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  • 1.
    Björck, Hanna M.
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Physiology. Linköping University, Faculty of Health Sciences.
    Renner, Johan
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Maleki, Shohreh
    Atherosclerosis Research Unit, Center for Molecular Medicine, Department of Medicine, Karolinska Institute, Sweden.
    Nilsson, Siv F.E.
    Linköping University, Department of Medical and Health Sciences, Pharmacology. Linköping University, Faculty of Health Sciences.
    Kihlberg, Johan
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Folkersen, Lasse
    Atherosclerosis Research Unit, Center for Molecular Medicine, Department of Medicine, Karolinska Institute, Sweden.
    Karlsson, Matts
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Ebbers, Tino
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Clinical Physiology UHL.
    Eriksson, Per
    Atherosclerosis Research Unit, Center for Molecular Medicine, Department of Medicine, Karolinska Institute, Sweden.
    Länne, Toste
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Thoracic and Vascular Surgery in Östergötland.
    Characterization of Shear-Sensitive Genes in the NormalRat Aorta Identifies Hand2 as a Major Flow-ResponsiveTranscription Factor2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 12Article in journal (Refereed)
    Abstract [en]

    Objective: Shear forces play a key role in the maintenance of vessel wall integrity. Current understanding regarding shear-dependent gene expression is mainly based on in vitro or in vivo observations with experimentally deranged shear, hence reflecting acute molecular events in relation to flow. Our objective was to determine wall shear stress (WSS) in the rat aorta and study flow-dependent vessel wall biology under physiological conditions.

    Methods and Results: Animal-specific aortic WSS magnitude and vector direction were estimated using computational fluid dynamic simulation based on aortic geometry and flow information acquired by MRI. Two distinct flow pattern regions were identified in the normal rat aorta; the distal part of the inner curvature being exposed to low WSS and a non-uniform vector direction, and a region along the outer curvature being subjected to markedly higher levels of WSS and a uniform vector direction. Microarray analysis revealed a strong differential expression between the flow regions, particularly associated with transcriptional regulation. In particular, several genes related to Ca2+-signalling, inflammation, proliferation and oxidative stress were among the most highly differentially expressed.

    Conclusions: Microarray analysis validated the CFD-defined WSS regions in the rat aorta, and several novel flow-dependent genes were identified. The importance of these genes in relation to atherosusceptibility needs further investigation.

  • 2.
    Gårdhagen, Roland
    et al.
    Linköping University, Department of Mechanical Engineering. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Renner, Johan
    Linköping University, Department of Mechanical Engineering. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Karlsson, Matts
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Assessment of Geometrical Influence on WSS Estimation in the Human Aorta2006In: WSEAS Transactions on Fluid Mechanics, ISSN 1790-5087, Vol. 4, no 1, p. 318-326Article in journal (Refereed)
    Abstract [en]

    Computational fluid dynamics simulations were performed on a stenosed human aorta with poststenotic dilatation, in order to estimate wall shear stress (WSS). WSS is important due to its correlation with atherosclerosis. Both steady-state and non-stationary simulations were conducted. Three different models were created from a set of MRI images. Comparison of geometrically different models was accomplished by using geometrical landmarks and a comparison parameter. Geometrical differences had larger influence on WSS magnitude than inflow rotation in steady-state results for the models used. In non-stationary flow the largest differences in WSS are found when the flow velocity near the wall is low e.g. when the inflow is low or in recirculation regions.

  • 3.
    Gårdhagen, Roland
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Renner, Johan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation .
    Computational Fluid Dynamics CFD TMMV532006Report (Other (popular science, discussion, etc.))
  • 4.
    Gårdhagen, Roland
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Renner, Johan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation .
    Computational Fluid Dynamics CFD TMMV53 Course Compendium2006Report (Other (popular science, discussion, etc.))
  • 5.
    Gårdhagen, Roland
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Renner, Johan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Länne, Toste
    Linköping University, Department of Medicine and Health Sciences, Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Karlsson, Matts
    Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation. Linköping University, The Institute of Technology.
    Subject Specific Wall Shear Stress in the Human Thoracic Aorta2006In: WSEAS Transaction on biology and biomedicine, ISSN 1109-9518, Vol. 10, no 3, p. 609-614Article in journal (Refereed)
    Abstract [en]

    Numerous studies have shown a correlation between Wall Shear Stress (WSS) and atherosclerosis, but few have evaluated the reliability of estimation methods and measures used to assessWSS, which is the subject of this work. A subject specific vessel model of the aortic arch and thoracic aorta is created fromMRI images and used for CFD simulations with MRI velocity measurements as inlet boundary condition. WSS is computed from the simulation results. Aortic WSS shows significant spatial as well as temporal variation during a cardiac cycle, which makes circumferential values very uninformative, and approximate estimates using Hagen-Poiseuille fails predict the averageWSS. Highly asymmetric flow, especially in the arch, causes the spatial WSS variations.

  • 6.
    Gårdhagen, Roland
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Svensson, Johan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation .
    CFD Analysis of Rotating Flows in Human Aorta2004Report (Other academic)
  • 7.
    Gårdhagen, Roland
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Svensson, Johan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation .
    CFD Studies of Rotating Blood Flows in Human Aorta - A Parameter Estimation2004In: 17th Nordic Seminar on Computational Mechanics,2004, 2004Conference paper (Refereed)
  • 8.
    Gårdhagen, Roland
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Svensson, Johan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation .
    Complex Flow Pattern in Realistic Geometry of Human Aorta2004In: 3rd International Conference on Computational Fluid Dynamics ICCFD3,2004, 2004Conference paper (Refereed)
  • 9.
    Gårdhagen, Roland
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Svensson, Johan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation .
    Non-Newtonian Effects in Blood Flow Through Constriction and Dillatiation - Steady Flow2005In: Svenska Mekanikdagar 2005,2005, 2005, p. 60-60Conference paper (Refereed)
  • 10.
    Gårdhagen, Roland
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Svensson, Johan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation .
    Wall shear stress in a human aorta with constriction and aneurysm - non-newtonian effects for unsteady flows2005In: 2005 Summer Bioengineering Conference,2005, Vail, USA: Summer Bioengineering Conference Committee , 2005, p. 99-Conference paper (Refereed)
  • 11.
    Gårdhagen, Roland
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Svensson, Johan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Loyd, Dan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation .
    Non-newtonian effects on wall shear stress in a human aorta with coarctation and dilatation2005In: NBC05 Umeå,2005, Umeå: International federation for medicac and biological engineering IFMBE , 2005, p. 275-Conference paper (Refereed)
  • 12.
    Karlsson, Matts
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Lantz, Jonas
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Gårdhagen, Roland
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Renner, Johan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Biofluid Mechanics -LES and FSI2011In: / [ed] B. Skallerud and H.I. Andersson, tapir academic press , 2011, p. 23-28Conference paper (Other academic)
  • 13.
    Lantz, Jonas
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Renner, Johan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Estimation of Wall Shear Stress in a Human Aorta Using Fluid-Structure Interaction2011In: The 6th international symposium on biomechanics in vascular biology and cardiovascular disease, 2011Conference paper (Refereed)
  • 14.
    Lantz, Jonas
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Renner, Johan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    MR-Based Imaging for Patient Specific, Fully Coupled 2-way Fluid-Structure Interaction of the Human Aorta2010Conference paper (Other academic)
  • 15.
    Lantz, Jonas
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Renner, Johan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Wall shear stress in a subject specific human aorta - Influence of fluid-structure interaction2011In: International Journal of Applied Mechanics, ISSN 1758-8251, Vol. 3, no 4, p. 759-778Article in journal (Refereed)
    Abstract [en]

