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  • 201.
    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.

  • 202.
    Schminder, Jörg
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Gårdhagen, Roland
    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).
    Nilsson, Elias
    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).
    Storck, Karl
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering. SAAB Dynamics AB, Linköping, Sweden.
    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).
    Development of a Cockpit-Pilot Model for Thermal Comfort Optimization During Long-Mission Flight2016In: AIAA Modeling and Simulation Technologies Conference San Diego, California, USA, AAAI Press, 2016Conference paper (Refereed)
    Abstract [en]

    The thermal comfort of a pilot is of crucial importance to maintain a high level ofconcentration and awareness during the entire ight mission. In this work a model for thethermal environment of the cockpit is developed and used as provider of input parametersto a thermoregulatory model, adopted from the literature, of a human. The cockpit-pilotmodel will be used to investigate and improve the thermal comfort for the pilot, particularlyduring longer ight missions. In the cockpit model a combination of lumped systems and nite dierence calculationsis used to obtain input parameters, which are provided to the pilot model. The body, withclothes, is divided into 16 segments and a nite dierence method is used to determine thetemperature distribution within these. Several physiological mechanisms are included inthe model. Simulations with dierent boundary conditions show that the models work properlyeven for longer missions.

  • 203.
    Schminder, Jörg
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics.
    Nilsson, Filip
    Linköping University.
    Lundberg, Paulina
    Linköping University.
    Nguyen, Nghiem-Anh
    Linköping University.
    Hag, Christoffer
    Linköping University.
    Nadali Najafabadi, Hossein
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics.
    An IVR Engineering Educational Laboratory Accommodating CDIO Standards2019In: The 15th International CDIO Conference: Proceedings – Full Papers, Aarhus, 2019, p. 647-658Conference paper (Refereed)
    Abstract [en]

    This paper presents the development of an educational immersive virtual reality (IVR) program considering both technological and pedagogical affordances of such learning environments. The CDIO Standards have been used as guidelines to ensure desirable outcomes of IVR for an engineering course. A learning model has been followed to use VR characteristics and learning affordances in teaching basic principles. Different game modes, considered as learning activities, are incorporated to benefit from experiential and spatial knowledge representation and to create a learning experience that fulfils intended learning outcomes (ILOs) (defined by CDIO Standard 2 and Bloom’s learning taxonomy) associated with the particular course moment. The evaluation of IVR laboratory highlights effectiveness of the approach in achieving ILOs provided that pedagogical models have been followed to create powerful modes of learning.

  • 204.
    Schminder, Jörg
    et al.
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Didacticum.
    Nilsson, Filip
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering.
    Lundberg, Paulina
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering.
    Nguyen, Nghiem-Ann
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering.
    Hag, Christoffer
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering.
    Nadali Najafabadi, Hossein
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Didacticum.
    An IVR Engineering Educational Laboratory AccommodatingCDIO Standards2019In: The 15th International CDIO Conference: Proceedings – Full Papers, Aarhus, 2019Conference paper (Refereed)
    Abstract [en]

    This paper presents the development of an educational immersive virtual reality (IVR) program considering both technological and pedagogical affordances of such learning environments. The CDIO Standards have been used as guidelines to ensure desirable outcomes of IVR for an engineering course. A learning model has been followed to use VR characteristics and learning affordances in teaching basic principles. Different game modes, considered as learning activities, are incorporated to benefit from experiential and spatial knowledge representation and to create a learning experience that fulfils intended learning outcomes (ILOs) (defined by CDIO Standard 2 and Bloom’s learning taxonomy) associated with the particular course moment. The evaluation of IVR laboratory highlights effectiveness of the approach in achieving ILOs provided that pedagogical models have been followed to create powerful modes of learning.

