| 1. |
- Alshamari, Muhammed, 1975-, et al.
(författare)
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Diagnostic accuracy of low-dose CT compared with abdominal radiography in non-traumatic acute abdominal pain : prospective study and systematic review
- 2016
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Ingår i: European Radiology. - New York : Springer. - 0938-7994 .- 1432-1084. ; 26:6, s. 1766-1774
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Forskningsöversikt (refereegranskat)abstract
- Objectives: Abdominal radiography is frequently used in acute abdominal non-traumatic pain despite the availability of more advanced diagnostic modalities. This study evaluates the diagnostic accuracy of low-dose CT compared with abdominal radiography, at similar radiation dose levels.Methods: Fifty-eight patients were imaged with both methods and were reviewed independently by three radiologists. The reference standard was obtained from the diagnosis in medical records. Sensitivity and specificity were calculated. A systematic review was performed after a literature search, finding a total of six relevant studies including the present.Results: Overall sensitivity with 95 % CI for CT was 75 % (66-83 %) and 46 % (37-56 %) for radiography. Specificity was 87 % (77-94 %) for both methods. In the systematic review the overall sensitivity for CT varied between 75 and 96 % with specificity from 83 to 95 % while the overall sensitivity for abdominal radiography varied between 30 and 77 % with specificity 75 to 88 %.Conclusions: Based on the current study and available evidence, low-dose CT has higher diagnostic accuracy than abdominal radiography and it should, where logistically possible, replace abdominal radiography in the workup of adult patients with acute non-traumatic abdominal pain.Key points: • Low-dose CT has a higher diagnostic accuracy than radiography. • A systematic review shows that CT has better diagnostic accuracy than radiography. • Radiography has no place in the workup of acute non-traumatic abdominal pain.
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| 2. |
- Alshamari, Muhammed, 1975-, et al.
(författare)
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Impact of iterative reconstruction on image quality of low-dose CT of the lumbar spine
- 2017
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Ingår i: Acta Radiologica. - London : Sage Publications. - 0284-1851 .- 1600-0455. ; 58:6, s. 702-709
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Tidskriftsartikel (refereegranskat)abstract
- Background: Iterative reconstruction (IR) is a recent reconstruction algorithm for computed tomography (CT) that can be used instead of the standard algorithm, filtered back projection (FBP), to reduce radiation dose and/or improve image quality.Purpose: To evaluate and compare the image quality of low-dose CT of the lumbar spine reconstructed with IR to conventional FBP, without further reduction of radiation dose.Material and Methods: Low-dose CT on 55 patients was performed on a Siemens scanner using 120 kV tube voltage, 30 reference mAs, and automatic dose modulation. From raw CT data, lumbar spine CT images were reconstructed with a medium filter (B41f) using FBP and four levels of IR (levels 2-5). Five reviewers scored all images on seven image quality criteria according to the European guidelines on quality criteria for CT, using a five-grade scale. A side-by-side comparison was also performed.Results: There was significant improvement in image quality for IR (levels 2-4) compared to FBP. According to visual grading regression, odds ratios of all criteria with 95% confidence intervals for IR2, IR3, IR4, and IR5 were: 1.59 (1.39-1.83), 1.74 (1.51-1.99), 1.68 (1.46-1.93), and 1.08 (0.94-1.23), respectively. In the side-by-side comparison of all reconstructions, images with IR (levels 2-4) received the highest scores. The mean overall CTDIvol was 1.70 mGy (SD 0.46; range, 1.01-3.83 mGy). Image noise decreased in a linear fashion with increased strength of IR.Conclusion: Iterative reconstruction at levels 2, 3, and 4 improves image quality of low-dose CT of the lumbar spine compared to FPB.
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| 3. |
- Alshamari, Muhammed, 1975-, et al.