    Vascular wall shear stress (WSS) has been correlated to the development of atherosclerosis in arteries. As WSS depends on the blood flow dynamics, it is sensitive to pulsatile effects and local changes in geometry. The aim of this study is therefore to investigate if the effect of wall motion changes the WSS or if a rigid wall assumption is sufficient. Magnetic resonance imaging (MRI) was used to acquire subject specific geometry and flow rates in a human aorta, which were used as inputs in numerical models. Both rigid wall models and fluid-structure interaction (FSI) models were considered, and used to calculate the WSS on the aortic wall. A physiological range of different wall stiffnesses in the FSI simulations was used in order to investigate its effect on the flow dynamics. MRI measurements of velocity in the descending aorta were used as validation of the numerical models, and good agreement was achieved. It was found that the influence of wall motion was low on time-averaged WSS and oscillating shear index, but when regarding instantaneous WSS values the e.ect from the wall motion was clearly visible. Therefore, if instantaneous WSS is to be investigated, a FSI simulation should be considered.

  • 16.
    Lantz, Jonas
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Renner, Johan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Wall shear stress in an MRI-Based Subject-Specific Human Aorta Using Fluid-Structure Interaction2010In: Proceedings of the ASME 2010 Summer Bioengineering Conference (SBC2010), NY, USA: ASME , 2010, p. 563-564Conference paper (Other academic)
    Abstract [en]

    Wall shear stress (WSS) is well established as an indicator of increased risk for development of atherosclerotic plaques, platelet activation and thrombus formation [1]. Prediction and simulation of the sites of wall shear stresses that are deemed dangerous before intervention would be of great aid to the surgeon. However, the geometries used for these types of simulations are often approximated to be rigid. To more accurately capture the flow and arterial wall response of a realistic human aorta, fluid-structure interaction (FSI) which allows movement of the wall, is needed. Hence, the pressure wave and its effect on the wall motion are resolved and enables a more physiological model as compared to a rigid wall case.

  • 17.
    Lantz, Jonas
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Science & Engineering. Swedish E Science Research Centre SeRC, Sweden.
    Renner, Johan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Länne, Toste
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Östergötlands Läns Landsting, Heart and Medicine Center, Department of Thoracic and Vascular Surgery.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Is aortic wall shear stress affected by aging? An image-based numerical study with two age groups2015In: Medical Engineering and Physics, ISSN 1350-4533, E-ISSN 1873-4030, Vol. 37, no 3, p. 265-271Article in journal (Refereed)
    Abstract [en]

    The size of the larger arteries increases during the entire life, but not much is known about how the change in size affects the blood flow. This study compares the flow field in a group of young males (N = 10, age = 23.5 +/- 1.4), with a group of older males (N = 8, age = 58.0 +/- 2.8). Aortic geometries were obtained by magnetic resonance imaging, and the aortic blood flow field was computed using computational fluid dynamics. The aortic wall shear stress was obtained from the computations, and it was concluded that time-averaged wall shear stress decreased with increased age, probably as a consequence of increased aortic diameter and decreased stroke volume, which in turn reduces the shear rates in the aorta. However, the oscillatory shear index, which is a measure of the oscillatory nature of the wall shear stress vector, seemed to be unaffected by aging.

  • 18.
    Maleki, Shohreh
    et al.
    Atherosclerosis Research Unit, Center for Molecular Medicine, Department of Medicine, Karolinska Institute, Sweden.
    Björck, Hanna M.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Physiology. Linköping University, Faculty of Health Sciences.
    Folkersen, Lasse
    Atherosclerosis Research Unit, Center for Molecular Medicine, Department of Medicine, Karolinska Institute, Sweden.
    Nilsson, R.
    Computational Medicine, Karolinska Institutet, Stockholm.
    Renner, Johan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Caidahl, K.
    Clinical Physiology, Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden.
    Franco‐Cereceda, A.
    7Cardiothoracic Surgery Unit, Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden.
    Länne, Toste
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Thoracic and Vascular Surgery.
    Eriksson, Per
    Atherosclerosis Research Unit, Center for Molecular Medicine, Department of Medicine, Karolinska Institute, Sweden.
    Identification of a novel flow-mediated gene expression signature in patients with bicuspid aortic valve2013In: Journal of Molecular Medicine, ISSN 0946-2716, E-ISSN 1432-1440, Vol. 91, no 1, p. 129-139Article in journal (Refereed)
    Abstract [en]

    Rationale: Individuals with bicuspid aortic valve (BAV) are at significantly higher risk of developing serious aortic complications including aortic aneurysm and dissection than individuals with a tricuspid aortic valve (TAV). Studies have indicated an altered aortic blood flow in patients with BAV, however the extent to which altered flow may influence the pathological state of BAV aorta is still unclear.

    Objective: To dissect flow-mediated gene expression potentially leading to increased aneurysm susceptibility in patients with BAV.

    Methods and Results: A large collection of publically available microarray data sets were screened for consistent co-expression with KLF2, KLF4, TIE1, THBD, and PKD2, five previously well-characterized flow-regulated genes. This identified 122 genes with coexpression probability of >0.5. Of these, 44 genes satisfied two additional filtering criteria in ascending aorta (127 arrays). The criteria were significant correlation with one or more of the 5 query genes (R>0.40) and differential expression between patients with BAV and TAV. No gene fulfilled the criteria in mammary artery (88 arrays). A large proportion of the identified genes were angiogenesis related genes. Further, 55% of the genes differentially expressed between BAV and TAV showed differential expression in disturbed vs. uniform flow pattern regions in rat aorta. Protein expression of ZFP36, PKD2 and GPR116 were analyzed by immunohistochemistry and their association with BAV were further discussed.

    Conclusions: With a new strategy to dissect flow-mediated gene expression, we identified novel genes associated with valve morphology. The complex pattern of blood flow, as a consequence of BAV

  • 19.
    Modin, Daniel
    et al.
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Renner, Johan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, The Institute of Technology.
    Gårdhagen, Roland
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, The Institute of Technology.
    Ebbers, Tino
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Länne, Toste
    Linköping University, Department of Medical and Health Sciences, Physiology. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Thoracic and Vascular Surgery.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, The Institute of Technology.
    Evaluation of Aortic Geometries created by MRI Data in Man2011In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 31, no 6, p. 485-491Article in journal (Refereed)
    Abstract [en]

    The development of atherosclerotic plaques has been associated with the patterns of wall shear stress (WSS). However, much is still uncertain with the methods used to calculate WSS. Correct vessel geometries are mandatory to get reliable estimations and the purpose of this study was to evaluate an in vivo method for creating aortic 3D geometry in man based on data from magnetic resonance imaging (MRI) with ultrasound as reference.