  • 205.
    Selskog, Pernilla
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Brandt, Einar
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Wigström, Lars
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Quantification and Visualization of myocardial strain-rate tensors from time-resolved 3D cine phase contrast MRI.2001In: Proc. Intl. Soc. Mag. Reson. Med.,2001, 2001, p. 1870-1870Conference paper (Refereed)
  • 206.
    Selskog, Pernilla
    et al.
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Heiberg, Einar
    Linköping University, Department of Biomedical Engineering. Linköping University, Department of Medicine and Care.
    Ebbers, Tino
    Linköping University, Department of Medicine and Care. Linköping University, Faculty of Health Sciences.
    Wigström, Lars
    Linköping University, Department of Biomedical Engineering. Linköping University, Department of Medicine and Care. Linköping University, Faculty of Health Sciences.
    Karlsson, Matts
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Kinematics of the heart: strain-rate imaging from time-resolved three-dimensional phase contrast MRI2002In: IEEE Transactions on Medical Imaging, ISSN 0278-0062, E-ISSN 1558-254X, Vol. 21, no 9, p. 1105-1109Article in journal (Refereed)
    Abstract [en]

    A four-dimensional mapping (three spatial dimensions + time) of myocardial strain-rate would help to describe the mechanical properties of the myocardium, which affect important physiological factors such as the pumping performance of the ventricles. Strain-rate represents the local instantaneous deformation of the myocardium and can be calculated from the spatial gradients of the velocity field. Strain-rate has previously been calculated using one-dimensional (ultrasound) or two-dimensional (2-D) magnetic resonance imaging techniques. However, this assumes that myocardial motion only occurs in one direction or in one plane, respectively. This paper presents a method for calculation of the time-resolved three-dimensional (3-D) strain-rate tensor using velocity vector information in a 3-D spatial grid during the whole cardiac cycle. The strain-rate tensor provides full information of both magnitude and direction of the instantaneous deformation of the myocardium. A method for visualization of the full 3-D tensor is also suggested. The tensors are visualized using ellipsoids, which display the principal directions of strain-rate and the ratio between strain-rate magnitude in each direction. The presented method reveals the principal strain-rate directions without a priori knowledge of myocardial motion directions.

  • 207. Storck, K
    et al.
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation .
    Ask, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Loyd, Dan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Heat transfer simulation in the evaluation of the nasal thermistor technique1996In: IEEE Transactions on Biomedical Engineering, ISSN 0018-9294, E-ISSN 1558-2531, Vol. 43, p. 1187-1191Article in journal (Refereed)
  • 208.
    Stålhand, Jonas
    et al.
    Linköping University, Department of Mechanical Engineering. Linköping University, The Institute of Technology.
    Klarbring, Anders
    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.
    Towards in vivo aorta material identification and stress estimation2004In: Biomechanics and Modeling in Mechanobiology, ISSN 1617-7959, E-ISSN 1617-7940, Vol. 2, no 3, p. 169-186Article in journal (Refereed)
    Abstract [en]

    This paper addresses the problem of constructing a mechanical model for the abdominal aorta and calibrating its parameters to in vivo measurable data. The aorta is modeled as a pseudoelastic, thick-walled, orthotropic, residually stressed cylindrical tube, subjected to an internal pressure. The model parameters are determined by stating a minimization problem for the model pressure and computing the optimal solution by a minimization algorithm. The data used in this study is in vivo pressure–diameter data for the abdominal aorta of a 24-year-old man. The results show that the axial, circumferential and radial stresses have magnitudes in the span 0 to 180 kPa. Furthermore, the results show that it is possible to determine model parameters directly from in vivo measurable data. In particular, the parameters describing the residual stress distribution can be obtained without interventional procedures.

  • 209.
    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)
  • 210.
    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.

  • 211.
    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)
  • 212.
    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)
  • 213.
    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)
  • 214.
    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)
  • 215.
    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.

