Initial stress and nonlinear material behavior in patient-specific AAA wall stress analysis |
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| Authors: | L Speelman EMH Bosboom GWH Schurink J Buth M Breeuwer MJ Jacobs FN van de Vosse |
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| Institution: | 1. Eindhoven University of Technology, Department of Biomedical Engineering, Eindhoven, The Netherlands;2. Maastricht University Medical Center, Department of General Surgery, The Netherlands;3. Catharina Hospital Eindhoven, Department of Vascular Surgery, The Netherlands;4. Philips Healthcare, Department of Healthcare Informatics – Clinical Informatics, The Netherlands;1. Tissue Engineering and Biological Systems Research Lab, School of Mechanical Engineering, Iran University of Science and Technology, Tehran 16846, Iran;2. School of Mechanical Engineering, Iran University of Science and Technology, Tehran 16846, Iran;3. Research Department, Basir Eye Center, Tehran 14186, Iran;4. Department of Ophthalmology, Baqiyatallah University of Medical Sciences, Tehran 14155, Iran;1. Cardiovascular Engineering Lab, Faculty of Biomedical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran;2. Tracheal Diseases Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran;1. Servei de Medicina Intensiva, Hospital Son Llàtzer, Palma de Mallorca, Illes Balears, Spain;2. Servei de Medicina Intensiva, Hospital Universitari Son Espases, Palma de Mallorca, Illes Balears, Spain;1. University of Pavia, Dept. of Industrial Eng. and Informatics, Via Ferrata 3, 27100 Pavia, Italy;2. University of Pavia, Dept. of Civil Eng. and Architecture, Via Ferrata 3, 27100 Pavia, Italy;3. IRCCS Policlinico San Matteo, Dept. of Cardiothoracic Surgery, Viale Golgi 19, 27100 Pavia, Italy;4. IRCCS Policlinico San Matteo, Institute of Radiology, Viale Golgi 19, 27100 Pavia, Italy;1. Department of Biological Sciences, Goethe University Frankfurt am Main, Germany;2. Department of Mechanical Engineering, University Siegen, Germany;3. Department of Vascular and Endovascular Surgery, Goethe University Frankfurt am Main, Germany;4. University Heart Centre, Philipps University Marburg, Germany |
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| Abstract: | Rupture risk estimation of abdominal aortic aneurysms (AAA) is currently based on the maximum diameter of the AAA. A more critical approach is based on AAA wall stress analysis. For that, in most cases, the AAA geometry is obtained from CT-data and treated as a stress free geometry. However, during CT imaging, the AAA is subjected to a time-averaged blood pressure and is therefore not stress free. The aim of this study is to evaluate the effect of neglecting these initial stresses (IS) on the patient-specific AAA wall stress as computed by finite element analysis. Additionally, the contribution of the nonlinear material behavior of the AAA wall is evaluated.Thirty patients with maximum AAA diameters below the current surgery criterion were scanned with contrast-enhanced CT and the AAA's were segmented from the image data. The mean arterial blood pressure (MAP) was measured immediately after the CT-scan and used to compute the IS corresponding with the CT geometry and MAP. Comparisons were made between wall stress obtained with and without IS and with linear and nonlinear material properties.On average, AAA wall stresses as computed with IS were higher than without IS. This was also the case for the stresses computed with the nonlinear material model compared to the linear material model. However, omitting initial stress and material nonlinearity in AAA wall stress computations leads to different effects in the resulting wall stress for each AAA. Therefore, provided that other assumptions made are not predominant, IS cannot be discarded and a nonlinear material model should be used in future patient-specific AAA wall stress analyses. |
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