Showing papers on "3D reconstruction published in 1997"

External marker-based automatic congruencing: A new method of 3D reconstruction from serial sections

Abstract: Background Computer-based three-dimensional (3D) visualizations reconstructed from sectional images represent a valuable tool in biomedical research and medical diagnosis Particularly with those imaging techniques that provide virtual sections, such as CT, MRI, and CLSM, 3D reconstructions have become routine Reconstructions from physical sections, such as those used in histological preparations, have not experienced an equivalent breakthrough, due to inherent shortcomings in sectional preparation that impede automated image-processing and reconstruction The increased use of molecular techniques in morphological research, however, generates an overwhelming amount of 3D molecular information, stored within series of physical sections This valuable information can be fully appreciated and interpreted only through an adequate method of 3D visualization Methods and results:In this paper we present a new method for a reliable and largely automated 3D reconstruction from physically sectioned material The ‘EMAC‘ concept (External Marker-based Automatic Congruencing) successfully approaches the three major obstacles to automated 3D reconstruction from serial physical sections: misalignment, distortion, and staining variation It utilizes the objectivity of external markers for realignment of the sectional images and for geometric correction of distortion A self-adapting dynamic thresholding technique compensates for artifactual staining variation and automatically selects the desired object contours Conclusions Implemented on a low-cost hardware platform, EMAC provides a fast and efficient tool that largely facilitates the use of computer-based 3D visualization for the analysis of complex structural, molecular, and genetic information in morphological research Due to its conceptual versatility, EMAC can be easily adapted for a broad range of tasks, including all modern molecular-staining techniques, such as immunohistochemistry and in situ hybridization Anat Rec 248:583-602, 1997 © 1997 Wiley-Liss, Inc

Resolving occlusion in augmented reality: a contour based approach without 3D reconstruction

Abstract: We present a new approach for resolving occlusions in augmented reality. The main interest is that it does not require 3D reconstruction of the considered scene. Our idea is to use a contour based approach and to label each contour point as being "behind" or "in front of", depending on whether it is in front of or behind the virtual object. This labeling step only requires that the contours can be tracked from frame to frame. A proximity graph is then built in order to group the contours that belong to the same occluding object. Finally, we use some kind of active contours to accurately recover the mask of the occluding object.

Automatic reconstruction of 3D objects using a mobile monoscopic camera

Abstract: A method for the automatic reconstruction of 3D objects from multiple camera views for 3D multimedia applications is presented. Conventional 3D reconstruction techniques use equipment that restrict the flexibility of the user. In order to increase this flexibility, the presented method is characterized by a simple measurement environment, that consists of a new calibration pattern placed below the object allowing object and pattern acquisition simultaneously. This ensures, that each view can be calibrated individually. From these obtained calibrated camera views, a textured 3D wireframe model is estimated using a shape-from-silhouette approach and texture mapping of the original camera views. Experiments with this system have confirmed a significant gain of flexibility for the user and a drastic reduction of costs for technical equipment while ensuring comparable model quality as conventional reconstruction techniques at the same time.

Parametric shape-from-shading by radial basis functions

Abstract: We present a new method of shape from shading by using radial basis functions to parameterize the object depth. The radial basis functions are deformed by adjusting their centers, widths, and weights such that the intensity errors are minimized. The initial centers and widths are arranged hierarchically to speed up convergence and to stabilize the solution. Although the smoothness constraint is used, it can be eventually dropped out without causing instabilities in the solution. An important feature of our parametric shape-from-shading method is that it offers a unified framework for integration of multiple sensory information. We show that knowledge about surface depth and/or surface normals anywhere in the image can be easily incorporated into the shape from shading process. It is further demonstrated that even qualitative knowledge can be used in shape from shading to improve 3D reconstruction. Experimental comparisons of our method with several existing ones are made by using both synthetic and real images. Results show that our solution is more accurate than the others.

