liu.seSearch for publications in DiVA
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Towards Subject Specific Aortic Wall Shear Stress: a combined CFD and MRI approach
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.
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The cardiovascular system is an important part of the human body since it transports both energy and oxygen to all cells throughout the body. Diseases in this system are often dangerous and cardiovascular diseases are the number one killer in the western world. Common cardiovascular diseases are heart attack and stroke, which origins from obstructed blood flow. It is generally important to understand the causes for these cardiovascular diseases. The main causes for these diseases are atherosclerosis development in the arteries (hardening and abnormal growth). This transform of the arterial wall is believed to be influenced by the mechanical load from the flowing blood on the artery and especially the tangential force the wall shear stress. To retrieve wall shear stress information in arteries invivo is highly interesting due to the coupling to atherosclerosis and indeed a challenge. The goal of this thesis is to develop, describe and evaluate an in-vivo method for subject specific wall shear stress estimations in the human aorta, the largest artery in the human body. The method uses an image based computational fluid dynamics approach in order to estimate the wall shear stress. To retrieve in-vivo geometrical descriptions of the aorta magnetic resonance imaging capabilities is used which creates image material describing the subject specific geometry of the aorta. Magnetic resonance imaging is also used to retrieve subject specific blood velocity information in the aorta. Both aortic geometry and velocity is gained at the same time. Thereafter the image material is interpreted using level-set segmentation in order to get a three-dimensional description of the aorta. Computational fluid dynamics simulations is applied on the subject specific aorta in order to calculate time resolved wall shear stress distribution at the entire aortic wall included in the actual model.

This work shows that it is possible to estimate subject specific wall shear stress in the human aorta. The results from a group of healthy volunteers revealed that the arterial geometry is very subject specific and the different wall shear stress distributions have general similarities but the level and local distribution are clearly different. Sensitivity (on wall shear stress) to image modality, the different segmentation methods and different inlet velocity profiles have been tested, which resulted in these general conclusions:

  • The aortic diameter from magnetic resonance imaging became similar to the reference diameter measurement method.
  • The fast semi-automatic level-set segmentation method gave similar geometry and wall shear stress results when compared to a reference segmentation method.
  • Wall shear stress distribution became different when comparing a simplified uniform velocity profile inlet boundary condition with a measured velocity profile.

The method proposed in this thesis has the possibility to produce subject specific wall shear stress distribution in the human aorta. The method can be used for further medical research regarding atherosclerosis development and has the possibility for usage in clinical work.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press , 2011. , 40 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1360
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:liu:diva-65910ISBN: 978-91-7393-244-8 (print)OAI: oai:DiVA.org:liu-65910DiVA: diva2:400295
Public defence
2011-04-12, ACAS, hus A, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2011-02-25 Created: 2011-02-25 Last updated: 2017-03-27Bibliographically approved
List of papers
1. Subject Specific Wall Shear Stress in the Human Thoracic Aorta
Open this publication in new window or tab >>Subject Specific Wall Shear Stress in the Human Thoracic Aorta
2006 (English)In: WSEAS Transaction on biology and biomedicine, ISSN 1109-9518, Vol. 10, no 3, 609-614 p.Article in journal (Refereed) Published
Abstract [en]

Numerous studies have shown a correlation between Wall Shear Stress (WSS) and atherosclerosis, but few have evaluated the reliability of estimation methods and measures used to assessWSS, which is the subject of this work. A subject specific vessel model of the aortic arch and thoracic aorta is created fromMRI images and used for CFD simulations with MRI velocity measurements as inlet boundary condition. WSS is computed from the simulation results. Aortic WSS shows significant spatial as well as temporal variation during a cardiac cycle, which makes circumferential values very uninformative, and approximate estimates using Hagen-Poiseuille fails predict the averageWSS. Highly asymmetric flow, especially in the arch, causes the spatial WSS variations.

Keyword
Wall shear stress, CFD, Aorta, Circumferential average values, Asymmetric flow
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-43727 (URN)74619 (Local ID)74619 (Archive number)74619 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-03-27Bibliographically approved
2. Feasibility of Patient Specific Aortic Blood Flow CFD Simulation
Open this publication in new window or tab >>Feasibility of Patient Specific Aortic Blood Flow CFD Simulation
Show others...
2006 (English)In: 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, 257-263 p.Conference paper, Published 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.

