| 1. |
- Lundin, Margareta
(författare)
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Aspects on Image Quality in Radiologic Evaluation of the Urinary Tract
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The focus of this document is on image quality as one of the factors fundamental for the diagnostic process. With the rising number of procedures and the trend towards more complicated examinations, urinary tract investigations was chosen in this work as a good clinical model for evaluation of the factors influencing image quality and of the ways of evaluating image quality.In paper I, a method is described for optimisation during the introduction of a new imaging system, with a focus on the maintenance of image quality relative to the older already optimised system. Image quality was assessed using the image criteria of the European guidelines for IVU with visual grading analysis. Equivalent image quality in image pairs was achieved at 30% of the dose. The CDRAD contrast-detail phantom makes it possible to find dose levels that give equal image quality using different imaging systems.In paper II, the influence of bowel purgation on image quality in urography is questioned. The aim of this study was to compare bowel purgation and two other preparation methods; dietary restrictions and no preparation at all. Image quality was assessed according to European Commission criteria for excretory urography. The effectiveness of bowel purgation and the amount of residual gas were scored separately. The results of our study show that the preparation methods are of equal value and further use of bowel purgation before excretory urography cannot be justified.In paper III, the image quality of the non-enhanced series is compared to a virtual noncontrast series obtained using two generations of dual-energy CT scanners and taking CT of the urinary tract as a model. The image quality of the VNC images was rated inferior to the single-energy variant for both scanners, the OR range being 11.5–67.3 for the Definition and 2.1–2.8 for the Definition Flash. Visual noise and overall quality were regarded as better with Flash than with Definition. Image quality of VNC images obtained with the new generation of DECT is still slightly inferior compared to native images.In paper IV, the accuracy of measurement of renal calculi in a dual-energy, virtual, nonenhanced-image series is compared to actual stone size and a single-energy image series in the phantom study. This study shows that detection of small stones is not reliable, despite better image quality, with the new DECT and that small stones will be missed with VNC imaging. With larger stones, the inherent measurement error with CT is magnified with VNC imaging.
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| 2. |
- Söderberg, Stefan, et al.
(författare)
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MEASURES OF WAIST AND HIP MODIFY SEX-SPECIFIC ASSOCIATIONS BETWEEN BODY MASS INDEX AND PREVALENCE OF CORONARY ARTERY CALCIFICATION IN OPPOSITE DIRECTIONS
- 2019
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Ingår i: Journal of the American College of Cardiology. - : ELSEVIER SCIENCE INC. - 0735-1097 .- 1558-3597. ; 73:9, s. 13-13
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Background: Obesity is associated with increased risk of cardiovascular disease. However, there is still a debate whether accumulation of fat in certain depots modifies this risk. Using data from the CArdioPulmonary bioImage Study (SCAPIS), we investigated if anthropometric measurements of obesity (waist and hip) modifies the risk of coronary artery calcification. Methods: In the first 15,810 participants in SCAPIS (mean age 58 years, 52% women), data on coronary artery calcification score (CACS) and anthropometry were recorded and traditional cardiovascular risk factors were measured. Body mass index (BMI) was categorized as; <25, 25-30, 30-35 and >35 kg/m2 , quartiles of waist and hip circumferences were constructed within each BMI category and compared using the lowest quartile as reference. Results were adjusted for site, age, smoking and diabetes status. Results: Obesity (BMI >30 kg/m2 ) was found in 21.9% of men and in 20.5% of women. In both sexes the odds ratio (OR) for CACS >0 increased with increasing BMI categories: comparing <25 and >35 kg/m2 , OR = 2.1 (95% CI: 1.6-2.7) for men and OR = 1.4 (1.2-1.8) for women. In addition, increasing quartiles of waist significantly increased the prevalence of CACS >0 for men [p = 0.05; OR = 1.2 (1.0-1.4) for highest quartile] and women [p = 0.005; OR = 1.3 (1.1-1.5)] while increasing quartiles of hip significantly decreased the prevalence for men [p = 0.005; OR = 0.8 (0.6-0.9)] and women [p = 0.04; OR = 0.8 (0.7-0.9)]. Data on education level and physical activity did not affect the model. Conclusion: Increased BMI is associated with increased prevalence of coronary artery calcification and the distribution of fat modifies this risk. Our results suggest that gluteofemoral adipose tissue (hip) counteracts the negative effects associated with BMI and abdominal adipose tissue (waist).
