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International conference on Machine Learning and Cybernetics

作者： Zhou, Lili Wang, Jiajun Hu, Danfeng Soochow Univ Sch Elect & Informat Engn Suzhou Peoples R China

ISBN: (纸本)9781479942152

Restrictions of the hardware conditions and spatial size usually limit the number of the measurements in photo acoustic imaging which will finally degrade the quality of the reconstructed image with the back projection algorithm. In order to recover larger number of measurements from incomplete ones, a compressed sensing (CS) based method was proposed. Different from most existed CS-based photoacoustic reconstruction method, the transform matrix for converting the measurement data to their compressed version is obtained by learning a dictionary with the K-SvD method. visual assessment and quantitative evaluations in terms of the mean squared error (MSE) and the peak signal-to-noise ratio (PSNR) demonstrate the superiorities of our proposed method.

关键词： Photoacoustic image Compressed sensing K-SvD Dictionary learning

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Effects of Attenuation in Single Slow Rotation Dynamic SPECT

Effects of Attenuation in Single Slow Rotation Dynamic SPECT

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IEEE Nuclear Science Symposium/Medical Imaging conference (NSS/MIC)/18th International Workshop on Room-Temperature Semiconductor X-Ray and Gamma-Ray Detectors

作者： Humphries, Thomas Celler, Anna Trummer, Manfred Simon Fraser Univ Dept Math Burnaby BC V5A 1S6 Canada Univ British Columbia Dept Radiol Vancouver BC V5Z 1L3 Canada

ISBN: (纸本)9781467301206

The goal of single slow rotation dynamic SPECT is to reconstruct a dynamic image from data acquired with a single slow rotation of the camera. In this approach, the distribution of activity is assumed to change with every stop made by the camera, and all time frames of the 4D image are simultaneously reconstructed, using a temporal constraint to link them together. The dSPECT algorithm, for instance (Farncombe et al., 2001), restricts the behaviour of the time activity curve (TAC) in every voxel of the image, requiring it either strictly increase, strictly decrease, or increase to a maximum and then decrease. Attenuation correction (AC) is critical to this approach, in order to separate the effects of attenuation on projection data from the actual tracer kinetics. Here we present new analysis indicating that modeling attenuation in the system matrix, although sufficient for AC in conventional (static) SPECT imaging, does not properly account for attenuation effects when reconstructing a dynamic image from data acquired with a single slow rotation. Noticeable artifacts occur in TACs extracted from the reconstructed image as a result. These artifacts correspond to periods of the acquisition where the amount of attenuating material between the camera and dynamic regions changes significantly. We investigate a post-reconstruction approach to correct for these artifacts, in which a template approximating the dynamic image is created, analytically projected, and then reconstructed. This procedure provides an indication of the nature of the artifacts present in the original reconstructed image, allowing for a correction to be applied. An experiment using a digital phantom and the dSPECT reconstruction algorithm indicates that this approach noticeably reduces most attenuation artifacts, although some still persist. Thus, the acquisition protocol in any single slow rotation dynamic SPECT study must be carefully chosen to minimize errors related to attenuation.

关键词： Analytical models Equations Mathematical model

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Exact, scaled image rotations in finite Radon transform space

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PATTERN RECOGNITION LETTERS 2011年第9期32卷 1415-1420页

作者： Svalbe, Imants Monash Univ Sch Phys Clayton Vic 3800 Australia

The Finite Radon Transform (FRT) is a discrete analogue of classical tomography. The FRT permits exact reconstruction of a discrete object from its discrete projections. The set of projection angles for the FRT is intrinsic to each image array size. It is shown here that the set of FRT angles is closed under a rotation by any of its members. A periodic re-ordering of the elements of the 10 FRT projections is then equivalent to an exact 2D image rotation. FRT-based rotations require minimal interpolation and preserve all of the original image pixel intensities. This approach has applications in image feature matching, multi-scale data representation and data encryption. (C) 2010 Elsevier B.v. All rights reserved.

关键词： Discrete Radon projection image rotation Affine transforms

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Interbands phase models for polychromatic image reconstruction in optical interferometry 5

Interbands phase models for polychromatic image reconstructi...

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conference on Optical and Infrared Interferometry and Imaging v

作者： Schutz, Antony Ferrari, Andre Thiebaut, Eric Soulez, Ferreol vannier, Martin Mary, David Univ Nice Sophia Antipolis Lab JL Lagrange CNRS Observ Cote Azur Parc Valrose F-06108 Nice 02 France Univ Lyon Univ Lyon 1 Ens Lyon CNRSCtr Rech Astrophys LyonUMR5574 F-69230 St Genis Laval France Ecole Polytech Fed Lausanne Biomed Imaging Grp CH-1015 Lausanne Switzerland

ISBN: (纸本)9781510601932

This paper presents an extension of the spatio-spectral ("3D") image reconstruction algorithm called PAINTER (Polychromatic opticAl INTErferometric reconstruction software). The algorithm is able to solve large scale problems and relies on an iterative process, which alternates estimation of polychromatic images and of complex visibilities. The complex visibilities are not only estimated from squared moduli and closure phases, but also from differential phases, which helps to constrain the polychromatic reconstruction. Alternative methods to construct the specific differential phases used in PAINTER are proposed. Simulations on synthetic data illustrate the specificities of the proposed methods.

