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  • 51.
    Petersson, Sven
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences.
    Dyverfeldt, Petter
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    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.
    Ebbers, Tino
    Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Physiology. Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics.
    Simulation of phase contrast MRI of turbulent flow2010In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 64, no 4, p. 1039-1046Article in journal (Refereed)
    Abstract [en]

    Phase contrast MRI is a powerful tool for the assessment of blood flow. However, especially in the highly complex and turbulent flow that accompanies many cardiovascular diseases, phase contrast MRI may suffer from artifacts. Simulation of phase contrast MRI of turbulent flow could increase our understanding of phase contrast MRI artifacts in turbulent flows and facilitate the development of phase contrast MRI methods for the assessment of turbulent blood flow. We present a method for the simulation of phase contrast MRI measurements of turbulent flow. The method uses an Eulerian-Lagrangian approach, in which spin particle trajectories are computed from time-resolved large eddy simulations. The Bloch equations are solved for each spin for a frame of reference moving along the spins trajectory. The method was validated by comparison with phase contrast MRI measurements of velocity and intravoxel velocity standard deviation (IVSD) on a flow phantom consisting of a straight rigid pipe with a stenosis. Turbulence related artifacts, such as signal drop and ghosting, could be recognized in the measurements as well as in the simulations. The velocity and the IVSD obtained from the magnitude of the phase contrast MRI simulations agreed well with the measurements.

  • 52.
    Petersson, Sven
    et al.
    Linköping University, Department of Medical and Health Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Dyverfeldt, Petter
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Sigfridsson, Andreas
    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 Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Lantz, Jonas
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Carlhäll, Carl-Johan
    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 Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Ebbers, Tino
    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 Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Quantification of Stenotic Flow Using Spiral 3D Phase-Contrast MRI2013Manuscript (preprint) (Other academic)
    Abstract [en]

    Purpose: To evaluate the feasibility of spiral 3D phase contrast MRI for the assessment of velocity, volume flow rate, peak velocity and turbulent kinetic energy in stenotic flow.

    Materials and Methods: A-stack-of-spirals 3D phase contrast MRI sequence was evaluated in-vitro against a conventional Cartesian sequence. Measurements were made in a flow phantom with a 75% stenosis. Both spiral and Cartesian imaging were performed using different scan orientations and flow rates. Volume flow rate, peak velocity and turbulent kinetic energy (TKE) were computed for both methods. For further validation, the estimated TKE was compared to computational fluid dynamics (CFD) data.

    Results: The volume flow rate, peak velocity and TKE obtained with spiral 4D flow MRI agreed well with Cartesian data and CFD data. As expected, the short echo time of the spiral sequence resulted in less prominent displacement artifacts compared to the Cartesian sequence. However, both spiral and Cartesian flow rate estimates were sensitive to displacement when the flow was oblique to the encoding directions.

    Conclusion: Spiral 3D phase contrast MRI appears favorable for the assessment of stenotic flow. The spiral sequence was more than three times faster and less sensitive to displacement artifacts when compared to a conventional Cartesian sequence.

  • 53.
    Petersson, Sven
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine.
    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). Region Östergötland, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Sigfridsson, Andreas
    Karolinska Institute, Sweden; Karolinska University Hospital, Sweden.
    Lantz, Jonas
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences.
    Carlhäll, Carljohan
    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).
    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).
    Quantification of turbulence and velocity in stenotic flow using spiral three-dimensional phase-contrast MRI2016In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 75, no 3, p. 1249-1255Article in journal (Refereed)
    Abstract [en]

    PurposeEvaluate spiral three-dimensional (3D) phase contrast MRI for the assessment of turbulence and velocity in stenotic flow. MethodsA-stack-of-spirals 3D phase contrast MRI sequence was evaluated in vitro against a conventional Cartesian sequence. Measurements were made in a flow phantom with a 75% stenosis. Both spiral and Cartesian imaging were performed using different scan orientations and flow rates. Volume flow rate, maximum velocity and turbulent kinetic energy (TKE) were computed for both methods. Moreover, the estimated TKE was compared with computational fluid dynamics (CFD) data. ResultsThere was good agreement between the turbulent kinetic energy from the spiral, Cartesian and CFD data. Flow rate and maximum velocity from the spiral data agreed well with Cartesian data. As expected, the short echo time of the spiral sequence resulted in less prominent displacement artifacts compared with the Cartesian sequence. However, both spiral and Cartesian flow rate estimates were sensitive to displacement when the flow was oblique to the encoding directions. ConclusionSpiral 3D phase contrast MRI appears favorable for the assessment of stenotic flow. The spiral sequence was more than three times faster and less sensitive to displacement artifacts when compared with a conventional Cartesian sequence.

