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Lantz, J., Gupta, V., Henriksson, L., Karlsson, M., Persson, A., Carlhäll, C.-J. & Ebbers, T. (2019). Impact of Pulmonary Venous Inflow on Cardiac Flow Simulations: Comparison with In Vivo 4D Flow MRI. Annals of Biomedical Engineering, 47(2), 413-424
Open this publication in new window or tab >>Impact of Pulmonary Venous Inflow on Cardiac Flow Simulations: Comparison with In Vivo 4D Flow MRI
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2019 (English)In: Annals of Biomedical Engineering, ISSN 0090-6964, E-ISSN 1573-9686, Vol. 47, no 2, p. 413-424Article in journal (Refereed) Published
Abstract [en]

Blood flow simulations are making their way into the clinic, and much attention is given to estimation of fractional flow reserve in coronary arteries. Intracardiac blood flow simulations also show promising results, and here the flow field is expected to depend on the pulmonary venous (PV) flow rates. In the absence of in vivo measurements, the distribution of the flow from the individual PVs is often unknown and typically assumed. Here, we performed intracardiac blood flow simulations based on time-resolved computed tomography on three patients, and investigated the effect of the distribution of PV flow rate on the flow field in the left atrium and ventricle. A design-of-experiment approach was used, where PV flow rates were varied in a systematic manner. In total 20 different simulations were performed per patient, and compared to in vivo 4D flow MRI measurements. Results were quantified by kinetic energy, mitral valve velocity profiles and root-mean-square errors of velocity. While large differences in atrial flow were found for varying PV inflow distributions, the effect on ventricular flow was negligible, due to a regularizing effect by mitral valve. Equal flow rate through all PVs most closely resembled in vivo measurements and is recommended in the absence of a priori knowledge.

Place, publisher, year, edition, pages
Springer-Verlag New York, 2019
Keywords
Sensitivity analysis, Design-of-experiments, Computational fluid dynamics, In vivo measurements
National Category
Medical Image Processing Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:liu:diva-153252 (URN)10.1007/s10439-018-02153-5 (DOI)000456383600007 ()30362080 (PubMedID)2-s2.0-85055724908 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation
Available from: 2018-12-06 Created: 2018-12-06 Last updated: 2019-03-22Bibliographically approved
Gupta, V., Lantz, J., Henriksson, L., Engvall, J., Karlsson, M., Persson, A. & Ebbers, T. (2018). Automated three-dimensional tracking of the left ventricular myocardium in time-resolved and dose-modulated cardiac CT images using deformable image registration. Journal of Cardiovascular Computed Tomography, 12(2), 139-148
Open this publication in new window or tab >>Automated three-dimensional tracking of the left ventricular myocardium in time-resolved and dose-modulated cardiac CT images using deformable image registration
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2018 (English)In: Journal of Cardiovascular Computed Tomography, ISSN 1934-5925, Vol. 12, no 2, p. 139-148Article in journal (Refereed) Published
Abstract [en]

Background Assessment of myocardial deformation from time-resolved cardiac computed tomography (4D CT) would augment the already available functional information from such an examination without incurring any additional costs. A deformable image registration (DIR) based approach is proposed to allow fast and automatic myocardial tracking in clinical 4D CT images.

Methods Left ventricular myocardial tissue displacement through a cardiac cycle was tracked using a B-spline transformation based DIR. Gradient of such displacements allowed Lagrangian strain estimation with respect to end-diastole in clinical 4D CT data from ten subjects with suspected coronary artery disease. Dice similarity coefficient (DSC), point-to-curve error (PTC), and tracking error were used to assess the tracking accuracy. Wilcoxon signed rank test provided significance of tracking errors. Topology preservation was verified using Jacobian of the deformation. Reliability of estimated strains and torsion (normalized twist angle) was tested in subjects with normal function by comparing them with normal strain in the literature.

