A Methodology for Verifying Abdominal Aortic Aneurysm Wall Stress

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Sergio Ruiz de Galarreta ◽  
Aitor Cazón ◽  
Raúl Antón ◽  
Ender A. Finol
Keyword(s):  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Experimental Testing ◽  
Wall Stress ◽  
Intraluminal Pressure ◽  
Maximum Diameter ◽  
Numerical Studies ◽  
Aneurysm Wall ◽  
Abdominal Aortic ◽  
Geometric Factors

An abdominal aortic aneurysm (AAA) is a permanent focal dilatation of the abdominal aorta of at least 1.5 times its normal diameter. Although the criterion of maximum diameter is still used in clinical practice to decide on a timely intervention, numerical studies have demonstrated the importance of other geometric factors. However, the major drawback of numerical studies is that they must be validated experimentally before clinical implementation. This work presents a new methodology to verify wall stress predicted from the numerical studies against the experimental testing. To this end, four AAA phantoms were manufactured using vacuum casting. The geometry of each phantom was subject to microcomputed tomography (μCT) scanning at zero and three other intraluminal pressures: 80, 100, and 120 mm Hg. A zero-pressure geometry algorithm was used to calculate the wall stress in the phantom, while the numerical wall stress was calculated with a finite-element analysis (FEA) solver based on the actual zero-pressure geometry subjected to 80, 100, and 120 mm Hg intraluminal pressure loading. Results demonstrate the moderate accuracy of this methodology with small relative differences in the average wall stress (1.14%). Additionally, the contribution of geometric factors to the wall stress distribution was statistically analyzed for the four phantoms. The results showed a significant correlation between wall thickness and mean curvature (MC) with wall stress.

scholarly journals The Role of Geometric Parameters in the Prediction of Abdominal Aortic Aneurysm Wall Stress

2010 ◽  
Vol 39 (1) ◽  
pp. 42-48 ◽  
Author(s):  
E. Georgakarakos ◽  
C.V. Ioannou ◽  
Y. Kamarianakis ◽  
Y. Papaharilaou ◽  
T. Kostas ◽  
...  
Keyword(s):  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Wall Stress ◽  
Geometric Parameters ◽  
Aneurysm Wall ◽  
Abdominal Aortic ◽  
Abdominal Aortic Aneurysm Wall

scholarly journals Improving the Efficiency of Abdominal Aortic Aneurysm Wall Stress Computations

PLoS ONE ◽  
2014 ◽  
Vol 9 (7) ◽  
pp. e101353 ◽  
Author(s):  
Jaime E. Zelaya ◽  
Sevan Goenezen ◽  
Phong T. Dargon ◽  
Amir-Farzin Azarbal ◽  
Sandra Rugonyi
Keyword(s):  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Wall Stress ◽  
Aneurysm Wall ◽  
Abdominal Aortic ◽  
Abdominal Aortic Aneurysm Wall

Assessment of Abdominal Aortic Aneurysm Risk: Asymmetry as an Additional Diagnostic Tool?

2008 ◽  
Author(s):  
Barry J. Doyle ◽  
Anthony Callanan ◽  
Michael T. Walsh ◽  
David A. Vorp ◽  
Timothy M. McGloughlin
Keyword(s):  
Risk Factors ◽  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Surgical Intervention ◽  
Current Trend ◽  
Wall Stress ◽  
Posterior Wall ◽  
Maximum Diameter ◽  
Infrarenal Aorta ◽  
Abdominal Aortic

An abdominal aortic aneurysm (AAA) can be defined as a permanent and irreversible localised dilation of the infrarenal aorta. This localised dilation is a result of a degradation of the elastic media of the arterial wall. This degradation of the aortic wall can be attributed to risk factors such as tobacco smoking, sex, age, hypertension, chronic obstructive pulmonary disease, hyperlipidaemia, and family history of the disorder [1]. With the recent advancements in medicine, more AAAs are being detected than ever. Approximately 500,000 new cases are diagnosed each year worldwide resulting in 15,000 deaths per year in the USA alone [2]. Currently, the rupture risk of AAAs is regarded as a continuous function of aneurysm size, with surgical intervention decided based on the maximum diameter of the AAA. Most AAA repairs are performed when the diameter exceeds 50–60mm. It has been shown that maximum diameter may not be a reliable predictor of rupture, as smaller AAAs can also rupture. It is believed by many researchers that there is a need to review the determination of the timing of surgical intervention based solely on aneurysm diameter, and include other relevant risk factors. These additional risk factors could, for example, include, AAA wall stress, AAA expansion rate, degree of asymmetry, presence of intraluminal thrombus (ILT), and hypertension. The addition of these parameters may aid the surgical decision-making process. Shifting the current trend towards more encompassing assessment of AAA rupture potential may help reduce the morbidity and mortality rates associated with AAA repair. It was previously reported [3] that 82% of AAA ruptures occur on the posterior wall. In this research, the asymmetry of the AAA is examined, with respect to both peak wall stress and posterior wall stress, in ten realistic cases, and a resulting threshold factor is presented.

Effect of Variations in Intraluminal Thrombus Constitutive Properties on Abdominal Aortic Aneurysm Wall Stress: A Parametric Study

2001 ◽  
Author(s):  
Elena S. Di Martino ◽  
David H. J. Wang ◽  
Alberto Redaelli ◽  
Michel S. Makaroun ◽  
David A. Vorp
Keyword(s):  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Parametric Study ◽  
Wall Stress ◽  
Transverse Diameter ◽  
Intraluminal Thrombus ◽  
Arterial Blood ◽  
Aneurysm Wall ◽  
Abdominal Aortic ◽  
Constitutive Parameters

Abstract The prevalence of abdominal aortic aneurysm (AAA) is growing together with population age, being 8.8% in a population above 65 years according to a recent study [1]. Deciding between elective surgical repair of AAA and watchful management is a complex issue due to the lack of reliable rupture risk indices. The maximum transverse diameter of AAA is most commonly used in clinical practice to base this decision. From a biomechanical viewpoint, AAA rupture is related to the balance between the stresses acting on the wall and strength of the wall tissue. Many different factors contribute to the stress within the aortic aneurysm wall, including the presence of intraluminal thrombus (ILT) [2–5], the local surface curvature [6] and material characteristics of the AAA wall [7], and the presence of local “stress concentrators” due to calcifications or local thinning. As regards the ILT, its role with respect to aneurysm wall stresses has given rise to many hypotheses. Some studies show that the pressure inside the thrombus is not reduced with respect to the arterial blood pressure, some, including studies from the authors, state a possible protective role [2–5]. Previously in our laboratory, a nonlinear, hyperelastic constitutive model was developed for ILT, and the parameters for which were determined through ex-vivo experimentation [8]. The purpose of this study was to investigate the reliability of using the same population-mean values of ILT constitutive parameters for estimates of wall stress distribution in all AAA. For this, we performed a parametric study in which the ELT constitutive parameters were varied within a physiological range and aortic wall stresses were evaluated.

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