| 1. |
- Fritzell, Peter, et al.
(författare)
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Bacteria : back pain, leg pain and Modic sign—a surgical multicentre comparative study
- 2019
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Ingår i: European spine journal. - : Springer. - 0940-6719 .- 1432-0932. ; 28:12, s. 2981-2989
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To compare bacterial findings in pain-generating degenerated discs in adults operated on for lumbar disc herniation (LDH), and mostly also suffering from low back pain (LBP), with findings in adolescent patients with non-degenerated non-pain-generating discs operated on for scoliosis, and to evaluate associations with Modic signs on magnetic resonance imaging (MRI). Cutibacterium acnes (Propionibacterium acnes) has been found in painful degenerated discs, why it has been suggested treating patients with LDH/LBP with antibiotics. As multidrug-resistant bacteria are a worldwide concern, new indications for using antibiotics should be based on solid scientific evidence.Methods: Between 2015 and 2017, 40 adults with LDH/LBP (median age 43, IQR 33–49) and 20 control patients with scoliosis (median age 17, IQR 15–20) underwent surgery at seven Swedish hospitals. Samples were cultured from skin, surgical wound, discs and vertebrae. Genetic relatedness of C. acnes isolates was investigated using single-nucleotide polymorphism analysis. DNA samples collected from discs/vertebrae were analysed using 16S rRNA-based PCR sequencing. MRI findings were assessed for Modic changes.Results: No bacterial growth was found in 6/40 (15%) LDH patients, compared with 3/20 (15%) scoliosis patients. Most positive samples in both groups were isolated from the skin and then from subcutis or deep within the wound. Of the four disc and vertebral samples from each of the 60 patients, 235/240 (98%) were DNA negative by bacterial PCR. A single species, C. acnes, was found exclusively in the disc/vertebra from one patient in each group. In the LDH group, 29/40 (72%) patients had at least one sample with growth of C. acnes, compared to 14/20 (70%) in the scoliosis group. Bacterial findings and Modic changes were not associated.Conclusions: Cutibacterium acnes found in discs and vertebrae during surgery for disc herniation in adults with degenerated discs may be caused by contamination, as findings in this group were similar to findings in a control group of young patients with scoliosis and non-degenerated discs. Furthermore, such findings were almost always combined with bacterial findings on the skin and/or in the wound. There was no association between preoperative Modic changes and bacterial findings. Antibiotic treatment of lumbar disc herniation with sciatica and/or low back pain, without signs of clinical discitis/spondylitis, should be seriously questioned.
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| 2. |
- Abramian, David, 1992-, et al.
(författare)
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Anatomically Informed Bayesian Spatial Priors for FMRI Analysis
- 2020
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Ingår i: ISBI 2020. - : IEEE. - 9781538693308
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Konferensbidrag (refereegranskat)abstract
- Existing Bayesian spatial priors for functional magnetic resonance imaging (fMRI) data correspond to stationary isotropic smoothing filters that may oversmooth at anatomical boundaries. We propose two anatomically informed Bayesian spatial models for fMRI data with local smoothing in each voxel based on a tensor field estimated from a T1-weighted anatomical image. We show that our anatomically informed Bayesian spatial models results in posterior probability maps that follow the anatomical structure.
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| 3. |
- Andersson, Kenneth, 1970-, et al.
(författare)
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A perception based velocity estimator and its use for motion compensated prediction
- 2001
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Ingår i: SCIA 2001 Scandinavian Conference on Image Analysis,2001. ; , s. 493-499
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Konferensbidrag (refereegranskat)abstract
- The use of temporal redundancy is of vital importance for a successful video coding algorithm. An effective approach is the hybrid video coder where motion estimation is used for prediction of the next image frame and code the prediction error, and the motion field. The standard method for motion estimation is block matching as in MPEG-2, typically resulting in block artifacts. In this paper a perception based velocity estimator and its use for pixel based motion compensated prediction of interlaced video is presented.
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| 4. |
- Andersson, Kenneth, 1970-, et al.