    Methods: The aortas of ten healthy males, 23.4 ± 1.6 years of age, were examined with MRI, and 3D geometries were created with manual segmentation of the images. Lumen diameters (LD) were measured in the abdominal aorta (AA) and the thoracic aorta (TA) with non-invasive B-mode ultrasound as a reference.

    Results: The anteroposterior diameter of the AA was 13.6 ± 1.1 mm for the MRI and 13.8 ± 1.3 mm for the ultrasound (NS). Intraobserver variability (CV) for MRI and ultrasound was <0.92% and <0.40% respectively . Interobserver variability MRI and ultrasound was 0.96% and 0.56% respectively. The diameter of the TA was 19.2 ± 1.4 mm for the MRI, and the intraobserver variability (CV) were <0.78% and interobserver variability (CV) were 0.92%.

    Conclusion: Specific arterial geometries can be constructed with a high degree of accuracy using MRI. This indicate that the MRI geometries may be used to create realistic and correct geometries in the calculation of WSS in the aorta of man.

  • 20.
    Renner, Johan
    Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Estimating patient specific wall shear stress in the human aorta: geometrical and post-processing considerations2006Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes a workflow to perform in-vivo wall shear stress (WSS) estimations in the human aorta using computational fluid dynamics (CFD) methods. An abnormal WSS distribution is believed to influence the development of many cardiovascular diseases, e.g. atherosclerosis. The focus in this thesis is on geometrical influence on the WSS results and interpretation methods tor non-stationary results. The work shows that results are sensitive to the choice of segmentation method (the process from medical images to a geometrical model) and a correct geometrical description of the artery is crucial in making WSS estimations. A new parameter for non-stationary WSS results has been proposed; Wall Shear Stress Angular Amplitude (WSSAA), making the analysis of non-stationary results more straight-forward. It has been shown that the workfiow can be used with confidence and that WSS can be estimated in-vivo. using the combination of MRI-based geometry definition and CFD.

    List of papers
    1. Geometrical Considerations in Patient Specific Models of a Human Aorta with Stenosis and Aneurysm
    Open this publication in new window or tab >>Geometrical Considerations in Patient Specific Models of a Human Aorta with Stenosis and Aneurysm
    2004 (English)In: Computational Fluid Dynamics 2004: Proceedings of the Third International Conference on Computational Fluid Dynamics, ICCFD3, Toronto, 12–16 July 2004, 2004, p. 335-340Conference paper, Published paper (Refereed)
    Abstract [en]

    The most important artery in the human body is the aorta that supplies the rest of the body with blood. Lesions in the aorta can cause serious complications, which can even lead to death. How the flow is behaving in lesions, what causes the problems and which lesions are dangerous are highly interesting to determine. Laminar, stationary CFD calculations are performed on two geometrically different models of the human aorta created from the same set of patient MRI (Magnetic Resonance Imaging) data. Differences in the CFD results due to different geometries are evaluated. Overview results e.g. pressure variations throughout the artery are not dependent on an exact description of the geometry. If absolute and local values e.g. wall shear stress are sought more robust geometry creation procedure is needed in order to get more reliable results.

    Keywords
    Geometrical considertions, Human Aorta
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-23244 (URN)10.1007/3-540-31801-1_46 (DOI)2661 (Local ID)978-3-540-31800-2 (ISBN)2661 (Archive number)2661 (OAI)
    Conference
    Third International Conference on Computational Fluid Dynamics, ICCFD3, Toronto, 12–16 July 2004
    Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2016-03-14
    2. Assessment of Geometrical Influence on WSS Estimation in the Human Aorta
    Open this publication in new window or tab >>Assessment of Geometrical Influence on WSS Estimation in the Human Aorta
    2006 (English)In: WSEAS Transactions on Fluid Mechanics, ISSN 1790-5087, Vol. 4, no 1, p. 318-326Article in journal (Refereed) Published
    Abstract [en]

    Computational fluid dynamics simulations were performed on a stenosed human aorta with poststenotic dilatation, in order to estimate wall shear stress (WSS). WSS is important due to its correlation with atherosclerosis. Both steady-state and non-stationary simulations were conducted. Three different models were created from a set of MRI images. Comparison of geometrically different models was accomplished by using geometrical landmarks and a comparison parameter. Geometrical differences had larger influence on WSS magnitude than inflow rotation in steady-state results for the models used. In non-stationary flow the largest differences in WSS are found when the flow velocity near the wall is low e.g. when the inflow is low or in recirculation regions.

    Keywords
    wall shear stress, human aorta, geometry influence, cfd, result, comparison
    National Category
    Engineering and Technology Radiology, Nuclear Medicine and Medical Imaging Medical Image Processing Fluid Mechanics and Acoustics
    Identifiers
    urn:nbn:se:liu:diva-37433 (URN)35727 (Local ID)35727 (Archive number)35727 (OAI)
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2016-03-14
    3. Post-Processing Dynamic Behavior of WSS in Aortic Blood Flow
    Open this publication in new window or tab >>Post-Processing Dynamic Behavior of WSS in Aortic Blood Flow
    2006 (English)Report (Other academic)
    Abstract [en]

    Pulsating flow simulations with CFD is performed on a stenosed human aorta with post-stenotic dilatation, for development of wall shear stress (WSS) dynamic parameters. WSS is of interest due to its correlation with atherosclerosis. The dynamic behavior and dynamic capturing parameters of WSS are usable in analyzing non-stationary results from blood flow simulations. The amount of wall back-flow is shown to be an very easy parameter to interpret and it showed an "washout" effect in the post-stenotic dilatation. A new dynamic capturing parameter describing the WSS angular amplitude (WSSAA) is presented. It has both differences and similarities with the widely used oscillating shear index (OSI) parameter. WSSA have a more direct physical interpretation then OSI.

    Place, publisher, year, edition, pages
    Linköping: Linköpings Universitetet, 2006
    Series
    LITH-IKP-R, ISSN 0281-5001 ; 6
    Keywords
    WallShear Stress, Human Aorta, CFD, WSS angular amplitude, Wall back-flow
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-36744 (URN)LITH-IKP-R--06/1417--SE (ISRN)32311 (Local ID)32311 (Archive number)32311 (OAI)
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2016-03-14
    4. Feasibility of Patient Specific Aortic Blood Flow CFD Simulation
    Open this publication in new window or tab >>Feasibility of Patient Specific Aortic Blood Flow CFD Simulation
    Show others...
    2006 (English)In: Medical Image Computing and Computer-Assisted Intervention – MICCAI 2006: 9th International Conference, Copenhagen, Denmark, October 1-6, 2006. Proceedings, Part I / [ed] Rasmus Larsen, Mads Nielsen and Jon Sporring, Springer Berlin/Heidelberg, 2006, 1, Vol. 4190, p. 257-263Conference paper, Published paper (Refereed)
    Abstract [en]

    Patient specific modelling of the blood flow through the human aorta is performed using computational fluid dynamics (CFD) and magnetic resonance imaging (MRI). Velocity patterns are compared between computer simulations and measurements. The workflow includes several steps: MRI measurement to obtain both geometry and velocity, an automatic levelset segmentation followed by meshing of the geometrical model and CFD setup to perform the simulations follwed by the actual simulations. The computational results agree well with the measured data.

