| 1. |
- Eklund, Anders, et al.
(författare)
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A Brain Computer Interface for Communication Using Real-Time fMRI
- 2010
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Ingår i: Proceedings of the 20th International Conference on Pattern Recognition. - Los Alamitos, CA, USA : IEEE Computer Society. - 9781424475421 ; , s. 3665-3669
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Konferensbidrag (refereegranskat)abstract
- We present the first step towards a brain computer interface (BCI) for communication using real-time functional magnetic resonance imaging (fMRI). The subject in the MR scanner sees a virtual keyboard and steers a cursor to select different letters that can be combined to create words. The cursor is moved to the left by activating the left hand, to the right by activating the right hand, down by activating the left toes and up by activating the right toes. To select a letter, the subject simply rests for a number of seconds. We can thus communicate with the subject in the scanner by for example showing questions that the subject can answer. Similar BCI for communication have been made with electroencephalography (EEG). The subject then focuses on a letter while different rows and columns of the virtual keyboard are flashing and the system tries to detect if the correct letter is flashing or not. In our setup we instead classify the brain activity. Our system is neither limited to a communication interface, but can be used for any interface where five degrees of freedom is necessary.
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| 2. |
- Forsberg, Daniel, et al.
(författare)
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Adaptive Anisotropic Regularization of Deformation Fields for Non-Rigid Registration
- 2010
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Ingår i: IEEE International Conference on Acoustics, Speech, and Signal Processing. - : IEEE. - 9781424442966 - 9781424442959 ; , s. 473-476
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Image registration is a crucial task in many applications and applied in a variety of different areas. In addition to the primary task of image alignment, the deformation field is valuable when studying structural/volumetric changes in the brain. In most applications a regularizing term is added to achieve a smoothly varying deformation field. This can sometimes cause conflicts in situations of local complex deformations. In this paper we present a new regularizer, which aims at handling local complex deformations while maintaining an overall smooth deformation field. It is based on an adaptive anisotropic regularizer and its usefulness is demonstrated by two examples, one synthetic and one with real MRI data from a pre- and post-op situation with normal pressure hydrocephalus.
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| 3. |
- Forsberg, Daniel, et al.
(författare)
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Classification of multivariate medical datasets using deformable models - A work in progress
- 2009
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents an overview of the project “Classification of multivariate medical datasets using deformable models” and the current work within the project. The project is a joint venture between the Department of Biomedical Engineering (Linköping University), the Center for Medical Image Science and Visualization (Linköping University) and Sectra Imtec AB (Linköping) and focuses on extending a deformable model approach, named the Morphon, to 3D and to utilize multi-variate data with multiple priors. Recent work in the project includes evaluating different methods for estimating the displacement field and automatic scale control.
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| 4. |
- Hemmendorff, Magnus, et al.
(författare)
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Phase-based Multidimensional Volume Registration
- 2000
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Konferensbidrag (refereegranskat)abstract
- We present a method for accurate image registration and motion estimation in multidimensional volumes, such as 3D CT and MR images. The method is based on phase from quadrature filters, which makes it insensitive to variations in luminance and other disturbance in the images. The theory is not restricted to any particular kind of motion model or number of dimensions. Experimental results for affine motions in 3D show high accuracy.
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| 5. |
- Knutsson, Hans, et al.
(författare)
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Respiratory Arifact Reduction in MRI using Dynamic Deformation Modelling
- 2002
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents a novel magnetic resonance imaging (MRI) reconstruction method that will reconstruct an object correctly despite the presence of respiratory-type motions. The basis for the method is the observation that affine deformations of an object will correspond to a different but unique affine coordinate transform of the Fourier representation (k-space) of the object. The resulting sample points will be irregularly distributed prohibiting the use of standard IFFT to reconstruct the object. The object can however be reconstructed through the use of a weighted regularized pseudo inverse. Short computing times are obtained using a novel fast sequential pseudo inverse algorithm.
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| 6. |
- Ohlsson, Henrik, 1981-, et al.
(författare)
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Direct Weight Optimization Applied to Discontinuous Functions
- 2008
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Ingår i: 47th IEEE Conference on Decision and Control, 2008. CDC 2008. - Cancun, Mexico : IEEE. - 9781424431236 ; , s. 117-122
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Konferensbidrag (refereegranskat)abstract
- The Direct Weight Optimization (DWO) approach is a nonparametric estimation approach that has appeared in recent years within the field of nonlinear system identification. In previous work, all function classes for which DWO has been studied have included only continuous functions. However, in many applications it would be desirable also to be able to handle discontinuous functions. Inspired by the bilateral filter method from image processing, such an extension of the DWO framework is proposed for the smoothing problem. Examples show that the properties of the new approach regarding the handling of discontinuities are similar to the bilateral filter, while at the same time DWO offers a greater flexibility with respect to different function classes handled.
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| 7. |
- Plumat, J., et al.
(författare)
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Image registration using Morphon algorithm: an ITK implementation
- 2009
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Ingår i: Insight Journal. - 2327-770X.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Medical image registration is becoming a more and more useful component of a large number of applications. The presented method aims to enrich the ITK library. This method, called Morphon registration algorithm, computes a dense deformation field accepting inputs from different intensity contrasts. This article presents its implementation within the Insight Toolkit. In this paper, we provide a brief description of the algorithm, a presentation of the implementation, the justification of our modified classes and the results given by the algorithm. We demonstrate the algorithm in application of different images intesity constrasts and dimensions.
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| 8. |
- Sigfridsson, Andreas, et al.
(författare)
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Retrospective Respiratory Motion Compensation for Cardiac MRI
- 2003
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Konferensbidrag (refereegranskat)abstract
- Cardiac MRI is known to be degraded by respiratory motion. Short scans can be performed using breath-hold techniques, while coronary artery imaging commonly use navigator gated sequences, acquiring data in a known static respiration position.
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| 9. |
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| 10. |
- Tautz, Lennart, et al.
(författare)
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Phase-Based Non-Rigid Registration of Myocardial Perfusion MRI Image Sequence
- 2010
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Ingår i: IEEE International Symposium on Biomedical Imaging: From Nano to Macro, 2010. - : IEEE. - 9781424441259 ; , s. 516-519
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Konferensbidrag (refereegranskat)abstract
- The condition of the heart muscle tissue can be inferred by analyzing the time-intensity curves obtained with myocardial perfusion MRI. Specifically, identifying tissue that is under-supplied with blood is important when choosing a suitable therapy for patients with coronary heart disease. Before an analysis can be carried out, the images must be registered to compensate for cardiac and respiratory motion. This is a difficult problem, as the motion is non-rigid and because the image contrast varies strongly over time due to the injection of a contrast agent into the blood stream. To address these problems, an automatic non-rigid registration approach is presented that utilizes local phase instead of intensity or gradient information.
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