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Sökning: WFRF:(Larsson Matilda)

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3.
  • Johnell, Matilda, et al. (författare)
  • Coagulation, fibrinolysis and cell activation in patients and shed mediastinal blood during coronary artery bypass grafting using a new heparin-coated surface
  • 2002
  • Ingår i: Journal of Thoracic and Cardiovascular Surgery. - : Elsevier BV. - 0022-5223 .- 1097-685X. ; 124:2, s. 321-332
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVES: Heparin coating of the cardiopulmonary bypass circuit is shown to improve the biocompatibility of the surface. We have studied a new heparin surface, the Corline Heparin Surface, applied to a complete set of an extracorporeal device used during coronary artery bypass grafting in terms of activation of inflammation, coagulation, and fibrinolysis in patients and in shed mediastinal blood. METHODS: Sixty patients scheduled for coronary artery bypass grafting were randomized to one of 3 groups with heparin-coated devices receiving either a standard, high, or low dose of systemic heparin or to an uncoated but otherwise identical circuit receiving a standard dose of systemic heparin. Samples were drawn before, during, and after the operation from the pericardial cavity and in shed mediastinal blood. No autotransfusion of shed mediastinal blood was performed. RESULTS: The Corline Heparin Surface significantly reduced the activation of coagulation, fibrinolysis, platelets, and inflammation compared with that seen with the uncoated surface in combination with a standard dose of systemic heparin during cardiac surgery with cardiopulmonary bypass. Both a decrease and an increase of systemic heparin in combination with the coated heparin surface resulted in higher activation of these processes. A significantly higher expression of all studied parameters was found in the shed mediastinal blood compared with in systemic blood at the same time. CONCLUSIONS: The Corline Heparin Surface used in cardiopulmonary bypass proved to be more biocompatible than an uncoated surface when using a standard systemic heparin dose. The low dose of systemic heparin might not be sufficient to maintain the antithrombotic activity, and the high dose resulted in direct cell activation rather than a further anti-inflammatory and anticoagulatory effect.
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4.
  • Larsson, David, et al. (författare)
  • An ex-vivo setup for characterization of atherosclerotic plaque using shear wave elastography and micro-computed tomography
  • 2016
  • Ingår i: IEEE International Ultrasonics Symposium, IUS. - : IEEE conference proceedings. - 9781467398978
  • Konferensbidrag (refereegranskat)abstract
    • Quantification of the mechanical properties of atherosclerotic plaque has shown to be important in assessing carotid artery plaque vulnerability. For such, shear wave elastography (SWE) has been applied on both in-vitro and in-vivo setups. The aim of this study was to build an ex-vivo setup for combined evaluation of plaque characteristics using SWE and micro-computed tomography (μCT). As a proof-of-concept of the constructed experimental setup, a single human carotid plaque specimen was extracted during carotid endarterectomy. The plaque was imaged in the μCT system, and subsequently imaged using SWE. For the SWE measurement, group and phase velocity was extracted from the obtained in-phase/quadrature data, with its spatial distribution being compared to anatomical features visible in the μCT images. The results indicated wave velocity changes at boundaries identified in the μCT, with group velocity data slightly increasing when entering a calcified nodule. Additionally, μCT images seemed to provide good contrast between several plaque constituens using the defined imaging settings. Overall, the study represents a proof-of-concept for detailed ex-vivo plaque analysis using combined SWE and μCT, with obtained wave speed and shear modulus values falling within observed values for atherosclerotic plaque tissue. With an experimental setup defined, future studies on carotid plaque behaviour both in SWE and μCT is enabled, where a large-scale plaque study could be performed to investigate the ability of SWE to differentiate between different plaque types.
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5.
  • Larsson, David, et al. (författare)
  • Estimation of left ventricular blood flow parameters : Clinical application of patient-specific CFD simulations from 4D echocardiography
  • 2017
  • Ingår i: Medical Imaging 2017. - : SPIE - International Society for Optical Engineering. - 9781510607231
  • Konferensbidrag (refereegranskat)abstract
    • Echocardiography is the most commonly used image modality in cardiology, assessing several aspects of cardiac viability. The importance of cardiac hemodynamics and 4D blood flow motion has recently been highlighted, however such assessment is still difficult using routine echo-imaging. Instead, combining imaging with computational fluid dynamics (CFD)-simulations has proven valuable, but only a few models have been applied clinically. In the following, patient-specific CFD-simulations from transthoracic dobutamin stress echocardiography have been used to analyze the left ventricular 4D blood flow in three subjects: two with normal and one with reduced left ventricular function. At each stress level, 4D-images were acquired using a GE Vivid E9 (4VD, 1.7MHz/3.3MHz) and velocity fields simulated using a presented pathway involving endocardial segmentation, valve position identification, and solution of the incompressible Navier-Stokes equation. Flow components defined as direct flow, delayed ejection flow, retained inflow, and residual volume were calculated by particle tracing using 4th-order Runge-Kutta integration. Additionally, systolic and diastolic average velocity fields were generated. Results indicated no major changes in average velocity fields for any of the subjects. For the two subjects with normal left ventricular function, increased direct flow, decreased delayed ejection flow, constant retained inflow, and a considerable drop in residual volume was seen at increasing stress. Contrary, for the subject with reduced left ventricular function, the delayed ejection flow increased whilst the retained inflow decreased at increasing stress levels. This feasibility study represents one of the first clinical applications of an echo-based patient-specific CFD-model at elevated stress levels, and highlights the potential of using echo-based models to capture highly transient flow events, as well as the ability of using simulation tools to study clinically complex phenomena. With larger patient studies planned for the future, and with the possibility of adding more anatomical features into the model framework, the current work demonstrates the potential of patient-specific CFD-models as a tool for quantifying 4D blood flow in the heart.
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  • Larsson, David, et al. (författare)
  • Multimodal validation of patient-specific intraventricular flow simulations from 4D echocardiography
  • 2016
  • Ingår i: 2016 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS). - : IEEE conference proceedings. - 9781467398978
  • Konferensbidrag (refereegranskat)abstract
    • The combination of refined medical imaging techniques and computational fluid dynamics (CFD) models has enabled the study of complex flow behavior on a highly regional level. Recently, we have developed a platform for patient-specific CFD modelling of blood flow in the left ventricle (LV), with input data and required boundary conditions acquired from 4D echocardiography. The platform robustness has been evaluated with respect to input variable variations, but for any clinical implementation model flow validation is essential. Therefore, the aim of this study is to evaluate the accuracy of the patient-specific CFD model against multimodal image-based flow measurements. For the validation, 4D echocardiography was acquired from two healthy subjects, from which LV velocity fields were simulated. In-vivo flows from the same two subjects were then acquired by pulsed wave (PW) Doppler imaging over both LV-valves, and by cine phase-contract magnetic resonance imaging (PC-MRI) at eight defined anatomical planes in the LV. By fusing PC-MRI and the ultrasound acquisitions using a three-chamber alignment algorithm, simulated and measured flows were quantitatively compared. General flow pattern correspondence was observed, with a mean error of 1.4 cm/s and root mean square deviation of 5.7 cm/s for all measured PC-MRI LV-planes. For the PW-Doppler comparison, a mean error of 3.6 cm/s was reported. Overall, the following work represents a validation of the proposed patient-specific CFD platform, and the agreement with clinical data highlight the potential for future clinical use of the models.
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7.
  • Larsson, David, et al. (författare)
  • Patient-specific flow simulation of the left ventricle from 4D echocardiography - feasibility and robustness evaluation
  • 2015
  • Ingår i: 2015 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS). - : IEEE. - 9781479981823
  • Konferensbidrag (refereegranskat)abstract
    • In recent years, computational fluid dynamics (CFD) simulations on in-silico models of the heart have provided a valuable insight into cardiac hemodynamic behaviour. However, so far most models have been either based on simplified geometries or on imaging acquisitions with relatively low temporal resolution. It has been suggested that models based entirely on subject-specific ultrasonic images should be used to capture transient flow changes. Therefore, the aim of this study is to present a pathway from routine 4D echocardiography to a patient-specific flow simulation of the left ventricle (LV), evaluating the model robustness and clinical feasibility. The created pathway consisted of initial LV segmentation and mitral/aortic valve positioning, being subsequently used as input for the CFD simulations (based on solving the Navier-Stokes equation using an Arbitrary Lagrangian-Eulerian approach). The output consisted of 4D blood flow velocities and relative pressures in the entire LV. On five subjects, the model robustness was evaluated with regards to variations in singular boundary conditions. The clinical feasibility of the output was compared to clinical PW Doppler measurements and, as a proof-of-concept, synthetic contrast enhanced ultrasound images were simulated on the flow field using the COLE-method. Results indicated a relatively robust model, with variations in regional flow of approximately 5.1/6.2% and 9.7/7.0% for healthy and pathological subject respectively (end diastole/end systole). Furthermore, showing similar behaviour to clinical Doppler measurements the technique serves as a promising tool for future clinical investigations. Additionally, the ability of simulating synthetic ultrasound images further underlines the applicability of the pathway, being potentially useful in studies on improved echocardiographic image analysis.