    Place, publisher, year, edition, pages
    Springer Berlin/Heidelberg, 2006 Edition: 1
    Series
    Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349 ; 4190
    National Category
    Medical Image Processing
    Identifiers
    urn:nbn:se:liu:diva-36902 (URN)10.1007/11866565_32 (DOI)000241556300032 ()32988 (Local ID)3-5404-4707-5 (ISBN)978-3-540-44727-6 (ISBN)978-3-540-44707-8 (ISBN)32988 (Archive number)32988 (OAI)
    Conference
    The 9th MICCAI Conference, Copenhagen, Denmark, 1-6 October 2006
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2018-02-20Bibliographically approved
  • 21.
    Renner, Johan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, The Institute of Technology.
    Towards Subject Specific Aortic Wall Shear Stress: a combined CFD and MRI approach2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The cardiovascular system is an important part of the human body since it transports both energy and oxygen to all cells throughout the body. Diseases in this system are often dangerous and cardiovascular diseases are the number one killer in the western world. Common cardiovascular diseases are heart attack and stroke, which origins from obstructed blood flow. It is generally important to understand the causes for these cardiovascular diseases. The main causes for these diseases are atherosclerosis development in the arteries (hardening and abnormal growth). This transform of the arterial wall is believed to be influenced by the mechanical load from the flowing blood on the artery and especially the tangential force the wall shear stress. To retrieve wall shear stress information in arteries invivo is highly interesting due to the coupling to atherosclerosis and indeed a challenge. The goal of this thesis is to develop, describe and evaluate an in-vivo method for subject specific wall shear stress estimations in the human aorta, the largest artery in the human body. The method uses an image based computational fluid dynamics approach in order to estimate the wall shear stress. To retrieve in-vivo geometrical descriptions of the aorta magnetic resonance imaging capabilities is used which creates image material describing the subject specific geometry of the aorta. Magnetic resonance imaging is also used to retrieve subject specific blood velocity information in the aorta. Both aortic geometry and velocity is gained at the same time. Thereafter the image material is interpreted using level-set segmentation in order to get a three-dimensional description of the aorta. Computational fluid dynamics simulations is applied on the subject specific aorta in order to calculate time resolved wall shear stress distribution at the entire aortic wall included in the actual model.

    This work shows that it is possible to estimate subject specific wall shear stress in the human aorta. The results from a group of healthy volunteers revealed that the arterial geometry is very subject specific and the different wall shear stress distributions have general similarities but the level and local distribution are clearly different. Sensitivity (on wall shear stress) to image modality, the different segmentation methods and different inlet velocity profiles have been tested, which resulted in these general conclusions:

    • The aortic diameter from magnetic resonance imaging became similar to the reference diameter measurement method.
    • The fast semi-automatic level-set segmentation method gave similar geometry and wall shear stress results when compared to a reference segmentation method.
    • Wall shear stress distribution became different when comparing a simplified uniform velocity profile inlet boundary condition with a measured velocity profile.

    The method proposed in this thesis has the possibility to produce subject specific wall shear stress distribution in the human aorta. The method can be used for further medical research regarding atherosclerosis development and has the possibility for usage in clinical work.

    List of papers
    1. Subject Specific Wall Shear Stress in the Human Thoracic Aorta
    Open this publication in new window or tab >>Subject Specific Wall Shear Stress in the Human Thoracic Aorta
    2006 (English)In: WSEAS Transaction on biology and biomedicine, ISSN 1109-9518, Vol. 10, no 3, p. 609-614Article in journal (Refereed) Published
    Abstract [en]

    Numerous studies have shown a correlation between Wall Shear Stress (WSS) and atherosclerosis, but few have evaluated the reliability of estimation methods and measures used to assessWSS, which is the subject of this work. A subject specific vessel model of the aortic arch and thoracic aorta is created fromMRI images and used for CFD simulations with MRI velocity measurements as inlet boundary condition. WSS is computed from the simulation results. Aortic WSS shows significant spatial as well as temporal variation during a cardiac cycle, which makes circumferential values very uninformative, and approximate estimates using Hagen-Poiseuille fails predict the averageWSS. Highly asymmetric flow, especially in the arch, causes the spatial WSS variations.

    Keywords
    Wall shear stress, CFD, Aorta, Circumferential average values, Asymmetric flow
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-43727 (URN)74619 (Local ID)74619 (Archive number)74619 (OAI)
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-03-27Bibliographically approved
    2. Feasibility of Patient Specific Aortic Blood Flow CFD Simulation
    Open this publication in new window or tab >>Feasibility of Patient Specific Aortic Blood Flow CFD Simulation
    Show others...
    2006 (English)In: Medical Image Computing and Computer-Assisted Intervention – MICCAI 2006: 9th International Conference, Copenhagen, Denmark, October 1-6, 2006. Proceedings, Part I / [ed] Rasmus Larsen, Mads Nielsen and Jon Sporring, Springer Berlin/Heidelberg, 2006, 1, Vol. 4190, p. 257-263Conference paper, Published paper (Refereed)
    Abstract [en]

    Patient specific modelling of the blood flow through the human aorta is performed using computational fluid dynamics (CFD) and magnetic resonance imaging (MRI). Velocity patterns are compared between computer simulations and measurements. The workflow includes several steps: MRI measurement to obtain both geometry and velocity, an automatic levelset segmentation followed by meshing of the geometrical model and CFD setup to perform the simulations follwed by the actual simulations. The computational results agree well with the measured data.

    Place, publisher, year, edition, pages
    Springer Berlin/Heidelberg, 2006 Edition: 1
    Series
    Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349 ; 4190
    National Category
    Medical Image Processing
    Identifiers
    urn:nbn:se:liu:diva-36902 (URN)10.1007/11866565_32 (DOI)000241556300032 ()32988 (Local ID)3-5404-4707-5 (ISBN)978-3-540-44727-6 (ISBN)978-3-540-44707-8 (ISBN)32988 (Archive number)32988 (OAI)
    Conference
    The 9th MICCAI Conference, Copenhagen, Denmark, 1-6 October 2006
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2018-02-20Bibliographically approved
    3. Evaluation of Aortic Geometries created by MRI Data in Man
    Open this publication in new window or tab >>Evaluation of Aortic Geometries created by MRI Data in Man
    Show others...
    2011 (English)In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 31, no 6, p. 485-491Article in journal (Refereed) Published
    Abstract [en]

    The development of atherosclerotic plaques has been associated with the patterns of wall shear stress (WSS). However, much is still uncertain with the methods used to calculate WSS. Correct vessel geometries are mandatory to get reliable estimations and the purpose of this study was to evaluate an in vivo method for creating aortic 3D geometry in man based on data from magnetic resonance imaging (MRI) with ultrasound as reference.

