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Annual International conference of the IEEE Engineering in Medicine and Biology Society (EMBC)

作者： v.K. Srivastava G.C. Ray Department of Electrical Engineering Indian Institute of Technology Kanpur India

ISBN: (纸本)0780364651

The reconstructed image from highly compressed JPEG data has noticeable degradation due to blocking artifacts. Linear, space-invariant filtering is inadequate to remove these artifacts. So, space-variant or adaptive filtering is required. These schemes are based on edge information extracted from the received blocky image, which contain false edges due to blocking artifacts. Based on analysis in frequency domain, it is found that artifacts in decoded image have periodic structure. These periodic-textures become more obvious after gradient operation since discontinuities due to block coding are highlighted in gradient image. According to signal processing theory, periodic texture will result in some peaks in frequency domain. Here, peaks are due to false edges in gradient image or due to blocking discontinuities in decoded image. A two-dimensional (2D) multiple-notch filter can kill these peaks to reduce the artificial edges due to blocking artifacts in gradient image. Here, a 2D IIR multiple-notch filter is designed from one-dimensional multiple bandpass filter using simple algebraic method. This approach is an extension of method used by Pei at el. (1994) in the domain of 2D. Discontinuities due to blocking artifacts are more in monotone area so this filter can be applied directly. Thus, improvement in the performance of space-variant/adaptive filter by removing of false edges from edge of blocky decoded image and reduction of blocking artifacts directly in monotone area, are the new possible application of multiple-notch filter which is considered in this work. Computational complexity is low because filtering is performed in DCT domain.

关键词： Band pass filters Adaptive filters Decoding IIR filters Filtering Frequency domain analysis image reconstruction image coding Transform coding Degradation

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Bidirectional optimization for reconstructing 3D shape from an image sequence with missing data

Bidirectional optimization for reconstructing 3D shape from ...

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International conference on image Processing (ICIP'99)

作者： Maruyama, Minoru Kurumi, Satoshi Shinshu Univ Nagano Japan

reconstruction of 3D structure from a 2D image sequence is very important for image understanding, image based rendering etc. Especially, in practice, reconstruction algorithms that can handle occlusion are necessary. In this paper we extend the factorization algorithm and propose a method to reconstruct 3D shape from an image sequence with missing data. In our method, treating missing elements as unknown parameters, parametric representation of a measurement matrix is given. Since the rank of the ideal measurement matrix should be three, parameter values should be specified so that the discrepancy between the parametric matrix and its associated `closest' rank three matrix is minimized. We describe an iterative algorithm to determine the unknown parameter so as to give rise to the decreasing sequence of the discrepancy. The procedure is nothing but the iterative bidirectional projection between the model space and the observation space (parametric representation of incomplete data). Several experimental results are also provided.

关键词： image reconstruction

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Comparison of FORE, OSEM and SAGE algorithms to 3DRP in 3D PET using phantom and human subject data

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IEEE TRANSACTIONS ON NUCLEAR SCIENCE 1999年第4期46卷 1114-1120页

作者： Krzywinski, M Sossi, v Ruth, TJ TRIUMF PET Program Vancouver BC V6T 2A3 Canada

Using phantom and human subject data, we have compared a number of reconstruction algorithms to the current "gold standard" method, 3D Reprojection Method (3DRP), in an effort to validate them as practical 3D reconstruction alternatives for dynamic PET scanning. The algorithms evaluated were (a) Fourier Rebinning (FORE) followed by 2D Filtered Back Projection (2D FBP), (b) FORE followed by Ordered Subsets Expectation-Maximization (OSEM) and (c) FORE followed by Space Alternating Generalized Expectation-Maximization (SAGE). The main benefits of these methods are two-fold: significantly shorter reconstruction times and improved signal-to-noise ratio at matched resolution for the iterative schemes. We demonstrate that FORE + 2D FBP can replace 3DRP with no significant impact on subsequent data analysis. In particular, distribution volume ratios (DvRs) obtained with FORE + 2D FBP differed from those obtained with 3DRP by 0.3 +/- 0.7% (n = 33) and -0.7 +/- 1.1%(n = 21) for cortical and cerebellar input functions, respectively. Both OSEM and SAGE performed well compared to 3DRP, with improved noise characteristics and DvR differences of < 3%.