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8.
  • Larsson, David, et al. (författare)
  • Patient-Specific Left Ventricular Flow Simulations From Transthoracic Echocardiography : Robustness Evaluation and Validation Against Ultrasound Doppler and Magnetic Resonance Imaging
  • 2017
  • Ingår i: IEEE Transactions on Medical Imaging. - : Institute of Electrical and Electronics Engineers (IEEE). - 0278-0062 .- 1558-254X. ; 36:11, s. 2261-2275
  • Tidskriftsartikel (refereegranskat)abstract
    • The combination of medical imaging with computational fluid dynamics (CFD) has enabled the study of 3D blood flow on a patient-specificlevel. However, with models based on gated high-resolution data, the study of transient flows, and any model implementation into routine cardiac care, is challenging. The present paper presents a novel pathway for patient-specific CFD modelling of the left ventricle (LV), using 4D transthoracic echocardiography (TTE) as input modality. To evaluate the clinical usability, two sub-studies were performed. First, a robustness evaluation was performed where repeated models with alternating input variables were generated for 6 subjects and changes in simulated output quantified. Second, a validation study was carried out where the pathway accuracy was evaluated against pulsed-wave Doppler (100 subjects), and 2D through-plane phase-contrast magnetic resonance imaging measurements over 7 intraventricular planes (6 subjects). The robustness evaluation indicated a model deviation of <12%, with highest regional and temporal deviations at apical segments and at peak systole, respectively. The validation study showed an error of < 11% (velocities < 10 cm/s) for all subjects, with no significant regional or temporal differences observed. With the patient-specific pathway shown to provide robust output with high accuracy, and with the pathway dependent only on 4DTTE, the method has a high potential to be used within future clinical studies on 3D intraventricular flowpatterns. To this, future model developments in the form of e.g. anatomically accurate LV valves may further enhance the clinical value of the simulations.
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9.
  • Larsson, Malin, 1983-, et al. (författare)
  • A new ultrasound-based approach to visualize target specific polymeric contrast agent
  • 2011
  • Ingår i: 2011 IEEE International Ultrasonics Symposium (IUS). - : IEEE. - 9781457712524 ; , s. 1626-1629
  • Konferensbidrag (refereegranskat)abstract
    • There are advantages of using a polymeric shelled contrast agent (CA) during ultrasound imaging instead of lipid shelled CA, e.g. particles can be attached to the surface, which enables an introduction of antibodies to the surface making the CA target specific. For this application it is essential to have a sensitive imaging technique suitable for polymeric CA. However, previously presented results have indicated difficulties in visualizing polymeric CA with commercially available contrast algorithms. Therefore a new subtraction algorithm (SA), was developed that define the difference between contrast and reference images. The aim of this study was to evaluate the response from a polymeric CA, when using the SA and compare it with existing contrast algorithms. Moreover, the possibility to detect a thin layer of CA was tested using the SA.Ultrasound short-axis images of a tissue-mimicking vessel phantom with a pulsating flow were obtained using a GE Vivid7 system (M12L) and a Philips iE33 system (S5-1). Repeated (n=91) contrast to tissue ratios (CTR) calculated at various mechanical index (MI) using the contrast algorithms pulse inversion (PI), power modulation (PM) and SA at a concentration of 105microbubbles/ml.The developed SA showed improvements in CTR compared to existing contrast algorithms. The CTRs were -0.99 dB ± 0.67 (MI 0.2), 9.46 dB ± 0.77 (MI 0.4) and 2.98 dB ± 0.60 (MI 0.8) with PI, 8.17 dB ± 1.15 (MI 0.2), 15.60 dB ± 1.29 (MI0.4) and 11.60 dB ± 0.73 (MI 0.8) with PM and 14.97 dB ± 3.97 (MI 0.2), 20.89 dB ± 3.54 (MI 0.4) and 21.93 dB ± 4.37 (MI 0.8) with the SA. In addition to this, the layer detection, when using the SA was successful.
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  • Larsson, Malin K., et al. (författare)
  • Endocardial border delineation capability of a multimodal polymer-shelled contrast agent
  • 2014
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • BackgroundA novel polymer-shelled contrast agent (CA) with high mechanical and chemical stability was recently developed [1]. In excess to its ultrasound properties, it also supports targeted and multimodal imaging [2-4]. Even though these new possibilities have the potential to lead to new methodologies and approaches for non-invasive diagnosis, it is important that the fundamental diagnostic features in contrast-enhanced ultrasound are preserved. The aim of this study was therefore to examine the clinical use of the polymer-shelled CA by analyzing the left ventricular endocardial border delineation capability in a porcine model. In addition, physiological effects due to CA injections were studied.MethodsThe endocardial border delineation capability was assessed in a comparative study, which included three doses (1.5 ml, 3 ml and 5 ml, [5x108 MBs/ml]) of the polymer-shelled CA and the commercially available CA SonoVue® (1.5 ml, [2-5x108 MBs/ml]). Ultrasound images of the left ventricle were evaluated manually by blinded observers (n=3) according to a 6-segment model, in which each segment was graded as 0=not visible, 1=barely visible or 2=well visible, as well as semi-automatically by a segmentation software. Furthermore, duration of clinically useful contrast enhancement and changes in physiological parameters were evaluated.ResultsFor the highest dose of the polymer-shelled CA, the obtained segment scores, time for clinically sufficient contrast enhancement and semi-automatic delineation capability were comparable to SonoVue®. Moreover, neither dose of the polymer-shelled CA did affect the physiological parameters.ConclusionThis study demonstrated that the polymer-shelled CA can be used in contrast-enhanced diagnostic imaging without influence on major physiological parameters.
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  • Larsson, Malin K., et al. (författare)
  • Endocardial border delineation capability of a novel multimodal polymer-shelled contrast agent
  • 2014
  • Ingår i: Cardiovascular Ultrasound. - : Springer Science and Business Media LLC. - 1476-7120. ; 12, s. 24-
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: A novel polymer-shelled contrast agent (CA) with multimodal and target-specific potential was developed recently. To determine its ultrasonic diagnostic features, we evaluated the endocardial border delineation as visualized in a porcine model and the concomitant effect on physiological variables. Methods: Three doses of the novel polymer-shelled CA (1.5 ml, 3 ml, and 5 ml [5 x 10(8) microbubbles (MBs)/ml]) and the commercially available CA SonoVue (1.5 ml [2-5 x 10(8) MBs/ml]) were used. Visual evaluations of ultrasound images of the left ventricle were independently performed by three observers who graded each segment in a 6-segment model as either 0 = not visible, 1 = weakly visible, or 2 = visible. Moreover, the duration of clinically useful contrast enhancement and the left ventricular opacification were determined. During anesthesia, oxygen saturation, heart rate, and arterial pressure were sampled every minute and the effect of injection of CA on these physiological variables was evaluated. Results: The highest dose of the polymer-shelled CA gave results comparable to SonoVue. Thus, no significant difference in the overall segment score distribution (2-47-95 vs. 1-39-104), time for clinically sufficient contrast enhancement (20-40 s for both) and left ventricular overall opacification was found. In contrast, when comparing the endocardial border delineation capacity for different regions SonoVue showed significantly higher segment scores for base and mid, except for the mid region when injecting 1.5 ml of the polymer-shelled CA. Neither high nor low doses of the polymer-shelled CA significantly affected the investigated physiological variables. Conclusions: This study demonstrated that the novel polymer-shelled CA can be used in contrast-enhanced diagnostic imaging without influence on major physiological variables.
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13.