  • 54.
    Petersson, Sven
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine.
    Sigfridsson, Andreas
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Center for Medical Image Science and Visualization (CMIV). Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping. Linköping University, Faculty of Medicine and Health Sciences.
    Dyverfeldt, Petter
    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.
    Carlhäll, Carl-Johan
    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.
    Ebbers, Tino
    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 Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Retrospectively Gated Intra-cardiac 4D Flow MRI using Spiral Trajectories2016In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 75, no 1, p. 196-206Article in journal (Refereed)
    Abstract [en]

    Background: Four-dimensional (4D) flow MRI is a powerful tool for the quantification of blood flow and enables calculation of a range of unique hemodynamic parameters. However, the application of cardiac 4D flow MRI is limited by long scan times (20-40 minutes). The high efficiency of spiral readouts can be used to reduce scan times without sacrificing SNR. The aim of this work was to develop and validate a retrospectively gated 4D flow MRI sequence using spiral readouts for the measurement of intra-cardiac velocities.

    Methods: A retrospectively ECG gated 4D flow sequence using stacks of spiral readouts was implemented on a clinical 1.5 T MRI scanner. The spiral 4D flow MRI sequence was validated in-vivo by comparisons with a two-dimensional (2D) through-plane velocity measurement and a conventional Cartesian 4D flow acquisition (SENSE factor 2) in 7 healthy volunteers (age 27 ± 3 years, four men) and 2 patients (age 19 and 52, women, only spiral 4D flow and 2D). Net volume flow was estimated from all three acquisition approaches and compared using one-way ANOVA. A quantitative pathline based validation was performed on the Cartesian and the spiral 4D flow MRI acquisitions by comparing the left ventricular inflow and outflow (two-tailed paired t-tests).

    Results: The scan time of the spiral 4D flow sequence was 44±6% of the Cartesian counterpart. Compared to time-resolved 2D flow in the aorta, the spiral and Cartesian 4D flow acquisitions provided similarly good data, as there was no significant difference between the net volume flow for all acquisitions (Spiral: 89±14 ml, Cartesian: 93±11 ml, 2D: 93±18 ml, p=0.878). There was no significant difference between pathline-based calculations of inflow and outflow with either Cartesian (In: 88±15, Out: 85±16, p = 0.168) or spiral (In: 93±17 ml, Out: 84±18, p = 0.055) 4D flow acquisitions.

    Conclusions: Retrospectively gated spiral cardiac 4D flow MRI permits more than two-fold reduction in scan time compared to conventional Cartesian 4D flow MRI without notable loss in data quality. The time-savings offered by spiral trajectories could provide a step towards the expanded clinical use of 4D flow MRI.

  • 55.
    Sigovan, Monica
    et al.
    UCSF, CA USA; University of Lyon, France; CNRS, France; INSERM, France; INSA Lyon, France; University of Lyon 1, France.
    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). UCSF, CA USA.
    Wrenn, Jarrett
    UCSF, CA USA.
    Tseng, Elaine E.
    UCSF, CA USA.
    Saloner, David
    UCSF, CA USA.
    Hope, Michael D.
    UCSF, CA USA.
    Extended 3D approach for quantification of abnormal ascending aortic flow2015In: Magnetic Resonance Imaging, ISSN 0730-725X, E-ISSN 1873-5894, Vol. 33, no 5, p. 695-700Article in journal (Refereed)
    Abstract [en]

