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conference on Computer Vision and Pattern Recognition (CVPR)

作者： C. Strecha R. Fransens L. Van Gool ESAT-PSI University of Leuven Belgium Belgium ESAT-PSI University of Leuven Belgium

This paper describes a method for dense depth reconstruction from a small set of wide-baseline images. In a wide-baseline setting an inherent difficulty which complicates the stereo-correspondence problem is self-occlusion. Also, we have to consider the possibility that image pixels in different images, which are projections of the same point in the scene, will have different color values due to non-Lambertian effects or discretization errors. We propose a Bayesian approach to tackle these problems. In this framework, the images are regarded as noisy measurements of an underlying 'true' image-function. Also, the image data is considered incomplete, in the sense that we do not know which pixels from a particular image are occluded in the other images. We describe an EM-algorithm, which iterates between estimating values for all hidden quantities, and optimizing the current depth estimates. The algorithm has few free parameters, displays a stable convergence behavior and generates accurate depth estimates. The approach is illustrated with several challenging real-world examples. We also show how the algorithm can generate realistic view interpolations and how it merges the information of all images into a new, synthetic view.

关键词： image reconstruction Layout Pixel Interpolation Bayesian methods Displays Convergence Video recording Digital cameras image resolution

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The effects of lead shielding of background organ activity in pinhole Single Photon Emission Computed Tomography (SPECT) breast tumor imaging

The effects of lead shielding of background organ activity i...

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IEEE Symposium on Nuclear Science (NSS/MIC)

作者： T. Lee K. Braun R. Jaszczak J. Bowsher K. Bobkov Department of Biomedical Engineering Duke University USA Department of Radiology and Biomedical Engineering Duke University Durham NC USA Department of Radiology Duke University Durham NC USA

The objective of this study was to investigate the effect on contrast and SNR (Signal-to-Noise Ratio) of shielding the patient bed with lead. Shielding reduces other-organ photon contamination, but may result in incomplete sampling of other organs and increased data inconsistency, if shielding attenuation is not modeled during reconstruction. A Trionix XLT scanner with one pinhole collimator was used to obtain experimental data on a breast phantom mounted on a torso phantom. The torso phantom contained the liver, lungs, and myocardium, all filled with varying amounts of /sup 99/Tc/sup m/-MIBI. The breast phantom contained two spherical lesions, also filled with /sup 99/Tc/sup m/-MIBI. The bed contained a cut-out for the prone breast attachment. Ten scans were performed with bed shielding, and without, in order to determine the statistical significance of the analysis. The incomplete circular orbit angular range was 186 degrees and consisted of 94 views with a 2 degree step between each view. The data were then reconstructed by OSEM with 8 subsets, using up to 30 iterations without modeling shielding attenuation. A 3D region-of-interest analysis was performed on a lesion to evaluate shielding effects. Post-filtering was applied for better image quality. The use of shielding slightly increased noise in contrast estimates, from about 0.25 to 0.30. In addition, shielding increased bias in contrast from 0.1+/-0.08 to 0.5+/-0.09. For a given cutoff frequency, SNR is lower with shielding than without. These results suggest that if shielding is to be of benefit, shielding attenuation must be modeled within iterative reconstruction.

关键词： Single photon emission computed tomography Breast tumors Imaging phantoms Attenuation image reconstruction Signal to noise ratio Torso Lesions Performance analysis Contamination

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Effect of normalization method on image uniformity and binding potential estimates on microPET

Effect of normalization method on image uniformity and bindi...

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IEEE Symposium on Nuclear Science (NSS/MIC)

作者： M.-L. Camborde A. Rhamim D.F. Newport S. Siegel K.R. Buckley E. Vandervoort T.J. Ruth V. Sossi University of British Columbia Vancouver BC Canada CTI Concorde MicroSystems LLC Knoxville TN USA TRIUMF Vancouver BC Canada

This study investigates different detector normalization procedures for a small animal scanner, specifically the Concorde microPET/sup /spl reg// R4. The procedures were compared in terms of: (i) image uniformity, (ii) performance as a function of count rate, and (iii) impact on the estimate of the binding potential (BP) in brain rat studies. image uniformity studies were performed on two cylindrical phantoms of different size filled with an aqueous concentration of /sup 11/C (38 kBq/mL and 615 kBq/mL). BP was estimated with the Logan graphical approach on 12 /sup 11/C-Methylphenidate and 9 /sup 11/C-Dihydrotetrabenazine rat studies processed with all the normalization procedures. We found that: 1) the combination, the geometry normalized combination, the component-point, and the geometry normalized component procedures significantly improve radial image uniformity compared to the direct-point and direct-cylinder procedures, 2) the geometry normalized combination procedure seems to provide the best radial and axial uniformity, 3) a mismatch between the count rates at which the normalization and the emission scans are acquired degrades the axial uniformity by 47% to 98% whereas this effect was not observed for radial uniformity, and 4) the difference in BP values obtained from data corrected with different normalization procedures is as high as 15% for normal striatum and 75% for lesion striatum.