Three dimensional reconstruction with contrast transfer compensation from defocus series

Abstract: Cryo-electron microscopy provides the means to quantitatively study macromolecules in their native state. However, the original mass distribution of the macromolecule is distorted by the contrast transfer function (CTF) of the electron microscope. In addition, the zeros of the CTF put a practical limit on the resolution that can be achieved. Substantial improvement to the quality of the results can be accomplished by collecting the data using a series of defocus settings. Such data sets can be combined and the resolution can be extended beyond the first zero of the CTF. This procedure can be applied either at the stage of raw data, or more effectively at the stage of reconstructed volumes which have a high signal-to-noise ratio as a result of averaging over many projections. A method of threedimensional (3D) reconstruction that combines an algebraic, iterative 3D reconstruction technique with CTF correction is proposed. The potential to incorporate a priori knowledge into the reconstruction process is discussed. This approach was used to obtain a 3D reconstruction of the E. coli 70S ribosome from energy filtered cryo-images.

CT-based software for 3-D localization and reconstruction in stepping source brachytherapy

Abstract: Describes innovative software for catheter localization and 3D reconstruction in stepping-source brachytherapy applications. The patient information is a set of computed tomography (CT) slices, scanned during the implantation of brachytherapy catheters. Catheter geometry and patient anatomy are exported for use with dose calculation software modules. The errors produced by the system are also encouragingly low. Time savings were achieved compared with other traditional reconstruction techniques. Various automated procedures, 3D graphics and a user-friendly GUI have contributed to providing a powerful, comprehensive software tool that is directly useable in clinical practice.

C-arm calibration method for 3D reconstruction

Abstract: A C-arm calibration method for 3D reconstruction in an imaging system comprising an imaging source and an imaging plane utilizes a planar transformation for relating voxels in a voxel space and pixels in the imaging plane, and comprises the steps of: defining a source coordinate system in reference to the imaging source; defining a normal plane in the voxel space, not including the origin of the source coordinate system and being substantially normal to an optical axis from the source to the imaging plane; defining a relationship between the source coordinate system and another coordinate system, herein referred to as a world coordinate system, by transformation parameters; identifying pixel location coordinates for a respective pixel corresponding to each voxel in the normal plane by utilizing a planar to planar transformation; storing a value of a filtered image at the respective pixel location; and accumulating contributions corresponding to a plurality of image projections so as to thereby reconstruct each voxel.

3D reconstruction of the human jaw from a sequence of images

Abstract: A novel approach is proposed to obtain a record of the patient's occlusion using computer vision. Data acquisition is obtained using intra-oral video cameras. The technique utilizes shape from shading to extract 3D information from 2D views of the jaw, and a novel technique for 3D data registration using genetic algorithms. The resulting 3D model can be used for diagnosis, treatment planning, and implant purposes. The overall purpose of this research is to develop a model-based vision system for orthodontics to replace traditional approaches. This system will be flexible, accurate, and will reduce the cost of orthodontic treatments.

Iterative reconstruction of PET images using a high-overrelaxation single-projection algorithm

Abstract: An iterative image reconstruction procedure is described which is able to calculate high-precision images within eight iterative steps. High initial overrelaxation parameters are used which drop down towards about one during continuing iteration. The parameters are determined pragmatically, postulating maximum gain of image quality during a sequence of iterative steps. Results with simulated and measured data show that parameters derived from one data set may be widely used for other data sets. The acceleration of iterative reconstruction achieved by the estimation of optimum overrelaxation parameters is important for large data sets, especially for fully 3D reconstruction.

An evaluation of the potential and limitations of three-dimensional reconstructions from intravascular ultrasound images.

Abstract: Three-dimensional (3D) reconstructions of arteries can be produced using two-dimensional (2D) intravascular ultrasound (IVUS) images. Any artefact that affects 2D images has the potential to limit the quality of a 3D reconstruction. Using a catheter withdrawal technique, a range of test rigs were used to assess: (i) the effect of rotation of the probe orientation; (ii) the ability to reconstruct the true path of a tortuous vessel; (iii) the effect of image distortion on diameter measurements; (iv) the number of images per unit length used to produce a 3D reconstruction; and (v) the quality of the IVUS 3D reconstruction of a stent. These investigations show that 3D IVUS imaging is prone to artefacts. For 3D IVUS images to be used to quantify the vessel path or to make accurate measurements of vessel dimensions, more information about the catheter tip position and orientation is required than is currently available with the pullback technique.

