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Publications (5 of 5) Show all publications
Berg, N., Fuchs, L. & Prahl Wittberg, L. (2019). Blood Flow Simulations of the Renal Arteries - Effect of Segmentation and Stenosis Removal. Flow Turbulence and Combustion, 102(1), 27-41
Open this publication in new window or tab >>Blood Flow Simulations of the Renal Arteries - Effect of Segmentation and Stenosis Removal
2019 (English)In: Flow Turbulence and Combustion, ISSN 1386-6184, E-ISSN 1573-1987, Vol. 102, no 1, p. 27-41Article in journal (Refereed) Published
Abstract [en]

Patient specific based simulation of blood flows in arteries has been proposed as a future approach for better diagnostics and treatment of arterial diseases. The outcome of theoretical simulations strongly depends on the accuracy in describing the problem (the geometry, material properties of the artery and of the blood, flow conditions and the boundary conditions). In this study, the uncertainties associated with the approach for a priori assessment of reconstructive surgery of stenoted arteries are investigated. It is shown that strong curvature in the reconstructed artery leads to large spatial- and temporal-peaks in the wall shear-stress. Such peaks can be removed by appropriate reconstruction that also handles the post-stenotic dilatation of the artery. Moreover, it is shown that the effects of the segmentation approach can be equally important as the effects of using advanced rheological models. This fact has not been recognized in the literature up to this point, making patient specific simulations potentially less reliable.

Place, publisher, year, edition, pages
SPRINGER, 2019
Keywords
Atherosclerotic indicators, Stenosis, Segmentation, Non-Newtonian, Hemodynamics, CFD
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-251230 (URN)10.1007/s10494-019-00009-z (DOI)000463881000003 ()2-s2.0-85061181367 (Scopus ID)
Note

QC 20190523

Available from: 2019-05-23 Created: 2019-05-23 Last updated: 2019-05-23Bibliographically approved
Berg, N., Fuchs, L. & Prahl Wittberg, L. (2019). Flow characteristics and coherent structures in a centrifugal blood pump. Flow Turbulence and Combustion, 102(2), 469-483
Open this publication in new window or tab >>Flow characteristics and coherent structures in a centrifugal blood pump
2019 (English)In: Flow Turbulence and Combustion, ISSN 1386-6184, E-ISSN 1573-1987, Vol. 102, no 2, p. 469-483Article in journal (Refereed) Published
Abstract [en]

Blood clot formation can be initiated by local flow conditions where regions of high shear and long residence time regions, such as flow separation and stagnation, have been identified as risk factors. This study highlights coherent structures,some of which not yet considered in the literature that may contribute to blood clot formation in the ECMO (Extra Corporeal Membrane Oxygenator) circuit. The centrifugal ECMO pump investigated in this study is compact and delivers adequate volume of blood with relatively high pressure in order to compensate for the large pressure drop in the membrane oxygenator. These requirements lead to regions with high shear in several different parts of the pump. In the narrow gap between the pump house and the impeller body (the magnet) a Taylor-Couette-like flow is observed with azimuthally aligned wavy vortices, which are also pushed towards the bottom of the pump-house by the flow generated by the blades. At the bottom gap between the impeller house and the pump house one finds spiraling flow structures, due to the rotation of the former structure. Separation bubbles are found near the tongue of the pump and at the lee sides of the blades. Such vortical structures have in literature been identified as regions where platelets may be activated whereby clots may develop.