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| 3. |
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| 4. |
- Berntsson, Thore, 1947, et al.
(författare)
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Towards Sustainabel Oil Refinery - Pre-study for larger co-operation project
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this report, the Chalmers EnergiCentrum (CEC) presents the results of a pre-study commissioned by Preem relating to the effective production of future vehicle fuels.This pre-study was made up of three studies focusing on energy streamlining, the utilisation of waste heat and carbon-dioxide separation and biorefinement relating to the gasification and hydration of vegetable oils. One of the common starting points for these studies was the current situation at the Preem refineries in Göteborg and Lysekil from where the measurement data were obtained and analysed. The report summarises the knowledge situation based on current research in the individual technical fields. The results present some interesting future opportunities for developing the sustainable production of future vehicle fuels. The sections vary, as the areas that have been examined differ and the sections have been written by different people. The reports ends with some joint conclusions and a number of questions which could be included and answered in a more extensive future main study, as part of a developed research partnership between Preem and the Chalmers University of Technology. The preliminary results of this work were analysed with the client at workshops on 1 October and 29 November 2007. The report is written in English combined with an extensive summary in Swedish including a proposal on a future main study. The study was conducted by the Chalmers EnergiCentrum (CEC), in collaboration with a number of researchers in the CEC’s network. They included Thore Berntsson, Jessica Algehed, Erik Hektor and Lennart Persson Elmeroth, all from Heat and Power Technology, Börje Gevert, Chemical and Biological Engineering, Tobias Richards, Forest Products and Chemical Engineering, Filip Johnsson and Anders Lyngfelt, Energy Technology, and Per-Åke Franck and Anders Åsblad, CIT Industriell Energianalys AB. The client, Preem, was represented by Bengt Ahlén, Sören Eriksson, Johan Jervehed, Bertil Karlsson, Gunnar Olsson, Ulf Kuylenstierna, Stefan Nyström, Martin Sjöberg and Thomas Ögren. Tobias Richards was responsible for compiling the report and Bertil Pettersson was the project manager.
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| 5. |
- Boman, Christoffer, et al.
(författare)
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Development of innovative small(micro)-scale biomass-based CHP technologies
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- To enhance the overall efficiency of the use of biomass in the energy sector in Europe, the large electricity production potential from small-scale biomass heating systems should be utilised. So far, no technologically sound (in terms of efficiency and reliability) and economically affordable micro- and small-scale biomass CHP technologies are, however, available. Therefore, the present ERA-NET project (MiniBioCHP) aimed at the further development and test of new CHP technologies based on small-scale biomass combustion in the electric capacity range between some W and 100 kW. Within the project, an international consortium consisting of 12 partners from 4 countries, including university institutions, institutes and industry (both engineering and manufacturing), collaborated closely to perform high level R&D on three promising micro/small-scale biomass based CHP technologies which are covering a broad range of applications in the residential heating sector. The Austrian engineering company BIOS, coordinated the international project. The project was based on earlier basic research and development work related to these promising new technologies and aimed at the achievement of a technological level which allows a first (commercial) demonstration after the end of the project. The three CHP concepts included in the MiniBioCHP project were;1. Pellet stoves with a thermoelectric generator (TEG)2. Small-scale biomass boilers (10-30 kWth) with a micro-ORC process3. High temperature heat exchanger (HT-HE) for an externally fired gas turbine (EFGT)The Swedish part of the project was focused on the development of the concept of biomass based EFGT with dedicated R&D activities related to the development of the HT-HE system. The Swedish project consisted of the research partners Umeå University (project leader), Luleå University of Technology, Chalmers University of Technology and