One-shot 3D-shape and Texture Acquisition of Facial Data

Abstract: In this paper we present new methods to simultaneously extract and exploit the three-dimensional shape of a face and its surface texture It is based on an active technique, ie special illumination, but in contrast to traditional active sensing does not require scanning or sequential projection of multiple patterns This one-shot nature of the devise allows to capture moving objects, eg for making a 3D reconstruction of a face even when the person is talking The use of the system is illustrated using simple methods to extract both textural and geometrical features from faces, that can be used for authentication purposes The advantage of using 3D data is that both types of features can be made more invariant under changes in head pose or illumination conditions

Estimating the viewing parameters of random, noisy projections of asymmetric objects for tomographic reconstruction

Abstract: The ability to determine the viewing parameters of objects from their projections has enabled well established tomographic techniques to be employed in the 3D reconstruction of objects from images obtained via modalities where the orientation of the objects cannot be controlled. A method is described for the determination of the viewing parameters of randomly acquired projections of asymmetric objects. It extends upon the common lines algorithm by determining the relative orientation of projections from the location of lines of intersection among the Fourier transforms of the projections in 3D Fourier space. A new technique for finding the lines of intersection in the presence of translational displacement, and for subsequently finding the translational displacement, is presented. The complete algorithm is described and its efficacy is demonstrated using real data. A new technique for dealing with noise is also discussed.

Robust camera calibration using 2D-to-3D feature correspondences

Abstract: The problem of calibrating a vision system is extremely important for practical applications such as 3D reconstruction and pose estimation of 3D objects. In this paper we present a method for optimally estimating the internal and external camera parameters from point or line correspondences. First we extend the linear method of Faugeras & Toscani (1986) to line correspondences, second, we develop for both point and line correspondences a new method based on the minimization of an error function. We show how to minimize this error function in order to compute the unknown parameters (i.e., the internal and external camera parameters). This minimization leads to a non-linear optimization problem. We introduce an elegant way to automatically establish 2D to 3D feature correspondences using projective geometry. We perform a stability analysis both for our method and for the linear method. In the light of this comparison, the non-linear method seems to be the most robust one with respect to noise. Finally, we present some experiments to completely calibrate a binocular stereo rig with different calibration patterns. This stereo rig forms the main vision sensor of the Janus humanoid robotics system we are currently developing.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Short Report. The study of early human embryos using interactive 3-dimensional computer reconstructions

Abstract: Tracings of serial histological sections from 4 human embryos at different Carnegie stages were used to create 3-dimensional (3D) computer models of the developing heart. The models were constructed using commercially available software developed for graphic design and the production of computer generated virtual reality environments. They are available as interactive objects which can be downloaded via the World Wide Web. This simple method of 3D reconstruction offers significant advantages for understanding important events in morphological sciences.

Vision for longitudinal vehicle control

Abstract: An important component of the drive towards intelligent vehicles is the ability to maintain a fixed distance from a lead vehicle using feedback provided by range sensors. We investigate the possibility of using stereo vision to provide the range information, in conjunction with a scanning laser radar sensor. The tracker utilizes a layered architecture wherein the bottom layer computes motion in both images using a simple correlation algorithm, and the upper level performs stereo fixation and reconstruction using an algorithm designed for active vision systems. We present details of the real-time implementation of the vision system on a network of C40 DSPs, and some initial results comparing the quality of range measurements provided by a vision system with the laser radar system.

A vision system for underwater real-time control tasks

Abstract: The framework of the research described in this paper is artificial object recognition in an unstructured environment. The mixture of natural and artificial objects as a general scenario has been an ill-defined problem up to now. One of the most interesting and challenging environments where the mentioned mixture appears is the sea-bed. This paper describes in-progress results in the development of a computer vision system capable of automatically detecting and tracking a submarine cable, using vision as the main source of information and producing results in real time.

In vitro 3D reconstruction of long bones using B-scan image processing.

Abstract: An echographic image processing method has been developed, and validated by in vitro experiments, for the 3D reconstruction of the long bones of the newborn. The reconstruction of successive parallel cross-sections is obtained by a 2D reconstruction technique using radial B-scan image processing. The automatic segmentation of all the calculated images allows the extraction of the external contours of the skeleton. After structuring the explored volume using a contour association method, a contour interpolation step is required to solve the anisotropy problem, to obtain a 3D representation with cubic voxel lists. The results are encouraging, and a new mechanical part prototype of the acquisition system is under test for in vivo experiments. The main originality of the paper lies in the combination of different steps to obtain a practical solution to a clinical problem.

Spatial transformation during 3D reconstruction in positron emission tomography.

Abstract: Spatial transformations of positron emission tomographic data for aligning images or transforming to standard anatomical space are usually performed with reconstructed images. However, they can also be performed during the reconstruction process, thereby interpolating the raw data fewer times. We investigated the performance of spatial transformations during reconstruction, implemented it in a standard 3D reconstruction algorithm, and tested it on phantom and patient H215O activation studies for the application of aligning both transmission and emission scans. Performing the transformations during reconstruction was shown to be equivalent to performing the transformations with reconstructed images for this particular application.

A low-cost real-time stereo vision system for looking at people

Abstract: Real-time computer vision systems that observe the actions of people have received increasing attention as they are important for a broad range of applications. Examples are intelligent man-machine interfaces or intelligent rooms that have the capability to understand the actions of their inhabitants. In this paper we present the design of a stereo vision system for the precise and robust real time tracking of human hands and heads that unlike previous systems uses low-cost industry standard components. The system uses color and motion information to find the human. Using previously calibrated cameras the 3D positions of hands and head are calculated. Because of its client-server architecture the system is scalable to an arbitrary number of cameras and application processes. Experimental results for the performance of the system are given.

Robust area matching

Abstract: We propose a general and robust solution to the problem of close-range 3D reconstruction of objects from stereo correspondence of luminance profiles. The method does not require a particular camera geometry, and can be implemented with an arbitrary number of CCD cameras. Its robustness can be mainly attributed to the physicality of the matching process, which is performed in the 3D space, while taking both geometric and radiometric distortions into account. Extensive tests have been performed over a variety of real scenes, using a calibrated trinocular camera system.

Methods to reconstruct emission and transmission data in 3D PET

Abstract: Methods of reconstruction and quantitation are developed for a 3D system and are evaluated on the HEAD PENN-PET scanner, which has a very large axial acceptance angle (/spl plusmn/28/spl deg/ in the center) and large axial field-of-view without septa (25.6 cm). To overcome the difficulties of data storage and reconstruction time with 3D reconstruction, the authors have reduced the size of the 4-D projection matrix required for 3D-RP reconstruction, and compared the results to the Fourier rebinning (FORE) algorithm. Both approaches achieve a favorable tradeoff in data storage requirements, reconstruction time, and accuracy that are suitable for clinical use. The authors have also studied the application of the FORE algorithm to transmission scans acquired with a singles point source (/sup 137/Cs) so that data quantitation can be performed.

3D x-ray angiography: study of factors affecting projection data consistency

Abstract: The use of a C-arm radiographic system for 3D reconstruction of opacified vasculature presents several computational and engineering challenges. Factors that may lead to inconsistency at the projection data set and subsequent reconstruction errors include image noise, variations in vessel opacification during the acquisition, and inaccurate determination of the imaging geometry. We have utilized simulations to study the effect of these factors on 3D reconstruction with algebraic reconstruction technique (ART) in order to identify possible artifacts and loss of image quality in the 3D image. Corrective measures designed to counter artifacts such as smoothing, averaging, and use of constraints with ART have been developed and validated. These studies have made it possible to identify the causes of artifacts in preliminary in vivo applications, and to estimate the tolerance for imperfections in data acquisition. Moreover, these works have established modifications to the reconstruction procedure for reducing image artifacts and improving image quality.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Parallel 3D Reconstruction of Spherical Virus Particles from Digitized Images of Entire Electron

Abstract: 1. Introduction. Cryo-electron microscopy and 3D image reconstruction are the methods of choice for 3D atomic structme determination of many non-crystalline biological macromolecules.

A system for 3D reconstruction and VRML conversion for virtual museums applications

Abstract: Describes a system for the 3D reconstruction and VRML conversion of objects. The system is conceived to expand the capabilities of virtual museums. The 3D data are reconstructed by means of a structured light approach. Fourier transform profilometry (FTP) has been used to recover the phase shift of the projected pattern due to the shape of an object. With FTP, the acquisition setup results are very easy to build and calibrate, and, moreover, FTP can also provide dense 3D maps over uniformly coloured regions. A novel phase unwrapping strategy based on region growing is presented. It allows one to strengthen FTP's flexibility. Knutsson filtering (H. Knutsson et al., 1993) is used to smooth and interpolate incomplete 3D data, as we are able to define a certainty function associated with each height estimate. Tests over a set of masks have been performed. Numerical and qualitative results are presented, and both prove to be excellent.