  • 216.
    Söderström, Andreas
    et al.
    Linköping University, Department of Science and Technology. 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.
    Museth, Ken
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    A PML Based Non-Reflective Boundary for Free Surface Fluid Animation2010In: ACM Transactions on Graphics, ISSN 0730-0301, E-ISSN 1557-7368, Vol. 29, no 5, p. 136-Article in journal (Refereed)
    Abstract [en]

    This article presents a novel non-reflective boundary condition for the free surface incompressible Euler and Navier-Stokes equations. Boundaries of this type are very useful when, for example, simulating water flow around a ship moving over a wide ocean. Normally waves generated by the ship will reflect off of the boundaries of the simulation domain and as these reflected waves returns towards the ship they will cause undesired interference patterns.By employing a Perfectly Matched Layer (PML) approach we have derived a boundary condition that absorbs incoming waves and thus efficiently prevents these undesired wave reflections. To solve the resulting boundary equations we present a fast and stable algorithm based on the Stable Fluids approach. Through numerical experiments we then show that our boundaries are significantly more effective than simpler reflection preventing techniques. We also provide a thorough analysis of the parameters involved in our boundary formulation and show how they effect wave absorption efficiency.

  • 217.
    Thore, Carl-Johan
    et al.
    Linköping University, Department of Management and Engineering, Mechanics . Linköping University, The Institute of Technology.
    Stålhand, Jonas
    Linköping University, Department of Management and Engineering, 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.
    Toward a noninvasive subject-specific estimation of abdominal aortic pressure2008In: American Journal of Physiology. Heart and Circulatory Physiology, ISSN 0363-6135, E-ISSN 1522-1539, Vol. 295, no 3Article in journal (Refereed)
    Abstract [en]

    A method for estimation of central arterial pressure based on linear one-dimensional wave propagation theory is presented in this paper. The equations are applied to a distributed model of the arterial tree, truncated by three-element windkessels. To reflect individual differences in the properties of the arterial trees, we pose a minimization problem from which individual parameters are identified. The idea is to take a measured waveform in a peripheral artery and use it as input to the model. The model subsequently predicts the corresponding waveform in another peripheral artery in which a measurement has also been made, and the arterial tree model is then calibrated in such a way that the computed waveform matches its measured counterpart. For the purpose of validation, invasively recorded abdominal aortic, brachial, and femoral pressures in nine healthy subjects are used. The results show that the proposed method estimates the abdominal aortic pressure wave with good accuracy. The root mean square error (RMSE) of the estimated waveforms was 1.61 ± 0.73 mmHg, whereas the errors in systolic and pulse pressure were 2.32 ± 1.74 and 3.73 ± 2.04 mmHg, respectively. These results are compared with another recently proposed method based on a signal processing technique, and it is shown that our method yields a significantly (P < 0.01) lower RMSE. With more extensive validation, the method may eventually be used in clinical practice to provide detailed, almost individual, specific information as a valuable basis for decision making. Copyright © 2008 the American Physiological Society.

  • 218.
    Thunberg, Per
    et al.
    Linköping University, Department of Biomedical Engineering. Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Karlsson, Matts
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Wigström, Lars
    Linköping University, Department of Biomedical Engineering. Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Accuracy and reproducibility in phase contrast imaging using SENSE2003In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 50, no 5, p. 1061-1068Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to evaluate the accuracy and reproducibility of phase contrast imaging using the sensitivity encoding (SENSE) method at different reduction factors. Analytical expressions were derived that state how reproducibility is influenced for velocity and flow measurements. Computer simulations, and in vitro and in vivo studies were performed in order to validate these expressions and to assess how accuracy is affected when different reduction factors are applied. It was shown that reproducibility depends on the reduction and geometry factors. Since the geometry factor varies spatially, so does the reproducibility for phase contrast imaging. In areas with high geometry factors, the standard deviation (SD) may become so large that aliasing occurs. The accuracy of phase contrast imaging is not influenced directly when SENSE is used, but may be indirectly influenced due to high SDs of the measured phase that may subsequently cause aliasing. The current results show that it is possible to achieve accurate flow measurements even at high reduction factors. By taking the geometry factor into account, it may be possible to find areas where phase contrast imaging is accurate even at high reduction factors.