  • Larsson, Malin, et al. (författare)
  • Visualization of multimodal polymer-shelled contrast agents using ultrasound contrast sequences : an experimental study in a tissue mimicking flow phantom
  • 2013
  • Ingår i: Cardiovascular Ultrasound. - : Springer Science and Business Media LLC. - 1476-7120. ; 11, s. 33-
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: A multimodal polymer-shelled contrast agent (CA) with target specific potential was recently developed and tested for its acoustic properties in a single element transducer setup. Since the developed polymeric CA has different chemical composition than the commercially available CAs, there is an interest to study its acoustic response when using clinical ultrasound systems. The aim of this study was therefore to investigate the acoustic response by studying the visualization capability and shadowing effect of three polymer-shelled CAs when using optimized sequences for contrast imaging. Methods: The acoustic response of three types of the multimodal CA was evaluated in a tissue mimicking flow phantom setup by measuring contrast to tissue ratio (CTR) and acoustic shadowing using five image sequences optimized for contrast imaging. The measurements were performed over a mechanical index (MI) range of 0.2-1.2 at three CA concentrations (10(6), 10(5), 10(4) microbubbles/ml). Results: The CTR-values were found to vary with the applied contrast sequence, MI and CA. The highest CTR-values were obtained when a contrast sequence optimized for higher MI imaging was used. At a CA concentration of 106 microbubbles/ml, acoustic shadowing was observed for all contrast sequences and CAs. Conclusions: The CAs showed the potential to enhance ultrasound images generated by available contrast sequences. A CA concentration of 106 MBs/ml implies a non-linear relation between MB concentration and image intensity.
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14.
  • Maksuti, Elira, et al. (författare)
  • ARTERIAL STIFFNESS ESTIMATION BY SHEAR WAVE ELASTOGRAPHY : VALIDATION IN PHANTOMS WITH MECHANICAL TESTING
  • 2016
  • Ingår i: Ultrasound in Medicine and Biology. - : Elsevier BV. - 0301-5629 .- 1879-291X. ; 42:1, s. 308-321
  • Tidskriftsartikel (refereegranskat)abstract
    • Arterial stiffness is an independent risk factor found to correlate with a wide range of cardiovascular diseases. It has been suggested that shear wave elastography (SWE) can be used to quantitatively measure local arterial shear modulus, but an accuracy assessment of the technique for arterial applications has not yet been performed. In this study, the influence of confined geometry on shear modulus estimation, by both group and phase velocity analysis, was assessed, and the accuracy of SWE in comparison with mechanical testing was measured in nine pressurized arterial phantoms. The results indicated that group velocity with an infinite medium assumption estimated shear modulus values incorrectly in comparison with mechanical testing in arterial phantoms (6.7 +/- 0.0 kPa from group velocity and 30.5 +/- 0.4 kPa from mechanical testing). To the contrary, SWE measurements based on phase velocity analysis (30.6 +/- 3.2 kPa) were in good agreement with mechanical testing, with a relative error between the two techniques of 8.8 +/- 6.0% in the shear modulus range evaluated (40-100 kPa). SWE by phase velocity analysis was validated to accurately measure stiffness in arterial phantoms.
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15.
  • Maksuti, Elira, et al. (författare)
  • Strain and strain rate generated by shear wave elastography in an ex vivo porcine aorta
  • 2017
  • Ingår i: 2017 IEEE International Ultrasonics Symposium (IUS). - : IEEE Computer Society. - 9781538633830
  • Konferensbidrag (refereegranskat)abstract
    • In order to generate trackable shear waves in soft tissues, transmitted pulses in shear wave elastography (SWE) are longer than conventional clinical ultrasound pulses. Nevertheless, they typically obey mechanical and thermal regulatory limits. In arterial applications, specific safety concerns may arise, as acoustic radiation (ARF)-induced stresses and strain rates could potentially affect the arterial wall. The aim of this study was to assess ARF-induced strain and strain rates in ex vivo arteries. A porcine aorta (diameters 8.5 mm, wall thickness 1.2 mm) was pressurized by a saline-filled water column at 60 and 120 mmHg. A Verasonics V1 system and a L7-4 transducer were used to generate the ARF in the middle of the anterior wall (F-number = 1, push length = [100, 200, 300] μs) and to perform plane-wave imaging (10 kHz). Cumulative axial displacement was estimated using 2D auto-correlation. The axial strain rate was calculated as the time-derivative of the axial strain, obtained by spatial linear regression of the displacement inside the anterior wall. The ex vivo peak strain and strain rate were compared with peak strain and strain rate values induced by the blood pressure changes in two healthy individuals and two patients with coronary artery disease at rest and measured by a dedicated in house speckle tracking algorithm. ARF-induced ex vivo peak strains were in the range 0.3-1% and strain rates in the range 6-23 s-1. Peak values were more affected by longer push duration than pressurization level. In vivo physiological peak strain was 33% and strain rate was 2 s-1. ARF-induced strain rates in vivo are likely to be lower than those assessed in this ex vivo setup due to ultrasound attenuation and the effect of surrounding tissue. Therefore, the results of the performed study suggest that SWE could be used in a safe manner for arterial applications even though specific effects of high strain rates are to be explored.
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16.
  • Maksuti, Elira, et al. (författare)
  • Strain and strain rate generated by shear wave elastography in ex vivo porcine aortas
  • 2017
  • Ingår i: IEEE International Ultrasonics Symposium, IUS. - : IEEE Computer Society. - 9781538633830
  • Konferensbidrag (refereegranskat)abstract
    • In shear wave elastography (SWE), acoustic radiation forces (ARF) are employed to generate shear waves within the tissue. Although the transmitted pulses are longer than those in conventional clinical ultrasound, they typically obey the mechanical and thermal regulatory limits. In arterial applications, specific safety concerns may arise, as ARF-induced stresses and strain rates could potentially affect the arterial wall. A previous simulation study (Doherty et al., J Biomech, 2013 Jan; 46(1):83-90) showed that stresses imposed by the ARF used in SWE are orders of magnitude lower than those caused by blood pressure. ARF-induced strain rates have not been investigated yet, therefore the aim of this study was to assess such strain rates in an ex vivo setup.
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  • Widman, Erik, et al. (författare)
  • Feasibility of shear wave elastography for plaque characterization
  • 2014
  • Ingår i: IEEE International Ultrasonics Symposium, IUS. - 9781479970490 ; , s. 1818-1821
  • Konferensbidrag (refereegranskat)abstract
    • Determining plaque vulnerability is critical when selecting the most suitable treatment for patients with atherosclerotic plaque in the common carotid artery and quantitative characterization methods are needed. In this study, shear wave elastography (SWE) was used to characterize soft plaque mimicking inclusions in three atherosclerotic arterial phantoms by using phase velocity analysis in a static environment. The results were validated with axial tensile mechanical testing (MT). SWE measured a mean shear modulus of 5.8 ± 0.3 kPa and 25.0 ± 1.2 kPa versus 3.0 kPa and 30.0 kPa measured by mechanical testing in the soft plaques and phantom walls respectively. The results show good agreement between MT and SWE for both the plaque and phantom wall.
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18.
  • Widman, Erik, et al. (författare)
  • Shear wave elastography plaque characterization with mechanical testing validation : a phantom study.
  • 2015
  • Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 0031-9155 .- 1361-6560. ; 60:8, s. 3151-3174
  • Tidskriftsartikel (refereegranskat)abstract
    • Determining plaque vulnerability is critical when selecting the most suitable treatment for patients with atherosclerotic plaque. Currently, clinical non-invasive ultrasound-based methods for plaque characterization are limited to visual assessment of plaque morphology and new quantitative methods are needed. In this study, shear wave elastography (SWE) was used to characterize hard and soft plaque mimicking inclusions in six common carotid artery phantoms by using phase velocity analysis in static and dynamic environments. The results were validated with mechanical tensile testing. In the static environment, SWE measured a mean shear modulus of 5.8±0.3kPa and 106.2±17.2kPa versus 3.3±0.5kPa and 98.3±3.4kPa measured by mechanical testing in the soft and hard plaques respectively. Furthermore, it was possible to measure the plaques' shear moduli throughout a simulated cardiac cycle. The results show good agreement between SWE and mechanical testing and indicate the possibility for in vivo arterial plaque characterization using SWE.
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19.
  • Alvén, Jennifer, 1989, et al. (författare)
  • Shape-aware label fusion for multi-atlas frameworks
  • 2019
  • Ingår i: Pattern Recognition Letters. - : Elsevier BV. - 0167-8655. ; 124, s. 109-117
  • Tidskriftsartikel (refereegranskat)abstract
    • Despite of having no explicit shape model, multi-atlas approaches to image segmentation have proved to be a top-performer for several diverse datasets and imaging modalities. In this paper, we show how one can directly incorporate shape regularization into the multi-atlas framework. Unlike traditional multi-atlas methods, our proposed approach does not rely on label fusion on the voxel level. Instead, each registered atlas is viewed as an estimate of the position of a shape model. We evaluate and compare our method on two public benchmarks: (i) the VISCERAL Grand Challenge on multi-organ segmentation of whole-body CT images and (ii) the Hammers brain atlas of MR images for segmenting the hippocampus and the amygdala. For this wide spectrum of both easy and hard segmentation tasks, our experimental quantitative results are on par or better than state-of-the-art. More importantly, we obtain qualitatively better segmentation boundaries, for instance, preserving topology and fine structures.