关键词： Detectors Positron emission tomography Geometry Animals Humans Imaging phantoms Degradation Lesions image reconstruction Frequency

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Comparison between segmented and nonsegmented attenuation correction on the HR+ tomograph

Comparison between segmented and nonsegmented attenuation co...

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IEEE Symposium on Nuclear Science (NSS/MIC)

作者： T.J. Spinks H. Kindler D. Hogg A. Alaradi Z. Alghazirr Hammersmith Hospital Hammersmith Imanet Limited London UK MRC Clinical Sciences Centre Hammersmith Hospital London UK Hammersmith Imanet Limited UK University of Surrey Guildford UK

Segmentation of transmission (TR) images is implemented to improve signal noise in attenuation correction (AC) and allow shorter TR scans. This study compares (i) measurement of myocardial glucose metabolic rate (MRGlu), (ii) correction for myocardial wall thickness and (iii) measurement of lung density, by using AC derived from transmission images (a) unsegmented (US), (b) segmented (S) and (c) reconstructed with OSEM. All data were acquired on a CTI HR+ tomograph and processed with standard scanner software. Methods: TR scans were carried out on a multi-cylinder phantom containing substances of varying density and mean mu-values (cm -1 ) were derived from TR images. A multi-compartment heart phantom was constructed as a simple simulation of varying myocardial wall thickness and left ventricular volume. MRGlu, using FDG (2D mode) and blood volume (C 15 O inhalation), was measured in 11 patients with coronary heart disease, following a 20 min TR scan. Results: Good linearity was found between NS mu-values and density but there were significant discrepancies with S over the typical range of lung density, and better agreement with OSEM. Overall mean ratios of MRGlu were within 2% for the three AC methods but there was systematic individual variation about the mean. The C.V. of regional MRGlu for each patient, using US AC, was not significantly different from S and OSEM. The heart phantom data demonstrated reasonable accuracy of correction for myocardial wall thickness. Conclusions: US AC on the HR+ gives more accurate measurement of the range of density encountered in the chest and more reliable measurement of MRGlu than S and OSEM. There appears to be no "statistical penalty" in the use of US AC, noise being dominated by that in emission data

关键词： Attenuation Density measurement Myocardium image segmentation Imaging phantoms Thickness measurement Lungs Heart Sugar image reconstruction

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image reconstruction from reduced-scan data in ultrasonic reflectivity tomography

Image reconstruction from reduced-scan data in ultrasonic re...

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Medical Imaging 2003 conference

作者： Pan, XC Yu, Z Anastasio, MA Sidky, E Univ Chicago Dept Radiol Chicago IL 60637 USA

ISBN: (纸本)0819448362

Reflectivity tomography is an imaging technique that seeks to reconstruct the reflectivity distribution that characterizes a weakly reflecting object. As in other tomographic imaging modalities, in certain applications of reflectivity tomography it may be necessary to reconstruct an accurate image from measurement data that are incomplete, e.g., reduced-scan measurement data. Recently, we have developed a so-called 'potato peeler' perspective for heuristically demonstrating the possibility of reconstructing accurate images from reduced-scan measurement data. In this work we describe a mathematical formulation of the potato peeler perspective, which provides a theoretical justification for the development and application of reduced-scan reconstruction algorithms in reflectivity tomography. Simulation results are presented to corroborate our theoretical assertions.

关键词： reflectivity tomography reduced-scan image reconstruction ultrasonic imaging

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Anisotropic diffusion of surface normals for feature preserving surface reconstruction 4

Anisotropic diffusion of surface normals for feature preserv...

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4th International conference on 3-D Digital Imaging and Modeling (3-DIM 2003)

作者： Tasdizen, T Whitaker, R Univ Utah Sch Comp Salt Lake City UT 84112 USA

ISBN: (纸本)0769519911

For 3D surface reconstruction problems with noisy and incomplete range data measured from complex scenes with arbitrary, topologies, a low-level representation, such as level set surfaces, is used. Such surface reconstruction is typically accomplished by minimizing a weighted stan of data-model discrepancy and model smoothness terms. This paper introduces a new, nonlinear model smoothness term for surface reconstruction based on variations of the surface normals. A direct solution requires solving a fourth-order partial differential equation (PDE), which is very difficult with conventional numerical techniques. Our solution is based on processing the normals separately from the surface, which allows its to separate the problem into two second-order PDEs. The proposed method can smooth complex, noisy surfaces, while preserving sharp, geometric features, and it is a natural generalization of edge-preserving methods in image processing, such as anisotropic diffusion.