    Background: Flow displacement quantifies eccentric flow, a potential risk factor for aneurysms in the ascending aorta, but only at a single anatomic location. The aim of this study is to extend flow displacement analysis to 3D in patients with aortic and aortic valve pathologies. Methods: 43 individuals were studied with 4DFlow MRI in 6 groups: healthy, tricuspid aortic valve (TAV) with aortic stenosis (AS) but no dilatation, TAV with dilatation but no AS, and TAV with both AS and dilatation, BAV without AS or dilatation, BAV without AS but with dilation. The protocol was approved by our institutional review board, and informed consent was obtained. Flow displacement was calculated for multiple planes along the ascending aorta, and 2D and 3D analyses were compared. Results: Good correlation was found between 2D flow displacement and both maximum and average 3D values (r greater than 0.8). Healthy controls had significantly lower flow displacement values with all approaches (p less than 0.05). The highest flow displacement was seen with stenotic TAV and aortic dilation (0.24 +/- 0.02 with maximum flow displacement). The 2D approach underestimated the maximum flow displacement by more than 20% in 13 out of 36 patients (36%). Conclusions: The extended 3D flow displacement analysis offers a more comprehensive quantitative evaluation of abnormal systolic flow in the ascending aorta than 2D analysis. Differences between patient subgroups are better demonstrated, and maximum flow displacement is more reliably assessed.

  • 56.
    Sigovan, Monica
    et al.
    University of California, San Francisco, USA.
    Hope, Michael D.
    University of California, San Francisco, USA.
    Dyverfeldt, Petter
    University of California, San Francisco, USA.
    Saloner, David
    University of California, San Francisco, USA.
    Comparison of four-dimensional flow parameters for quantification of flow eccentricity in the ascending aorta2011In: Journal of Magnetic Resonance Imaging, ISSN 1053-1807, E-ISSN 1522-2586, Vol. 34, no 5, p. 1226-1230Article in journal (Refereed)
    Abstract [en]

    Purpose:

    To compare quantitative parameters for assessing the degree of eccentric systolic blood flow in the ascending thoracic aorta (AsAo).

    Materials and Methods:

    Forty-one patients were studied with three-dimensional (3D), cine phase-contract MRI (4D Flow). Analysis was performed at peak systole for a cross-sectional plane in the AsAo just distal to the sinotubular junction. AsAo flow was graded as normal, mildly, or markedly eccentric based on qualitative visual assessment. For quantitative analysis, flow jet angle and normalized flow displacement from the vessel center were calculated.

    Results:

    Patients with normal AsAo systolic flow (n = 25) had an average flow jet angle of 13.7 degrees and flow displacement 0.04. These parameters were significantly elevated for patients with mild eccentric systolic flow (n = 6): 24.6 degrees (P = 0.012) and 0.12 (P = 0.001), respectively. However, for patients with marked eccentric flow (n = 10), only flow displacement was significantly elevated compared with the mild eccentric group (0.18; P = 0.04); flow angle was 25.7 degrees.

    Conclusion:

    Flow displacement is a more reliable quantitative parameter for measuring eccentric AsAo systolic flow than flow jet angle, and should be evaluated in studies investigating the role of eccentric flow in the promotion of aortic pathology.

     

  • 57.
    Zajac, Jacub
    et al.
    Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Eriksson, Jonatan
    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 Health Sciences.
    Dyverfeldt, Petter
    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).
    Bolger, Ann F.
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping. Department of Medicine, University of California San Francisco, San Francisco, CA, USA.
    Ebbers, Tino
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Carlhäll, Carl-Johan
    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 Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Turbulent Kinetic Energy in Normal and Myopathic Left Ventricles2015In: Journal of Magnetic Resonance Imaging, ISSN 1053-1807, E-ISSN 1522-2586, Vol. 41, no 4, p. 1021-1029Article in journal (Refereed)
    Abstract [en]

    Purpose: To assess turbulent kinetic energy (TKE) within the left ventricle (LV) of healthy subjects using novel 4D flow MRI methods and to compare TKE values to those from a spectrum of patients with dilated cardiomyopathy (DCM).

    Methods: 4D flow and morphological MRI-data were acquired in 11 healthy subjects and 9 patients with different degrees of diastolic dysfunction. TKELV was calculated within the LV at each diastolic time frame. At peak early (E) and late (A) diastolic filling, the TKELV was compared to transmitral peak velocity, LV diameter and mitral annular diameter.

    Results: In the majority of all subjects, peaks in TKELV could be observed at E and A. Peak TKELV at E was not different between the groups, and correlated with mitral annular dimensions. Peak TKELV at A was higher in DCM patients compared to healthy subjects, and was related to LV diameter and transmitral velocity.

    Conclusions: In normal LVs, TKE values are low. Values are highest during early diastole, and diminish with increasing LV size. In a heterogeneous group of DCM patients, late diastolic TKE values are higher than in healthy subjects. Kinetic energy loss due to elevated late diastolic TKE may reflect inefficient flow in dilated LVs.

12 51 - 57 of 57
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