  • 219.
    Thunberg, Per
    et al.
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Wigström, Lars
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Comparison of different methods for combining phase-contrast images obtained with multiple coils2005In: Magnetic Resonance Imaging, ISSN 0730-725X, E-ISSN 1873-5894, Vol. 23, no 7, p. 795-799Article in journal (Refereed)
    Abstract [en]

    The ability to determine coil sensitivities implies that a method optimized in terms of maximized signal-to-noise ratio (SNR) can be applied to the combination of multiple coil images. An optimization of SNR subsequently results in a minimized variance in quantitative velocity measurements using phase-contrast imaging. When coil sensitivities are unknown, the weighted mean method, utilizing the square of the signal magnitude as weights, is suitable for combination of multiple phase images. In this study, the optimized method using estimated coil sensitivities was compared to the weighted mean method both theoretically and experimentally. It is shown that absence of noise correlation between the different coil images implies no difference between the methods regarding the variance of the phase. In the practical situation, noise correlation does exist, implying an opportunity for further reduction of phase variance using the optimized method. In vitro and in vivo studies showed, however, no significant difference between the two methods studied.

  • 220.
    Thunberg, Per
    et al.
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Wigström, Lars
    Linköping University, Department of Biomedical Engineering. Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Optimization of gradient waveforms for velocity measurements and concurrent reduction of displacement artifacts in phase contrast imagingManuscript (preprint) (Other academic)
    Abstract [en]

    The purpose of the present study was to develop gradient waveforms for phase contrast magnetic resonance imaging that provides concurrent reduction of displacement artifacts. A framework was developed which was based on a linear combination of three individual gradients, each gradient having a trapezoidal shape. The amplitude of each gradient trapezoid was determined by the desired values of the zeroth, first and second moments of the combined tripolar waveform. All calculations of moments of the tripolar gradient waveform were performed with the expansion point set equal to the echo time. The times of spatial and velocity encoding are simultaneous in all three encoding directions, implying elimination of the displacement artifact. The proposed phase contrast pulse sequence using tripolar gradients was compared to a conventional phase contrast pulse sequence based on bipolar gradients. The echo time increased with the use of tripolar gradients compared to the conventional pulse sequence. Compensation for the increase in scan time can be achieved with the use of parallel imaging techniques.

  • 221.
    Thunberg, Per
    et al.
    Linköping University, Department of Biomedical Engineering. Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Wigström, Lars
    Linköping University, Department of Biomedical Engineering. Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Ebbers, Tino
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Karlsson, Matts
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Correction for displacement artifacts in 3D phase contrast imaging2002In: Journal of Magnetic Resonance Imaging, ISSN 1053-1807, E-ISSN 1522-2586, Vol. 16, no 5, p. 591-597Article in journal (Refereed)
    Abstract [en]

    Purpose

    To correct for displacement artifacts in 3D phase contrast imaging.

    Materials and Methods

    A 3D phase contrast pulse sequence was modified so that displacements of velocity measurements were restricted to one direction. By applying a postprocessing method, displaced measurements could be traced back to their accurate positions. Flow studies were performed using a phantom that generated flow through a stenosis, directed oblique relative to the phase and frequency encoding directions. Velocity profiles and streamline visualization were used to compare displaced and corrected velocity data to a reference.

    Results

    Velocity profiles obtained from the original measurement showed skewed profiles due to the displacement artifact, both at close proximity to the orifice as well as further downstream. After correction, concordance with the reference improved considerably.

    Conclusion

    The displacement artifact, which restricts the accuracy of phase contrast measurements, can be corrected for using the proposed method. Correction of the phase contrast velocity data may improve the accuracy of subsequent flow analysis and visualization.

  • 222.
    Thunberg, Per
    et al.
    Linköping University, Department of Biomedical Engineering. Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Wigström, Lars
    Linköping University, Department of Biomedical Engineering. Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Wranne, Bengt
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Engvall, Jan
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Karlsson, Matts
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Correction for acceleration-induced displacement artifacts in phase contrast imaging2000In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 43, no 5, p. 734-738Article in journal (Refereed)
    Abstract [en]

    The acceleration-induced displacement artifact impairs the accuracy of MR velocity measurements. This study proposes a post processing method for correction of this artifact. Velocity measurements were performed in a flow phantom containing a constriction. Velocity curves were obtained from streamlines parallel to the frequency, phase, and slice directions, respectively. The acceleration-induced displacement artifact was most prominent when the frequency encoding direction was aligned with the flow direction. After correction, velocity assignment improved and a more accurate description of the flow was obtained. In vivo measurements were performed in the aorta in a patient with a repaired aortic coarctation. The correction method was applied to velocity data along a streamline parallel to the frequency encoding direction. The result after correction was a new location of the peak velocity and improved estimates of the velocity gradients.