RISE Research Institutes of Sweden, together with the industrial partners Enertech AB/Osby Parca and Ecergy. The expertise of the Swedish partners regarding ash related problems, grate boiler combustion and modelling, deposit formation and high temperature corrosion, were combined with the know-how of a Polish partner regarding HT-HE design, construction, testing and optimisation.The HT-HE is the most crucial component in EFGT processes significantly influencing the investment costs, availabilities as well as the efficiencies that can be achieved. With a thermal capacity from several hundred kW up to 2-3 MWth) the CHP technology based on a biomass boiler and an EFGT is suitable for district heating systems, or process heat consumers. The electricity produced by the gas turbine (up to some 100 kWel) can be used to cover the own electricity consumption of a company and/or fed into the grid. Even though the concept of biomass based EFGT has been an interesting alternative for small-scale CHP production for some decades, and R&D activities have been undertaken, tackling both economic and technical aspects, only a few pilot-plants have been in operation and no initiative has so far reached the level of commercial implementation. Thus, the concept of EFGT fed with biomass is still considered to be in a rather early development stage and the main technical challenges are related to alkali deposit induced corrosion and thermal stress of the HT-HE material, turbine design/operation and system integration.Within the present project, a HT-HE prototype aimed for an EFGT system was therefore designed, constructed and successfully tested at flue gas temperatures up to 900°C. Thus, appropriate guidelines for a compact design of the HT-HE and recommendations have been worked out to minimize thermal stresses as well as ash related problems regarding ash deposit formation and high temperature corrosion in a biomass boiler system. Furthermore, different concepts for the overall biomass based EFGT system have been worked out and evaluated. The outcome of the project will hopefully be used in the further development work and form the basis for a first testing and demonstration plant within the coming years.
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| 6. |
- Dimopoulou, Angeliki, 1975-
(författare)
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CT with 3D-Image Reconstructions in Preoperative Planning
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Computed tomography is one of the most evolving fields of modern radiology. The current CT applications permit among other things angiography, 3D image reconstructions, material decomposition and tissue characterization. CT is an important tool in the assessment of specific patient populations prior to an invasive or surgical procedure. The aim of this dissertation was to demonstrate the decisive role of CT with 3D-image reconstructions in haemodialysis patients scheduled to undergo fistulography, in patients undergoing surgical breast reconstructions with a perforator flap and in patients with complicated renal calculi scheduled to undergo percutaneous nephrolithotomy.CT Angiography with 3D image reconstructions was performed in 31 patients with failing arteriovenous fistulas and grafts, illustrating the vascular anatomy in a comprehensive manner in 93.5% of the evaluated segments and demonstrating a sensitivity of 95% compared to fistulography.In 59 mastectomy patients scheduled to undergo reconstructive breast surgery with a deep inferior epigastric perforator flap, the preoperative planning with CT Angiography with 3D image reconstructions of the anterior abdominal wall providing details of its vascular supply, reduced surgery time significantly (p< 0.001) and resulted in fewer complications.Dual Energy CT Urography with advanced image reconstructions in 31 patients with complicated renal calculi scheduled to undergo PNL, resulted in a new method of material characterisation (depicting renal calculi within excreted contrast) and in the possibility of reducing radiation dose by 28% by omitting the nonenhanced scanning phase. Detailed analysis of the changes renal calculi undergo when virtually reconstructed was performed and a comparison of renal calculi number, volume, height and attenuation between virtual nonenhanced and true nonenhanced images was undertaken. All parameters were significantly underestimated in the virtual nonenhanced images.CT with 3D-reconstructions is more than just “flashy images”. It is crucial in preoperative planning, optimizes various procedures and can reduce radiation dose.
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| 7. |
- Fahnestock, Jesse, et al.