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20.
  • Alvén, Jennifer, 1989, et al. (författare)
  • Shape-aware multi-atlas segmentation
  • 2016
  • Ingår i: Proceedings - International Conference on Pattern Recognition. - 1051-4651. ; 0, s. 1101-1106
  • Konferensbidrag (refereegranskat)abstract
    • Despite of having no explicit shape model, multi-atlas approaches to image segmentation have proved to be a top-performer for several diverse datasets and imaging modalities. In this paper, we show how one can directly incorporate shape regularization into the multi-atlas framework. Unlike traditional methods, our proposed approach does not rely on label fusion on the voxel level. Instead, each registered atlas is viewed as an estimate of the position of a shape model. We evaluate and compare our method on two public benchmarks: (i) the VISCERAL Grand Challenge on multi-organ segmentation of whole-body CT images and (ii) the Hammers brain atlas of MR images for segmenting the hippocampus and the amygdala. For this wide spectrum of both easy and hard segmentation tasks, our experimental quantitative results are on par or better than state-of-the-art. More importantly, we obtain qualitatively better segmentation boundaries, for instance, preserving fine structures.
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21.
  • Arvidsson, Matilda, 1976, et al. (författare)
  • Law and Disorder in the Postcolony? Law, Missionaries, and the Utopias of Pre-colonial to Present-day Kongo DRC
  • 2022
  • Ingår i: Law and Society Association Annual Meeting 2022.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Our panel turns to history to understand challenges to law and order in the present; examining the present-day ‘failed state’ of the Democratic Republic of the Congo (DRC). Drawing on unique archival material, centring on the activities of Mission Covenant Church of Sweden (Svenska Missionskyrkan) in lower Congo, 1881–1961, we take on the well-established thesis that ‘disorder’ in the contemporary ‘postcolony’ flows from how the introduction of law and order was pursued during the pre-colonial and colonial era. In this panel Christian and Global North contributions towards the establishment of the Rule of Law, as well as the international legal interests and investments, in contemporary Congo DRC are examined through critical international legal, social-anthropological, and historical trajectories.
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22.
  • Arvidsson, Matilda, 1976, et al. (författare)
  • The Past as Present: Law, Anthropology and History
  • 2022
  • Ingår i: The Past as Present: Research project on past and present legal fragmentation in the Kongo/DRC.
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • This site communicates the findings and activities in our project. In our project we turn to history in order to better understand challenges to law and order in our present time; specifically, examining the present-day fragmented and ‘failed state’ of Congo (DRC), often described as lacking in terms of the Rule of Law and adequate legal institutions is re-examined in light of the rule of law activities pursued in the lower Congo by Swedish missionaries from the Mission Covenant Church of Sweden (Svenska Missionskyrkan), 1881-1961. Following the well-established thesis that ‘disorder’ in the contemporary ‘postcolony’ flows from how the introduction of law and order was pursued during the pre-colonial and colonial era, our project revisits the Swedish contribution to the establishment of the Rule of Law in contemporary DRC, in order to better understand legal fragmentation and pluralism was introduced in the pre-colonial and colonial era. We draw on unique archival material, as well as contemporary empirical data, with the aim to develop a substantiated holistic approach to legal fragmentation and state state-building initiatives in the contemporary DRC.
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23.
  • Bjällmark, Anna, et al. (författare)
  • A system to quantify and visualize ventricular rotation pattern of the heart
  • 2009
  • Patent (populärvet., debatt m.m.)abstract
    • Different modalities have been used to describe the rotational motion of the ventricles of the heart and studies have indicated LV twist to be an additional integral component in LV function. So far, only amplitudes and timings of rotation have been reported, whereas no method is available to fully describe the rotation pattern of the ventricles. The object of the present application is to achieve a system that presents a novel way to quantify and visualize the ventricular rotation pattern of the heart. We present a novel method that assesses and describes the rotation pattern by calculating the rotation axis of the ventricle. Non- invasive image acquisition is required to collect rotation values from different positions of the myocardium. Thereafter, a kinematic model of a ventricle is constructed to determine the rotation planes at different levels of the heart. The motion of the rotation planes are visualized by plotting the normal vectors of the planes over time, i.e. the rotation axis of the planes. This new method is different to all other methods used today for assessing cardiac function, as it does not describe the amplitude of a motion but the relationship in motion between different parts within a ventricle. Preliminary results indicate that the rotation axis is more sensitive to changes in the rotation pattern than conventional measurements of ventricular rotation. This new method could be used for early detection of cardiac diseases and for selection of patients for and optimization of cardiac resynchronization therapy.
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24.
  • Bjällmark, Anna, et al. (författare)
  • Differences in myocardial velocities during supine and upright exercise stress echocardiography in healthy adults
  • 2009
  • Ingår i: Clinical Physiology and Functional Imaging. - 1475-0961 .- 1475-097X. ; 29:3, s. 216-223
  • Tidskriftsartikel (refereegranskat)abstract
    • Tissue Velocity Imaging (TVI) is a method for quantitative analysis of longitudinal myocardial velocities, which can be used during exercise and pharmacological stress echocardiography. It is of interest to evaluate cardiac response to different types of stress tests and the differences between upright and supine bicycle exercise tests have not been fully investigated. Therefore, the aim of this study was to compare cardiac response during supine and upright exercise stress tests. Twenty young healthy individuals underwent supine and upright stress test. The initial workload was set to 30 W and was increased every minute by a further 30 W until physical exhaustion. Tissue Doppler data from the left ventricle were acquired at the end of every workload level using a GE Vivid7 Dimension system (> 200 frames s(-1)). In the off-line processing, isovolumic contraction velocity (IVCV), peak systolic velocity (PSV), isovolumic relaxation velocity (IVRV), peak early diastolic velocity (E') and peak late diastolic velocity (A') were identified at every workload level. No significant difference between the tests was found in PSV. On the contrary, E' was shown to be significantly higher (P < 0.001) during supine exercise than during upright exercise and IVRV was significantly lower (P < 0.001) during supine exercise compared to upright exercise. Upright and supine exercise stress echocardiography give a comparable increase in measured systolic velocities and significant differences in early diastolic velocities.
  •  
25.
  • Bjällmark, Anna, et al. (författare)
  • Effects of hemodialysis on the cardiovascular system: Quantitative analysis using wave intensity wall analysis and tissue velocity imaging
  • 2010
  • Ingår i: Heart and Vessels. - : Springer Science and Business Media LLC. - 0910-8327 .- 1615-2573.
  • Tidskriftsartikel (refereegranskat)abstract
    • Cardiovascular disease is the leading cause of death in patients with end stage renal disease (ESRD). The aim of this study was to investigate the changes in cardiovascular function induced by a single session of hemodialysis (HD) by the analysis of cardiovascular dynamics using wave intensity wall analysis (WIWA) and of systolic and diastolic myocardial function using tissue velocity imaging (TVI). Grey-scale cine loops of the left common carotid artery, conventional echocardiography and TVI images of the left ventricle were acquired before and after HD in 45 patients (17 women, mean age 54) with ESRD. The WIWA indexes, W1 preload-adjusted W1, W2 and preload-adjusted W2, and the TVI variables, isovolumic contraction velocity (IVCV), isovolumic contraction time (IVCT), peak systolic velocity (PSV), displacement, isovolumic relaxation velocity (IVRV), isovolumic relaxation time (IVRT), peak early diastolic velocity (E’) and peak late diastolic velocity (A’), were compared before and after HD. The WIWA measurements showed significant increases in W1 (p < 0.05) and preload-adjusted W1 (p < 0.01) after HD. W2 was significantly decreased (p < 0.05) after HD, whereas the change in preload-adjusted W2 was not significant. Systolic velocities, IVCV (p < 0.001) and PSV (p < 0.01), were increased after HD, whereas the AV-plane displacement were decreased (p < 0.01). For the measured diastolic variables, E’ was significantly decreased (p < 0.01) and IVRT was significantly prolonged (p < 0.05), after HD. A few correlations were found between WIWA and TVI variables. The WIWA and TVI measurements indicate that a single session of HD improves systolic function. The load dependency of the diastolic variables seems to be more pronounced than for the systolic variables. Preload-adjusted wave intensity indexes may contribute in the assessment of true LV contractility and relaxation.
  •  
26.