  • 223. Tibayan, Frederick A.
    et al.
    Rodriguez, Filiberto
    Langer, Frank
    Zasio, Mary K.
    Bailey, Lynn
    Liang, David
    Daughters, George T
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation.
    Ingels, Neil B.
    Miller, Craig
    Increases in mitral leaflet radii of curvature with chronic ischemic mitral regurgitation2004In: Journal of Heart Valve Disease, ISSN 0966-8519, E-ISSN 2053-2644, Vol. 13, no 5, p. 772-778Article in journal (Refereed)
  • 224.
    Voigt, Jens-Uwe
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Arnold, Martina
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Hübbert, Laila
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Cardiology. Östergötlands Läns Landsting, Heart Centre, Department of Cardiology.
    Kukulski, Tomasz
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Hatle, Liv
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Cardiology.
    Sutherland, George
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Assessment of regional longitudinal myocardial strain rate derived from Doppler myocardial imaging indexes in normal and infarcted myocardium.2000In: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 13, p. 588-598Article in journal (Refereed)
  • 225.
    Wang, Lieke
    et al.
    Siemens Ind Turbomachinery AB, Sweden.
    Kinell, Mats
    Siemens Ind Turbomachinery AB, Sweden.
    Nadali Najafabadi, Hossein
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    A THREE-REGIME BASED METHOD FOR CORRELATING FILM COOLING EFFECTIVENESS FOR CYLINDRICAL AND SHAPED HOLES2015In: ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2015, VOL 5B, AMER SOC MECHANICAL ENGINEERS , 2015, no UNSP V05BT12A004Conference paper (Refereed)
    Abstract [en]

    To cope with high temperature of the gas from combustor, cooling is often used in the hot gas components in gas turbines. Film cooling is one of the effective methods used in this application. Both cylindrical and fan-shaped holes are used in film cooling. There have been a number of correlations published for both cylindrical and fan-shaped holes regarding film cooling effectiveness. Unfortunately there are no definitive correlations for either cylindrical or fan-shaped holes. This is due to the nature of the complexity of film cooling where many factors influence its performance, e.g., blowing ratio, density ratio, surface angle, downstream distance, expansion angle, hole length, turbulence level, etc. A test rig using infrared camera was built to test the film cooling performance for a scaled geometry from a real nozzle guide vane. Both cylindrical and fan-shaped holes were tested. To correlate the experimental data, a three-regime based method was developed for predicting the film cooling effectiveness. Based on the blowing ratio, the proposed method divides the film cooling performance in three regimes: fully attached (or no jet lift-off), fully jet lift-off, and the transition regime in between. Two separate correlations are developed for fully attached and full jet lift-off regimes, respectively. The method of interpolation from these two regimes is used to predict the film cooling effectiveness for the transition regime, based on the blowing ratio. It has been found this method can give a good correlation to match the experimental data, for both cylindrical and fan-shaped holes. A comparison with literature was also carried out, and it showed a good agreement.

  • 226.
    Wigström, Lars
    et al.
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Ebbers, Tino
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Fyrenius, Anna
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Karlsson, Matts
    Linköping University, Department of Biomedical Engineering. Linköping University, Department of Mechanical Engineering. Linköping University, The Institute of Technology.
    Engvall, Jan
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Wranne, Bengt
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Bolger, Ann F.
    Division of Biomedical Science, University of California at Riverside, Riverside, California.
    Particle trace visualization of intracardiac flow using time-resolved 3D phase contrast MRI1999In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 41, no 4, p. 793-799Article in journal (Refereed)
    Abstract [en]

