| 1. |
- Bigun, Josef, et al.
(författare)
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Orientation fields filtering by derivates of a Gaussian
- 2003
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Ingår i: Image Analysis. - Berlin : Springer. - 3540406018 ; , s. 307-313, s. 19-27
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Bokkapitel (refereegranskat)abstract
- We suggest a set of complex differential operators, symmetry derivatives, that can be used for matching and pattern recognition. We present results on the invariance properties of these. These show that all orders of symmetry derivatives of Gaussians yield a remarkable invariance : they are obtained by replacing the original differential polynomial with the same polynomial but using ordinary scalars. Moreover, these functions are closed under convolution and they are invariant to the Fourier transform. The revealed properties have practical consequences for local orientation based feature extraction. This is shown by two applications: i) tracking markers in vehicle tests ii) alignment of fingerprints.
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| 2. |
- Danielsson, Per-Erik, et al.
(författare)
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A modified fast marching method
- 2003
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Ingår i: Image Analysis. - : Springer Berlin/Heidelberg. - 3540406018 - 9783540451037 - 9783540406013 ; , s. 1154-1161
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Bokkapitel (refereegranskat)abstract
- In most, if not all fast marching methods published hitherto, the input,cost function and the output arrival time are sampled on exactly the same grid. But since the input data samples are differences of the output samples. we found it natural to separate the input and output grid half a sampling unit in all coordinates (two or three). We also employ 8-neighborhood (26-neighborhood in the 3D-case) in the basic updating step of the algorithm. Some simple numerical experiments verify that the modified method improves the accuracy considerably. However, we also feel the modified method leads itself more naturally to image processing applications like tracking and segmentation.
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| 3. |
- Eriksson Bylund, Nina, et al.
(författare)
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3D Wiener filtering to reduce reverberations in ultrasound image sequences
- 2003
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Ingår i: Image Analysis. - : Springer. - 3540406018 - 9783540406013 ; , s. 579-586
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Bokkapitel (refereegranskat)abstract
- One of the most frequently occuring artifacts in ultrasound imaging is reverberations. These are multiple reflection echoes that result in ghost echoes in the ultrasound image. A method for reducing these unwanted artifacts using a three-dimensional (3D) Wiener filter is presented. The Wiener filter is a global filter and produces an estimate of the uncorrupted signal by minimizing the mean square error between the estimate and the uncorrupted signal in a statistical sense. The procedure works as follows: In a graphic interface the operator is displayed an image sequence. The operator marks two areas in one of the images, one area which contains a typical reverberation artifact, and one area free from artifact. Using these areas to produce noise and signal estimates, a Wiener filter is created and applied to the sequence. The 3D Wiener filters display excellent selection capabilities, and the developed method significantly reduces the magnitude of the reverberation artifact in the tested sequences.
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| 4. |
- Farnebäck, Gunnar
(författare)
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Two-Frame Motion Estimation Based on Polynomial Expansion
- 2003
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Ingår i: SCIA13. - : Springer Berlin/Heidelberg. ; , s. 363-370, s. 363-370
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Konferensbidrag (refereegranskat)abstract
- This paper presents a novel two-frame motion estimation algorithm. The first step is to approximate each neighborhood of both frames by quadratic polynomials, which can be done efficiently using the polynomial expansion transform. From observing how an exact polynomial transforms under translation a method to estimate displacement fields from the polynomial expansion coefficients is derived and after a series of refinements leads to a robust algorithm. Evaluation on the Yosemite sequence shows good results.
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| 5. |
- Flood, Katarina, et al.
(författare)
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On 3D scanning, reconstruction, enhancement, and segmentation of logs
- 2003
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Ingår i: Image Analysis. - : Springer Berlin/Heidelberg. - 3540406018 - 9783540406013 - 9783540451037 ; , s. 733-740
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Bokkapitel (refereegranskat)abstract
- This paper presents novel results from an ongoing feasibility study of fully 3D X-ray scanning of Pinus Sylvestris (Scots Pine) logs. Logs are assumed to be translated through two identical and static cone beam systems with the beams rotated 90degrees relative to eachother, providing a dual set of 2D-projections. For reasons of both cost and speed, each 2D-detector in these two systems consists of a limited number of line detectors. The quality of the reconstructed images is far from perfect, due to sparse detector data and missing projection angles. In spite of this we show that by employing a shape- and direction discriminative technique based on second derivatives, we are able to enhance knot-like features in these data. In the enhanced images it is then possible to detect and localize the pith for each whorl of knots, and subsequently also to perform a full segmentation of the knots in the heartwood.
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| 6. |
- Karlsson, Adam, et al.
(författare)
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Segmentation of Histopathological Sections Using Snakes
- 2003
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Ingår i: Image Analysis. - : Springer. - 9783540406013 - 9783540451037 ; 2749, s. 595-602
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Konferensbidrag (refereegranskat)abstract
- This paper presents a semi-automatic method for segmentation of digital images. The segmentation method is based on snakes and a novel implementation of the snake evolution algorithm is presented. Analytical expressions describing the snake evolution are derived using the Fourier transform. These expressions can be sampled and used in a fast algorithm for snake propagation. Experiments are carried out on images of histopathological tissue sections and the results are very promising. In particular the method is able to cope with overlapping nuclei.
