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  • 1.
    Ebbers, Tino
    et al.
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Department of Biomedical Engineering. Linköping University, Faculty of Health Sciences.
    Wigström, Lars
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Department of Biomedical Engineering. Linköping University, Faculty of Health Sciences.
    Bolger, Ann
    Department of Medicine, University of California, San Francisco, CA.
    Wranne, Bengt
    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, Faculty of Health Sciences.
    Noninvasive measurement of time-varying three-dimensional relative pressure fields within the human heart2002In: Journal of Biomechanical Engineering, ISSN 0148-0731, E-ISSN 1528-8951, Vol. 124, no 3, p. 288-293Article in journal (Refereed)
    Abstract [en]

    Understanding cardiac blood flow patterns is important in the assessment of cardiovascular function. Three-dimensional flow and relative pressure fields within the human left ventricle are demonstrated by combining velocity measurements with computational fluid mechanics methods. The velocity field throughout the left atrium and ventricle of a normal human heart is measured using time-resolved three-dimensional phase-contrast MRL. Subsequently, the time-resolved three-dimensional relative pressure is calculated from this velocity field using the pressure Poisson equation. Noninvasive simultaneous assessment of cardiac pressure and flow phenomena is an important new tool for studying cardiac fluid dynamics.

  • 2. Fleming Braden, C.
    et al.
    Good, Lars
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Neuroscience and Locomotion, Orthopaedics and Sports Medicine. Östergötlands Läns Landsting, Orthopaedic Centre, Department of Orthopaedics Linköping.
    Calibration and application on intraarticular.....1999In: Journal of Biomechanical Engineering, ISSN 0148-0731, E-ISSN 1528-8951, Vol. 121, p. 393-398Article in journal (Refereed)
  • 3.
    Gårdhagen, Roland
    et al.
    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.
    Carlsson, Fredrik
    ANSYS Sweden.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics . Linköping University, The Institute of Technology.
    Quantifying Turbulent Wall Shear Stress in a Stenosed Pipe Using Large Eddy Simulation2010In: Journal of Biomechanical Engineering, ISSN 0148-0731, E-ISSN 1528-8951, Vol. 132, no 6Article in journal (Refereed)
    Abstract [en]

    Large eddy simulation was applied for flow of Re = 2000 in a stenosed pipe in order to undertake a thorough investigation of the wall shear stress (WSS) in turbulent flow. A decomposition of the WSS into time averaged and fluctuating components is proposed. It was concluded that a scale resolving technique is required to completely describe the WSS pattern in a subject specific vessel model, since the poststenotic region was dominated by large axial and circumferential fluctuations. Three poststenotic regions of different WSS characteristics were identified. The recirculation zone was subject to a time averaged WSS in the retrograde direction and large fluctuations. After reattachment there was an ante grade shear and smaller fluctuations than in the recirculation zone. At the reattachment the fluctuations were the largest, but no direction dominated over time. Due to symmetry the circumferential time average was always zero. Thus, in a blood vessel, the axial fluctuations would affect endothelial cells in a stretched state, whereas the circumferential fluctuations would act in a relaxed direction.

  • 4.
    Johansson, Lars
    et al.
    Linköping University, Department of Management and Engineering, Mechanics . Linköping University, The Institute of Technology.
    Edlund, Ulf
    Linköping University, Department of Management and Engineering, Mechanics . Linköping University, The Institute of Technology.
    Fahlgren, Anna
    Linköping University, Department of Clinical and Experimental Medicine, Orthopaedics and Sports Medicine . Linköping University, Faculty of Health Sciences.
    Aspenberg, Per
    Linköping University, Department of Clinical and Experimental Medicine, Orthopaedics and Sports Medicine . Linköping University, Faculty of Health Sciences.
    Bone Resorption Induced by Fluid Flow2009In: Journal of Biomechanical Engineering, ISSN 0148-0731, E-ISSN 1528-8951, Vol. 131, no 9, p. 094505-1-094505-5Article in journal (Refereed)
    Abstract [en]

    A model where bone resorption is driven by stimulus from fluid flow is developed and used as a basis for computer simulations, which are compared with experiments. Models for bone remodeling are usually based on the state of stress, strain, or energy density of the bone tissue as the stimulus for remodeling. We believe that there is experimental support for an additional pathway, where an increase in the amount of osteoclasts, and thus osteolysis, is caused by the time history of fluid flow velocity, fluid pressure, or other parameters related to fluid flow at the bone/soft tissue interface of the porosities in the bone.