Results Comparison with manual tracking showed high accuracy (DSC: 0.99± 0.05; PTC: 0.56mm± 0.47 mm) and resulted in determinant(Jacobian) > 0 for all subjects, indicating preservation of topology. Average radial (0.13 mm), angular (0.64) and longitudinal (0.10 mm) tracking errors for the entire cohort were not significant (p > 0.9). For patients with normal function, average strain [circumferential, radial, longitudinal] and peak torsion estimates were: [-23.5%, 31.1%, −17.2%] and 7.22°, respectively. These estimates were in conformity with the reported normal ranges in the existing literature.

Conclusions Accurate wall deformation tracking and subsequent strain estimation are feasible with the proposed method using only routine time-resolved 3D cardiac CT.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Cardiac computed tomography; 4D CT; Image registration; Strain analysis; Myocardial deformation; Torsion
National Category
Medical Image Processing
Identifiers
urn:nbn:se:liu:diva-147433 (URN)10.1016/j.jcct.2018.01.005 (DOI)000428247900008 ()29402736 (PubMedID)
Funder
Knut and Alice Wallenberg Foundation, KAW 2013.0076
Available from: 2018-05-17 Created: 2018-05-17 Last updated: 2019-04-30Bibliographically approved
Lantz, J., Gupta, V., Henriksson, L., Karlsson, M., Persson, A., Carlhäll, C. & Ebbers, T. (2018). Intracardiac Flow at 4D CT: Comparison with 4D Flow MRI. Radiology, 289(1), 51-58
Open this publication in new window or tab >>Intracardiac Flow at 4D CT: Comparison with 4D Flow MRI
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2018 (English)In: Radiology, ISSN 0033-8419, E-ISSN 1527-1315, Vol. 289, no 1, p. 51-58Article in journal (Refereed) Published
Abstract [en]

Purpose

To investigate four-dimensional (4D) flow CT for the assessment of intracardiac blood flow patterns as compared with 4D flow MRI.

Materials and Methods

This prospective study acquired coronary CT angiography and 4D flow MRI data between February and December 2016 in a cohort of 12 participants (age range, 36–74 years; mean age, 57 years; seven men [age range, 36–74 years; mean age, 57 years] and five women [age range, 52–73 years; mean age, 64 years]). Flow simulations based solely on CT-derived cardiac anatomy were assessed together with 4D flow MRI measurements. Flow patterns, flow rates, stroke volume, kinetic energy, and flow components were quantified for both techniques and were compared by using linear regression.

Results

Cardiac flow patterns obtained by using 4D flow CT were qualitatively similar to 4D flow MRI measurements, as graded by three independent observers. The Cohen κ score was used to assess intraobserver variability (0.83, 0.79, and 0.70) and a paired Wilcoxon rank-sum test showed no significant change (P > .05) between gradings. Peak flow rate and stroke volumes between 4D flow MRI measurements and 4D flow CT measurements had high correlation (r = 0.98 and r = 0.81, respectively; P < .05 for both). Integrated kinetic energy quantified at peak systole correlated well (r = 0.95, P < .05), while kinetic energy levels at early and late filling showed no correlation. Flow component analysis showed high correlation for the direct and residual components, respectively (r = 0.93, P < .05 and r = 0.87, P < .05), while the retained and delayed components showed no correlation.

Conclusion

Four-dimensional flow CT produced qualitatively and quantitatively similar intracardiac blood flow patterns compared with the current reference standard, four-dimensional flow MRI.

Place, publisher, year, edition, pages
Oak Brook, IL United States: Radiological Society of North America, Inc., 2018
National Category
Fluid Mechanics and Acoustics Cardiac and Cardiovascular Systems Medical Image Processing
Identifiers
urn:nbn:se:liu:diva-149320 (URN)10.1148/radiol.2018173017 (DOI)000444990900009 ()29944089 (PubMedID)
Funder
Knut and Alice Wallenberg Foundation, Seeing Organ FunctionSwedish Heart Lung Foundation
Available from: 2018-06-28 Created: 2018-06-28 Last updated: 2019-04-12Bibliographically approved
Casas Garcia, B., Lantz, J., Dyverfeldt, P. & Ebbers, T. (2016). 4D Flow MRI-Based Pressure Loss Estimation in Stenotic Flows: Evaluation Using Numerical Simulations. Magnetic Resonance in Medicine, 75(4), 1808-1821
Open this publication in new window or tab >>4D Flow MRI-Based Pressure Loss Estimation in Stenotic Flows: Evaluation Using Numerical Simulations
2016 (English)In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 75, no 4, p. 1808-1821Article in journal (Refereed) Published
Abstract [en]

Purpose: To assess how 4D flow MRI-based pressure and energy loss estimates correspond to net transstenotic pressure gradients (TPG(net)) and their dependence on spatial resolution. Methods: Numerical velocity data of stenotic flow were obtained from computational fluid dynamics (CFD) simulations in geometries with varying stenosis degrees, poststenotic diameters and flow rates. MRI measurements were simulated at different spatial resolutions. The simplified and extended Bernoulli equations, Pressure-Poisson equation (PPE), and integration of turbulent kinetic energy (TKE) and viscous dissipation were compared against the true TPG(net). Results: The simplified Bernoulli equation overestimated the true TPG(net) (8.74 +/- 0.67 versus 6.76 +/- 0.54 mmHg). The extended Bernoulli equation performed better (6.57 +/- 0.53 mmHg), although errors remained at low TPG(net). TPG(net) estimations using the PPE were always close to zero. Total TKE and viscous dissipation correlated strongly with TPG(net) for each geometry (r(2) &gt; 0.93) and moderately considering all geometries (r(2) = 0.756 and r(2) = 0.776, respectively). TKE estimates were accurate and minorly impacted by resolution. Viscous dissipation was overall underestimated and resolution dependent. Conclusion: Several parameters overestimate or are not linearly related to TPG(net) and/or depend on spatial resolution. Considering idealized axisymmetric geometries and in absence of noise, TPG(net) was best estimated using the extended Bernoulli equation. (C) 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance.

Place, publisher, year, edition, pages
WILEY-BLACKWELL, 2016
Keywords
pressure loss; phase contrast magnetic resonance imaging; aortic valve disease; aortic coarctation
National Category
Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-127426 (URN)10.1002/mrm.25772 (DOI)000372910900043 ()26016805 (PubMedID)
Note

Funding Agencies|European Research Council [310612]; Swedish Research Council

Available from: 2016-05-01 Created: 2016-04-26 Last updated: 2018-10-10
Lantz, J., Henriksson, L., Persson, A., Karlsson, M. & Ebbers, T. (2016). Importance Of Including Papillary Muscles And Trabeculae In Cardiac Flow Simulations. In: Proceedings of the 2016 Summer Biomechanics, Bioengineering and Biotransport Conference: . Paper presented at SB3C 2016 - Summer Biomechanics, Bioengineering and Biotransport Conference, National Harbor, MD, USA, June 29 – July 2, 2016. Organizing Committee for the 2016 Summer Biomechanics, Bioengineering and Biotransport
Open this publication in new window or tab >>Importance Of Including Papillary Muscles And Trabeculae In Cardiac Flow Simulations
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2016 (English)In: Proceedings of the 2016 Summer Biomechanics, Bioengineering and Biotransport Conference, Organizing Committee for the 2016 Summer Biomechanics, Bioengineering and Biotransport , 2016Conference paper, Oral presentation with published abstract (Other academic)
Place, publisher, year, edition, pages
Organizing Committee for the 2016 Summer Biomechanics, Bioengineering and Biotransport, 2016
National Category
Medical and Health Sciences Applied Mechanics
Identifiers
urn:nbn:se:liu:diva-131097 (URN)978-0-692-71816-2 (ISBN)
Conference
SB3C 2016 - Summer Biomechanics, Bioengineering and Biotransport Conference, National Harbor, MD, USA, June 29 – July 2, 2016
Available from: 2016-09-08 Created: 2016-09-08 Last updated: 2016-09-14Bibliographically approved
Petersson, S., Dyverfeldt, P., Sigfridsson, A., Lantz, J., Carlhäll, C. & Ebbers, T. (2016). Quantification of turbulence and velocity in stenotic flow using spiral three-dimensional phase-contrast MRI. Magnetic Resonance in Medicine, 75(3), 1249-1255
Open this publication in new window or tab >>Quantification of turbulence and velocity in stenotic flow using spiral three-dimensional phase-contrast MRI
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2016 (English)In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 75, no 3, p. 1249-1255Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
WILEY-BLACKWELL, 2016
Keywords
phase contrast mri; 4d flow; turbulence mapping; spiral; stenosis
National Category
Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-126831 (URN)10.1002/mrm.25698 (DOI)000370593700030 ()25846511 (PubMedID)
Note