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| 7. |
- Knutsson, Hans, et al.
(författare)
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Loglets : Generalized quadrature and phase for local spatio-temporal structure estimation
- 2003
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Ingår i: Image Analysis. - : Springer Berlin/Heidelberg. - 3540406018 - 9783540406013 - 9783540451037 ; , s. 741-748
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Bokkapitel (refereegranskat)abstract
- The question of which properties of a local structure estimator are important is discussed. Answers are provided via the introduction of a number of fundamental invariances. Mathematical formulations corresponding to the required invariances leads up to the introduction of a new class of filter sets termed loglets. Using loglets it is shown how the concepts of quadrature and phase can be defined in n-dimensions. A number of experiments support the claim that loglets are preferable to other designs. In particular it is demonstrated that the loglet approach outperforms a Gaussian derivative approach in resolution and robustness to variations in object illumination. It is also shown how a measure of the certainty of the estimate can be obtained using the consistency of the generalized phase with respect to orientation.
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| 8. |
- Bååth, Lars, 1948-
(författare)
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To See What You Cannot See
- 2003
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Ingår i: Image Analysis. - Heidelberg : Springer. - 9783540406013 ; , s. 108-108
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Bokkapitel (populärvet., debatt m.m.)abstract
- This paper discusses imaging with complex data from micro-wave, mm-wave, and optical interferometers. An overview of methods to extract physical parameters as images from interferometer data is made and two- and three-dimensional images of gas flows, quasi-stellar objects, steel melts, and fiber material such as wood are presented.
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| 9. |
- Ericsson, Anders, et al.
(författare)
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Automated interpretation of ventilation-perfusion lung scintigrams for the diagnosis of pulmonary embolism using support vector machines
- 2003
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Ingår i: 13th Scandinavian Conference, SCIA 2003 Halmstad, Sweden, June 29 – July 2, 2003 Proceedings/Lecture Notes in Computer Science. - 0302-9743 .- 1611-3349. - 9783540406013 ; 2749, s. 415-421
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Konferensbidrag (refereegranskat)abstract
- The purpose of this study was to develop a new completely automated method for the interpretation of ventilation-perfusion (V-P) lung scintigrams for the diagnosis of pulmonary embolism. A new way of extracting features, characteristic for pulmonary embolism is presented. These features are then used as input to a Support Vector Machine, which discriminates between pulmonary embolism or no embolism. Using a material of 509 training cases and 104 test cases, the performance of the system, measured as the area under the ROC curve, was 0.86 in the test group. It is concluded that a completely automatic method can be used for interpretation of V-P scintigrams. It is faster and more robust than a previously presented method [4,5] and the accuracy is at the same level as the the previous method. It also handles abnormalities in the lungs.
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| 10. |
- Forssén, Per-Erik, et al.
(författare)
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Robust multi-scale extraction of blob features
- 2003
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Ingår i: Proceedings or the 13th Scandinavian Conference, SCIA 2003. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783540406013 ; , s. 769-769
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Konferensbidrag (refereegranskat)abstract
- This paper presents a method for detection of homogeneous regions in grey-scale images, representing them as blobs. In order to be fast, and not to favour one scale over others, the method uses a scale pyramid. In contrast to most multi-scale methods this one is non-linear, since it employs robust estimation rather than averaging to move through scale-space. This has the advantage that adjacent and partially overlapping clusters only affect each other's shape, not each other's values. It even allows blobs within blobs, to provide a pyramid blob structure of the image.
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| 11. |
- Hammarstedt, P, et al.
(författare)
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Affine structure from translational motion in image sequences
- 2003
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Ingår i: Lecture Notes in Computer Science. - 1611-3349 .- 0302-9743. - 9783540406013 ; 2749, s. 387-394
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Konferensbidrag (refereegranskat)abstract
- In this paper a method for obtaining affine structure from an image sequence taken by a translating camera with constant intrinsic parameters is presented. A general geometric constraint, expressed using the camera matrices, is derived and this constraint is used in a least squares solution of the problem. The first step is to obtain a projective reconstruction, in the form of a sequence of camera matrices (and a sparse set of feature points), and then these constraints are used to upgrade to an affine reconstruction. The proposed algorithm extends previous results of affine structure recovery from two images with a translating camera to the general case of a sequence of images. The proposed method is illustrated in both simulated and real experiments.
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| 12. |
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| 13. |
- Persson, Martin, et al.
(författare)
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Protein spot detection by symmetry derivatives of Gaussians
- 2003
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Ingår i: Image analysis, 13th Scandinavian Conference, SCIA 2003, Halmstad, Sweden, June 29 - July 2, 2003, Proceedings. - : Springer. - 9783540406013 ; , s. 520-525
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Konferensbidrag (refereegranskat)abstract
- Two-dimensional gel electrophoresis is the preferred method for simultaneously separating and visualising thousands of proteins. An important part of the computer aided analysis of the proteome is the ability to automatically detect, identify, and quantify the proteins by means of automatic Image processing. We present a fast and sensitive method for protein spot detection using the Circular Symmetry Tensor. It is based upon the work of Bigun on Symmetry derivatives of Gaussians.
