| 1. |
- Sandstedt, Mårten, 1972-
(författare)
-
Computed Tomography of the Coronary Arteries : Developmental and Prognostic Investigations
- 2020
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Computed tomography (CT) is an increasingly used modality for investigations of patients with suspected coronary artery disease (CAD). Technical advances could improve diagnostic accuracy and lead to clinical workflow improvements. Also, more prognostic information can optimize clinical follow-up strategies and treatments.The general aim of this thesis was to explore the use of CT for CAD investigations. Three studies aimed to examine new technologies, including the evaluation of an on-site, computed tomography-based fractional flow reserve (CT-FFR) software (study I), the evaluation of an AI-based, calcium scoring computed tomography (CSCT) software (study III), and the evaluation of an photon-counting detector (PCD)-CT (study IV). One study aimed to evaluate the long-term prognostic value of coronary computed tomography angiography (CCTA) in symptomatic patients with no history of CAD (study II).The software evaluation studies (study I and III) and the prognostic study (study II) utilized CT data from clinical patients, while the PCD-CT evaluation study (study IV) used CT data from cadaveric specimens. The performances of both software programs were compared with standard references, being represented by fractional flow reserve (FFR) measurements (study I), and coronary artery calcification (CAC) scores from a semi-automatic software (study III), respectively. The PCD-CT performance on CAC quantification was compared with corresponding results from an energy integrating detector (EID)-CT, using micro-CT as the standard reference (study IV). The prognostic study merged registries to identify major adverse cardiac events (MACE), having a follow-up time of up to 7.5 years (study II).The CT-FFR and CSCT software correlation and agreement to corresponding standard references were good and excellent, respectively. Also, both software programs had time-saving potential (study I and III). The CAC quantification was more accurate using PCD-CT than EID-CT (study IV). The prognosis was excellent in patients with normal coronary arteries, and progressively impaired in non-obstructive and obstructive CAD (study II).The results in this thesis convey developmental, technical CT technology advances for CAD investigations. In addition, prognostic follow-up data is communicated. The results may benefit patients by an increased accuracy in the CT evaluation of CAD and can contribute to improve clinical follow-up strategies. Furthermore, the results suggest possibilities to improve the workflow in clinical radiology, which potentially could impact health care costs.
|
|
| 2. |
- Grönberg, Fredrik
(författare)
-
Spectral Photon-Counting Computed Tomography with Silicon Detectors: New Models and Applications
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- X-ray computed tomography (CT) is a widely used imaging modality that enables visualization of nearly every part of the human body. It is used for diagnosis of disease and injury as well as medical treatment planning. The vast majority of CT scanners in clinical use today have energy-integrating x-ray detectors, which measure the total incident energy in a given measurement.Spectral photon-counting detectors operate by counting individual photons and measuring their energy, and are expected to yield the next major advance in CT, with improvements in spatial resolution, dose efficiency, material differentiation and quantitative imaging capabilities compared to the current state-of-the-art.In this Thesis, a set of new models and applications for a spectral photon-counting silicon detector developed for CT is investigated. The first part of the Thesis is dedicated to the modeling of spectral photon-counting silicon detectors. A new statistical model for the effects of pulse pileup is presented. Also, the effects on image quality from intra-detector Compton scatter in silicon detectors are investigated via spatio-energetic modeling. In the second part of the Thesis, potential applications for spectral photon-counting detectors are investigated. An experimental study of ex vivo CT imaging of an excised human heart with calcified plaque is presented. It demonstrates the feasibility of unconstrained projection-based three-material decomposition with iodine as a third basis material and explores the potential improvements in spatial resolution and material differentiation that can be achieved with a spectral photon-counting silicon detector compared to a conventional dual-energy CTsystem. Two other applications are investigated with simulations: a method for reconstructing CT images from spectral photon-counting CT data that accurately mimic conventional CT images; and a method for estimating iron concentration in mixtures of liver and adipose tissue when using three basis functions instead of only two to describe the linear attenuation coefficient of tissues in the human body. Although the methods presented in this Thesis have been specifically developed for a spectral photon-counting silicon detector, they are also applicable for other types of photon-counting detectors.
|
|
| 3. |
- Bergström, Göran, 1964, et al.
