposed cepstral method for fingerprint recognition at low as well as high signal to noise ratios (SNRs). Results also show that the discrete cosine transform (DCT) is the most appropriate domain for feature extraction.     

Automated Planning and Optimization of Lumber Production Using Machine Vision and Computed Tomography

An automated system for planning and optimization of lumber production using Machine Vision and Computed Tomography (CT) is proposed. Cross-sectional CT images of hardwood logs are analyzed using machine vision algorithms. Internal defects in the hardwood logs pockets are identified and localized. A virtual in silico 3-D reconstruction of the hardwood log and its internal defects is generated using Kalman filter-based tracking algorithms. Various sawing operations are simulated on the virtual 3-D reconstruction of the log and the resulting virtual lumber products automatically graded using rules stipulated by the National Hardwood Lumber Association (NHLA). Knowledge of the internal log defects is suitably exploited to formulate sawing strategies that optimize the value yield recovery of the resulting lumber products. A prototype implementation shows significant gains in value yield recovery when compared with lumber processing strategies that use only the information derived from the external log structure.     

Fusion of range camera and photogrammetry: a systematic procedure for improving 3-D models metric accuracy

The generation of three-dimensional (3-D) digital models produced by optical technologies in some cases involves metric errors. This happens when small high-resolution 3-D images are assembled together in order to model a large object. In some applications, as for example 3-D modeling of Cultural Heritage, the problem of metric accuracy is a major issue and no methods are currently available for enhancing it. The authors present a procedure by which the metric reliability of the 3-D model, obtained through iterative alignments of many range maps, can be guaranteed to a known acceptable level. The goal is the integration of the 3-D range camera system with a close range digital photogrammetry technique. The basic idea is to generate a global coordinate system determined by the digital photogrammetric procedure, measuring the spatial coordinates of optical targets placed around the object to be modeled. Such coordinates, set as reference points, allow the proper rigid motion of few key range maps, including a portion of the targets, in the global reference system defined by photogrammetry. The other 3-D images are normally aligned around these locked images with usual iterative algorithms. Experimental results on an anthropomorphic test object, comparing the conventional and the proposed alignment method, are finally reported.