    The flow patterns in the human heart are complex and difficult to visualize using conventional two-dimensional (2D) modalities, whether they depict a single velocity component (Doppler echocardiography) or all three components in a few slices (2D phase contrast MRI). To avoid these shortcomings, a temporally resolved 3D phase contrast technique was used to derive data describing the intracardiac velocity fields in normal volunteers. The MRI data were corrected for phase shifts caused by eddy currents and concomitant gradient fields, with improvement in the accuracy of subsequent flow visualizations. Pathlines describing the blood pathways through the heart were generated from the temporally resolved velocity data, starting from user-specified locations and time frames. Flow trajectories were displayed as 3D particle traces, with simultaneous demonstration of morphologic 2D slices. This type of visualization is intuitive and interactive and may extend our understanding of dynamic and previously unrecognized patterns of intracardiac flow.

  • 227.
    Wigström, Lars
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Ebbers, Tino
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Fyrenius, Anna
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation .
    Engvall, Jan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Wranne, Bengt
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Bolger, Ann F
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    The effects of maxwell terms on particle traces calculated from 3D cine phase contrast images1999In: Journal of Cardiovascular Magnetic Resonance,1999, 1999, p. 93-93Conference paper (Other academic)
  • 228.
    Wren, Joakim
    et al.
    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.
    heat transfer analysis model of microwave thermal therapy of the prostate2000In: World Congress on Medical Physics and Biomedical Engineering,2000, 2000Conference paper (Refereed)
  • 229.
    Wren, Joakim
    et al.
    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 .
    Loyd, Dan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    A hybrid equation for simulation of perfused tissue during thermal treatment2001In: International Journal of Hyperthermia, ISSN 0265-6736, E-ISSN 1464-5157, Vol. 17, no 6, p. 483-498Article in journal (Refereed)
    Abstract [en]

    Bio-heat equations (BHEs) are necessary for predicting tissue temperature during thermal treatment. For some applications, however, existing BHEs describe the convective heat transfer by the blood perfusion in an unsatisfactory way. The two most frequently used equations, the BHE of Pennes and the keff equation, use for instance either a heat sink or an increased thermal conductivity in order to account for the blood perfusion. Both these methods introduce modelling inaccuracies when applied to an ordinary tissue continuum with a variety of vessel sizes. In this study, a hybrid equation that includes both an increased thermal conductivity and a heat sink is proposed. The equation relies on the different thermal characteristics associated with small, intermediate and large sized vessels together with the possibilities of modelling these vessels using an effective thermal conductivity in combination with a heat sink. The relative importance of these two terms is accounted for by a coefficient ▀. For ▀ = 0 and ▀ = 1, the hybrid equation coincides with the BHE of Pennes and the keff equation, respectively. The hybrid equation is used here in order to simulate temperature fields for two tissue models. The temperature field is greatly affected by ▀, and the effect is dependent on, e.g. the boundary conditions and the power supply. Since the BHE of Pennes and the keff equation are included in the hybrid equation, this equation can also be useful for evaluation of the included equations. Both these heat transfer modes are included in the proposed equation, which enables implementation in standard thermal simulation programmes.

  • 230.
    Wren, Joakim
    et al.
    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 .
    Loyd, Dan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Transient temperature response of the myocardium investigated by the hybrid bioheat model2004In: IASME Transactions, ISSN 1790-031X, Vol. 1, no 3, p. 560-565Article in journal (Refereed)
  • 231.
    Wren, Joakim
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics . Linköping University, The Institute of Technology.
    Loyd, Dan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Sjödin, Jörgen
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Energy Systems.
    Erlandsson, B-E
    A Heat Transfer Analysis of Microwave Thermal Therapy of the Prostate2000In: Annual International Conference of the IEEE Engineering in Medicine biology Society,2000, 2000Conference paper (Other academic)
  • 232.
    Wren, Joakim
    et al.
    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 .
    Investigation of medical thermal treatment using a hybrid bio-heat model2004In: 26th Annual International Conference of the IEEE Engineering in Medicine and Biology Society,2004, 2004Conference paper (Refereed)
  • 233.
    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.