(författare)
-
Prevalence of Subclinical Coronary Artery Atherosclerosis in the General Population
- 2021
-
Ingår i: Circulation. - Philadelphia : American Heart Association. - 0009-7322 .- 1524-4539. ; 144:12, s. 916-929
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Early detection of coronary atherosclerosis using coronary computed tomography angiography (CCTA), in addition to coronary artery calcification (CAC) scoring, may help inform prevention strategies. We used CCTA to determine the prevalence, severity, and characteristics of coronary atherosclerosis and its association with CAC scores in a general population.Methods: We recruited 30 154 randomly invited individuals age 50 to 64 years to SCAPIS (the Swedish Cardiopulmonary Bioimage Study). The study includes individuals without known coronary heart disease (ie, no previous myocardial infarctions or cardiac procedures) and with high-quality results from CCTA and CAC imaging performed using dedicated dual-source CT scanners. Noncontrast images were scored for CAC. CCTA images were visually read and scored for coronary atherosclerosis per segment (defined as no atherosclerosis, 1% to 49% stenosis, or ≥50% stenosis). External validity of prevalence estimates was evaluated using inverse probability for participation weighting and Swedish register data.Results: In total, 25 182 individuals without known coronary heart disease were included (50.6% women). Any CCTA-detected atherosclerosis was found in 42.1%; any significant stenosis (≥50%) in 5.2%; left main, proximal left anterior descending artery, or 3-vessel disease in 1.9%; and any noncalcified plaques in 8.3% of this population. Onset of atherosclerosis was delayed on average by 10 years in women. Atherosclerosis was more prevalent in older individuals and predominantly found in the proximal left anterior descending artery. Prevalence of CCTA-detected atherosclerosis increased with increasing CAC scores. Among those with a CAC score >400, all had atherosclerosis and 45.7% had significant stenosis. In those with 0 CAC, 5.5% had atherosclerosis and 0.4% had significant stenosis. In participants with 0 CAC and intermediate 10-year risk of atherosclerotic cardiovascular disease according to the pooled cohort equation, 9.2% had CCTA-verified atherosclerosis. Prevalence estimates had excellent external validity and changed marginally when adjusted to the age-matched Swedish background population.Conclusions: Using CCTA in a large, random sample of the general population without established disease, we showed that silent coronary atherosclerosis is common in this population. High CAC scores convey a significant probability of substantial stenosis, and 0 CAC does not exclude atherosclerosis, particularly in those at higher baseline risk.
|
|
| 4. |
- Ekblad, Kristin, 1975-
(författare)
-
The economics of sickness absence : social interactions, local cultures and working conditions
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The focus of this thesis is the study of social and psychosocial aspects of sickness absence. In Essay 1, Sickness Absence and Peer Effects – Evidence from a Swedish Municipality, detailed employment records from a Swedish public employer are used to investigate whether sick leave among work group colleagues influences individual sick leave. Our results indicate that a worker’s level of sick leave is positively correlated with sick leave among peers. When length of employment is taken into account, however, we find that this positive peer effect emerges initially after the first few years of employment. In Essay 2, Who Cares about the Colleagues? – Insights into Peer Effect Heterogeneities in Sickness Absence across Gender and Age, I scrutinize the data used in Essay 1 to further investigate the nature of peer effects in sickness absence in relation to gender and age. The results indicate that men, as well as women, are sensitive to their female colleagues but not to their male peers. Moreover, somewhat surprisingly, I find that young and middle-aged workers are sensitive to younger peers, whereas the oldest workers are not sensitive to any of their peers. Essay 3, Sickness Absence and Local Culture, investigates the effect of geographical and presumed cultural context on sickness absence. Our results indicate that the region of residence is important to individual ‘illness-related absence’. In Essay 4, Sickness Absence, Working Conditions and Gender – An Empirical Analysis using Multiltvel Models, I analyse how psychosocial working conditions are related to short- and longterm sick leave and if, and how, these relation-ships vary with gender. The results show that employees who enjoy higher levels of autonomy in their post take fewer periods of short-term sick leave, and that this effect is significantly greater for male workers. The results also show that for female workers, stronger work-group cohesion is related to a lower likelihood of long-term sick leave.
|
|
| 5. |
- Frölich, Emilia, 1982-
(författare)
-
Från Kingston till Göinge : autencitet, identitet och representationer av det förflutna i svensk reggaekultur
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis explores the role of history in popular culture with a particular focus on the Swedish reggae scene. It examines how cultural meaning applied to music bears strong connections to historical representations, and how individuals understand, communicate, and reproduce selective notions of the past in relationship to popular music. History is viewed as an essential cultural component in this thesis, a component equipped with the ability to articulate political resistance, and express a sense of identity and belonging. The overall purpose is to examine how history is constructed, represented and used in the Swedish reggae scene, and how notions of origin and authenticity are expressed. The empirical chapters examine how different representations of the past in Swedish reggae relates to notions of origin, place and authenticity. These representations are constructed through social interactions, but also through interaction with texts, objects, and cultural practices.As the thesis shows, different representations of pasts and notions of origins exists in Swedish reggae, connecting to various geographical, cultural, and historical contexts. The hybridization of reggae becomes an important factor that contributes to making Swedish reggae something special and unique. In the Swedish reggae scene, which is predominatly white, the hybridization can be understood as an attempt to free oneself from aspects of reggae associated with Black experiences of white oppression. The use of local, regional, and national cultural expressions and representations of the past creates a distance to the Jamaican reggae traditions, and the historical narratives of slavery, colonialism and racial discrimination that reinforces the Black identification in Jamaican reggae. Instead, by relating to Swedish historical milieus, traditions and events, a closer and more relatable understanding of reggae is created. However, the thesis also shows that not all actors who consume and produce reggae in Sweden identify with the Swedish hybrid version. In such cases, its typical Swedishness is seen as an undesirable departure from the history and traditions of Jamaican reggae. Jamaican reggae is then perceived as a cultural heritage that should be preserved and respected in its original form - not in a copied or remodelled version.
|
|
| 6. |
- Hall, Emma
(författare)
-
Mellan rörelse och stillhet : minne och flykt i unga människors berättande 2009-2021.
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this thesis is to highlight young people’s experiences of forced migration along irregular migration routes and to examine how they understand themselves in relation to different contexts in time and space. The participants consist of young people with experience of forced migration and of being categorized as ”ensamkommande barn” (unaccompanied minors) upon arrival in Sweden. Using oral and written sources, the thesis explores what and how they remember. The theoretical perspectives are connected by movement as an overarching metaphor. Movement refers to the physical movements made by the participants as well as the assumption that movement characterizes the process of remembering. This is connected to oral history theory and method and the exploration of the past as well as the relationship between past and present in everyday lives. The thesis also leans on several theoretical perspectives from cultural memory studies, which highlight the process in which an individual memory is shaped and reshaped depending on social context and over time. In order to explore how the participants remember different places and times, from origin to destination, a systems approach to migrant trajectories has been applied as a heuristic tool.The analysis shows that there are shared historical contexts despite the fact that the participants make a heterogenous group. During the period of investigation, migration to and within Europe has been characterized by restrictions and control. This means that the participants have travelled via irregular routes, and they have been confronted with strict border controls. When the participants arrived in Sweden, migration policy underwent significant changes that led to consequences for the participants themselves. Furthermore, those labelled ”ensamkommande barn” were at the center of the migration policy debate in the wake of the so called ”refugee crisis” in 2015. An important conclusion in this dissertation is that to a large extent, movements in time and space have led to a development of how the participants understand themselves. In addition to movements over time, shifts in social contexts bring changes to what and how the participants remember. To conclude, this thesis contributes to research on ”ensamkommande barn” as it illuminates the different ways in which the participants understand themselves and experience a sense of belonging. Another contribution is the thesis' approach to historical contextualization and the understanding of the participants as actors in relation to larger historical change.
|
|
| 7. |
- Kuzmin, Leonid, 1958-
(författare)
-
Investigation of the most essential factors influencing ski glide
- 2006
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There are many different parameters of a ski running surface (material, roughness, hydrophobicity, etc.). All the parameters have an influence on ski glide, some more and some less. Furthermore, some parameters with only minor relevance are commonly declared as critical, while truly critical parameters, as far as we know, never been investigated. In this thesis, we try to identify and structure the different stages of ski running surface preparation. In our experiments, we have applied well-established, commonly used treatments parallel with alternative preparations. The unexpected result of our experiments is that the treatments commonly used today are not as good as alternative treatments, namely; stone grinding and glide wax application are far from an optimal ski treatment if minimising friction over a given distance is the major goal.
|
|
| 8. |
- Larsson, Carina, 1969-
(författare)
-
Communicating performance measures : Supporting continuous improvement in manufacturing companies
- 2017
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Manufacturing enterprises are a key driver of economic growth (Eurostat, 2016). Implementing continuous improvement (CI) is commonly used to increase competitiveness (Hyland et al., 2007), but despite the well-known theory of CI, many manufacturing companies fail in implementing it (Bhasin, 2012; Nordin et al., 2012; Tiwari et al., 2007).An identified critical success factor in CI implementation is the evaluation of performance, including the performance evaluation system itself, the linkage between targets at different company levels, and continual evaluation of performance (Bakås et al., 2011; Scherrer-Rathje et al., 2009; Ukko et al., 2009). Another critical success factor in CI implementation is the communication of performance measures (Bakås et al., 2011; Ukko et al., 2009).This research explores the communication of performance measures. The aim is to support CI by improving the communication of performance measures, and to this end, this thesis concentrates on identifying the main challenges in the communication of performance measures supporting CI. The research scope is manufacturing companies in general, and manufacturing SMEs in particular. The relevant literature concerning the communication of performance measures in manufacturing companies is identified and summarized. Also, current practice is explored, focusing on how performance measures are communicated in manufacturing companies, and whether and how the communication supports CI. This has been done to identify divergences between current practice and theory. Finally, theory and empirical findings are synthesized to identify some of the main challenges to be addressed in order to succeed in CI.The main task is to support CI efforts in manufacturing SMEs, eliminating the identified divergences in the communication of performance measures by adapting these measures to these manufacturing SMEs. These challenges can be summarized as follows: - using both financial performance measures as well as objective and subjective, non-financial performance measures - aligning performance measures with strategy and targets - integrating all performance measure communication, as related to both daily performance and CI, in the same communication loop. - forming two-way communication channels between managers and operators - aligning oral and written communication channels - exploring how information systems can facilitate the communication of performance measures - using and optimizing the visual communication of performance measures
|
|
| 9. |
- Mai, Anh, 1986-
(författare)
-
Organizing for efficiency : Essays on merger policies, independence of authorities, and technology diffusion
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Institutions are fundamentally sets of rules in a society that help create stability. Organizations are groups of people who may share the same goal. Changes in organizations and institutions will have large effects on the performance of economies. This thesis explores empirical aspects concerning two elements of institutional and organizational design: economic regulations and independent regulatory authorities (IRAs).Essay 1 studies the impact of the 2004 EU merger policy reform on how mergers are reviewed by the European Commission. The EU policy appears to have softened after the reform for unilateral mergers and this may suggest an improvement of merger policy efficiency.Essay 2 compares the merger enforcements in the EU and the US. Our approach is to decompose the differences into policy effects and casemix effects. The EU policy has significantly changed after its 2004 reform. Overall, the results show a convergence between the two policies for dominance mergers after the EU policy reform.Essay 3 constructs an independence index for 109 European IRAs in six different sectors: competition, energy, financial markets, pharmaceuticals, food safety, and telecom. Factor analysis suggests that the heads of the agencies are mostly constrained by four factors: collegial bodies, the judicial system, politics and scope of tasks, and resources.Essay 4 explores a correlation between independence of regulatory authorities and corruption. We find that the authorities in corrupt countries to a large extent rely on collegial bodies but are less tightly controlled by the judicial system, compared with those in “clean” countries.Essay 5 studies the impact of regulation on broadband diffusion speed. The results imply that a strict local loop unbundling policy appears to slow the diffusion speed of fixed broadband. In contrast, a procompetition policy that aims to promote entry has a significant positive impact on the diffusion speed of mobile broadband.
|
|
| 10. |
- Målqvist, Mats, 1971-
(författare)
-
Who can save the unseen? : Studies on neonatal mortality in Quang Ninh province, Vietnam
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Globally, neonatal mortality has remained basically unchanged for the last three to four decades and every year almost four million newborns die before reaching one month of age. This persistent mortality is related to an invisibility of the newborn child in policies and statistics and a neglect of health care decision-makers, planners and practitioners to deliver a perinatal continuum of care. In recent years attention has however been brought to the unchanged neonatal mortality in an effort to improve survival. The present thesis seeks to increase understanding of obstacles for better neonatal survival. The studies performed are undertaken as sub-studies to the NeoKIP project in Quang Ninh province in northern Vietnam, a randomized controlled trial of knowledge implementation for improved neonatal survival (Neonatal Health – Knowledge Into Practice, ISRCTN 44599712). In the first paper we investigated and discussed the scope of invisibility of neonatal mortality through measuring the accuracy of official statistics on neonatal deaths. The second paper reports an inquiry of determinants of neonatal mortality by use of a population-based case-referent design. Paper III and IV analyse delivery care utilization and care seeking patterns prior to and at delivery using narratives and GIS technique. There was a substantial under-reporting of neonatal mortality in the official statistics, with study results showing a four times higher neonatal mortality rate in Quang Ninh province than reported to the Ministry of Health. This neonatal mortality rate of 16/1000 live births (as compared to 4.2/1000 in official reports) was unevenly distributed in the province, showing large geographical discrepancies. In the rural and remote areas of Vietnam education level is lower and the concentrations of ethnic minorities and poor households are higher. Ethnic minority belonging was associated with a more than doubled risk of neonatal death compared to the hegemonic group of Kinh (OR 2.08 CI 95 % 1.39 – 3.10). This increased risk was independent of household economic status or maternal education level. Neonatal mortality was also associated with home deliveries, non-attendance to antenatal care and distance to the health care facilities. However, ethnic minority mothers still had an increased risk of experiencing a neonatal death even if they attended antenatal care, delivered at or lived close to a health facility. The invisibility of the neonatal period in health information systems hides the true width of the neonatal mortality challenge. By not acknowledging the problem, the marginalization of already disadvantaged groups continues, leaving ethnic minority babies with an elevated risk of dying during the first month in life. This example of ethnic inequity highlights the importance to target those most in need. The studies of the present thesis should therefore be looked upon as a contribution to the struggle to illuminate the global burden of neonatal mortality.
|
|