关键词： Anisotropic magnetoresistance Density measurement image reconstruction Layout Level set Multi-stage noise shaping Noise measurement Shape Surface reconstruction Topology

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Building extraction from digital elevation models

Building extraction from digital elevation models

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IEEE International conference on Acoustics, Speech, and Signal Processing

作者： Ortner, M Descombes, X Zerubia, J UNSA CNRS INRIA Ariana Res Grp F-06902 Sophia Antipolis France

ISBN: (纸本)0780376633

To extract buildings from Digital Elevation Models, we define a point process whose points represent buildings. We then define a density for this point process which is split into two parts, consisting in an "internal field" that allows us to model the prior knowledge we have on patterns of buildings in urban areas and an "external field" that makes the point process fit the data. We then use a Metropolis Hastings Green sampler coupled with a simulated annealing that gives the configuration of buildings minimizing the energy we have defined. We present results on real data provided by the French Mapping Institute (IGN).

关键词： image reconstruction

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New approach for determination of time delay for reconstruction of phase space from time series of satellite observations

New approach for determination of time delay for reconstruct...

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conference on Optical Remote Sensing of the Atmosphere and Clouds iii

作者： Xu, L Ding, JL Chen, GY Chengdu Univ Informat Technol Inst Space Informat & Nonlinear Sci Atmospher Radiat & Satellite Remote Sensing Lab Chengdu Peoples R China

ISBN: (纸本)0819446777

Based on the analyses of nonlinear time series of satellite observations, some critical issues relevant to the choice of time delay for phase space reconstruction, i.e., the mutual information calculations, and the effects of the possible periodic components on the choice of the best time delay and their extraction from the satellite signals, are studied. Some important results are obtained.

关键词： nonlinear time series analyses GMS-5 satellite image data mutual information calculations probability distribution effect of periodic components extraction of possible periodic components derivative of the signals choice of the time delay

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Scanning of logs with linear cone-beam tomography

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COMPUTERS AND ELECTRONICS IN AGRICULTURE 2003年第1-3期41卷 45-62页

作者： Seger, MM Danielsson, PE Linkoping Univ Dept Elect Engn Comp Vis Lab SE-58183 Linkoping Sweden

This paper reports an ongoing feasibility study in industrial X-ray tomography. Full volume scanning of logs may have a large potential in terms of increased sales value. On the other hand, there is no technology commercially available today which can meet the requirements for speed. In conventional medical 3D-tomography, the source-detector system rotates around a slowly translating patient. We do not believe such an arrangement is able to reach our speed requirements. Instead, we have been simulating an arrangement with two fixed source-detector systems rotated 90degrees relative to each other. Each system consists of an X-ray source and a 2D detector. The logs are to be translated through this arrangement at relatively high speed (2-3 m/s) lengthwise on a conveyor belt, while cone-beam projections are acquired by each of the source-detector systems. The 2D-detectors are composed of a number of ID-detectors side by side. For cost reasons we will try to limit the number of rows to nine, forming a 2D-array of 256 x 9 detector elements. Due to the unconventional scanning geometry, we have developed a new reconstruction algorithm, which also takes special care to avoid many artifacts due to sparse and/or missing data. Experiments (still simulated), performed on voxelized CT data, indicate that the knots are reconstructed with sufficient accuracy to allow for quantitative optimization. Due to the missing data, however, heartwood can barely be distinguished from sapwood, but his fact does not seem to compromise the subsequent knot detection. Note that this paper only describes the reconstruction part of the simulated experiments. To be complete, the feasibility study should also include segmentation, which is outside the scope of this paper. (C) 2003 Elsevier Science B.V. All rights reserved.

关键词： x-ray log scanning 3D linear cone-beam tomography incomplete data

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Scanning of logs with linear cone-beam tomography

Scanning of logs with linear cone-beam tomography

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4th International conference on image Processing and Scanning of Wood

作者： Seger, MM Danielsson, PE Linkoping Univ Dept Elect Engn Comp Vis Lab SE-58183 Linkoping Sweden

关键词： x-ray log scanning 3D linear cone-beam tomography incomplete data

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