| 1. |
- Almroth, Gabriel, 1953-, et al.
(författare)
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Acute glomerulonephritis associated with streptococcus pyogenes with concomitant spread of streptococcus constellatus in four rural families
- 2005
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Ingår i: Upsala Journal of Medical Sciences. - 0300-9734 .- 2000-1967. ; 110:3, s. 217-231
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Tidskriftsartikel (refereegranskat)abstract
- We studied history, renal histopathology and microbiology of an epidemic of acute glomerulonephritis associated with throat infections and uncommon culture results in four neighbour families. A 40-year-old man (index patient) was referred to a university hospital for dialysis and kidney biopsy due to a suspected acute glomerulonephritis. An acute tonsillitis had preceded the condition. Penicillin treatment had been started four days before the discovery of renal failure. Throat swabs were positive for β-hemolytic streptococci, group C (GCS). GCS were also found in throat cultures from his wife and two of their children. The bacteria were typed as Streptococcus constellatus. A third child had S. constellatus expressing Lancefield antigen group G. A neighbour and two of his children fell ill the following week with renal involvement. Throat swabs from both these children were positive for S. constellatus. His third child had erythema multiforme and S. constellatus in the throat while a fourth child had β-hemolytic streptococci group A, Streptococcus pyogenes. Kidney biopsies on the index patient and his neighbour showed an acute diffuse prolipherative glomerulonephritis compatible with acute post-streptococcal nephritis and microbiological analysis of renal tissue revealed in both cases S. pyogenes and S. constellatus. The families had had much contact and had consumed unpasteurized milk from our index patient's farm. In four of seven persons in two additional neighbouring families S. constellatus was found in throat swabs during the same month while two persons carried Streptococcus anginosus expressing the Lancefield C antigen. In conclusion spread of S. constellatus coincided with the occurrence of four cases of acute glomerulonephritis. The two biopsied patients had both S. pyogenes and S. constellatus present in renal tissue. The epidemic either suggested that the outbreak of glomerulonephritis was due to S. pyogenes but coincided with the transmission and colonization of S. constellatus or that the S. constellatus strains were highly pathogenic or nephritogenic and that this organism can be transmitted in such cases.
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| 2. |
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| 3. |
- Dornbusch, Kathrine, et al.
(författare)
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Kinolonresistens hos gramnegativa tarmbakterier
- 2003
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Ingår i: Smittnytt : information från smittskyddet och mikrobiologen. - Linköping : Smittskyddsenheten. ; 36, s. 18-21
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 4. |
- Moores, B M, et al.
(författare)
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RADIUS--closing the circle on the assessment of imaging performance.
- 2005
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Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 114:1-3, s. 450-7
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Tidskriftsartikel (refereegranskat)abstract
- The RADIUS (Radiological Imaging Unification Strategy) project addresses the assessment of image quality in terms of both physical and clinically relevant measures. The aim is to unify our understanding of both types of measure as well as the numerous underlying factors that play a key role in the assessments of imaging performance. In this way it is expected to provide a solid basis for the improvement in radiological safety management, where not only radiation risks are considered but also diagnostic risks of incorrect clinical outcomes (i.e. false positive/false negative). The project has applied a variety of relevant experimental and theoretical methods to this problem, which is generic to medical imaging as a whole. Digital radiography of the chest and the breast has been employed as the clinical imaging domain vehicles for the study. The project addressed the problem from the following directions: role and relevance of pathology, human observer studies including receiver operating characteristics, image quality criteria analysis, structural noise analysis, physical measurements on clinical images, physical measurements on imaging system, modelling of imaging system, modelling of visual processes, modelling of doses delivered and IT-based scientific support strategies. This paper presents an overview of the main outcomes from this project and highlights how the research outcomes actually apply to the real world. In particular, attention will be focused on new and original findings and methods and techniques that have been developed within the framework of the project. The relevance of the project's outcomes to future European research will also be presented.
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| 5. |
- Sandborg, Michael, 1961-, et al.
(författare)
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Demonstration of correlations between clinical and physical image quality measures in chest and lumbar spine screen-film radiography
- 2001
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Ingår i: British Journal of Radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 74:882, s. 520-528
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Tidskriftsartikel (refereegranskat)abstract
- The ability to predict clinical image quality from physical measures is useful for optimization in diagnostic radiology. In this work, clinical and physical assessments of image quality are compared and correlations between the two are derived. Clinical assessment has been made by a group of expert radiologists who evaluated fulfilment of the European image criteria for chest and lumbar spine radiography using two scoring methods: image criteria score (ICS) and visual grading analysis score (VGAS). Physical image quality measures were calculated using a Monte Carlo simulation model of the complete imaging system. This model includes a voxelized male anatomy and was used to calculate contrast and signal-to-noise ratio of various important anatomical details and measures of dynamic range. Correlations between the physical image quality measures on the one hand and the ICS and VGAS on the other were sought. 16 chest and 4 lumbar spine imaging system configurations were compared in frontal projection. A statistically significant correlation with clinical image quality was found in chest posteroanterior radiography for the contrast of blood vessels in the retrocardiac area and a measure of useful dynamic range. In lumbar spine anteroposterior radiography, a similar significant correlation with clinical image quality was found between the contrast and signal-to-noise ratio of the trabecular structures in the L1-L5 vertebrae. The significant correlation shows that clinical image quality can, at least in some cases, be predicted from appropriate measures of physical image quality.
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| 6. |
- Tingberg, Anders, et al.
(författare)
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Evaluation of image quality of lumbar spine images: a comparison between FFE and VGA.
- 2005
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Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 114:1-3, s. 53-61
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: The aim of the present study is to compare two different methods for evaluation of the quality of clinical X-ray images. METHODS: Based on fifteen lumbar spine radiographs, two new sets of images were created. A hybrid image set was created by adding two distributions of artificial lesions to each original image. The image quality parameters spatial resolution and noise were manipulated and a total of 210 hybrid images were created. A set of 105 disease-free images was created by applying the same combinations of spatial resolution and noise to the original images. The hybrid images were evaluated with the free-response forced error experiment (FFE) and the normal images with visual grading analysis (VGA) by nine experienced radiologists. RESULTS: In the VGA study, images with low noise were preferred over images with higher noise levels. The alteration of the MTF had a limited influence on the VGA score. For the FFE study, the visibility of the lesions was independent of the sharpness and the noise level. No correlation was found between the two image quality measures. CONCLUSIONS: FFE is a precise method for evaluation of image quality, but the results are only valid for the type of lesion used in the study, whereas VGA is a more general method for clinical image quality assessment. The results of the FFE study indicate that there might be a potential to lower the dose levels in lumbar spine radiography without losing important diagnostic information.
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| 7. |
- Tingberg, Anders, et al.
(författare)
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Influence of the characteristic curve on the clinical image quality of lumbar spine and chest radiographs.
- 2004
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Ingår i: The British journal of radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 77:915, s. 204-15
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Tidskriftsartikel (refereegranskat)abstract
- The "European Guidelines on Quality Criteria for Diagnostic Radiographic Images" do not address the choice of the film characteristic (H&D) curve, which is an important parameter for the description of a radiographic screen-film system. The image contrast of clinical lumbar spine and chest radiographs was altered by digital image processing techniques, simulating images with different H&D curves, both steeper and flatter than the original. The manipulated images were printed on film for evaluation. Seven experienced radiologists evaluated the clinical image quality by analysing the fulfilment of the European Image Criteria (ICS) and by visual grading analysis (VGA) of in total 224 lumbar spine and 360 chest images. A parallel study of the effect of the H&D curve has also been made using a theoretical model. The contrast (DeltaOD) of relevant anatomical details was calculated, using a Monte Carlo simulation-model of the complete imaging system including a 3D voxel phantom of a patient. Correlations between the calculated contrast and the radiologists' assessment by VGA were sought. The results of the radiologists' assessment show that the quality in selected regions of lumbar spine and chest images can be significantly improved by the use of films with a steeper H&D curve compared with the standard latitude film. Significant (p<0.05) correlations were found between the VGA results and the calculations of the contrast of transverse processes and trabecular details in the lumbar spine vertebrae, and with the contrast of blood vessels in the retrocardiac area of the chest.
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| 8. |
- Tingberg, Anders, et al.
(författare)
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Inter-observer variation in masked and unmasked images for quality evaluation of clinical radiographs.
- 2005
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Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 114:1-3, s. 62-8
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To investigate the influence of masking on the inter-observer variation in image quality evaluation of clinical radiographs of chest and lumbar spine. BACKGROUND: Inter-observer variation is a big problem in image quality evaluation since this variation is often much bigger than the variation in image quality between, for example, two radiographic systems. In this study, we have evaluated the effect of masking on the inter-observer variation. The idea of the masking was to force every observer to view exactly the same part of the image and to avoid the effect of the overall 'first impression' of the image. A discussion with a group of European expert radiologists before the study indicated that masking might be a good way to reduce the inter-observer variation. METHODS: Five chest and five lumbar spine radiographs were collected together with detailed information regarding exposure conditions. The radiographs were digitised with a high-performance scanner and five different manipulations were performed, simulating five different exposure conditions. The contrast, noise and spatial resolution were manipulated by this method. The images were printed onto the film and the individual masks were produced for each film, showing only the parts of the images that were necessary for the image quality evaluation. The quality of the images was evaluated on ordinary viewing boxes by a large group of experienced radiologists. The images were examined with and without the masks with a set of image criteria (if fulfilled, 1 point; and not fulfilled, 0 point), and the mean score was calculated for each simulated exposure condition. RESULTS: The results of this study indicate that-contrary to what was supposed-the inter-observer variation increased when the images were masked. In some cases, especially for chest, this increase was statistically significant. CONCLUSIONS: Based on the results of this study, image masking in studies of fulfilment of image criteria cannot be recommended.
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