    Methods: The aortas of ten healthy males, 23.4 ± 1.6 years of age, were examined with MRI, and 3D geometries were created with manual segmentation of the images. Lumen diameters (LD) were measured in the abdominal aorta (AA) and the thoracic aorta (TA) with non-invasive B-mode ultrasound as a reference.

    Results: The anteroposterior diameter of the AA was 13.6 ± 1.1 mm for the MRI and 13.8 ± 1.3 mm for the ultrasound (NS). Intraobserver variability (CV) for MRI and ultrasound was <0.92% and <0.40% respectively . Interobserver variability MRI and ultrasound was 0.96% and 0.56% respectively. The diameter of the TA was 19.2 ± 1.4 mm for the MRI, and the intraobserver variability (CV) were <0.78% and interobserver variability (CV) were 0.92%.

    Conclusion: Specific arterial geometries can be constructed with a high degree of accuracy using MRI. This indicate that the MRI geometries may be used to create realistic and correct geometries in the calculation of WSS in the aorta of man.

    Place, publisher, year, edition, pages
    Wiley-Blackwell, 2011
    Keywords
    human aorta, lumen diameter, magnetic resonance imaging, manual segmentation, ultrasound
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-65905 (URN)10.1111/j.1475-097X.2011.01035.x (DOI)000296198100011 ()
    Available from: 2011-02-25 Created: 2011-02-25 Last updated: 2017-12-11Bibliographically approved
    4. Wall Shear Stress Estimations using Semi-Automatic Segmentation
    Open this publication in new window or tab >>Wall Shear Stress Estimations using Semi-Automatic Segmentation
    Show others...
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Atherosclerosis development is strongly believed to be influenced by hemodynamic forces such as wall shear stress (WSS). To estimate such entity in-vivo in humans, is image based computational fluid dynamics (CFD) a powerful tool. In this paper we use a combination of magnetic resonance imaging (MRI) and CFD to estimate WSS. In such method a number of steps is included. One important step is the image interpretation into 3D models, named segmentation. The choice of segmentation method can influence the resulting WSS distribution in the human aorta. This is studied by comparingWSS results gained from the use of two different segmentation approaches: manual and semi-automatic, where the manual approach is considered to be the reference method. The investigation is performed on a group of 8 healthymale volunteers. The different segmentation methods give slightly different geometrical descriptions of the human aorta. However there is a very good agreement between the resultingWSS distribution for the two segmentation approaches. The small differences in WSS between the methods increase in the late systole and early diastolic cardiac cycle time position indicating that theWSS is more sensitive to local geometry differences in these parts of the cardiac cycle. We can conclude that the results show that the semi-automatic segmentation method can be used in the future to estimate WSS with relevant accuracy.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-65906 (URN)
    Available from: 2011-02-25 Created: 2011-02-25 Last updated: 2017-03-27Bibliographically approved
    5. A method for subject specific estimation of aortic wall shear stress
    Open this publication in new window or tab >>A method for subject specific estimation of aortic wall shear stress
    Show others...
    2009 (English)In: WSEAS Transactions on Biology and Biomedicine, ISSN 1109-9518, Vol. 6, no 3, p. 49-57Article in journal (Refereed) Published
    Abstract [en]

    Wall shear stress (WSS) distribution in the human aorta is a highly interesting hemodynamic factor for atherosclerosis development. We present a magnetic resonance imaging (MRI) and computational fluid dynamics (CFD) based subject specific WSS estimation method and demonstrate it on a group of nine healthy volunteers (males age 23.6 ± 1.3 years). In all nine subjects, the aortic blood flow was simulated in a subject specific way, where the 3D segmented geometries and inflow profiles were obtained using MRI. No parameter settings were tailored using data from the nine subjects. Validation was performed by comparing CFD gained velocity with magnetic resonance imaging (MRI) velocity measurements. CFD and MRI velocity profiles were comparable, but the temporal variations of the differences during the cardiac cycle were significant. Spatio-temporal analyzes on the WSS distribution showed a strong subject specific influence. Subject specific models are decisive to estimate WSS distribution.

    Place, publisher, year, edition, pages
    WSEAS Press, 2009
    Keywords
    3D segmentation; Aorta; CFD; MRI; Subject specific; Velocity validation; WSS
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-57056 (URN)
    Available from: 2010-06-11 Created: 2010-06-09 Last updated: 2017-03-27Bibliographically approved
    6. Is a flat inlet profile sufficient for WSS estimation in the aortic arch?
    Open this publication in new window or tab >>Is a flat inlet profile sufficient for WSS estimation in the aortic arch?
    2009 (English)In: WSEAS Transactions on Fluid Mechanics, ISSN 1790-5087, Vol. 4, no 4, p. 148-160Article in journal (Refereed) Published
    Abstract [en]

    Atherosclerosis is one of the main reasons for cardivascular disease which cause many deaths every year especially in the Western world. The development of atherosclerosis is strongly believed to be influenced by hemodynamic forces in the arteries e.g. wall shear stress (WSS). Estimations of WSS are therefore very important. By combining magnetic resonance imaging (MRI), image processing and computational fluid dynamic (CFD) simulations, it is possible to estimate subject specific WSS in the human arteries. The framework for performing such work includes i.e. using inlet boundary conditions which, however, will influence the final result i.e. the WSS distribution. This paper aims to investigate the influence of the inflow boundary condition in the human aorta with comparing two settings for the inflow: 1) subject specific inlet profile measured with MRI and 2) uniform profile with the subject specific mass flow rate. The analysis of WSS will be performed both on spatial location along the artery as well as on the temporal location in the cardiac cycle. Subject specific data have been used for geometry, inflow velocity profile and blood viscosity. The recommendation due to our findings from nine healthy subjects, is that a measured subject specific inlet boundary condition must be used in order to get a subject specific WSS distribution; the difference in WSS is 8-34% compared to using a mass-flow correct uniform profile. Temporal variations were clearly seen in the WSS differences due to the different inflow velocity profiles used. The lowest influence of the inlet boundary condition was found at peak velocity in the cardiac cycle. The aortic geometry does not form the flow in such extent (compared to the influence by inlet boundary condition) to obtain a more correct WSS distribution further away from the inlet at the systolic parts of the cardiac cycle. The shape of the vessel has only a significant influence at low velocities i.e. the diastolic phase of the cardiac cycle.