关键词： image reconstruction multiwavelengths phases estimation optical interferometry

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EM reconstruction of Dual Isotope PET with Staggered Injections and Prompt Gamma Positron Emitters

EM Reconstruction of Dual Isotope PET with Staggered Injecti...

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IEEE Nuclear Science Symposium / Medical Imaging conference Record (NSS/MIC) / 19th Room-Temperature Semiconductor X-ray and Gamma-ray Detector Workshop

作者： Andreyev, Andriy Sitek, Arkadiusz Celler, Anna Univ British Columbia Med Imaging Res Grp Vancouver BC V5Z 1M9 Canada Brigham & Womens Hosp Harvard Med Sch Dept Radiol Boston MA 02115 USA

ISBN: (纸本)9781467320306;9781467320283

The aim of Dual Isotope Positron Emission Tomography (DIPET) is to create two independent images of two co-injected radiotracers. DIPET shortens the duration of the study, reduces patient discomfort and produces perfectly co-registered images. Its implementation is difficult because positron decay of any isotope creates only 511 kev photons. Recently, we have proposed a DIPET technique that uses a combination of radiotracer A which is a pure positron emitter (such as F-18 or C-11) and radiotracer B in which positron decay is followed by the emission of a high-energy (HE) prompt gamma (such as K-38 or Cu-60). Events that are detected as triple coincidences of HE gammas with the corresponding two 511 kev photons identify the line-of-responses (LORs) that originate from isotope B (similar to 10% of all events). These LORs are used to separate the two intertwined distributions, using a dedicated image reconstruction algorithm based on Expectation Maximization (EM). However, this approach is suboptimal as it combines high-statistics data (radiotracers A and B), with low-statistics (radiotracer B) to create separate images of radiotracers A and B. We hypothesize that from the performance of DIPET could be improved if an independent estimate of radiotracer A distribution is available by using staggered injections method. Here we investigate this hypothesis by developing and testing an EM-based algorithm for image reconstruction of such data. Our algorithm is general, i.e. can reconstruct staggered data, positron and HE gamma data or a combination of both. reconstruction of DIPET data obtained from Monte-Carlo simulations shows that the combined method provides the best results in terms of separation of images corresponding to radiotracers A and B. Our EM algorithm provides not only good image separation for the combined method but also when only staggered injections or only prompt gamma data are used.

关键词： Monte Carlo methods expectation-maximisation algorithm image reconstruction medical image processing positron emission tomography

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reconstruction of a Three-Dimensional Scene from its Projections in Computer vision Systems

Reconstruction of a Three-Dimensional Scene from its Project...

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conference on Intelligent Technologies and Electronic Devices in vehicle and Road Transport Complex (TIRvED)

作者： Gadasin, D., v Shvedov, A., v Kuzin, I. A. Moscow Tech Univ Commun & Informat Moscow Russia

ISBN: (纸本)9781665400756

The problem of reconstructing a three-dimensional scene from its projections is one of the most urgent and studied among the problems solved by computer vision methods. Most often, such systems are implemented by creating geographically distributed complexes that require the transfer of a large amount of data between their components, which creates a large load on the transmission lines. Scene reconstruction using projections obtained from several observation points is a special case and is not always possible, especially when used in unmanned aerial vehicles or autonomous vehicles. To resolve these limitations, the possibility of using a computer stereoscopic vision system and a three-dimensional convolutional neural network capable of reconstructing a complete scene from a single image containing subjective characteristics of scene objects, such as color and depth, is considered in this work, creating its three-dimensional representation. The article describes the architecture and principle of operation of a neural network, and also builds a model of a computer stereo vision stand for image registration. An image formation algorithm is proposed for this model.

关键词： Three-dimensional reconstruction computer vision depth map scene reconstruction three-dimensional images stereo mapping CNN

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Implementation of an analytically based scatter correction in SPECT reconstructions

Implementation of an analytically based scatter correction i...