Place, publisher, year, edition, pages
Springer Berlin/Heidelberg, 2006 Edition: 1
Series
Lecture Notes in Computer Science, ISSN 0302-9743 (print), 1611-3349 (online) ; 4190
National Category
Medical Image Processing
Identifiers
urn:nbn:se:liu:diva-36902 (URN)10.1007/11866565_32 (DOI)000241556300032 ()32988 (Local ID)3-5404-4707-5 (ISBN)978-3-540-44727-6 (ISBN)978-3-540-44707-8 (ISBN)32988 (Archive number)32988 (OAI)
Conference
The 9th MICCAI Conference, Copenhagen, Denmark, 1-6 October 2006
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-03-27Bibliographically approved
3. Evaluation of Aortic Geometries created by MRI Data in Man
Open this publication in new window or tab >>Evaluation of Aortic Geometries created by MRI Data in Man
Show others...
2011 (English)In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 31, no 6, 485-491 p.Article in journal (Refereed) Published
Abstract [en]

The development of atherosclerotic plaques has been associated with the patterns of wall shear stress (WSS). However, much is still uncertain with the methods used to calculate WSS. Correct vessel geometries are mandatory to get reliable estimations and the purpose of this study was to evaluate an in vivo method for creating aortic 3D geometry in man based on data from magnetic resonance imaging (MRI) with ultrasound as reference.

Methods: The aortas of ten healthy males, 23.4 ± 1.6 years of age, were examined with MRI, and 3D geometries were created with manual segmentation of the images. Lumen diameters (LD) were measured in the abdominal aorta (AA) and the thoracic aorta (TA) with non-invasive B-mode ultrasound as a reference.

Results: The anteroposterior diameter of the AA was 13.6 ± 1.1 mm for the MRI and 13.8 ± 1.3 mm for the ultrasound (NS). Intraobserver variability (CV) for MRI and ultrasound was <0.92% and <0.40% respectively . Interobserver variability MRI and ultrasound was 0.96% and 0.56% respectively. The diameter of the TA was 19.2 ± 1.4 mm for the MRI, and the intraobserver variability (CV) were <0.78% and interobserver variability (CV) were 0.92%.

Conclusion: Specific arterial geometries can be constructed with a high degree of accuracy using MRI. This indicate that the MRI geometries may be used to create realistic and correct geometries in the calculation of WSS in the aorta of man.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2011
Keyword
human aorta, lumen diameter, magnetic resonance imaging, manual segmentation, ultrasound
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-65905 (URN)10.1111/j.1475-097X.2011.01035.x (DOI)000296198100011 ()
Available from: 2011-02-25 Created: 2011-02-25 Last updated: 2017-12-11Bibliographically approved
4. Wall Shear Stress Estimations using Semi-Automatic Segmentation
Open this publication in new window or tab >>Wall Shear Stress Estimations using Semi-Automatic Segmentation
Show others...
(English)Manuscript (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.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-65906 (URN)
Available from: 2011-02-25 Created: 2011-02-25 Last updated: 2017-03-27Bibliographically approved
5. A method for subject specific estimation of aortic wall shear stress
Open this publication in new window or tab >>A method for subject specific estimation of aortic wall shear stress
Show others...
2009 (English)In: WSEAS Transactions on Biology and Biomedicine, ISSN 1109-9518, Vol. 6, no 3, 49-57 p.Article in journal (Refereed) Published
Abstract [en]

Wall shear stress (WSS) distribution in the human aorta is a highly interesting hemodynamic factor for atherosclerosis development. We present a magnetic resonance imaging (MRI) and computational fluid dynamics (CFD) based subject specific WSS estimation method and demonstrate it on a group of nine healthy volunteers (males age 23.6 ± 1.3 years). In all nine subjects, the aortic blood flow was simulated in a subject specific way, where the 3D segmented geometries and inflow profiles were obtained using MRI. No parameter settings were tailored using data from the nine subjects. Validation was performed by comparing CFD gained velocity with magnetic resonance imaging (MRI) velocity measurements. CFD and MRI velocity profiles were comparable, but the temporal variations of the differences during the cardiac cycle were significant. Spatio-temporal analyzes on the WSS distribution showed a strong subject specific influence. Subject specific models are decisive to estimate WSS distribution.