    Keywords
    Aorta; CFD; Inlet boundary condition; Subject specific; Uniform velocity profile; Wall shear stress
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-53002 (URN)
    Available from: 2010-01-14 Created: 2010-01-14 Last updated: 2017-03-27Bibliographically approved
  • 22.
    Renner, Johan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Using Industrial Projects in a Heat Transfer Course for Engineering Students2011Conference paper (Other (popular science, discussion, etc.))
  • 23.
    Renner, Johan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Ghavami Nejad, Mehdi
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Nadali Najafabadi, Hossein
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Skoog, Pontus
    SAPA Heat Transfer AB.
    Abrahamsson, David
    SAPA Heat Transfer AB.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Conduction and convection heat transfer for aluminum ingot in preheating furnace2011In: Proceedings of 6th Baltic Heat Transfer Conference 2011 / [ed] Reijo Karvinen & Matti Lindstedt, 2011Conference paper (Refereed)
    Abstract [en]

    Aluminium is a widely used material, which is found in a number of products e.g. thin aluminium bands that is the base material in many heat exchangers. Rolling processes are used to produce these thin aluminium bands, in order to get the right properties and to get the aluminium easier to roll, heat treatment is needed. This heat treatment of aluminium ingots prior to the rolling is in focus in this work, where computational fluid dynamics and computational heat transfer techniques is used to predict the heating process in a hot air pre-heating furnace. The used approach includes steady state computational fluid dynamics simulations combined with transient computational heat transfer simulations. The simulation results in form of spatial and temporal distributed aluminium ingot temperature was compared with temperature measurement in a thermocouple prepared ingot in the actual pre-heating furnace. Simulation results correspond well with the measurements and there are small differences. Results of the described simulation approach open the possibility to predict spatial and temporal temperature distribution in these kinds of pre-heating processes.

  • 24.
    Renner, Johan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, The Institute of Technology.
    Gårdhagen, Roland
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, The Institute of Technology.
    Ebbers, Tino
    Linköping University, Department of Medicine and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Heiberg, Einar
    Department of Clinical Physiology, Lund University Hospital, Sweden.
    Länne, Toste
    Linköping University, Department of Medicine and Health Sciences, Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, The Institute of Technology.
    A method for subject specific estimation of aortic wall shear stress2009In: WSEAS Transactions on Biology and Biomedicine, ISSN 1109-9518, Vol. 6, no 3, p. 49-57Article in journal (Refereed)
    Abstract [en]

    Wall shear stress (WSS) distribution in the human aorta is a highly interesting hemodynamic factor for atherosclerosis development. We present a magnetic resonance imaging (MRI) and computational fluid dynamics (CFD) based subject specific WSS estimation method and demonstrate it on a group of nine healthy volunteers (males age 23.6 ± 1.3 years). In all nine subjects, the aortic blood flow was simulated in a subject specific way, where the 3D segmented geometries and inflow profiles were obtained using MRI. No parameter settings were tailored using data from the nine subjects. Validation was performed by comparing CFD gained velocity with magnetic resonance imaging (MRI) velocity measurements. CFD and MRI velocity profiles were comparable, but the temporal variations of the differences during the cardiac cycle were significant. Spatio-temporal analyzes on the WSS distribution showed a strong subject specific influence. Subject specific models are decisive to estimate WSS distribution.

  • 25.
    Renner, Johan
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Gårdhagen, Roland
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Heiberg, Einar
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Ebbers, Tino
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care.
    Länne, Toste
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation .
    Validation of Simulated Velocity of Blood in Patient Specific Aorta2006In: VIII Svenska Kardiovaskulära Vårmöte,2006, Linköping, Sweden: Linköpings universitet , 2006Conference paper (Refereed)
  • 26.
    Renner, Johan
    et al.
    Linköping University, Department of Mechanical Engineering. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Gårdhagen, Roland
    Linköping University, Department of Mechanical Engineering. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Karlsson, Matts
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Post-Processing Dynamic Behavior of WSS in Aortic Blood Flow2006Report (Other academic)
    Abstract [en]

    Pulsating flow simulations with CFD is performed on a stenosed human aorta with post-stenotic dilatation, for development of wall shear stress (WSS) dynamic parameters. WSS is of interest due to its correlation with atherosclerosis. The dynamic behavior and dynamic capturing parameters of WSS are usable in analyzing non-stationary results from blood flow simulations. The amount of wall back-flow is shown to be an very easy parameter to interpret and it showed an "washout" effect in the post-stenotic dilatation. A new dynamic capturing parameter describing the WSS angular amplitude (WSSAA) is presented. It has both differences and similarities with the widely used oscillating shear index (OSI) parameter. WSSA have a more direct physical interpretation then OSI.

  • 27.
    Renner, Johan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Gårdhagen, Roland
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Subject Specific In-Vivo CFD Estimated Aortic WSS: Comparison Between Manual and Automated Segmentation Methods2009In: ASME 2008 Summer Bioengineering Conference: Parts A and B, The American Society of Mechanical Engineers (ASME) , 2009, no PART A, p. 425-426Conference paper (Refereed)
    Abstract [en]

    When making computational fluid dynamics (CFD) based estimations of wall shear stress (WSS) in the human aorta, medical image converting processes to 3D geometries are important as the result is strongly dependent on the quality of the geometry [1]. The image interpretation process or segmentation can be more or less automated; however in clinical work today the gold standard is to manually interpret the medical image information. This combined magnetic resonance imaging (MRI) and CFD method aims to estimate WSS in human arteries in-vivo as WSS is strongly linked to atherosclerosis [2]. More or less automated segmentation has been used in previous studies but normally based on a stack of 2D individually segmented slices which is combined into a 3D model [3]. The aim of this work is to compare manual 2D and automatic 3D segmentations.

  • 28.
    Renner, Johan
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Lantz, Jonas
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Ebbers, Tino
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Clinical Physiology UHL.
    Länne, Toste
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Physiology. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Thoracic and Vascular Surgery in Östergötland.
    Karlsson, Matts
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Altered WSS in the human aorta with age – implications for wall remodeling and lesions?2012Conference paper (Other academic)
  • 29.
    Renner, Johan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, The Institute of Technology.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Länne, Toste
    Linköping University, Department of Medicine and Health Sciences, Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, The Institute of Technology.
    Is a flat inlet profile sufficient for WSS estimation in the aortic arch?2009In: WSEAS Transactions on Fluid Mechanics, ISSN 1790-5087, Vol. 4, no 4, p. 148-160Article in journal (Refereed)
    Abstract [en]

    Atherosclerosis is one of the main reasons for cardivascular disease which cause many deaths every year especially in the Western world. The development of atherosclerosis is strongly believed to be influenced by hemodynamic forces in the arteries e.g. wall shear stress (WSS). Estimations of WSS are therefore very important. By combining magnetic resonance imaging (MRI), image processing and computational fluid dynamic (CFD) simulations, it is possible to estimate subject specific WSS in the human arteries. The framework for performing such work includes i.e. using inlet boundary conditions which, however, will influence the final result i.e. the WSS distribution. This paper aims to investigate the influence of the inflow boundary condition in the human aorta with comparing two settings for the inflow: 1) subject specific inlet profile measured with MRI and 2) uniform profile with the subject specific mass flow rate. The analysis of WSS will be performed both on spatial location along the artery as well as on the temporal location in the cardiac cycle. Subject specific data have been used for geometry, inflow velocity profile and blood viscosity. The recommendation due to our findings from nine healthy subjects, is that a measured subject specific inlet boundary condition must be used in order to get a subject specific WSS distribution; the difference in WSS is 8-34% compared to using a mass-flow correct uniform profile. Temporal variations were clearly seen in the WSS differences due to the different inflow velocity profiles used. The lowest influence of the inlet boundary condition was found at peak velocity in the cardiac cycle. The aortic geometry does not form the flow in such extent (compared to the influence by inlet boundary condition) to obtain a more correct WSS distribution further away from the inlet at the systolic parts of the cardiac cycle. The shape of the vessel has only a significant influence at low velocities i.e. the diastolic phase of the cardiac cycle.