Place, publisher, year, edition, pages
Springer Nature, 2019
Keywords
Coherent structures, Blood flow, ECMO, Centrifugal pump, CFD
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-239059 (URN)10.1007/s10494-018-9994-3 (DOI)000465588800014 ()2-s2.0-85058486537 (Scopus ID)
Note

QC 20181116

Available from: 2018-11-15 Created: 2018-11-15 Last updated: 2019-07-09Bibliographically approved
Fuchs, A., Berg, N. & Prahl Wittberg, L. (2019). Stenosis Indicators Applied to Patient-Specific Renal Arteries without and with Stenosis. FLUIDS, 4(1), Article ID 26.
Open this publication in new window or tab >>Stenosis Indicators Applied to Patient-Specific Renal Arteries without and with Stenosis
2019 (English)In: FLUIDS, ISSN 2311-5521, Vol. 4, no 1, article id 26Article in journal (Refereed) Published
Abstract [en]

Pulsatile flow in the abdominal aorta and the renal arteries of three patients was studied numerically. Two of the patients had renal artery stenosis. The aim of the study was to assess the use of four types of indicators for determining the risk of new stenosis after revascularization of the affected arteries. The four indicators considered include the time averaged wall shear stress (TAWSS), the oscillatory shear index (OSI), the relative reference time (RRT) and a power law model based in platelet activation modeling but applied to the endothelium, named endothelium activation indicator (EAI). The results show that the indicators can detect the existing stenosis but are less successful in the revascularized cases. The TAWSS and, more clearly, the EAI approach seem to be better in predicting the risk for stenosis relapse at the original location and close to the post-stenotic dilatation. The shortcomings of the respective indicators are discussed along with potential improvements to endothelial activation modeling and its use as an indicator for risks of restenosis.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
renal artery stenosis, blood flow simulation, atherosclerosis, reconstructed arteries, stenosis indicators
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-251364 (URN)10.3390/fluids4010026 (DOI)000464457900001 ()2-s2.0-85063386762 (Scopus ID)
Note

QC 20190513

Available from: 2019-05-13 Created: 2019-05-13 Last updated: 2019-05-23Bibliographically approved
Fuchs, G., Berg, N., Broman, M. & Prahl Wittberg, L. (2017). Blood clots in the ECMO-system - a theoretical platelet activation study. Acta Anaesthesiologica Scandinavica, 61(8), 964-965
Open this publication in new window or tab >>Blood clots in the ECMO-system - a theoretical platelet activation study
2017 (English)In: Acta Anaesthesiologica Scandinavica, ISSN 0001-5172, E-ISSN 1399-6576, Vol. 61, no 8, p. 964-965Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
Wiley, 2017
National Category
Anesthesiology and Intensive Care
Identifiers
urn:nbn:se:kth:diva-243510 (URN)000407231100018 ()
Note

QC 20190211

Available from: 2019-02-11 Created: 2019-02-11 Last updated: 2019-02-11Bibliographically approved
Berg, N., Fuchs, L. & Prahl Wittberg, L. Blood flow simulations of the renal arteries - effect of segmentation and stenosis removal. Flow Turbulence and Combustion
Open this publication in new window or tab >>Blood flow simulations of the renal arteries - effect of segmentation and stenosis removal
(English)In: Flow Turbulence and Combustion, ISSN 1386-6184, E-ISSN 1573-1987Article in journal (Refereed) Submitted
Abstract [en]

Patient specic based simulation of blood flows in arteries has been proposed as a future approach for better diagnostics and treatment of arterial diseases.The outcome of theoretical simulations strongly depends on the accuracy in describing the problem (the geometry, material properties of the artery and of the blood, flow conditions and the boundary conditions). In this study, the uncertainties associated with the approach for a priori assessment of reconstructive surgery of stenoted arteries are investigated. It is shown that strong curvature in the reconstructed artery leads to large spatial- and temporal-peaks in the wall shear-stress. Such peaks can be removed by appropriate reconstruction that also handles the post-stenotic dilatation of the artery. Moreover, it is shown that the effects of the segmentation approach can be equally important as the effects of using advanced rheological models. Unfortunately, this fact has not been recognized in the literature up to this point, making patient specic simulations potentially less reliable.

Keywords
Atherosclerotic indicators, Stenosis, Segmentation, Non-newtonian, Hemodynamics, CFD
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-239060 (URN)
Note

QC 20181116

Available from: 2018-11-15 Created: 2018-11-15 Last updated: 2019-01-28Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6881-2094

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