(författare)
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Waste Incineration for the Future : Scenario analysis and action plans
- 2019
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report is a deliverable from a project within the Swedish Strategic Innovation Program RE:Source, financed by the Swedish Energy Agency, Formas and Vinnova. The project, Waste Incineration for the Future, aims to produce a knowledge base for the development of energy recovery from waste that suits the future circular economy. In order to identify and prioritize relevant innovations, a scenario process has been undertaken with stakeholders from the energy, waste and recycling, and manufacturing industries. The result is two distinct, complementary scenarios for the circular economy in Sweden, each with different implications for innovation in waste incineration and energy recovery.With these scenarios as a starting point, the project has defined prioritized areas for innovation and produced action plans for promoting innovation.
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| 8. |
- Gyllensvärd, Frida, 1980-
(författare)
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Efficient Methods for Volumetric Illumination
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Modern imaging modalities can generate three-dimensional datasets with a very high detail level. To transfer all the information to the user in an efficient way there is a need for three-dimensional visualization. In order to enhance the diagnostic capabilities the utilized methods must supply the user with fast renderings that are easy to interpret correctly.It can thus be a challenge to visualize a three-dimensional dataset in a way that allows the user to perceive depth and shapes. A number of stereoscopic solutions are available on the market but it is in many situations more practical and less expensive to use ordinary two-dimensional displays. Incorporation of advanced illumination can, however, improve the perception of depth in a rendering of a volume. Cast shadows provide the user with clues of distances and object hierarchy. Simulating realistic light conditions is, however, complex and it can be difficult to reach interactive frame rates. Approximations and clever implementations are consequently required.This thesis presents efficient methods for calculation of illumination with the objective of providing the user with high spatial and shape perception. Two main types of light conditions, a single point light source and omni-directional illumination, are considered. Global transport of light is efficiently estimated using local piecewise integration which allows a graceful speed up compared to brute force techniques. Ambient light conditions are calculated by integrating the incident light along rays within a local neighborhood around each point in the volume.Furthermore, an approach that allows the user to highlight different tissues, using luminous materials, is also available in this thesis. A multiresolution data structure is employed in all the presented methods in order to support evaluation of illumination for large scale data at interactive frame rates.
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| 9. |
- Hagstrom, Emil, et al.
(författare)
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IMPACT OF BODY WEIGHT AT AGE 20 AND WEIGHT GAIN DURING ADULTHOOD ON MIDLIFE CORONARY ARTERY CALCIUM IN 15,000 MEN AND WOMEN : AN INTERIM ANALYSIS OF THE SWEDISH CARDIOPULMONARY BIOIMAGE STUDY
- 2019
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Ingår i: Journal of the American College of Cardiology. - : ELSEVIER SCIENCE INC. - 0735-1097 .- 1558-3597. ; 73:9, s. 1692-1692
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- BackgroundElevated body weight in adolescence is strongly associated with early cardiovascular disease, but whether this association is traceable to weight in early adulthood, or to weight gain with subsequent high adult weight is not known. Using data from the Swedish CArdioPulmonary bioImage Study (SCAPIS), we investigated the association between weight at age 20, weight gain to midlife and coronary artery calcium score (CACS) at midlife.MethodsIn the first 15,810 participants in SCAPIS (mean age 58 years, 52% women), data on CACS at midlife, self-reported body weight at age 20 and weight at examination in SCAPIS were recorded.ResultsCACS in midlife was significantly higher with increasing weight at age 20 (p<0.001 for both sexes), and then increased with weight gain until midlife at all levels of body weight at age 20 after adjusting for age, height, smoking, alcohol intake, education level, exercise levels and LDL cholesterol. However, the association with weight gain was only significant in men (p = 0.047), not in women (p=0.474). No significant interaction was seen between weight at age 20 and midlife weight with CACS. The effect of weight at age 20 on CACS was significantly more marked in men than in women, as was the effect of weight gain (p<0.001 for both interactions).ConclusionWeight at age 20 and weight gain to midlife were both related to CACS, but much more markedly so in men than in women, indicating a generally larger effect of both early adult weight and further weight gain until midlife on CACS in men, compared to women.
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