  • 30.
    Renner, Johan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Nadali Najafabadi, Hossein
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Modin, Daniel
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Länne, Toste
    Linköping University, Department of Medical and Health Sciences, Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Thoracic and Vascular Surgery. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Subject-specific aortic wall shear stress estimations using semi-automatic segmentation2012In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 32, no 6, p. 481-491Article in journal (Refereed)
    Abstract [en]

    Atherosclerosis development is strongly believed to be influenced by hemodynamic forces such as wall shear stress (WSS). To estimate such an entity in-vivo in humans, image-based computational fluid dynamics (CFD) is a useful tool. In this study, we use a combination of magnetic resonance imaging (MRI) and CFD to estimate WSS. In such method, a number of steps are included. One important step is the interpretation of images into 3D models, named segmentation. The choice of segmentation method can influence the resulting WSS distribution in the human aorta. This is studied by comparing WSS results gained from the use of two different segmentation approaches: manual and semi-automatic, where the manual approach is considered to be the reference method. The investigation is performed on a group of eight healthy male volunteers. The different segmentation methods give slightly different geometrical depictions of the human aorta (difference in the mean thoracic Aorta lumen diameter were 0.7% Pandlt;0.86). However, there is a very good agreement between the resulting WSS distribution for the two segmentation approaches. The small differences in WSS between the methods increase in the late systole and early diastolic cardiac cycle time point indicating that the WSS is more sensitive to local geometric differences in these parts of the cardiac cycle (correlation coefficient is 0.96 at peak systole and 0.68 at early diastole). We can conclude that the results show that the semi-automatic segmentation method can be used in future to estimate relevant aortic WSS.

  • 31.
    Renner, Johan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, The Institute of Technology.
    Nadali Najafabadi, Hossein
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Modin, Daniel
    Linköping University, Department of Medicine and Health Sciences. Linköping University, Faculty of Health Sciences.
    Länne, Toste
    Linköping University, Department of Medicine and Health Sciences, Physiology. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Thoracic and Vascular Surgery in Östergötland.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, The Institute of Technology.
    Wall Shear Stress Estimations using Semi-Automatic SegmentationManuscript (preprint) (Other academic)
    Abstract [en]

    Atherosclerosis development is strongly believed to be influenced by hemodynamic forces such as wall shear stress (WSS). To estimate such entity in-vivo in humans, is image based computational fluid dynamics (CFD) a powerful tool. In this paper we use a combination of magnetic resonance imaging (MRI) and CFD to estimate WSS. In such method a number of steps is included. One important step is the image interpretation into 3D models, named segmentation. The choice of segmentation method can influence the resulting WSS distribution in the human aorta. This is studied by comparingWSS results gained from the use of two different segmentation approaches: manual and semi-automatic, where the manual approach is considered to be the reference method. The investigation is performed on a group of 8 healthymale volunteers. The different segmentation methods give slightly different geometrical descriptions of the human aorta. However there is a very good agreement between the resultingWSS distribution for the two segmentation approaches. The small differences in WSS between the methods increase in the late systole and early diastolic cardiac cycle time position indicating that theWSS is more sensitive to local geometry differences in these parts of the cardiac cycle. We can conclude that the results show that the semi-automatic segmentation method can be used in the future to estimate WSS with relevant accuracy.

  • 32.
    Simonsson, Kjell
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Renner, Johan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, The Institute of Technology.
    Hallberg, Peter
    Linköping University, Department of Management and Engineering, Machine Design. Linköping University, The Institute of Technology.
    Simonsson, Maria
    Linköping University, Department of Social and Welfare Studies, Learning, Aesthetics, Natural science. Linköping University, The Institute of Technology.
    Kamratutvärdering i kurser med stort datorlaborativt inslag2014Report (Other academic)
    Abstract [sv]

    De mångfacetterade krav som idag ställs på yrkesverksamma högskole- och civilingenjörer handlar inte enbart om rena ämnesmässiga kunskaper och förmågor, utan även om t.ex. erfarenhet och förmåga att delta i och leda projekt samt (kopplat till detta) kommunikativ skicklighet (såväl muntlig som skriftlig). En annan uppgift som yrkesverksamma ingenjörer måste kunna bemästra i sin profession är att (individuellt, eller som medlemmar i olika typer av styrgrupper) bedöma och utvärdera andras ingenjörsmässiga arbete, en oerhört central uppgift i ett projekt- och kvalitetssäkringsperspektiv.

    Det övergripande syftet med arbetet har varit att studera hur kamratbedömning kan implementeras i redan existerande kurser, för att på så sätt ge de studerande möjlighet att träna på att ge och ta emot kritisk bedömning, att förbättra de studerandes lärande via ett större aktivt engagemang under kursen samt att se om potential finns att effektivisera undervisningen m.a.p. lärarinsatsen, genom att lyfta över en del av enklare rutinkontroller till de studerande själva.

    Kamratbedömning har implementerats i två sinsemellan likartade kurser inom beräkningsmekanik vid högskole- resp. civilingenjörsprogrammen i Maskinteknik, LiTH (600 studenter ingick i studien). Mer specifikt har till två enklare inledande laborationsuppgifter inkluderats ett moment av kamratbedömning. Utvärderingen av det genomförda arbetet har skett via en kvalitativ studie, där de studerandes perspektiv/synpunkter inhämtats i samband med skriftlig redovisning av inlämningsuppgifter. Utöver detta har den kursansvarige gjort observationer av hur kamratutvärderingsarbetet fortskridit under laborationstid.

    Resultatet visar att de studerande har uppskattat granskningen av såväl det egna som kamraternas arbeten, och att de sett det som ett led i lärandeprocessen. Även professionsperspektivet har lyfts fram där de studerande betonar vikten av moment och uppgifter i utbildningen som har en direkt relevans i det kommande yrkeslivet. Den kursansvariges bedömning är vidare att andelen ”viktiga” och ”relevanta” frågor ökat, vilket ger indikationer på att kamratbedömning kan vara en såväl pedagogiskt som effektivitetsmässigt gynnsam metodik. De studerande har dock upplevt logistiken/administrationen kring kamratvärderingen som i vissa avseenden besvärlig.

    Sammanfattningsvis är det vår slutsats att kamratbedömning har en stor potential att berika utbildningar m.a.p. förmåga till kritisk granskning, djupinlärning och effektivisering, men att verksamheten inte bara skall implementeras kursvis (med risk för suboptimering och ineffektivitet), utan att den bör inlemmas i ett större perspektiv, med progression genom utbildningen som riktmärke.

  • 33.
    Sjögren, Jane
    et al.
    Lund University Hospital.
    Renner, Johan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics . Linköping University, The Institute of Technology.
    Arheden, Håkan
    Lund University Hospital.
    Heiberg, Einar
    Lund University Hospital.
    Prototype Based Image Segmentation - A Novel Method to Incorporate a Priori Information in a Level Set Method2008In: SSBA Symposium Lund 13-14 mars 2008,2008, 2008Conference paper (Refereed)
  • 34.
    Svensson, Johan
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Gårdhagen, Roland
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation .
    Comparison of flow parameters between different geometries of a human aorta with coarctation and aneurysm2005In: 2005 Summer Bioengineering Conference,2005, Vail, USA: Summer Bioengineering Conference Committee , 2005Conference paper (Refereed)
  • 35.
    Svensson, Johan
    et al.
    Linköping University, Department of Mechanical Engineering. Linköping University, The Institute of Technology.
    Gårdhagen, Roland
    Linköping University, Department of Mechanical Engineering. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Geometrical Considerations in Patient Specific Models of a Human Aorta with Stenosis and Aneurysm2004In: Computational Fluid Dynamics 2004: Proceedings of the Third International Conference on Computational Fluid Dynamics, ICCFD3, Toronto, 12–16 July 2004, 2004, p. 335-340Conference paper (Refereed)
    Abstract [en]

    The most important artery in the human body is the aorta that supplies the rest of the body with blood. Lesions in the aorta can cause serious complications, which can even lead to death. How the flow is behaving in lesions, what causes the problems and which lesions are dangerous are highly interesting to determine. Laminar, stationary CFD calculations are performed on two geometrically different models of the human aorta created from the same set of patient MRI (Magnetic Resonance Imaging) data. Differences in the CFD results due to different geometries are evaluated. Overview results e.g. pressure variations throughout the artery are not dependent on an exact description of the geometry. If absolute and local values e.g. wall shear stress are sought more robust geometry creation procedure is needed in order to get more reliable results.

  • 36.
    Svensson, Johan
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Gårdhagen, Roland
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation .
    Geometrical Influence on CFD Analysis of Human Aorta2004Report (Other academic)
  • 37.
    Svensson, Johan
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Gårdhagen, Roland
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation .
    Patient Specific Human Aorta Geometry Influence on CFD Simulation Parameters2004In: 17th Nordic Seminar on Computational Mechanics NSCM17,2004, 2004Conference paper (Refereed)
  • 38.
    Svensson, Johan
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Gårdhagen, Roland
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation .
    Wall Back Flow Variations During Pulsative Flow in a Human Aorta2005In: Svenska Mekanikdagar 2005,2005, 2005, p. 61-62Conference paper (Refereed)
  • 39.
    Svensson, Johan
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Gårdhagen, Roland
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Loyd, Dan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation .
    Wall back flow in human aorta: influence of geometry2005In: NBC05 Umeå,2005, Umeå: Int'l federation for medical anc Biological Engineering IFMBE , 2005, p. 85-Conference paper (Refereed)
  • 40.
    Svensson (Renner), Johan
    et al.
    Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Gårdhagen, Roland
    Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Heiberg, Einar
    Department of Clinical Physiology, Lund University, Sweden.
    Ebbers, Tino
    Linköping University, Department of Medicine and Care. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Loyd, Dan
    Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Länne, Toste
    Linköping University, Department of Medicine and Care, Physiology. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Karlsson, Matts
    Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Feasibility of Patient Specific Aortic Blood Flow CFD Simulation2006In: Medical Image Computing and Computer-Assisted Intervention – MICCAI 2006: 9th International Conference, Copenhagen, Denmark, October 1-6, 2006. Proceedings, Part I / [ed] Rasmus Larsen, Mads Nielsen and Jon Sporring, Springer Berlin/Heidelberg, 2006, 1, Vol. 4190, p. 257-263Conference paper (Refereed)
    Abstract [en]

    Patient specific modelling of the blood flow through the human aorta is performed using computational fluid dynamics (CFD) and magnetic resonance imaging (MRI). Velocity patterns are compared between computer simulations and measurements. The workflow includes several steps: MRI measurement to obtain both geometry and velocity, an automatic levelset segmentation followed by meshing of the geometrical model and CFD setup to perform the simulations follwed by the actual simulations. The computational results agree well with the measured data.

  • 41.
    Wren, Joakim
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Renner, Johan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Enhancing Student Engagement – A CDIO Approach in anEngineering Physics Master Program2011In: Third International Symposium on Project Approaches in Engineering Education (PAEE’2011):Aligning Engineering Education with Engineering Challenges / [ed] Natascha van Hattum-Janssen Rui M. Lima Dinis Carvalho, 2011, p. 283-289Conference paper (Refereed)
  • 42.
    Wren, Joakim
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics . Linköping University, The Institute of Technology.
    Renner, Johan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics . Linköping University, The Institute of Technology.
    Gårdhagen, Roland
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics . Linköping University, The Institute of Technology.
    Johansson, Kristina
    n/a.
    Learning More with Demonstration Based Education2009In: INTERNATIONAL JOURNAL OF ENGINEERING EDUCATION, ISSN 0949-149X, Vol. 25, no 2, p. 374-380Article in journal (Refereed)
    Abstract [en]

    The purpose of this case study is to present an alternative way of teaching, using demonstrations as a teaching aid. A system for visualisation and demonstration of fluid mechanics, particularly laminar and turbulent flow, has been dei,eloped, used, and evaluated in a basic fluid mechanics course for students in Mechanical Engineering. The idea underlying the demonstrations was to enhance the students conceptual understanding of phenomena that emerged in fluid mechanics. In order to investigate the outcome, we asked the students from two different groups to fill out a questionnaire in a cross-sectional manner. The results indicate that demonstration-based education had increased the students motivation and probably enhanced their learning. This could imply that the student moved from a surface approach to a deep-level approach to learning.

  • 43.
    Wren, Joakim
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics.
    Renner, Johan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics.
    THERMODYNAMICS OF MAN – A CDIO-APPROACH TO UNDERSTANDHUMAN PHYSIOLOGY FROM THE FIRST PRINCIPLE2013In: Proceedings of the 9th International CDIO Conference, Massachusetts Institute of Technology and Harvard UniversitySchool of Engineering and Applied Sciences, Cambridge, Massachusetts, June 9 – 13, 2013, 2013Conference paper (Refereed)
    Abstract [en]

    A multi-disciplinary CDIO project ranging from physiology to thermodynamics are used tointroduce first year engineering students to an engineering task, and to introduce generalengineering skills like project management, group dynamics, human interaction as well aswritten and oral presentations.

  • 44.
    Wren, Joakim
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Svensson, Johan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Gårdhagen, Roland
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Engstrand, Ulf
    Learning more with demonstration based education2005In: CUL-dagen 2005,2005, 2005Conference paper (Other academic)
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