  • Bjällmark, Anna, et al. (författare)
  • Velocity tracking - a novel method for quantitative analysis of longitudinal myocardial function
  • 2007
  • Ingår i: Journal of the American Society of Echocardiography. - : Elsevier. - 0894-7317 .- 1097-6795. ; 20:7, s. 847-856
  • Tidskriftsartikel (refereegranskat)abstract
    • Doppler tissue imaging is a method for quantitative analysis of longitudinal myocardial velocity. Commercially available ultrasound systems can only present velocity information using a color Dopplerbased overlapping continuous color scale. The analysis is time-consuming and does not allow for simultaneous analysis in different projections. We have developed a new method, velocity tracking, using a stepwise color coding of the regional longitudinal myocardial velocity. The velocity data from 3 apical projections are presented as static and dynamic bull's-eye plots to give a 3-dimensional understanding of the function of the left ventricle. The static bull's-eye plot can display peak systolic velocity, late diastofic tissue velocity, or the sum of peak systolic velocity and early diastolic tissue velocity. Conversely, the dynamic bull's-eye plot displays how the myocardial velocities change over one heart cycle. Velocity tracking allows for a fast, simple, and hituitive visual analysis of the regional longitudinal contraction pattern of the left ventricle with a great potential to identify characteristic pathologic patterns.
  •  
27.
  • Brodin, Lars-Åke, et al. (författare)
  • Global and local detection of blood vessel elasticity
  • 2006
  • Patent (populärvet., debatt m.m.)abstract
    • The present invention is a non-invasive analysis system for detection of global and local blood vessel elasticity. The analysis system comprises two subsystems where subsystem 1 is data collecting unit and subsystem 2 is an analysis unit. The data collecting unit comprises one or many non-invasive image generating systems, or the data collecting system makes the registration possible of movement parameters that quantifies the dynamics of the blood vessel wall in longitudinal and radial directions. Subsystem 2 performs Wave Intensity Analysis which is an analysis method using co-related parts of the circulation system by measuring the intensity change (dl) of the blood vessel during a heart cycle. The intensity change is calculated as the product of the pressure derivate and the flow velocity derivate. In subsystem 2 the changes of pressure and flow are approximated by the deformation velocity or velocity of the radial and longitudinal direction, respectively. By calculating time constants and amplitudes of the intensity change graph a measure is obtained of the local and global elasticity of the blood vessel and atherosclerotic constrictions of arterial vessels may then be identified at an early stage.
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28.
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29.
  • Eliasson, Pernilla, et al. (författare)
  • Hypoxia mediates low cell-cycle activity and increases the proportion of long-term reconstituting hematopoietic stem cells during in vitro culture
  • 2010
  • Ingår i: Experimental Hematology. - : Elsevier. - 0301-472X .- 1873-2399. ; 38:4, s. 301-310
  • Tidskriftsartikel (refereegranskat)abstract
    • Objective. Recent evidence suggests that hematopoietic stem cells (HSCs) in the bone marrow (BM) are located in areas where the environment is hypoxic. Although previous studies have demonstrated positive effects by hypoxia, its role in HSC maintenance has not been fully elucidated, neither has the molecular mechanisms been delineated. Here, we have investigated the consequence of in vitro incubation of HSCs in hypoxia prior to transplantation and analyzed the role of hypoxia-inducible factor (HIF)-1 alpha. Materials and Methods. HSC and progenitor populations isolated from mouse BM were cultured in 20% or 1% O-2, and analyzed for effects on cell cycle, expression of cyclin-dependent kinase inhibitors genes, and reconstituting ability to lethally irradiated mice. The involvement of HIF-1 alpha was studied using methods of protein stabilization and gene silencing. Results. When long-term FLT3(-)CD34(-)Lin(-)Sca-1(+)c-Kit(+) (LSK) cells were cultured in hypoxia, cell numbers were significantly reduced in comparison to normoxia. This was due to a decrease in proliferation and more cells accumulating in G(0). Moreover, the proportion of HSCs with long-term engraftment potential was increased. Whereas expression of the cyclin-dependent kinase inhibitor genes p21(cip1), p27(Kip1), and p57(Kip2) increased in LSK cells by hypoxia, only p21(cip1) was upregulated in FLT3(-)CD34(-)LSK cells. We could demonstrate that expression of p27(KiP1) and p57(Kip2) was dependent of HIF-1 alpha. Surprisingly, overexpression of constitutively active HIF-1 alpha or treatment with the HIF stabilizer agent FG-4497 led to a reduction in HSC reconstituting ability. Conclusions. Our results imply that hypoxia, in part via HIF-1 alpha, maintains HSCs by decreasing proliferation and favoring quiescence.
  •  
30.
  • Falkmer, Marita, et al. (författare)
  • Recognition of facially expressed emotions and visual search strategies in adults with Asperger syndrome
  • 2011
  • Ingår i: RES AUTISM SPECTR DISORD. - : Elsevier BV. - 1750-9467 .- 1878-0237. ; 5:1, s. 210-217
  • Tidskriftsartikel (refereegranskat)abstract
    • Can the disadvantages persons with Asperger syndrome frequently experience with reading facially expressed emotions be attributed to a different visual perception, affecting their scanning patterns? Visual search strategies, particularly regarding the importance of information from the eye area, and the ability to recognise facially expressed emotions were compared between 24 adults with Asperger syndrome and their matched controls. While wearing a head mounted eye tracker, the participants viewed 12 pairs of photos of faces. The first photo in each pair was cut up into puzzle pieces. Six of the 12 puzzle pieced photos had the eyes bisected. The second photo showed a happy, an angry and a surprised face of the same person as in the puzzle pieced photo. Differences in visual search strategies between the groups were established. Adults with Asperger syndrome had greater difficulties recognizing these basic emotions than controls. The distortion of the eye area affected the ability to identify emotions even more negatively for participants with Asperger syndrome.
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31.
  • Falkmer, Marita, et al. (författare)
  • The importance of the eye area in face identification abilities and visual search strategies in persons with Asperger syndrome
  • 2010
  • Ingår i: Research in Autism Spectrum Disorders. - : Elsevier BV. - 1750-9467 .- 1878-0237. ; 4:4, s. 724-730
  • Tidskriftsartikel (refereegranskat)abstract
    • Partly claimed to explain social difficulties observed in people with Asperger syndrome, face identification and visual search strategies become important. Previous research findings are, however, disparate. In order to explore face identification abilities and visual search strategies, with special focus on the importance of the eye area, 24 adults with Asperger syndrome and matched controls viewed puzzle pieced photos of faces, in order to identify them as one of three intact photos of persons. Every second puzzle pieced photo had the eyes distorted. Fixation patterns were measured by an eye tracker. Adults with Asperger syndrome had greater difficulties in identifying faces than controls. However, the entire face identification superiority in controls was found in the condition when the eyes were distorted supporting that adults with Aspergers syndrome do use the eye region to a great extent in face identification. The visual search strategies in controls were more effective and relied on the use of the 'face information triangle', i.e. the two eyes and the mouth, while adults with Asperger syndrome had more fixations on other parts of the face, both when obtaining information and during the identification part, suggesting a less effective use of the 'face information triangle'.
  •  
32.
  • Falkmer, Marita, et al. (författare)
  • The influences of static and interactive dynamic facial stimuli on visual strategies in persons with Asperger syndrome
  • 2011
  • Ingår i: Research in Autism Spectrum Disorders. - : Elsevier BV. - 1750-9467 .- 1878-0237. ; 5:2, s. 935-940
  • Tidskriftsartikel (refereegranskat)abstract
    • Several studies, using eye tracking methodology, suggest that different visual strategies in persons with autism spectrum conditions, compared with controls, are applied when viewing facial stimuli. Most eye tracking studies are, however, made in laboratory settings with either static (photos) or non-interactive dynamic stimuli, such as video clips. Whether or not these results are transferable to a "real world" dialogue situation remains unclear. In order to examine the consistency of visual strategies across conditions, a comparison of two static conditions and an interactive dynamic "real world" condition, in 15 adults with Asperger syndrome and 15 matched controls, was made using an eye tracker. The static stimuli consisted of colour photos of faces, while a dialogue between the participants and the test leader created the interactive dynamic condition. A within-group comparison showed that people with AS, and their matched controls, displayed a high degree of stability in visual strategies when viewing faces, regardless of the facial stimuli being static or real, as in the interactive dynamic condition. The consistency in visual strategies within the participants suggests that results from studies with static facial stimuli provide important information on individual visual strategies that may be generalized to "real world" situations.
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33.