Funding Agencies|European Research Council [310612]; Swedish Research Council; Swedish e-Science Research Centre

Available from: 2016-04-07 Created: 2016-04-05 Last updated: 2017-05-03
Lantz, J., Renner, J., Länne, T. & Karlsson, M. (2015). Is aortic wall shear stress affected by aging? An image-based numerical study with two age groups. Medical Engineering and Physics, 37(3), 265-271
Open this publication in new window or tab >>Is aortic wall shear stress affected by aging? An image-based numerical study with two age groups
2015 (English)In: Medical Engineering and Physics, ISSN 1350-4533, E-ISSN 1873-4030, Vol. 37, no 3, p. 265-271Article in journal (Refereed) Published
Abstract [en]

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

Place, publisher, year, edition, pages
Elsevier, 2015
Keywords
Aorta; Wall shear stress; Oscillatory shear index; Computational fluid dynamics; Aging; Magnetic resonance imaging
National Category
Mechanical Engineering Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-117663 (URN)10.1016/j.medengphy.2014.12.011 (DOI)000352249800002 ()25630809 (PubMedID)
Note

Funding Agencies|Swedish e-Science Research Centre; Centre for Industrial Information Technology [99.11]; Swedish Research Council [2010-4282]; Swedish Heart and Lung Foundation

Available from: 2015-05-12 Created: 2015-05-06 Last updated: 2017-12-04
Lantz, J., Carlhäll, C.-J. & Ebbers, T. (2015). Quantification of Helical Flow Patterns in Left Ventricles of Healthy Subjects and Patients with Dilated Cardiomyopathy. In: : . Paper presented at 2015 Summer Biomechanics, Bioengineering and Biotransport Conference.
Open this publication in new window or tab >>Quantification of Helical Flow Patterns in Left Ventricles of Healthy Subjects and Patients with Dilated Cardiomyopathy
2015 (English)Conference paper, Oral presentation with published abstract (Refereed)
National Category
Fluid Mechanics and Acoustics Medical Image Processing
Identifiers
urn:nbn:se:liu:diva-120384 (URN)
Conference
2015 Summer Biomechanics, Bioengineering and Biotransport Conference
Available from: 2015-08-03 Created: 2015-08-03 Last updated: 2015-08-27
Andersson, M., Lantz, J., Ebbers, T. & Karlsson, M. (2015). Quantitative Assessment of Turbulence and Flow Eccentricity in an Aortic Coarctation - Impact of Virtual Interventions. Cardiovascular Engineering and Technology, 6(6), 281-293
Open this publication in new window or tab >>Quantitative Assessment of Turbulence and Flow Eccentricity in an Aortic Coarctation - Impact of Virtual Interventions
2015 (English)In: Cardiovascular Engineering and Technology, ISSN 1869-408X, E-ISSN 1869-4098, Vol. 6, no 6, p. 281-293Article in journal (Refereed) Published
Abstract [en]

Turbulence and flow eccentricity can be measured by magnetic resonance imaging (MRI) and may play an important role in the pathogenesis of numerous cardiovascular diseases. In the present study, we propose quantitative techniques to assess turbulent kinetic energy (TKE) and flow eccentricity that could assist in the evaluation and treatment of stenotic severities. These hemodynamic parameters were studied in a pre-treated aortic coarctation (CoA) and after several virtual interventions using computational fluid dynamics (CFD), to demonstrate the effect of different dilatation options on the flow field. Patient-specific geometry and flow conditions were derived from MRI data. The unsteady pulsatile flow was resolved by large eddy simulation (LES) including non-Newtonian blood rheology. Results showed an inverse asymptotic relationship between the total amount of TKE and degree of dilatation of the stenosis, where turbulent flow proximal the constriction limits the possible improvement by treating the CoA alone. Spatiotemporal maps of TKE and flow eccentricity could be linked to the characteristics of the jet, where improved flow conditions were favored by an eccentric dilatation of the CoA. By including these flow markers into a combined MRI-CFD intervention framework, CoA therapy has not only the possibility to produce predictions via simulation, but can also be validated pre- and immediate post treatment, as well as during follow-up studies.

Place, publisher, year, edition, pages
Springer, 2015
Keywords
Computational fluid dynamics, Large eddy simulation, Turbulent kinetic energy, Flow displacement, Non-Newtonian, Virtual treatment, Magnetic resonance imaging
National Category
Applied Mechanics
Identifiers
urn:nbn:se:liu:diva-114496 (URN)10.1007/s13239-015-0218-x (DOI)000380356800007 ()
Note

Funding agencies: Swedish Research Council; Center for Industrial Information Technology (CENIIT); Swedish National Infrastructure for Computing (SNIC)

Available from: 2015-02-24 Created: 2015-02-24 Last updated: 2017-12-04Bibliographically approved
Lantz, J., Dyverfeldt, P. & Ebbers, T. (2014). Improving Blood Flow Simulations by Incorporating Measured Subject-Specific Wall Motion. Cardiovascular Engineering and Technology, 5(3), 261-269
Open this publication in new window or tab >>Improving Blood Flow Simulations by Incorporating Measured Subject-Specific Wall Motion
2014 (English)In: Cardiovascular Engineering and Technology, ISSN 1869-408X, E-ISSN 1869-4098, Vol. 5, no 3, p. 261-269Article in journal (Refereed) Published
Abstract [en]

Physiologically relevant simulations of blood flow require models that allow for wall deformation. Normally a fluid–structure interaction (FSI) approach is used; however, this method relies on several assumptions and patient-specific material parameters that are difficult or impossible to measure in vivo. In order to circumvent the assumptions inherent in FSI models, aortic wall motion was measured with MRI and prescribed directly in a numerical solver. In this way is not only the displacement of the vessel accounted for, but also the interaction with the beating heart and surrounding organs. In order to highlight the effect of wall motion, comparisons with standard rigid wall models was performed in a healthy human aorta. The additional computational cost associated with prescribing the wall motion was low (17%). Standard hemodynamic parameters such as time-averaged wall shear stress and oscillatory shear index seemed largely unaffected by the wall motion, as a consequence of the smoothing effect inherent in time-averaging. Conversely, instantaneous wall shear stress was greatly affected by the wall motion; the wall dynamics seemed to produce a lower wall shear stress magnitude compared to a rigid wall model. In addition, it was found that if wall motion was taken into account the computed flow field agreed better with in vivo measurements. This article shows that it is feasible to include measured subject-specific wall motion into numerical simulations, and that the wall motion greatly affects the flow field. This approach to incorporate measured motion should be considered in future studies of arterial blood flow simulations.

Place, publisher, year, edition, pages
Springer, 2014
Keywords
Computational fluid dynamics, Magnetic resonance imaging, Fluid–structure interaction, Aorta, Time averaged wall shear stress, Prescribed wall motion
National Category
Fluid Mechanics and Acoustics Medical Image Processing
Identifiers
urn:nbn:se:liu:diva-107479 (URN)10.1007/s13239-014-0187-5 (DOI)000209839800004 ()
Available from: 2014-06-12 Created: 2014-06-12 Last updated: 2017-12-05Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-1942-7699

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