Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • 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
Influence of differing material properties in media and adventitia on arterial adaptation: application to aneurysm formation and rupture
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Biomechanics.ORCID iD: 0000-0002-2749-3381
Show others and affiliations
2013 (English)In: Computer Methods in Biomechanics and Biomedical Engineering, ISSN 1025-5842, E-ISSN 1476-8259, Vol. 16, no 1, 33-53 p.Article in journal (Refereed) Published
Abstract [en]

Experimental and computational studies suggest a substantial variation in the mechanical responses and collagen fibre orientations of the two structurally important layers of the arterial wall. Some observe the adventitia to be an order of magnitude stiffer than the media whilst others claim the opposite. Furthermore, studies show that molecular metabolisms may differ substantially in each layer. Following a literature review that juxtaposes the differing layer-specific results we create a range of different hypothetical arteries: (1) with different elastic responses, (2) different fibre orientations, and (3) different metabolic activities during adaptation. We use a finite element model to investigate the effects of those on: (1) the stress response in homeostasis; (2) the time course of arterial adaptation; and (3) an acute increase in luminal pressure due to a stressful event and its influence on the likelihood of aneurysm rupture. Interestingly, for all hypothetical cases considered, we observe that the adventitia acts to protect the wall against rupture by keeping stresses in the media and adventitia below experimentally observed ultimate strength values. Significantly, this conclusion holds true in pathological conditions.

Place, publisher, year, edition, pages
2013. Vol. 16, no 1, 33-53 p.
Keyword [en]
media, adventitia, layer-specific, growth, arterial adaptation, abdominal aneurysm
National Category
Applied Mechanics
Research subject
Engineering Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-142646DOI: 10.1080/10255842.2011.603309ISI: 000316056100004Scopus ID: 2-s2.0-84872580188OAI: oai:DiVA.org:kth-142646DiVA: diva2:703965
Note

QC 20140311

Available from: 2014-03-10 Created: 2014-03-10 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Computational model of abdominal aortic aneurysm inception and evolution
Open this publication in new window or tab >>Computational model of abdominal aortic aneurysm inception and evolution
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Incidence of abdominal aortic aneurysm (AAA) is increasing in the aging society of the western world. Development of AAA is mostly asymptomatic and is characterized by a bulge in the abdominal aorta. However, AAA may suddenly rupture, which results in an internal bleeding associated with a high mortality rate. Patients with AAA undergo regular screening until treatment indication. To date, statistical criteria are used to decide whether the risk of rupture exceeds the risk of intervention. Models of AAA development help to understand the disease progression and to yield patient-specific criterion for AAA rupture.

Up to date, sophisticated models of AAA development exist. These models assume the abdominal aorta as a thin-walled structure, which saves the computational effort. This thesis aims at investigating the importance of employing a thick-walled model of the aorta. The effects on AAA development that cannot be captured with a thin-walled model are of interest. In Paper A, the thick-walled model of growth and remodeling of one layer of a AAA slice has been extended to a two-layered model. The parameter study has been performed to investigate the influence of mechanical properties and growth and remodeling (G&R) parameters of two individual layers on the gross mechanical response and G&R of the artery. It was concluded that the adventitia acts to protect the arterial wall against rupture even in pathological state.

In Paper B, the model was extended to an organ level model of AAA development. Furthermore, the model was incorporated into a so-called Fluid-Solid-Growth (FSG) framework, where the AAA development is loosely coupled to the blood flow conditions such as wall shear stress. One patient-specific geometry of the abdominal aorta is used to illustrate the model capabilities. A transmurally non-uniform distribution of the strains of individual arterial constituents was observed. In addition, an increased aneurysm tortuosity was observed in comparison to a thin-walled approach. These findings signify the importance of a thick-walled approach to model the aneurysm development. Finally, the proposed methodology provides a realistic basis to further explore the growth and remodeling of AAA on a patient-specific basis.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2014. viii, 8 p.
Series
TRITA-HFL. Report / Royal Institute of Technology, Solid Mechanics, ISSN 1654-1472 ; 0553
Keyword
aneurysm, three dimensional, elastin degradation, growth, remodeling, fluid-solid-growth model
National Category
Applied Mechanics
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-142649 (URN)978-91-7595-065-5 (ISBN)
Presentation
2014-03-19, Seminarierummet, Teknikringen 8d, KTH, Stockholm, 10:15 (English)
Opponent
Supervisors
Note

QC 20140311

Available from: 2014-03-11 Created: 2014-03-10 Last updated: 2014-03-11Bibliographically approved
2. Abdominal aortic aneurysm inception and evolution - A computational model
Open this publication in new window or tab >>Abdominal aortic aneurysm inception and evolution - A computational model
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Abdominal aortic aneurysm (AAA) is characterized by a bulge in the abdominal aorta. AAA development is mostly asymptomatic, but such a bulge may suddenly rupture, which is associated with a high mortality rate. Unfortunately, there is no medication that can prevent AAA from expanding or rupturing. Therefore, patients with detected AAA are monitored until treatment indication, such as maximum AAA diameter of 55 mm or expansion rate of 1 cm/year. Models of AAA development may help to understand the disease progression and to inform decision-making on a patient-specific basis. AAA growth and remodeling (G&R) models are rather complex, and before the challenge is undertaken, sound clinical validation is required.