  • Falkmer, Torbjörn, et al. (författare)
  • Fixation identification in centroid versus start-point modes using eye-tracking data
  • 2008
  • Ingår i: Perceptual and Motor Skills. - : Sage Publications. - 0031-5125 .- 1558-688X. ; 106:3, s. 710-724
  • Tidskriftsartikel (refereegranskat)abstract
    • Fixation-identification algorithms, needed for analyses of eye movements, may typically be separated into three categories, viz. (i) velocity-based algorithms, (ii) area-based algorithms, and (iii) dispersion-based algorithms. Dispersion-based algorithms are commonly used but this application introduces some difficulties, one being optimization. Basically, there are two modes to reach this goal of optimization, viz., the start-point mode and the centroid mode. The aim of the present study was to compare and evaluate these two dispersion-based algorithms. Manual inspections were made of 1,400 fixations in each mode. Odds ratios showed that by using the centroid mode for fixation detection, a valid fixation is 2.86 times more likely to be identified than by using the start-point mode. Moreover, the algorithm based on centroid mode dispersion showed a good interpretation speed, accuracy, robustness, and ease of implementation, as well as adequate parameter settings.
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34.
  • Fejne, Frida, 1986, et al. (författare)
  • Multiatlas Segmentation Using Robust Feature-Based Registration
  • 2017
  • Ingår i: , Cloud-Based Benchmarking of Medical Image Analysis. - Cham : Springer International Publishing. - 9783319496429 ; , s. 203-218
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • This paper presents a pipeline which uses a multiatlas approach for multiorgan segmentation in whole-body CT images. In order to obtain accurate registrations between the target and the atlas images, we develop an adapted feature-based method which uses organ-specific features. These features are learnt during an offline preprocessing step, and thus, the algorithm still benefits from the speed of feature-based registration methods. These feature sets are then used to obtain pairwise non-rigid transformations using RANSAC followed by a thin-plate spline refinement or NiftyReg. The fusion of the transferred atlas labels is performed using a random forest classifier, and finally, the segmentation is obtained using graph cuts with a Potts model as interaction term. Our pipeline was evaluated on 20 organs in 10 whole-body CT images at the VISCERAL Anatomy Challenge, in conjunction with the International Symposium on Biomedical Imaging, Brooklyn, New York, in April 2015. It performed best on majority of the organs, with respect to the Dice index.
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35.
  • Fröberg, Asa, et al. (författare)
  • High variability in strain estimation errors when using a commercial ultrasound speckle tracking algorithm on tendon tissue
  • 2016
  • Ingår i: Acta Radiologica. - : Sage Publications. - 0284-1851 .- 1600-0455. ; 57:10, s. 1223-1229
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Ultrasound speckle tracking offers a non-invasive way of studying strain in the free Achilles tendon where no anatomical landmarks are available for tracking. This provides new possibilities for studying injury mechanisms during sport activity and the effects of shoes, orthotic devices, and rehabilitation protocols on tendon biomechanics. Purpose: To investigate the feasibility of using a commercial ultrasound speckle tracking algorithm for assessing strain in tendon tissue. Material and Methods: A polyvinyl alcohol (PVA) phantom, three porcine tendons, and a human Achilles tendon were mounted in a materials testing machine and loaded to 4% peak strain. Ultrasound long-axis cine-loops of the samples were recorded. Speckle tracking analysis of axial strain was performed using a commercial speckle tracking software. Estimated strain was then compared to reference strain known from the materials testing machine. Two frame rates and two region of interest (ROI) sizes were evaluated. Results: Best agreement between estimated strain and reference strain was found in the PVA phantom (absolute error in peak strain: 0.21 +/- 0.08%). The absolute error in peak strain varied between 0.72 +/- 0.65% and 10.64 +/- 3.40% in the different tendon samples. Strain determined with a frame rate of 39.4Hz had lower errors than 78.6Hz as was the case with a 22mm compared to an 11mm ROI. Conclusion: Errors in peak strain estimation showed high variability between tendon samples and were large in relation to strain levels previously described in the Achilles tendon.
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36.
  • Fröberg, Åsa, et al. (författare)
  • Altered patterns of displacement within the Achilles tendon following surgical repair
  • 2017
  • Ingår i: Knee Surgery, Sports Traumatology, Arthroscopy. - : Springer Science and Business Media LLC. - 0942-2056 .- 1433-7347. ; 25:6, s. 1857-1865
  • Tidskriftsartikel (refereegranskat)abstract
    • Ultrasound speckle tracking was used to compare tendon deformation patterns between uninjured and surgically repaired Achilles tendons at 14-27-month follow-up. The hypothesis was that the non-homogenous displacement pattern previously described in uninjured tendons, where displacement within deep layers of the tendons exceeds that of superficial layers, is altered following tendon rupture and subsequent surgical repair. In the first part of this study, an in-house-developed block-matching speckle tracking algorithm was evaluated for assessment of displacement on porcine flexor digitorum tendons. Displacement data from speckle tracking were compared to displacement data from manual tracking. In the second part of the study, eleven patients with previous unilateral surgically treated Achilles tendon rupture were investigated using ultrasound speckle tracking. The difference in superficial and deep tendon displacement was assessed. Displacement patterns in the surgically repaired and uninjured tendons were compared during passive motion (Thompson's squeeze test) and during active ankle dorsiflexion. The difference in peak displacement between superficial and deep layers was significantly (p < 0.01) larger in the uninjured tendons as compared to the surgically repaired tendons both during Thompson's test (-0.7 +/- 0.2 mm compared to -0.1 +/- 0.1 mm) and active dorsiflexion (3.3 +/- 1.1 mm compared to 0.3 +/- 0.2 mm). The evaluation of the speckle tracking algorithm showed correlations of r ae 0.89 between displacement data acquired from speckle tracking and the reference displacement acquired from manual tracking. Speckle tracking systematically underestimated the magnitude of displacement with coefficients of variation of less than 11.7%. Uninjured Achilles tendons display a non-uniform displacement pattern thought to reflect gliding between fascicles. This pattern was altered after a mean duration of 19 +/- 4 months following surgical repair of the tendon indicating that fascicle sliding is impaired. This may affect modulation of the action between different components of the triceps surae, which in turn may affect force transmission and tendon elasticity resulting in impaired function and risk of re-rupture.
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37.
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38.
  • Hayashi, Shirley Yumi, et al. (författare)
  • Left ventricular mechanical dyssynchrony in patients with different stages of chronic kidney disease and the effects of hemodialysis
  • 2013
  • Ingår i: Hemodialysis International. - : Wiley-Blackwell. - 1492-7535 .- 1542-4758. ; 17:3, s. 346-358
  • Tidskriftsartikel (refereegranskat)abstract
    • Left ventricular (LV) dyssynchrony is a known cause of mortality in patients with heart failure and may possibly play a similar role in patients with chronic kidney disease (CKD) in whom sudden death is one of the most common and as yet not fully explained cause of death. LV synchronicity and its relationship with increased volume load and various biomarkers was analyzed in 145 patients including 53 patients with CKD stages 3 and 4 and in 92 CKD stage 5 patients undergoing hemodialysis (HD) or peritoneal dialysis (PD) using color tissue Doppler imaging and tissue synchronization imaging. The HD patients were evaluated both before and after a single HD session. LV dyssynchrony was defined as a regional difference in time to peak systolic myocardial velocity, between 12 LV segments>105milliseconds. LV dyssynchrony was present in 54% of the patients with no difference between CKD 3 and 4 (58%), HD (48%), and PD (51%). LV dyssynchrony was independently associated with LV mass index and increased estimation of LV end-diastolic pressure. A single HD session resulted in significant changes in LV synchronicity variableswith improvement in 50% of the patientsespecially in patients with higher myocardial systolic velocities and lower LV mass index. Abnormalities in LV synchronicity are highly prevalent in CKD patients already prior to dialysis treatment and are associated with LV hypertrophy, LV dysfunction and load conditions, underlining the importance of volume status for LV synchronicity in CKD patients.
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39.
  • Johnell, Matilda, et al. (författare)
  • Cell adhesion and tissue factor upregulation in oxygenators used during coronary artery bypass grafting are modified by the Corline Heparin Surface
  • 2002
  • Ingår i: Scandinavian Cardiovascular Journal. - : Informa UK Limited. - 1401-7431 .- 1651-2006. ; 36:6, s. 351-357
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVE: Cardiopulmonary bypass (CPB) is associated with inflammatory response and activation of coagulation. We investigated the influence of a new heparin surface on the activation of cells retrieved from oxygenators used during coronary artery bypass grafting (CABG). DESIGN: Sixty patients undergoing CABG with CPB were randomly assigned to either uncoated or completely Corline Heparin Surface (CHS)-coated circuits with one of three different levels of systemic heparin: standard, high or low. At end of surgery adhered cells were retrieved from the oxygenators and cell count, tissue factor (TF)- and CD11b-expression on monocytes and monocytic TFmRNA were analysed. RESULTS: The heparin coating of the oxygenator prevented adhesion of granulocytes, monocytes and platelets. TF-expression on monocytes from the oxygenators was significantly higher than on circulating cells in all groups. Monocytes from the uncoated oxygenators showed low levels of TF-expression with high levels of TFmRNA. The coated group with high level of heparin showed higher surface-expression of TF with low levels of TFmRNA. CONCLUSION: The CHS was most biocompatible with the standard level of heparin used during CABG whereas elevation of systemic heparin rather increased the activation and TF upregulation in monocytes from oxygenators.