  • 234.
    Ziegler, Magnus
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences.
    Welander, Martin
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Thoracic and Vascular Surgery.
    Lantz, Jonas
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences.
    Lindenberger, Marcus
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Cardiology in Linköping.
    Bjarnegård, Niclas
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences.
    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).
    Ebbers, Tino
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Clinical Physiology in Linköping. 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 Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Thoracic and Vascular Surgery. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Dyverfeldt, Petter
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Visualizing and quantifying flow stasis in abdominal aortic aneurysms in men using 4D flow MRI2019In: Magnetic Resonance Imaging, ISSN 0730-725X, E-ISSN 1873-5894, Vol. 57, p. 103-110Article in journal (Refereed)
    Abstract [en]

    Purpose: To examine methods for visualizing and quantifying flow stasis in abdominal aortic aneurysms (AAA) using 4D Flow MRI. Methods: Three methods were investigated: conventional volumetric residence time (VRT), mean velocity analysis (MVA), and particle travel distance analysis (TDA). First, ideal 4D Flow MRI data was generated using numerical simulations and used as a platform to explore the effects of noise and background phase-offset errors, both of which are common 4D Flow MRI artifacts. Error-free results were compared to noise or offset affected results using linear regression. Subsequently, 4D Flow MRI data for thirteen (13) subjects with AAA was acquired and used to compare the stasis quantification methods against conventional flow visualization. Results: VRT (R-2 = 0.69) was more sensitive to noise than MVA (R-2 = 0.98) and TDA (R-2 = 0.99) at typical noncontrast signal-to-noise ratio levels (SNR = 20). VRT (R-2 = 0.14) was more sensitive to background phase-offsets than MVA (R-2 = 0.99) and TDA (R-2 = 0.96) when considering a 95% effective background phase-offset correction. Qualitatively, TDA outperformed MVA (Wilcoxon p amp;lt; 0.005, mean score improvement 1.6/5), and had good agreement (median score 4/5) with flow visualizations. Conclusion: Flow stasis can be quantitatively assessed using 4D Flow MRI. While conventional residence time calculations fail due to error accumulation as a result of imperfect measured velocity fields, methods that do not require lengthy particle tracking perform better. MVA and TDA are less sensitive to measurement errors, and TDA generates results most similar to those obtained using conventional flow visualization.

  • 235.
    Åstrand, Håkan
    et al.
    Linköping University, Department of Medical and Health Sciences, Physiology. Linköping University, Faculty of Health Sciences.
    Stålhand, Jonas
    Linköping University, Department of Management and Engineering, 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.
    Sonesson, B.
    Malmö University Hospital.
    Länne, Toste
    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.
    Karlsson, J
    Linköping University, Department of Medical and Health Sciences, Physiology. Linköping University, Faculty of Health Sciences.
    In vivo estimation of the contribution of elastin and collagen on the mechanical properties in the abdominal aorta of man: effect of age and gender2011In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 110, no 1, p. 8750-8757Article in journal (Refereed)
    Abstract [en]

    The mechanical properties of the aorta affect cardiac function and are related to cardiovascular morbidity/mortality. This study was designed to evaluate the isotropic (mainly elastin, elastiniso) and anisotropic (mainly collagen, collagenani) material parameters within the human aorta in vivo. Thirty healthy men and women in three different age categories (23–30, 41–54, and 67–72 yr) were included. A novel mechanical model was used to identify the mechanical properties and the strain field with aid of simultaneously recorded pressure and radius in the abdominal aorta. The magnitudes of the material parameters relating to both the stiffness of elastiniso and collagenani were in agreement with earlier in vitro studies. The load-bearing fraction attributed to collagenani oscillated from 10 to 30% between diastolic and systolic pressures during the cardiac cycle. With age, stiffness of elastiniso increased in men, despite the decrease in elastin content that has been found due to elastolysis. Furthermore, an increase in stiffness of collagenani at high physiological pressure was found. This might be due to increased glycation, as well as changed isoforms of collagen in the aortic wall with age. A marked sex difference was observed, with a much less age-related effect, both on elastiniso and collagenani stiffness in women. Possible factors of importance could be the effect of sex hormones, as well as differing collagen isoforms, between the sexes.

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