(författare)
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Low dose CT of the lumbar spine compared with radiography : a study on image quality with implications for clinical practice
- 2016
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Ingår i: Acta Radiologica. - London, United Kingdom : Sage Publications. - 0284-1851 .- 1600-0455. ; 57:5, s. 602-611
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Tidskriftsartikel (refereegranskat)abstract
- Background: Lumbar spine radiography is often performed instead of CT for radiation dose concerns.Purpose: To compare image quality and diagnostic information from low dose lumbar spine CT at an effective dose of about 1 mSv with lumbar spine radiography.Material and Methods: Fifty-one patients were examined by both methods. Five reviewers scored all examinations on eight image quality criteria using a five-graded scale and also assessed three common pathologic changes.Results: Low dose CT scored better than radiography on the following: sharp reproduction of disc profile and vertebral end-plates (odds ratio [OR], 1.8; 95% confidence interval [CI], 1.3-2.5), intervertebral foramina and pedicles (OR, 4.3; 95% CI, 3.1-5.9), intervertebral joints (OR, 139; 95% CI, 59-326), spinous and transverse processes (OR, 7.0; 95% CI, 4.3-11.2), sacro-iliac joints (OR, 4.2; 95% CI, 3.2-5.7), reproduction of the adjacent soft tissues (OR, 2.9; 95% CI, 2.1-4.0), and absence of any obscuring superimposed gastrointestinal gas and contents (OR, 188; 95% CI, 66-539). Radiography scored better on sharp reproduction of cortical and trabecular bone (OR, 0.3; 95% CI, 0.2-0.4). The reviewers visualized disk degeneration, spondylosis/diffuse idiopathic skeletal hyperostosis (DISH) and intervertebral joint osteoarthritis more clearly and were more certain with low dose CT. Mean time to review low dose CT was 204 s (95% CI, 194-214 s.), radiography 152 s (95% CI, 146-158 s.). The effective dose for low dose CT was 1.0-1.1 mSv, for radiography 0.7 mSv.Conclusion: Low dose lumbar spine CT at about 1 mSv has superior image quality to lumbar spine radiography with more anatomical and diagnostic information.
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| 4. |
- Andersson, Karin M., 1989-, et al.
(författare)
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Metal artefact reduction in CT imaging of hip prostheses-an evaluation of commercial techniques provided by four vendors
- 2015
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Ingår i: British Journal of Radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 88:1052
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The aim of this study was to evaluate commercial metal artefact reduction (MAR) techniques in X-ray CT imaging of hip prostheses.Methods: Monoenergetic reconstructions of dual-energy CT (DECT) data and several different MAR algorithms, combined with single-energy CT or DECT, were evaluated by imaging a bilateral hip prosthesis phantom. The MAR images were compared with uncorrected images based on CT number accuracy and noise in different regions of interest.Results: The three MAR algorithms studied implied a general noise reduction (up to 67%, 74% and 77%) and an improvement in CT number accuracy, both in regions close to the prostheses and between the two prostheses. The application of monoenergetic reconstruction, without any MAR algorithm, did not decrease the noise in the regions close to the prostheses to the same extent as did the MAR algorithms and even increased the noise in the region between the prostheses.Conclusion: The MAR algorithms evaluated generally improved CT number accuracy and substantially reduced the noise in the hip prostheses phantom images, both close to the prostheses and between the two prostheses. The study showed that the monoenergetic reconstructions evaluated did not sufficiently reduce the severe metal artefact caused by large orthopaedic implants.Advances in knowledge: This study evaluates several commercially available MAR techniques in CT imaging of large orthopaedic implants.
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| 5. |
- Andersson, Karin M., 1989-, et al.
(författare)
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Metal Artifacts in CT Imaging of Hip Prostheses : Evaluation of Metal Artifact Reduction Techniques Provided by Four Vendors
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- PURPOSE: The aim of this study was to evaluate metal artifact reduction (MAR) techniques, provided by four vendors, in CT imaging of hip prostheses.METHOD AND MATERIALS: A water phantom containing hip prostheses mounted in calf bones was scanned with four CT scanners; Philips Ingenuity; Toshiba Aquilion ONE Vision edition; GE Discovery 750 HD and Siemens SOMATOM Definition Flash. An uncorrected (reference) image was obtained for every CT and compared with images acquired with the scanner specific MAR technique; either monoenergetic reconstruction of Dual Energy CT (DECT) data (GE and Siemens) or the use of a MAR algorithm software (Philips and Toshiba), or a combination of the two (GE). The MAR techniques were applied for varying tube voltage, kernel and reconstruction technique. The reference images were quantitatively compared to the MAR images by analyzing the noise and the CT number accuracy in region of interests (ROIs). Visual grading was performed by five radiologists based on ten image quality (IQ) criteria.RESULTS: The MAR algorithms implied a general noise reduction (by up to 77%) and improved IQ based on the majority of the visual grading criteria. The use of monoenergetic reconstructions of DECT data, without any MAR algorithm, did not decrease the noise in the ROIs to the same extent as the MAR algorithms (up to 41%) and did even increase the noise in one ROI. The visual grading evaluation showed that monoenergetic reconstructions in general degraded the IQ for one of the DECT scanners and improved the IQ for only a few of the criteria for the other DECT scanner.CONCLUSION: The quantitative analysis and the visual grading evaluation showed that the IQ was generally improved when the MAR algorithms were used. However, additional artifacts and degradation of the IQ were noted in some MAR image regions. The use of monoenergetic reconstruction was concluded to not reduce metal artifacts to the same extent as the MAR algorithms and to even degrade the IQ in several image regions.CLINICAL RELEVANCE/APPLICATION: This study points out advantages and potential risks of using MAR techniques in CT imaging of hip prostheses and will be useful for clinics when optimizing CT scan protocols and purchasing new CT systems.
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| 6. |
- Andersson, Karin M., 1989-, et al.
(författare)
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Visual grading evaluation of commercially available metal artefact reduction techniques in hip prosthesis computed tomography
- 2016
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Ingår i: British Journal of Radiology. - London, United Kingdom : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 89:1063
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: To evaluate metal artefact reduction (MAR) techniques from four computed tomography (CT) vendors in hip prosthesis imaging.Methods: Bilateral hip prosthesis phantom images, obtained by using MAR algorithms for single energy CT data or dual energy CT (DECT) data and by monoenergetic reconstructions of DECT data, were visually graded by five radiologists using ten image quality criteria. Comparisons between the MAR images and a reference image were performed for each scanner separately. Ordinal probit regression analysis was used.Results: The MAR algorithms in general improved the image quality based on the majority of the criteria (up to between 8/10 and 10/10) with a statistically improvement in overall image quality (P<0.001). However, degradation of image quality, such as new artefacts, was seen in some cases. A few monoenergetic reconstruction series improved the image quality (P<0.004) for one of the DECT scanners, but it was only improved for some of the criteria (up to 5/10). Monoenergetic reconstructions resulted in worse image quality for the majority of the criteria (up to 7/10) for the other DECT scanner.Conclusions: The MAR algorithms improved the image quality of the hip prosthesis CT images. However, since additional artefacts and degradation of image quality were seen in some cases, all algorithms should be carefully evaluated for every clinical situation. Monoenergetic reconstructions were in general concluded to be insufficient for reducing metal artifacts. Advances in knowledge: Qualitative evaluation of the usefulness of several MAR techniques from different vendors in CT imaging of hip prosthesis.
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| 7. |
- Andersson, Karin, 1989-
(författare)
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Metal artifacts in computed tomography : impact of reduction methods on image quality and radiotherapy treatment planning
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Degradation of image quality by metal artifacts is a common problem in computed tomography (CT) imaging, which can limit the diagnostic value of a CT examination and also introduce inaccuracies in radiotherapy (RT) treatment planning. In recent years, commercial metal artifact reduction (MAR) methods have been launched by several CT vendors. The overall aim of this thesis was to evaluate MAR methods in diagnostic imaging and RT treatment planning.Evaluations of hip prosthesis phantom CT images showed that MAR algorithms in general improved image quality, based on both visual grading analysis and quantitative measures, while the application of virtual monoenergetic reconstructions insufficiently reduced metal artifacts. In some cases additional artifacts were introduced by the MAR algorithms. MAR algorithms were also evaluated in hip prosthesis phantom CT imaging used for proton therapy treatment planning, where improvements in dose calculation accuracy were observed.Studies of Head & Neck (H&N) implant CT images in RT treatment planning were also performed. By visual grading of anatomy visualization with respect to target delineation in dental implant patient images, MAR algorithms were shown to significantly improve image quality. However, only minor effects of H&N implant artifacts on proton dose distributions were seen. The impact might be greater for more severe artifacts than those studied here, and thus further investigations of such cases are needed.In conclusion, MAR algorithms have been shown to enhance image quality for diagnostic applications and to improve anatomy visualization in RT treatment planning. The MAR algorithms led to increased proton dose calculation accuracy in some cases, while in other situations only minor changes were seen.