关键词： Positron emission tomography Humans Imaging phantoms Sampling methods Testing Statistics Computer hacking image reconstruction Convergence Hardware

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Dynamic SPECT imaging using a single camera rotation (dSPECT)

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IEEE TRANSACTIONS ON NUCLEAR SCIENCE 1999年第4期46卷 1055-1061页

作者： Farncombe, T Celler, A Noll, D Maeght, J Harrop, R Univ British Columbia Dept Phys Vancouver BC Canada Vancouver Hosp & Hlth Sci Ctr Div Nucl Med Vancouver BC V5Z 1M9 Canada Univ Toulouse 3 Lab Math Ind & Phys F-31062 Toulouse France

Techniques to estimate dynamic parameters from the data acquired during a single rotation of a standard (single, dual and triple head) SPECT camera are being investigated. The performance of the constrained linear least squares (C-LS) method is being assessed. This method uses a simple assumption that the activity within each pixel at a given projection angle is less than or equal to the activity seen at the prior angle. In simulations, we have used an analytical heart model with single and bi-exponential activity decrease, with and without background activity and statistical noise in the data. Studies using a single, a 90 degrees dual and a 120 degrees triple head camera were modeled with a total acquisition time of 20min, performing rotation over 180 degrees. These simulations were followed by experimental scans of our dynamic phantom used with and without attenuation and subsequently a preliminary study involving a human subject was performed. Dynamic images from simulations and phantom experiments reconstruct well with an accuracy of reconstructed half-lives for most reconstructions within a 20% en or range. Some streaking artifacts which are evident in images corresponding to early reconstruction times subside upon incorporating further constraints and regularizations.

关键词： Computerized tomography Medical imaging data acquisition Parameter estimation Optical rotation Least squares approximations Mathematical models Computer simulation Cameras Photons image reconstruction Error analysis Single photon emission computed tomography (SPECT) Parameter estimation simulating Medical imaging image reconstruction acquisition time human subject Cameras X-Ray Computed Tomography Photon

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Model-based reconstruction of organ surfaces from two-dimensional CT or MRT data of the head

Model-based reconstruction of organ surfaces from two-dimens...

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Medical Imaging 1999 conference - image Processing

作者： von Klinski, S Glausch, A Tolxdorff, T Free Univ Berlin Hosp Benjamin Franklin Dept Med Informat D-1000 Berlin Germany

ISBN: (纸本)0819431338

Surface-based interpolation and registration, radiation treatment, and three-dimensional visualization of two-dimensional sliced data from CT or MRT require a precise reconstruction of three-dimensional organ surfaces from two-dimensional segmentation results. Current surface-reconstruction algorithms are based on surface triangulations using heuristics to correlate and connect adjacent object slices. The approaches described in the literature can be divided into triangulations using optimization procedures, Delauny triangulations, and topology-based correlations. All approaches assume a global and invariant vertically oriented correlation strategy that can be applied equally to every organ and every slice. Surface and correlation characteristics vary greatly among bony structures and organs such as the eyes and the brain. An adjusted reconstruction of each organ according to its individual tissue characteristics is necessary to avoid errors in following processing steps such as interpolation, registration, and radiation treatment. To this end, we have designed a model-based surface-reconstruction algorithm that takes individual surface characteristics into account and allows the integration of anatomical knowledge. Three-dimensional surface models are generated from sliced data or any other source of anatomical knowledge. These models are later adjusted to the segmentations, compensating for artifacts and incomplete data.

关键词： reconstruction triangulation warping interpolation

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reconstruction from slow rotation dynamic SPECT using a factor model 16th

Reconstruction from slow rotation dynamic SPECT using a fact...

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16th International conference on Information Processing in Medical Imaging, IPMI 1999

作者： Sitek, Arkadiusz Di Bella, Edward v. R. Gullberg, Grant T. Department of Radiology University of Utah Salt Lake CityUT84108 United States

ISBN: (纸本)3540661670

Slow rotation acquisition of dynamic data has several advantages over fast rotation acquisition which is currently the method of choice used for the acquisition of dynamic data in SPECT. Slow rotation is currently not used because of error from inconsistent data. In this work, we develop a method of reconstructing from projections that are inconsistent in time due to being acquired during a slow acquisition. Our method is based on a factor model of physiological data. A series of dynamic images are reconstructed, where each reconstructed image corresponds in time to only one projection. Such an under-determined reconstruction is shown to be possible through utilization of a factor model. Computer simulations are performed using simple phantoms. We found that we are able to accurately reconstruct the dynamic sequence for simple phantoms with temporal behavior corresponding to teboroxime-Tc-99m heart imaging. © Springer-verlag Berlin Heidelberg 1999.