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IEEE Nuclear Science Symposium/Medical Imaging conference

作者： vandervoort, E Celler, A Wells, G Blinder, S Dixon, K Pang, YX Univ British Columbia Dept Phys & Astron Vancouver BC V5Z 1M9 Canada

ISBN: (纸本)0780382579

Photon scattering is one of the main effects contributing to the degradation of image quality and to quantitative inaccuracy in nuclear imaging. We have developed a scatter correction based on the analytic photon distribution (APD) method, and implemented it in an iterative image reconstruction algorithm. The performance of the method was evaluated using computer simulated projection data, experimental data obtained from physical phantoms, and patient data. The scatter corrected images were compared to images that were only corrected for attenuation and collimator blurring. In the simulation studies our results could also be compared to an ideal scatter correction in which images were reconstructed only from unscattered photon data. In all cases, our scatter corrected images demonstrate improved image contrast. In the simulated data the contrast for images only corrected for attenuation and collimator blurring were on average 29% poorer than the ideal correction. images for which our scatter correction was applied had contrast that was on average within 3% of the ideal correction. The scatter corrected reconstruction requires between 4 to 5 hours of total CPU time, on a 1.7 GHz processor with 1Gb RDRAM, using clinical data.

关键词： Scattering

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Generic and real-time structure from motion using local bundle adjustment

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image AND vISION COMPUTING 2009年第8期27卷 1178-1193页

作者： Mouragnon, E. Lhuillier, M. Dhome, M. Dekeyser, F. Sayd, P. Univ Blaise Pascal CNRS LASMEA UMR 6602 F-63177 Clermont Ferrand France CEA Image & Embedded Comp Lab LIST DTSI SARC F-91191 Gif Sur Yvette France

This paper describes a method for estimating the motion of a calibrated camera and the three-dimensional geometry of the filmed environment. The only data used is video input. Interest points are tracked and matched between frames at video rate. Robust estimates of the camera motion are computed in real-time, key frames are selected to enable 3D reconstruction of the features. We introduce a local bundle adjustment allowing 3D points and camera poses to be refined simultaneously through the sequence. This significantly reduces computational complexity when compared with global bundle adjustment. This method is applied initially to a perspective camera model, then extended to a generic camera model to describe most existing kinds of cameras. Experiments performed using real-world data provide evaluations of the speed and robustness of the method. Results are compared to the ground truth measured with a differential GPS. The generalized method is also evaluated experimentally, using three types of calibrated cameras: stereo rig, perspective and catadioptric. (C) 2008 Elsevier B.v. All rights reserved.

关键词： Structure from motion Bundle adjustment Generic camera

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Registration and fusion of intensity and range data for 3D modelling of real world scenes 4

Registration and fusion of intensity and range data for 3D m...

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

作者： Dias, P Sequeira, v vaz, F Gonçalves, JGM Univ Aveiro IEETA P-3800 Aveiro Portugal

ISBN: (纸本)0769519911

In this paper, a novel technique combining intensity and range data is presented Passive (intensity based) and active (range based) techniques used for 3D reconstruction have their limitations and separately, none of these techniques can solve all the problems inherent to the modelling of real environments. Our technique aims to demonstrate how both intensity and range data can be registered and combined into a long-range 3D system. The procedure needs an initial estimation for internal and external camera parameters for two or more intensity images. The technique uses passive triangulation of the intensity data to refine the initial camera calibrations and ensure a good registration of range and video data sets. Once a reliable calibration is achieved, corresponding points from the intensity images are triangulated and introduced in the original range data With our technique, it is possible to complete the models in areas where data is missing or to increase the resolution in areas of high interest and 3D contents.

关键词： Calibration Cameras Costs image reconstruction image resolution Layout Lighting Machine vision Spatial resolution video sequences

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Improving image quality in compressed ultrafast photography with a space- and intensity-constrained reconstruction algorithm

Improving image quality in compressed ultrafast photography ...

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conference on High-Speed Biomedical Imaging and Spectroscopy - Toward Big data Instrumentation and Management

作者： Zhu, Liren Chen, Yujia Liang, Jinyang Gao, Liang Ma, Cheng Wang, Lihong v. Washington Univ Dept Biomed Engn Opt Imaging Lab 1 Brookings Dr St Louis MO 63130 USA Univ Illinois Dept Elect & Comp Engn 405 North Mathews Ave Urbana IL 61801 USA

ISBN: (纸本)9781628419542

The single-shot compressed ultrafast photography (CUP) camera is the fastest receive-only camera in the world. In this work, we introduce an external CCD camera and a space-and intensity-constrained (SIC) reconstruction algorithm to improve the image quality of CUP. The CCD camera takes a time-unsheared image of the dynamic scene. Unlike the previously used unconstrained algorithm, the proposed algorithm incorporates both spatial and intensity constraints, based on the additional prior information provided by the external CCD camera. First, a spatial mask is extracted from the time-unsheared image to define the zone of action. Second, an intensity threshold constraint is determined based on the similarity between the temporally projected image of the reconstructed datacube and the time-unsheared image taken by the external CCD. Both simulation and experimental studies showed that the SIC reconstruction improves the spatial resolution, contrast, and general quality of the reconstructed image.

关键词： Ultrafast imaging computational imaging compressed sensing image reconstruction

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