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| 8. |
- Norrman, Andreas, et al.
(författare)
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Systematiska och processorienterade mätsystem : En teoriöversikt
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Rapporten är en teoriöversikt över systematiska mätsystem och hur de kan utformas med hänsyn till olika perspektiv, såsom strategi, process, försörjningsnätverk och anläggning, men också för att ge en integrerad helhetssyn. Rapporten identifierar intressanta fördjupningsområden för framtida forskningsområden i uppdrag av Trafikverket.Med ett kritiskt förhållningssätt har en systematisk genomgång av litteraturen gjorts. Litteraturstudien pekar på att det finns problem med terminologin och standardisering av vad som menas med systematiska mätsystem. Trots att forskning kring mätsystem har bedrivits under lång tid är problembilden den samma idag som för tjugo år sedan och få konkreta lösningar på dessa problem har forskats fram. Det finns konceptuella modeller kring design och implementering av mätsystem, men det finns lite forskning kring användning av mätsystem och dess effekter på organisationen.Ur ett akademiskt perspektiv innebär det att mätsystem är inte är ett etablerat forskningsområde. Det finns med andra ord brister i teoribasen, brister i utvärderingen av mätsystemen, brister i empiri och kvalitet när det gäller forskningen.I praktiken innebär det att det är en liten koppling mellan teori och praktik. Det finns ett analytiskt synsätt snarare än en systemsyn. Konceptuellt finns en stark koppling mellan strategi och mätsystemet, men i praktiken finns det brister i kopplingen och få empiriska bevis. Processorientering är underutvecklat och kartläggningen av processer ignoreras. Det brister även i kopplingen mellan intressenter och mätsystemet. Speciellt ur ett kund- eller medborgarfokus. Det finns också lite fokus på förändringsarbete och vilka framgångsfaktorer som medför lyckade utformningar och implementeringar av mätsystem.Trafikverket är till stor del beroende av underleverantörer för att leverera sin prestation. Det är därför relevant att mäta också påverkan och prestation av partners och leverantörer. Denna ansats, att mäta i försörjningskedjor med en systemansats, har börjat uppmärksammas inom logistikforskningen de senaste femton åren. Denna forskning har för övrigt samma grundperspektiv, och kan tillskrivas samma kritik, som övrig forskning.Det finns framtida forskningsbehov kring både implementera och utvärdera mätsystem samt i högre grad testa och bevisa konceptuella modeller empiriskt. Det finns också ett behov av större teori- och metoddriven forskning. Att utforma processorienterade mätsystem med ett underliggande försörjnings- och systemsynsätt, kan vara länken till att stärka kopplingen mellan strategier, mätsystemet och dess effekt.
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| 9. |
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| 10. |
- Norrman Brandt, Eva, et al.
(författare)
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The future trip : A story of transformational change
- 2019
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Ingår i: Journal of Organizational Change Management. - : Emerald Group Publishing Limited. - 0953-4814 .- 1758-7816. ; 32:7, s. 669-686
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Tidskriftsartikel (refereegranskat)abstract
- Purpose – The study of successful transformational change processes in organizations has been limited. The aim was to understand a change process and the type of change that occurred in a pharmaceutical company in Sweden 2005–2014.Method – An interactive research design was used, and semi-structured interviews were conducted with 19 individuals, asking about their views on the change journey. Meetings and dialogue with leaders from the organization also took place. Observations from feedback meetings with leaders were included in the analysis. The results were analysed using a time-ordered display identifying key events, interpreted by a theoretical lens determining the type of change over a period of 10 years.Findings – This was a transformational change caused by external pressure, supported by visionary and transparent leadership, collaborative methods aiming at broad involvement, and systemic understanding. The results indicated a 40% increase in productivity and altered organizational design and culture. Sense-making activities, persistent adoption of quality improvement tools, dispersed power, and sequential change activities underpinned the success.Practical implications – The results provide insight into the processes of transformational change. Change leaders were provided with knowledge, inspiration and insight when facing transformations.Social implications – Increased prevalence of transformational change calls for new organizational competencies and altered roles for leaders and employees. There is a need for new ways of developing competence and new recruitment policies for leaders.Originality/value – This case presents unique empirical evidence of a successful cultural transformation led by a leader using post-conventional principles.
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