In Paper A, an existing thick-walled model of growth and remodeling of one layer of an AAA slice has been extended to a two-layered model, which better reflects the layered structure of the vessel wall. A parameter study was performed to investigate the influence of mechanical properties and G&R parameters of such a model on the aneurysm growth.

In Paper B, the model from Paper A was extended to an organ level model of AAA growth. Furthermore, the model was incorporated into a Fluid-Solid-Growth (FSG) framework. A patient-specific geometry of the abdominal aorta is used to illustrate the model capabilities.

In Paper C, the evolution of the patient-specific biomechanical characteristics of the AAA was investigated. Four patients with five to eight Computed Tomography-Angiography (CT-A) scans at different time points were analyzed. Several non-trivial statistical correlations were found between the analyzed parameters.

In Paper D, the effect of different growth kinematics on AAA growth was investigated. The transverse isotropic in-thickness growth was the most suitable AAA growth assumption, while fully isotropic growth and transverse isotropic in-plane growth produced unrealistic results. In addition, modeling of the tissue volume change improved the wall thickness prediction, but still overestimated thinning of the wall during aneurysm expansion.

Abstract [sv]

Bukaortaaneurysm (AAA) kännetecknas av en utbuktning hos aortaväggen i buken. Tillväxt av en AAA är oftast asymtomatisk, men en sådan utbuktning kan plö̈tsligt brista, vilket har hög dödlighet. Tyvärr finns det inga mediciner som kan förhindra AAA från att expandera eller brista. Patienter med upptä̈ckt AAA hålls därför under uppsikt tills operationskrav är uppnådda, såsom maximal AAA-diameter på 55 mm eller expansionstakt på 1 cm/år. Modeller för AAA-tillväxt kan bidra till att öka förståelsen för sjukdomsförloppet och till att förbättra beslutsunderlaget på en patientspecifik basis. AAA modeller för tillväxt och strukturförändring (G&R) är ganska komplicerade och innan man tar sig an denna utmaning krävs de god klinisk validering.

I Artikel A har en befintlig tjockväggig modell för tillväxt av ett skikt av en AAA-skiva utö̈kats till en två-skiktsmodell. Denna modell återspeglar bättre den skiktade strukturen hos kärlväggen. Genom en parameterstudie undersö̈ktes påverkan av mekaniska egenskaper och G&R-parametrar hos en sådan modell för AAA-tillväxt.

I Artikel B utvidgades modellen från Artikel A till en organnivå-modell för AAA-tillväxt. Vidare inkorporerades modellen i ett “Fluid–Solid–Growth” (FSG) ramverk. En patientspecifik geometri hos bukaortan användes för att illustrera möjligheterna med modellen.

I Artikel C undersöktes utvecklingen av patientspecifika biomekaniska egenskaper hos AAA. Fyra patienter som skannats fem till åtta gånger med “Computed Tomography-Angiography” (CT-A) vid olika tillfällen analyserades. Flera icke triviala statistiska samband konstaterades mellan de analyserade parametrarna.

I Artikel D undersöktes effekten av olika tillväxt-kinematik för AAA tillväxt. En modell med transversellt-isotrop-i-tjockleken-tillväxt var den bäst lämpade för AAA tillväxt, medans antagandet om fullt-isotrop-tillväxt och transversellt-isotrop-i-planet-tillväxt producerade orimliga resultat. Dessutom gav modellering av vävnadsvolymsförändring ett förbättrat väggtjockleks resultat men en fortsatt överskattning av väggförtunningen under AAA-expansionen.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 24 p.
Series
TRITA-HFL. Report / Royal Institute of Technology, Solid Mechanics, ISSN 1654-1472 ; 0605
Keyword
Aorta, Aneurysm, AAA, Blood Flow, Wall Shear Stress, Growth and Remodeling, Mixture Model, Growth Kinematics, Fluid-Solid-Growth, Aorta, Aneurysm, AAA, Blodflöde, Vägg Skjuvspänning, Tillväxt och Strukturförändring, Blandning Modell, Tillväxt Kinematik
National Category
Biomaterials Science Other Materials Engineering
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-197289 (URN)978-91-7729-216-6 (ISBN)
Public defence
2016-12-20, F3, Lindstedtsvägen 22, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20161201

Available from: 2016-12-01 Created: 2016-12-01 Last updated: 2016-12-01Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
Grytsan, Andrii
By organisation
Biomechanics
In the same journal
Computer Methods in Biomechanics and Biomedical Engineering
Applied Mechanics

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 85 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • 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