  •  
40.
  • Johnell, Matilda, 1961- (författare)
  • Monocytes, Tissue Factor and Heparin-coated Surfaces : Clinical and Experimental Studies
  • 2003
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Cardiopulmonary bypass (CPB) is associated with inflammatory response and activation of coagulation. Heparin coating of the CPB circuit is shown to improve the biocompatibility of the surface. The biological effects of a new heparin surface, the Corline Heparin Surface (CHS), prepared according to a new principle, have been studied. The CHS used during coronary artery bypass grafting with CPB in sixty patients prevented adhesion of cells to the extracorporeal device. The activation of inflammation, coagulation, and fibrinolysis was significantly reduced by the use of CHS. Both a reduced and an increased dose of systemic heparin in combination with the heparin-coated surface resulted in more activation of inflammation and coagulation. Photoelectron spectroscopy studies of the molecular structure of the CHS demonstrated that a single layer of the heparin surface, equivalent to what was used in the in vivo studies, did not completely cover the substrate surface. Additional layer of immobilized heparin has resulted in a complete coverage. We examined the biological effects, i.e. activation of inflammation and coagulation, by CHS in one and two layers in an in vitro-study. The data from this study clearly demonstrated that a uniform surface coating of the CHS results in only minor activation of coagulation, inflammation and cell activation. Monocytes do not normally express tissue factor (TF), initiator of the coagulation in vivo, but can be induced upon adhesion to artificial surfaces. TF is receptor for coagulation factor VIIa (FVIIa) and binding subsequently leads to formation of thrombin. Other biological effects beyond coagulation, as inflammation and angiogenesis, has recently been associated with the formation of TF·FVIIa. The TF∙FVIIa signal transduction induced an increased sensitivity to PDGF-BB-stimulated migration and an increased production of IL-8 and TNF-α in monocytes. These could be important mechanisms for continued recruitment of cells to sites of inflammation.
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41.
  • Johnell, Matilda, et al. (författare)
  • The influence of different heparin surface concentrations and antithrombin-binding capacity on inflammation and coagulation
  • 2005
  • Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 26:14, s. 1731-1739
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • The corline heparin surface (CHS) used in the extracorporeal circuit during coronary artery bypass grafting is shown to decrease the activation of inflammation and coagulation. Synchrotron radiation studies have shown that a single layer of the CHS may not completely cover the substrate surface. However, a double layer of CHS results in a uniform surface. We investigated the effect of surfaces with different surface concentrations of heparin on cell activation and coagulation compared to an uncoated surface. The CHS is prepared by a conditioning layer of polymeric amine onto which a macromolecular heparin conjugate is attached. We used PVC tubing, uncoated or modified with a single or double layer of the CHS, and circulated fresh whole blood from healthy volunteers in a loop model system at 37 degrees C up to 4 h. Blood was drawn from the loops at different times and activation of inflammation and coagulation was studied by real-time PCR, flow cytometry and ELISA. The activation of leukocytes and platelets and formation of leukocyte-platelet aggregates were reduced by use of the single-layered CHS compared to the uncoated surface. Use of double-layered CHS resulted in significantly reduced cell activation and thrombin generation. Development of the CHS obtained by the double layer of the coating has improved the biocompatibility of the surface.
  •  
42.
  • Kahl, Fredrik, 1972, et al. (författare)
  • Good Features for Reliable Registration in Multi-Atlas Segmentation
  • 2015
  • Ingår i: CEUR Workshop Proceedings. - 1613-0073. ; 1390:January, s. 12-17
  • Konferensbidrag (refereegranskat)abstract
    • This work presents a method for multi-organ segmentation in whole-body CT images based on a multi-atlas approach. A robust and efficient feature-based registration technique is developed which uses sparse organ specific features that are learnt based on their ability to register different organ types accurately. The best fitted feature points are used in RANSAC to estimate an affine transformation, followed by a thin plate spline refinement. This yields an accurate and reliable nonrigid transformation for each organ, which is independent of initialization and hence does not suffer from the local minima problem. Further, this is accomplished at a fraction of the time required by intensity-based methods. The technique is embedded into a standard multi-atlas framework using label transfer and fusion, followed by a random forest classifier which produces the data term for the final graph cut segmentation. For a majority of the classes our approach outperforms the competitors at the VISCERAL Anatomy Grand Challenge on segmentation at ISBI 2015.
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43.
  • Kaldo, Viktor, Professor, et al. (författare)
  • An open-ended primary-care group intervention for insomnia based on a self-help book : A randomized controlled trial and 4-year follow-up
  • 2020
  • Ingår i: Journal of Sleep Research. - : Wiley. - 0962-1105 .- 1365-2869. ; 29:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Chronic insomnia is a common and burdensome problem for patients seeking primary care. Cognitive behavioural therapy has been shown to be effective for insomnia, also when presented with co-morbidities, but access to sleep therapists is limited. Group-treatment and self-administered treatment via self-help books have both been shown to be efficacious treatment options, and the present study aimed to evaluate the effect of an open-ended group intervention based on a self-help book for insomnia, adapted to fit a primary-care setting. Forty primary-care patients with insomnia (mean age 55 years, 80% women) were randomized to the open-ended group intervention based on a cognitive behavioural therapy for insomnia self-help book or to a care as usual/wait-list control condition. Results show high attendance to group sessions and high treatment satisfaction. Participants in the control group later received the self-help book, but without the group intervention. The book-based group treatment resulted in significantly improved insomnia severity, as well as shorter sleep-onset latency, less wake time after sleep onset, and less use of sleep medication compared with treatment as usual. The improvements were sustained at a 4-year follow-up assessment. A secondary analysis found a significant advantage of the combination of the book and the open-ended group intervention compared with when the initial control group later used only the self-help book. An open-ended treatment group based on a self-help book for insomnia thus seems to be an effective and feasible intervention for chronic insomnia in primary-care settings.
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44.
  • Karlsson, Matilda, et al. (författare)
  • Biosynthetic cellulose compared to porcine xenograft in the treatment of partial-thickness burns : A randomised clinical trial.
  • 2022
  • Ingår i: Burns. - : Elsevier. - 0305-4179 .- 1879-1409. ; 48:5, s. 1236-1245
  • Tidskriftsartikel (refereegranskat)abstract
    • AIM: The aim was to compare two dressing treatments for partial-thickness burns: biosynthetic cellulose dressing (BsC) (Epiprotect® S2Medical AB, Linköping, Sweden) and porcine xenograft (EZ Derm®, Mölnlycke Health Care, Gothenburg, Sweden).METHODS: Twenty-four adults with partial-thickness burns were included in this randomized clinical trial conducted at The Burn Centers in Linköping and Uppsala, Sweden between June 2016 and November 2018. Time to healing was the primary outcome. Secondary outcomes were wound infection, pain, impact on everyday life, length of hospital stay, cost, and burn scar outcome (evaluated with POSAS).RESULTS: We found no significant differences between the two dressing groups regarding time to healing, wound infection, pain, impact on everyday life, duration of hospital stay, cost, or burn scar outcome at the first follow up. Burn scar outcome at the 12-month follow up showed that the porcine xenograft group patients scored their scars higher on the POSAS items thickness (p = 0.048) and relief (p = 0.050). This difference was, however, not confirmed by the observer.CONCLUSIONS: The results showed the dressings performed similarly when used in adults with burns evaluated as partial thickness.
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45.
  • Kremer, F., et al. (författare)
  • Spatial compounding for 2D strain estimation in the mouse heart : a pilot study
  • 2010
  • Konferensbidrag (refereegranskat)abstract
    • Estimating cardiac strain in the mouse in the lateral direction usingspeckle tracking with adapted clinical equipment was shown to be challenging dueto the fast heart rate and the large speckle size relative to the wallthickness. Compounding axial motion estimates acquired from different insonationangles can potentially improve lateral strain estimates. Therefore, the aim ofthis study was to test the feasibility of this methodology in the murine heartbased on simulated data sets. A 3D kinematic model of a murine left ventriclewas simulated and filled randomly with scatterers. Ultrasound short-axis images(10mm 6mm) were obtained by assuming a linear array transducer. Beam steeringwas simulated at 3 different angles (22, 0, 22). Axial motion was estimated ineach data set by 1D cross-correlation. A dynamic programming approach wasintegrated in the motion estimation algorithm to avoid discontinuities. Axialcomponents were combined to reconstruct the in-plane motion vector. The 2Ddisplacement fields were subsequently accumulated over the whole cycle. Theprocedure was repeated for 10 different distributions of scatterers to acquire10 different RF data sets (5 for parameter tuning and 5 for comparing themethods). Radial and circumferential RMS strain errors calculated from theaccumulated motion fields were compared with those obtained with 2D speckletracking. Spatial compounding yielded significantly better radial (RMSE: 0.07370.0078 vs. 0.112 0.0094) as well as circumferential strain (RMSE: 0.102 0.0097vs. 0.281 0.054).