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| 14. |
- Richter, J, et al.
(författare)
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Automated interpretation of cardiac scintigrams
- 2003
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Ingår i: Lecture Notes in Computer Science (Image Analysis, Proceedings). - 0302-9743 .- 1611-3349. - 9783540406013 ; 2749, s. 565-570
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Konferensbidrag (refereegranskat)abstract
- The purpose of this study was to develop an automated method for the segmentation of the heart in a 3-D cardiac scintigram. This is immediately useful for eliminating a manual step in a previous version of a decision support system. The automatic segmentation method uses a statistical 3D-model, inspired by Active Shape, which locates the base and apex automatically from a cardiac scintigram. Key features of this algorithm are that it can handle cases where there is no or very little activity in the apex and also if there axe additional parts of the heart where there is little activity. The algorithm has been tested on approximately 2000 cardiac scintigrams.
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| 15. |
- Sladoje, Natasa, et al.
(författare)
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Measuring perimeter and area in low resolution images using a fuzzy approach
- 2003
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Ingår i: Proceedings of 13th Scandinavian Conference on Image Analysis (SCIA 2003). - 9783540406013 ; , s. 853-860
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Konferensbidrag (refereegranskat)abstract
- To overcome the problems of low quality of image segmentation, as well as significant loss of the data, it seems promising to retain the data inaccuracies as realistic as possible during the image analysis procedures, instead of making hard decisions in t
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| 16. |
- Spies, Hagen, et al.
(författare)
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Two-dimensional channel representation for multiple velocities
- 2003
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Ingår i: Proceedings of the 13th Scandinavian Conference of Image Analysis, SCIA 2003. - Berlin, Heidelberg : SpringerLink. - 9783540406013 ; , s. 356-362
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Konferensbidrag (refereegranskat)abstract
- We present a two-dimensional information representation, where small but overlapping Gaussian kernels are used to encode the data in a matrix. Apart from points we apply this to constraints that restrict the solution to a linear subspace. A localised decoding scheme accurately extracts multiple solutions together with an estimate of the covariances. We employ the method in optical flow computations to determine multiple velocities occurring at motion discontinuities.
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| 17. |
- Stewenius, Henrik
(författare)
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Simplified vehicle calibration using multilinear constraints
- 2003
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Ingår i: Lecture Notes in Computer Science (Image Analysis, Proceedings). - 0302-9743 .- 1611-3349. - 9783540406013 ; 2749, s. 669-676
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Konferensbidrag (refereegranskat)abstract
- An Autonomously Guided Vehicle using both odometry and visual data for navigation needs calibration parameters. These include camera placement as well as parameters relating odometry to vehicle motion. Calibration of these parameters is related to the Hand-Eye calibration problem. Instead of using a calibration target or trying to solve for structure and motion a novel method using the continuous multilinear constraint to test parameter combinations is proposed. A low order polynomial target function is calculated in linear time over the sample size resulting in very fast iterations in the optimisation step. The method is tested on simulated data and increased sample size improves the parameter estimates.
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| 18. |
- Svensson, Charlotte, et al.
(författare)
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Structure estimation and surface triangulation of deformable objects
- 2003
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Ingår i: Lecture Notes in Computer Science (Image Analysis, Proceedings). - 0302-9743 .- 1611-3349. - 9783540406013 ; 2749, s. 709-716
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Konferensbidrag (refereegranskat)abstract
- A system is developed that from an image sequence of a deformable object automatically extracts features and tracks them through the sequence, estimates the non-rigid 3D structure and finally computes a surface triangulation. Also the camera motion is acquired. The object is supposed to deform according to a linear model, while the motion of the camera can be arbitrary. No domain specific prior of the object is required. For the structure estimation a two-step approach is used, where we first obtain an initial estimate of the structure and motion, and then obtain an optimal solution via a non-linear optimization scheme. The triangulation is optimized to yield a non-rigid faceted surface that well approximates the true 3D surface.
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| 19. |
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| 20. |
- Åhlén, Julia, et al.
(författare)
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Bottom Reflectance Influence on a Color Correction Algorithm for Underwater Images
- 2003
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Ingår i: Proceedings of the 13th Scandinavian Conference on Image Analysis. - Berlin : Springer. - 3540406018 ; , s. 922-926
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Konferensbidrag (refereegranskat)abstract
- Diminishing the negative effects of water column introduced on digital underwater images is the aim of a color correction algorithm presented by the authors in a previous paper. The present paper describes an experimental result and set of calculations for determining the impact of bottom reflectance on the algorithm's performance. This concept is based on the estimation of the relative reflectance of various bottom types such as sand, bleached corals and algae. We describe the adverse effects of extremely low and high bottom reflectances on the algorithm.
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| 21. |
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