关键词： Phantoms

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SEXAFS and NIXSW investigation of the Rh(111)-(√7 x √7)R19.1°-P surface

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SURFACE SCIENCE 1999年 433卷 267-271页

作者： Shard, AG Dhanak, vR Muryn, CA Robert Gordon Univ Sch Appl Sci Aberdeen AB9 1FR Scotland Univ Liverpool IRC Surface Sci Liverpool L69 3BX Merseyside England Univ Manchester Dept Chem Manchester M13 9PL Lancs England

P K-edge surface extended X-ray absorption fine structure (SEXAFS) of the Rh(111)-(root 7x root 7)R19.1 degrees-P surface is reported. The results indicate that a recently proposed model for this surface is valid in which a mixed overlayer of composition Rh5P3 is formed on the Rh(111) surface. However, some modifications to atomic positions are necessary to acheive consistency with the Rh-P bond lengths determined by SEXAFS;this leads to a reappraisal of our normal incidence X-ray standing wavefield (NIXSW) data from the same surface. (C) 1999 Elsevier Science B.v. All rights reserved.

关键词： low index single crystal surfaces phosphorus rhodium surface reconstruction surface structure

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Bidirectional optimization for reconstructing 3D shape from an image sequence with missing data

Bidirectional optimization for reconstructing 3D shape from ...

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IEEE International conference on image Processing

作者： M. Maruyama S. Kurumi Department Information Engineering Shinshu University Nagano Japan

reconstruction of 3D structure from a 2D image sequence is very important for image understanding, image based rendering etc. especially, in practice, reconstruction algorithms that can handle occlusion are necessary. In this paper we extend the factorization algorithm and propose a method to reconstruct 3D shape from an image sequence with missing data. In our method, treating missing elements as unknown parameters, parametric representation of a measurement matrix is given. Since the rank of the ideal measurement matrix should be three, parameter values should be specified so that the discrepancy between the parametric matrix and its associated "closest" rank three matrix is minimized. We describe an iterative algorithm to determine the unknown parameter so as to give rise to the decreasing sequence of the discrepancy. The procedure is nothing but the iterative bidirectional projection between the model space and the observation space (parametric representation of incomplete data). Several experimental results are also provided.

关键词： image reconstruction Shape image sequences Matrix decomposition Position measurement Cameras Rendering (computer graphics) Iterative algorithms image recognition Robustness

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Real time telemedicine using shared 3-dimensional workspaces over ATM

Real time telemedicine using shared 3-dimensional workspaces...

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conference on visual data Exploration and Analysis vI

作者： Cahoon, P Forsey, D Hutchison, S Univ British Columbia Media & Graph Interdisciplinary Ctr Vancouver BC V5Z 1M9 Canada

ISBN: (纸本)0819431141

During the past five years a high speed ATM network has been developed at UBC that provides a campus testbed, a local testbed to the hospitals, and a National testbed between here and the BADLAB in Ottawa. This testbed has been developed to combine a commercial shared audio/video/whiteboard environment coupled with a shared interactive 3-dimensional solid model. This solid model ranges from a skull reconstructed from a CT scan with muscles and an overlying skin, to a model of the ventricle system of the human brain. Typical interactions among surgeon, radiologist and modeler consist of having image slices of the original scan shared by all and the ability to adjust the surface of the model to conform to each individuals perception of what the final object should look like. The purpose of this interaction can range from forensic reconstruction from partial remains to pre-maxillofacial surgery. A joint project with the forensic unit of the R.C.M.P. in Ottawa using the BADLAB is now in the stages of testing this methodology on a real case beginning with a CT scan of partial remains. A second study underway with the department of Maxiofacial reconstruction at Dalhousie University in Halifax Nova Scotia and concerns a subject who is about to undergo orthognathic surgery, in particular a mandibular advancement. This subject has been MRI scanned, a solid model constructed of the mandible and the virtual surgery constructed on the model. This model and the procedure have been discussed and modified by the modeler and the maxillofacial specialist using these shared workspaces. The procedure will be repeated after the actual surgery to verify the modeled procedure. The advantage of this technique is that none of the specialists need be in the same room, or city. Given the scarcity of time and specialists this methodology shows great promise. In November of this last year a shared live demonstration of this facial modeler was done beteen vancouver and Dalhousie University in H

关键词： 3-dimensional craniofacial reconstruction ATM interactive

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An SGML based viewer for form documents

An SGML based viewer for form documents

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International conference on Document Analysis and Recognition

作者： v. Atalay E. Arslan Department of Computer Engineering Middle East Technical University Ankara Turkey

Proposes a viewer for visual reconstruction and retrieval of form documents. The structure of the form document and the filled-in data are stored in an SGML (Standard Generalised Markup Language) instance. A DSSSL (Document Style Semantics and Specification Language) instance holds style properties of the data. Filled-in data is kept in a relational database. The viewer uses SGML and DSSSL instances as input and visually reconstructs a form document image by retrieving the corresponding filled-in data from the database.

关键词： SGML image reconstruction Spread spectrum communication Relational databases Markup languages Specification languages Information retrieval image retrieval image databases visual databases

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