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46.
  • Larsson, Andreas, 1977-, et al. (författare)
  • Heat Angels and Paper Cups: Pupils’ Use of Metaphoric Relations When Engaging Thermal Cameras to Investigate Heat
  • 2019
  • Ingår i: Bridging Research and Practice in Science Education. Contributions from Science Education Research, vol 6.. - Cham : Springer. - 9783030172183 - 9783030172190 ; , s. 74-89
  • Bokkapitel (refereegranskat)abstract
    • Thermal science is a perennial obstacle for learners. Infrared camera technology provides an opportunity for pupils to confront challenging thermal ideas. From an embodied cognition perspective, sensory experiences form metaphoric relations that underpin conceptualisation and reasoning about abstract scientific phenomena. This study investigated eight groups of fourth grade pupils’ use of metaphoric relations when engaging thermal cameras to explore “heat” at a science centre. Pupils were videorecorded while collaboratively exploring thermal properties of the surroundings and during a thermos modelling exercise. Qualitative metaphor analyses of pupils’ dialogue and behaviour revealed various metaphoric and metonymic relations around spatial properties, colour, movement and change in their conceptualisation of thermal phenomena. “Heat” was almost exclusively conceptualised as a noun, manifested in utterances such as “harder for the heat to escape” and “it wants to get yellow”. In addition, pupils used colour as both a metonym and metaphor for heat and temperature. Expressions of heat as an entity were closely related to experiences of movement, indicating that spatial cognition is central to children’s conceptualisation of heat. Engagement with the cameras provided access to thermodynamic phenomena through unique sensory and nonsensory experiences. Future research will explore how these metaphoric relations can be exploited as a meaning-making resource in the classroom.
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47.
  • Larsson, Matilda, et al. (författare)
  • A novel measure to express tracking quality in ultrasound block matching
  • 2010
  • Ingår i: Proceedings - IEEE Ultrasonics Symposium. - 9781457703829 ; , s. 1636-1639
  • Konferensbidrag (refereegranskat)abstract
    • Speckle de-correlation is a major problem in block matching based ultrasound methodologies as it limits the accuracy of the tracking result. It would be of benefit to have a quantitative measure expressing the local tracking quality as it would allow discarding unreliable motion estimates. We hypothesized that kernels showing sufficient gray scale pattern would more reliably track than kernels with more homogenous gray scale distributions. The aim of this study was to test this hypothesis in-silico. Ultrasound B-mode sequences were simulated from a kinematic model of the carotid artery. Two-dimensional motion was estimated using block matching with the normalized cross-correlation function as similarity measure. For each kernel, two measures of tracking quality were stored: the normalized cross-correlation coefficient (Ccc) and a measure of the amount of edges inside the kernel detected using a canny filter and counted on a pixel-by-pixel basis. As such, a quality measure (Cedge) between 0 (no edges) and 1 (nothing but edges) was obtained. Axial and lateral strains were subsequently obtained by linear regression in regions of interest (ROIs) with best/worst mean tracking quality scores. The root-mean-squared-error (RMSE) was significantly lower in regions with low Ccc (worst ROI) compared to ROIs with high Ccc. However, more edges in the kernel did indeed result in better overall tracking (lower RMSE). Thus, the proposed edge-detection method showed to be a better tracking quality measure than the commonly used Ccc.
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48.
  • Larsson, Matilda, et al. (författare)
  • Assessment of longitudinal strain in the Carotid artery wall using ultrasound-based Speckle tracking - validation in a sheep model
  • 2013
  • Ingår i: Proceedings of the IEEE International Ultrasonics symposium, 2013.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Assessment of strain in the longitudinal direction of the arterial wall has been suggested to improve the evaluation of arterial stiffness and atherosclerosis. Recently, we showed the feasibility of ultrasound speckle tracking to assess carotid longitudinal strain in-silico and in-vitro. However, validation in the more challenging in-vivo setting is still lacking. The aim of this study was to validate longitudinal strain assessment in the common carotid artery (CCA) in an animal setup. The left CCAs of five sheep were exposed during Isoflurane anesthesia and sonomicrometry crystals were sutured onto the artery wall to obtain reference longitudinal strain. Ultrasound long-axis images were recorded at baseline and hypertension (Phenylephrine) and an in-house speckle tracking algorithm was applied to estimate longitudinal strain. The estimated strain curves varied cyclically throughout the cardiac cycles, showing a lengthening of the arterial segment in systole. A significant correlation between peak systolic estimated and reference strain was found (r=0.95, p < 0.001). The results indicate the feasibility of arterial longitudinal strain assessment in-vivo using ultrasound speckle tracking.
  •  
49.
  • Larsson, Matilda, et al. (författare)
  • Carotid strain estimation using an ultrasound-based speckle tracking algorithm
  • 2012
  • Ingår i: 2012 IEEE International Ultrasonics Symposium (IUS). - : IEEE. - 9781467345613 ; , s. 1394-1397
  • Konferensbidrag (refereegranskat)abstract
    • Carotid strain imaging using ultrasound-based speckle tracking has showed potential in risk stratification of cardiovascular diseases. However, assessing strain in the artery wall and in atherosclerotic plaques is challenging because of small dimensions and low deformations in relation to the applied ultrasound wavelength. High-resolution ultrasound has potential to improve the speckle tracking performance by increasing spatial resolution. The aim of this study was to compare carotid strain estimation by speckle tracking using standard clinical ultrasound and high-resolution ultrasound in an experimental setup. Ultrasound long-axis images were obtained using a standard clinical ultrasound system (Vivid7) and a high-resolution ultrasound system (Vevo2100) in dynamic phantoms mimicking the carotid artery. Speckle tracking was performed to estimate radial and longitudinal strain whereas sonomicrometry was used as reference. The results showed a significant better performance for speckle tracking applied on images from the high-resolution system compared to the standard clinical system.
  •  
50.
  • Larsson, Matilda, et al. (författare)
  • Effect of hydrophobically modified graphene oxide on the properties of poly(3-hydroxybutyrate-co-4-hydroxybutyrate)
  • 2017
  • Ingår i: Polymer. - : Elsevier BV. - 0032-3861. ; 108, s. 66-77
  • Tidskriftsartikel (refereegranskat)abstract
    • Nanocomposites of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3,4HB)] and hydrophobically modified graphene oxide (GO) were prepared via melt blending and characterised with respect to processability, polymer degradation, as well as thermal, rheological and mechanical properties. GO prepared via the modified Hummer’s method was alkylated by reactions with butyl-, octyl- and hexadecylamine, respectively. The successful functionalisation was verified by IR spectroscopy, X-ray diffraction measurements, transmission electron microscopy and elemental analysis. The thermal decomposition temperature of the alkylated GOs increased with increasing alkyl chain length. Moreover, the alkylated GOs showed a much improved compatibility with P(3,4HB) in the melt compared to the unmodified GO, and microscopy showed an even distribution in the polymer matrix. The molecular weight of P(3,4HB) was found to decrease during the melt extrusion, and the chain degradation was found to increase after the addition of alkylated GO. However, this effect decreased with increasing alkyl chain length. Melt rheology measurements showed that percolating networks appeared at filler contents above ~2 wt%. These networks were detected as increases in shear storage modulus and decreased phase shifts towards more elastic materials over time and at low frequencies. During cooling of the melts, calorimetric measurements showed an increase in the crystallisation temperature and enthalpy with increasing filler contents up to ~2 wt%. However, at higher filler contents a decreased propensity for crystallisation was noted, which again indicated network formation. Tensile testing showed that the nanocomposites containing the GO with hexadecyl chains displayed the highest elongation at break and yield stress. However, the numbers were lower compared to the unfilled P(3,4HB), most probably because of the lower molecular weight of the P(3,4HB) in the nanocomposites. The results of the present study demonstrated that alkylation of GO greatly improves the compatibility with the polymer, and that the processability and thermo-mechanical properties of the nanocomposites are systematically influenced by the GO content and the alkyl chain length.
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