(författare)
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Backward-forward motion compensated prediction
- 2002
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Ingår i: Proceedings of ACIVS 2002 (Advanced Concepts for Intelligent Vision Systems), Ghent, Belgium, September 9-11, 2002. ; , s. 260-267
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Konferensbidrag (refereegranskat)abstract
- This paper presents new methods for use of dense motion fields for motion compensation of interlaced video. The motion is estimated using previously decoded field-images. An initial motion compensated prediction is produced using the assumption that the motion is predictable in time. The motion estimation algorithm is phase-based and uses two or three field-images to achieve motion estimates with sub-pixel accuracy. To handle non-constant motion and the specific characteristics of the field-image to be coded, the initially predicted image is refined using forward motion compensation, based on block-matching. Tests show that this approach achieves higher PSNR than forward block-based motion estimation, when coding the residual with the same coder. The subjective performance is also better.
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| 5. |
- Andersson, Kenneth, 1970-, et al.
(författare)
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Continuous normalized convolution
- 2002
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Ingår i: Multimedia and Expo, 2002. ICME '02. Proceedings. 2002 IEEE International Conference on (Volume:1). - : IEEE. - 0780373049 ; , s. 725-728
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Konferensbidrag (refereegranskat)abstract
- The problem of signal estimation for sparsely and irregularly sampled signals is dealt with using continuous normalized convolution. Image values on real-valued positions are estimated using integration of signals and certainties over a neighbourhood employing a local model of both the signal and the used discrete filters. The result of the approach is that an output sample close to signals with high certainty is interpolated using a small neighbourhood. An output sample close to signals with low certainty is spatially predicted from signals in a large neighbourhood.
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| 6. |
- Andersson, Kenneth, 1970-, et al.
(författare)
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Motion compensation using backward prediction and prediction refinement
- 2003
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Ingår i: Signal Processing: Image Communication. - 0923-5965. ; 18:5, s. 381-400
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents new methods for use of dense motion fields for motion compensation of interlaced video. The motion estimation is based on previously decoded field-images. The motion is then temporally predicted and used for motion compensated prediction of the field-image to be coded. The motion estimation algorithm is phase-based and uses two or three field-images to achieve motion estimates with sub-pixel accuracy. To handle non-constant motion and the specific characteristics of the field-image to be coded, the initially predicted image is refined using forward motion compensation, based on block-matching. Tests show that this approach achieves higher PSNR than forward block-based motion estimation, when coding the residual with the same coder. The subjective performance is also better.
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| 7. |
- Andersson, Kenneth, 1970-, et al.
(författare)
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Multiple hierarchical motion estimation
- 2002
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Ingår i: Signal Processing, Pattern Recognition, and Applications - 2002. - : ACTA Press. ; , s. 80-
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Konferensbidrag (refereegranskat)abstract
- This paper introduce multiple hierarchical motion estimation to achieve motion estimates with high spatial resolution. The approach is based on phase-based motion estimation. Results show that the algorithm deal with the smooth motion field of hierarchical motion estimation while keeping the advantages of such an approach.
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| 8. |
- Andersson, Kenneth, 1970-, et al.
(författare)
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Prediction from off-grid samples using continuous normalized convolution
- 2007
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Ingår i: Signal Processing. - : Elsevier BV. - 0165-1684 .- 1872-7557. ; 87:3, s. 353-365
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a novel method for performing fast estimation of data samples on a desired output grid from samples on an irregularly sampled grid. The output signal is estimated using integration of signals over a neighbourhood employing a local model of the signal using discrete filters. The strength of the method is demonstrated in motion compensation examples by comparing to traditional techniques.
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| 9. |
- Andersson, Mats, 1960-, et al.
(författare)
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Transformation of local spatio-temporal structure tensor fields
- 2003
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Ingår i: Acoustics, Speech, and Signal Processing, 2003. Proceedings. (ICASSP '03). 2003 IEEE International Conference on (Volume:3 ). - : IEEE. - 0780376633 ; , s. 285-288
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Konferensbidrag (refereegranskat)abstract
- Tensors and tensor fields are commonly used in multidimensional signal processing to represent the local structure of the signal. This paper focuses on the case where the sampling on the original signal is anisotropic, e.g when the resolution of the multidimensional image varies depending on the direction which is common e.g. in medical imaging devices. To obtain a geometrically correct description of the local structure there are mainly two possibilities. To resample the image prior to the computation of the local structure tensor field or to compute the tensor field on the original grid and transform the result to obtain a correct geometry of the local structure. This paper deals with the latter alternative and contains an in depth theoretical analysis establishing the appropriate rules for tensor transformations induced by changes in space-time geometry with emphasis on velocity and motion estimation.
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| 10. |
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