Place, publisher, year, edition, pages
WSEAS Press, 2009
Keyword
3D segmentation; Aorta; CFD; MRI; Subject specific; Velocity validation; WSS
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-57056 (URN)
Available from: 2010-06-11 Created: 2010-06-09 Last updated: 2017-03-27Bibliographically approved
6. Is a flat inlet profile sufficient for WSS estimation in the aortic arch?
Open this publication in new window or tab >>Is a flat inlet profile sufficient for WSS estimation in the aortic arch?
2009 (English)In: WSEAS Transactions on Fluid Mechanics, ISSN 1790-5087, Vol. 4, no 4, 148-160 p.Article in journal (Refereed) Published
Abstract [en]

Atherosclerosis is one of the main reasons for cardivascular disease which cause many deaths every year especially in the Western world. The development of atherosclerosis is strongly believed to be influenced by hemodynamic forces in the arteries e.g. wall shear stress (WSS). Estimations of WSS are therefore very important. By combining magnetic resonance imaging (MRI), image processing and computational fluid dynamic (CFD) simulations, it is possible to estimate subject specific WSS in the human arteries. The framework for performing such work includes i.e. using inlet boundary conditions which, however, will influence the final result i.e. the WSS distribution. This paper aims to investigate the influence of the inflow boundary condition in the human aorta with comparing two settings for the inflow: 1) subject specific inlet profile measured with MRI and 2) uniform profile with the subject specific mass flow rate. The analysis of WSS will be performed both on spatial location along the artery as well as on the temporal location in the cardiac cycle. Subject specific data have been used for geometry, inflow velocity profile and blood viscosity. The recommendation due to our findings from nine healthy subjects, is that a measured subject specific inlet boundary condition must be used in order to get a subject specific WSS distribution; the difference in WSS is 8-34% compared to using a mass-flow correct uniform profile. Temporal variations were clearly seen in the WSS differences due to the different inflow velocity profiles used. The lowest influence of the inlet boundary condition was found at peak velocity in the cardiac cycle. The aortic geometry does not form the flow in such extent (compared to the influence by inlet boundary condition) to obtain a more correct WSS distribution further away from the inlet at the systolic parts of the cardiac cycle. The shape of the vessel has only a significant influence at low velocities i.e. the diastolic phase of the cardiac cycle.

Keyword
Aorta; CFD; Inlet boundary condition; Subject specific; Uniform velocity profile; Wall shear stress
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-53002 (URN)
Available from: 2010-01-14 Created: 2010-01-14 Last updated: 2017-03-27Bibliographically approved

Open Access in DiVA

Towards Subject Specific Aortic Wall Shear Stress : a combined CFD and MRI approach(2652 kB)1356 downloads
File information
File name FULLTEXT01.pdfFile size 2652 kBChecksum SHA-512
b4bb7b43a842b2db2471fbcadf2450fa0d727849ca70eca9827fca923d35c7fa532302058a49915ea187b7977a046a48be13c1cfff6ac835d4476dadaa95c68b
Type fulltextMimetype application/pdf
cover(2852 kB)75 downloads
File information
File name COVER01.pdfFile size 2852 kBChecksum SHA-512
9a7fe553c7195e97a5ceaef975266cc7a53dd788af724e331099741dda25fcdea40995c301cec6c5373fa4b96d328ae1b0c3e9f7048f67ca8de406130f63f91e
Type coverMimetype application/pdf

Authority records BETA

Renner, Johan

Search in DiVA

By author/editor
Renner, Johan
By organisation
Applied Thermodynamics and Fluid MechanicsCenter for Medical Image Science and Visualization, CMIVThe Institute of Technology
Fluid Mechanics and Acoustics

Search outside of DiVA

GoogleGoogle Scholar
Total: 1356 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 1422 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf