| 1. |
- Bustamante, Mariana, 1983-, et al.
(författare)
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Automated multi-atlas segmentation of cardiac 4D flow MRI
- 2018
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Ingår i: Medical Image Analysis. - : Elsevier. - 1361-8415 .- 1361-8423. ; 49, s. 128-140
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Tidskriftsartikel (refereegranskat)abstract
- Four-dimensional (4D) flow magnetic resonance imaging (4D Flow MRI) enables acquisition of time-resolved three-directional velocity data in the entire heart and all major thoracic vessels. The segmentation of these tissues is typically performed using semi-automatic methods. Some of which primarily rely on the velocity data and result in a segmentation of the vessels only during the systolic phases. Other methods, mostly applied on the heart, rely on separately acquired balanced Steady State Free Precession (b-SSFP) MR images, after which the segmentations are superimposed on the 4D Flow MRI. While b-SSFP images typically cover the whole cardiac cycle and have good contrast, they suffer from a number of problems, such as large slice thickness, limited coverage of the cardiac anatomy, and being prone to displacement errors caused by respiratory motion. To address these limitations we propose a multi-atlas segmentation method, which relies only on 4D Flow MRI data, to automatically generate four-dimensional segmentations that include the entire thoracic cardiovascular system present in these datasets. The approach was evaluated on 4D Flow MR datasets from a cohort of 27 healthy volunteers and 83 patients with mildly impaired systolic left-ventricular function. Comparison of manual and automatic segmentations of the cardiac chambers at end-systolic and end-diastolic timeframes showed agreements comparable to those previously reported for automatic segmentation methods of b-SSFP MR images. Furthermore, automatic segmentation of the entire thoracic cardiovascular system improves visualization of 4D Flow MRI and facilitates computation of hemodynamic parameters.
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| 2. |
- Mikhaylova, Tatiana, 1981-
(författare)
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Shifting Shadows : Private Tutoring and the Formation of Education in Imperial, Soviet and Post-Soviet Russia
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation aims to provide a genealogy of the relations between the public and the private in education. It does so by the exploring how public education and private tutoring form and transform each other and why they are seen as legitimate or problematic in different historical and cultural contexts. Drawing on curriculum theory and Foucault’s genealogical approach to history, the study examines how private tutoring has been problematised in Imperial, Soviet and post-Soviet Russia and discusses how these problematisations reflect and shape the dominant visions of education. The results show that norms and values in relation to which private education has been problematised and addressed in Russia have varied in line with nationalist, communist and neoliberal visions of education. Although most questions, such as tutor competence, individual privilege, inequality, ethics, governance, and ideological conformity, have constantly been in the focus of critical reflection, they were ‘answered’ differently in different historical periods. Others, such as spatial inequality and ethical concern for corrupt tutoring practices, are of more recent origin. In contrast to previous research into shadow education, the study argues that the mimicking character of supplementary tutoring is not its natural feature. Rather, in the Russian case, it is the result of constant problematisation and the corresponding regulation of its conformity with what is regarded as ‘sacred’ national values.In general, private tutoring in Russia has often been treated as a ‘symptom’ of other educational and societal problems, and addressed indirectly, through reforms in public education. Paradoxically, in fighting against undesirable effects of private tutoring, Russian schools had to adopt some of the traits commonly associated with just that industry, namely individualisation, exam drills, and the promotion of private and positional good. Conversely, changes in the structure, content, pedagogy, or assessment procedures in the mainstream system have provoked considerable changes in tutoring practices, which, however, are not limited to imitation and supplementation. The study concludes that this symbiotic relationship cannot be reduced to imitation, reproduction, or supplementation. Rather, it changes like shifting shadows reflecting and ultimately shaping the dominant perceptions of what education is and ought to be.
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| 3. |
- Niskanen, Ilpo, et al.
(författare)
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Determination of relative solids concentration in homogeneous dual component pulp-filler suspension by multi-spectrophotometer
- 2020
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 35:1, s. 71-77
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Tidskriftsartikel (refereegranskat)abstract
- The concentration of fibers and fillers in the pulp suspension is an important parameter in the monitoring process. This paper proposes a versatile optical measurement system to estimate the concentration of a solids mixture in water. The geometry used in a multi-spectrophotometer (MSM) enables the controlled observation of transmission, and forward scattering light from the suspension in the UV-visible spectral range. We have developed the new fibers mixing system which gives a homogenous distribution of the fines and fillers making it possible to increase the reproducibility and accuracy of the measurement. The data analysis is based on the Beer-Lambert law and CIELAB color space equations. The results show that the proposed method is accurate for measuring the fines and filler concentrations in multicomponent suspensions.
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| 4. |
- Vavruch, Ludvig, et al.
(författare)
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Vertebral Axial Asymmetry in Adolescent Idiopathic Scoliosis.
- 2018
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Ingår i: Spine Deformity. - : Elsevier. - 2212-134X. ; 6:2, s. 112-120.e1
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Tidskriftsartikel (refereegranskat)abstract
- Study DesignRetrospective study.ObjectivesTo investigate parameters of axial vertebral deformation in patients with scoliosis compared to a control group, and to determine whether these parameters correlated with the severity of spine curvature, measured as the Cobb angle.Summary of Background DataAdolescent idiopathic scoliosis (AIS) is the most common type of spinal deformity. Many studies have investigated vertebral deformation, in terms of wedging and pedicle deformations, but few studies have investigated actual structural changes within vertebrae.MethodsThis study included 20 patients with AIS (Lenke 1–3, mean age: 15.6 years, range: 11–20). We compared preoperative low-dose computed tomography(CT) examinations of patients with AIS to those of a control group matched for age and sex. The control individuals had no spinal deformity, but they were admitted to the emergency department for trauma CTs. We measured the Cobb angles and the axial vertebral rotation (AVR), axial vertebral bodyasymmetry (AVBA), and frontal vertebral body rotation (FVBR) for the superior end, inferior end, and apical vertebrae, with in-house–developed software. Correlations between entities were investigated with the Pearson correlation test.ResultsThe average Cobb angles were 49.3° and 1.3° for the scoliotic and control groups, respectively. The patient and control groups showed significant differences in the AVRs of all three vertebra levels (p < .01), the AVBAs of the superior end and apical vertebrae (p < .008), and the FVBR of the apical vertebra (p = .011). Correlations were only found between the AVBA and FVBR in the superior end vertebra (r = 0.728, p < .001) and in the apical vertebra (r = 0.713, p < .001).ConclusionsCompared with controls, patients with scoliosis showed clear morphologic differences in the midaxial plane vertebrae. Differences in AVR, AVBA, and FVBR were most pronounced at the apical vertebra. The FVBR provided valuable additional information about the internal rotation and deformation of vertebrae.Level of EvidenceLevel III.
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| 5. |
- Wagner, Kevin, et al.
(författare)
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Imaging low-mass planets within the habitable zone of α Centauri
- 2021
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Giant exoplanets on wide orbits have been directly imaged around young stars. If the thermal background in the mid-infrared can be mitigated, then exoplanets with lower masses can also be imaged. Here we present a ground-based mid-infrared observing approach that enables imaging low-mass temperate exoplanets around nearby stars, and in particular within the closest stellar system, alpha Centauri. Based on 75-80% of the best quality images from 100h of cumulative observations, we demonstrate sensitivity to warm sub-Neptune-sized planets throughout much of the habitable zone of alpha Centauri A. This is an order of magnitude more sensitive than state-of-the-art exoplanet imaging mass detection limits. We also discuss a possible exoplanet or exozodiacal disk detection around alpha Centauri A. However, an instrumental artifact of unknown origin cannot be ruled out. These results demonstrate the feasibility of imaging rocky habitable-zone exoplanets with current and upcoming telescopes. Imaging of low-mass exoplanets can be achieved once the thermal background in the mid-infrared (MIR) wavelengths can be mitigated. Here, the authors present a ground-based MIR observing approach enabling imaging low-mass temperate exoplanets around nearby stars.
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