  • 5.
    Kindberg, Katarina
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation.
    Ingels, NB Jr
    Stanford University Medical Center.
    Criscione, JC
    Texas AM University.
    Nonhomogeneous strain from sparse marker arrays for analysis of transmural myocardial mechanics2007In: Journal of Biomechanical Engineering, ISSN 0148-0731, E-ISSN 1528-8951, Vol. 129, no 4, p. 603-610Article in journal (Refereed)
    Abstract [en]

    Background: Knowledge of normal cardiac kinematics is important when attempting to understand the mechanisms that impair the contractile function of the heart during disease. The complex kinematics of the heart can be studied by inserting radiopaque markers in the cardiac wall and study the pumping heart with biplane cineradiography. In order to study the local strain, the bead array was developed where small radiopaque beads are inserted along three columns transmurally in the left ventricle. Method: This paper suggests a straightforward method for strain computation, based on polynomial least-squares fitting and tailored for combined marker and bead array analyses. Results: This polynomial method gives small errors for a realistic bead array on an analytical test case. The method delivers an explicit expression of the Lagrangian strain tensor as a polynomial function of the coordinates of material points in the reference configuration. The method suggested in this paper is validated with analytical strains on a deforming cylinder resembling the heart, compared to a previously suggested finite element method, and applied to in vivo ovine data. The errors in the estimated strain components are shown to remain unchanged on an analytical test case when evaluating the effects of one missing bead. In conclusion, the proposed strain computation method is accurate and robust, with errors smaller or comparable to the current gold standard when applied on an analytical test case.

  • 6.
    Lantz, Jonas
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Medicine and Health Sciences.
    Henriksson, Lilian
    Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Persson, Anders
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Radiology in Linköping.
    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, Center for Medical Image Science and Visualization (CMIV). 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.
    Patient-Specific Simulation of Cardiac Blood Flow From High-Resolution Computed Tomography2016In: Journal of Biomechanical Engineering, ISSN 0148-0731, E-ISSN 1528-8951, Vol. 138, no 12Article in journal (Refereed)
    Abstract [en]

    Cardiac hemodynamics can be computed from medical imaging data, and results could potentially aid in cardiac diagnosis and treatment optimization. However, simulations are often based on simplified geometries, ignoring features such as papillary muscles and trabeculae due to their complex shape, limitations in image acquisitions, and challenges in computational modeling. This severely hampers the use of computational fluid dynamics in clinical practice. The overall aim of this study was to develop a novel numerical framework that incorporated these geometrical features. The model included the left atrium, ventricle, ascending aorta, and heart valves. The framework used image registration to obtain patient-specific wall motion, automatic remeshing to handle topological changes due to the complex trabeculae motion, and a fast interpolation routine to obtain intermediate meshes during the simulations. Velocity fields and residence time were evaluated, and they indicated that papillary muscles and trabeculae strongly interacted with the blood, which could not be observed in a simplified model. The framework resulted in a model with outstanding geometrical detail, demonstrating the feasibility as well as the importance of a framework that is capable of simulating blood flow in physiologically realistic hearts.

  • 7.
    Smedby, Örjan
    et al.
    Department of Diagnostic Radiology, Uppsala University.
    Fuchs, L
    Tillmark, N
    Separated flow demonstrated by digitized cineangiography compared with LDV1991In: Journal of Biomechanical Engineering, ISSN 0148-0731, E-ISSN 1528-8951, Vol. 113, no 3, p. 336-341Article in journal (Refereed)
    Abstract [en]

    In order to demonstrate separated flow in vivo, a method for the computerized analysis of cineangiographies has been developed, tested in vitro, and compared with LDV. A pulsatile flow was created in a glass model bifurcation, and velocity profiles were obtained with LDV at several phase angles. The flow was cinefilmed during contrast injection and the images were digitized. The computer then transformed the image sequence into parametric images representing arrival times of the contrast. The separation regions demonstrated with LDV were identified as areas with delayed contrast arrival. A preliminary analysis of a cineangiography in vivo is also included.

  • 8.
    Thompson, M.S.
    et al.
    Department of Orthopaedics, Lund University Hospital, Lund 22185, Sweden.
    McCarthy, I.D.
    Department of Orthopaedics, Lund University Hospital, Lund 22185, Sweden.
    Lidgren, L.
    Department of Orthopaedics, Lund University Hospital, Lund 22185, Sweden.
    Ryd, Leif
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Clinical and Experimental Medicine, Orthopaedics and Sports Medicine .
    Compressive and Shear Properties of Commercially Available Polyurethane Foams2003In: Journal of Biomechanical Engineering, ISSN 0148-0731, E-ISSN 1528-8951, Vol. 125, no 5, p. 732-734Article in journal (Refereed)
    Abstract [en]

    Background: The shear properties of rigid polyurethane (PU-R) foams, routinely used to simulate cancellous bone, are not well characterized. Method of approach: The present assessment of the shear and compressive properties of four grades of Sawbones "Rigid cellular" PU-R foam tested 20 mm gauge diameter dumb-bell specimens in torsion and under axial loading. Results: Shear moduli ranged from 13.3 to 99.7 MPa, shear strengths from 0.7 MPa to 4.2 MPa. Compressive yield strains varied little with density while shear yield strains had peak values with "200 kgm-3" grade. Conclusions: PU-R foams may be used to simulate the elastic but not failure properties of cancellous bone.

  • 9.
    Wren, Joakim
    et al.
    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.
    Andersson, U.
    Vattenfall Utveckling AB, Älvkarleby, Sweden.
    Karlsson, R.
    Chalmers University of Technology, Gothenburg, Sweden.
    Thermally induced convective movements in a standard experimental model for characterization of lesions prior to radiofrequency functional neurosurgery2007In: Journal of Biomechanical Engineering, ISSN 0148-0731, E-ISSN 1528-8951, Vol. 129, no 1, p. 26-32Article in journal (Refereed)
    Abstract [en]

    Experimental exploration of equipment for stereotactic functional neurosurgery based on heating induced by radio-frequency current is most often carried out prior to surgery in order to secure a correct function of the equipment. The experiments are normally conducted in an experimental model including an albumin solution in which the treatment electrode is submerged, followed by a heating session during which a protein clot is generated around the electrode tip. The clot is believed to reflect the lesion generated in the brain during treatment. It is thereby presupposed that both the thermal and electric properties of the model are similar to brain tissue. This study investigates the presence of convective movements in the albumin solution using laser Doppler velocimetry. The result clearly shows that convective movements that depend on the time dependent heating characteristics of the equipment arise in the solution upon heating. The convective movements detected show a clear discrepancy compared with the in vivo situation that the experimental model tries to mimic, both the velocity (maximum velocity of about 5 mm/s) and mass flux are greater in this experimental setting. Furthermore the flow geometry is completely different since only a small fraction of the tissue surrounding the electrode in vivo consists of moving blood, whereas the entire surrounding given by the albumin solution in the experimental model is moving. Earlier investigations by our group (Eriksson et al., 1999, Med. Biol. Eng. Comput. 37, pp. 737-741, Wren, 2001, Ph.D. thesis, and Wren et al., 2001, Med. Biol. Eng. Comput. 39, pp. 255-262) indicate that the heat flux is an essential parameter for the lesion growth and final size, and that presence of convective movements in the model might substantially increase the heat flux. Thus, convective movements of the magnitude presented here will very likely underestimate the size of the brain lesion, a finding that definitely should be taken into consideration when using the model prior to patient treatment. Copyright © 2007 by ASME.

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