Effect of Wall Variable Thickness on Patient Specific Finite Element Abdominal Aortic Aneurysm Models
DOI:
https://doi.org/10.14738/jbemi.55.5262Keywords:
Abdominal aortic aneurysm, Wall thickness.Abstract
The aim of this study is to analyze the possibilities to measure the wall stress on the thinnest and thickest side of the AAA by using patient’s Specific Finite Element (SFE) models, in order for understanding the rupture of AAA in a better approach. Patient specific model with different in position, Finite Element Analysis (FEA) models that were studied earlier by Di Martino et al. (1998) [1], was adopted. The AAA was modelled as a homogenous, isotropic, incompressible, linear elastic material with Young’s modulus (E) and Poisson’s ratio (µ) having value of 0.11 MPa and µ = 0.45, respectively. The values of E and µ was determined from uniaxial loading tests performed on specimens of AAA. In order to cast peak systolic blood pressure of a healthy patient, pressure of 145 mmHg was directed to the internal surface of the models. FEA models of AAA were analysed using ANSYS Finite Element Package 15.0 version. Values of stress was observed on the scale of von-Mises, this method helps to locate area with highest stress i.e. to calculate failure criteria by combining the stress in three-dimensions. In order to determine the collapse of AAA wall von-Mises stress is commonly use for the assessment of the AAA stress. Our findings and results strengthens the earlier studies performed by Polzer et al. (2010) [2] and Altuwaijri (2015) [3], where AAA wall stress was reduced by formation of thrombus. Thus reducing the chance of AAA rupture and supporting the wall strength. Our findings suggest that thrombus clearly works as a shield to guard the AAA wall from rupture. However, more research and further studies are required that corroborate the relation between the biological and mechanical factors to understand the role of the thrombus for AAA rupture.
References
(1) Di Martino, E.S., et al., Fluid–structure interaction within realistic three-dimensional models of the aneurysmatic aorta as a guidance to assess the risk of rupture of the aneurysm. Medical engineering & physics, 2001. 23(9): p. 647-655.
(2) Polzer, S. and J. Bursa. Poroelastic model of intraluminal thrombus in FEA of aortic aneurysm. in 6th World Congress of Biomechanics (WCB 2010). August 1-6, 2010 Singapore. 2010. Springer.
(3) Altuwaijri, O. Finite Element Analysis OF Abdominal Aortic Aneurysms to Predict Risk of Rupture-The Role of The Thrombosis Thicknesses. in World Congress on Medical Physics and Biomedical
Engineering, June 7-12, 2015, Toronto, Canada. 2015. Springer.
(4) Doyle, B.J., et al., An experimental and numerical comparison of the rupture locations of an abdominal aortic aneurysm. Journal of Endovascular Therapy, 2009. 16(3): p. 322-335.
(5) Vorp, D.A. and J.P.V. Geest, Biomechanical determinants of abdominal aortic aneurysm rupture. Arteriosclerosis, thrombosis, and vascular biology, 2005. 25(8): p. 1558-1566.
(6) McGloughlin, T.M. and B.J. Doyle, New approaches to abdominal aortic aneurysm rupture risk assessment: engineering insights with clinical gain. Arteriosclerosis, thrombosis, and vascular biology, 2010. 30(9): p. 1687-1694.
(7) Martufi, G., et al., Three-dimensional geometrical characterization of abdominal aortic aneurysms: image-based wall thickness distribution. Journal of biomechanical engineering, 2009. 131(6): p. 061015.
(8) Vorp, D.A., Biomechanics of abdominal aortic aneurysm. Journal of biomechanics, 2007. 40(9): p. 1887-1902.
(9) Fillinger, M.F., et al., Prediction of rupture risk in abdominal aortic aneurysm during observation: wall stress versus diameter. Journal of vascular surgery, 2003. 37(4): p. 724-732.
(10) Darling, R.C., et al., Autopsy study of unoperated abdominal aortic aneurysms. The case for early resection. Circulation, 1977. 56(3 Suppl): p. II161-4.
(11) Nicholls, S.C., et al., Rupture in small abdominal aortic aneurysms. Journal of vascular surgery, 1998. 28(5): p. 884-888.
(12) Thubrikar, M.J., J. Al-Soudi, and F. Robicsek, Wall stress studies of abdominal aortic aneurysm in a clinical model. Annals of vascular surgery, 2001. 15(3): p. 355-366.
(13) Geest, J.P.V., et al., Towards a noninvasive method for determination of patient-specific wall strength distribution in abdominal aortic aneurysms. Annals of biomedical engineering, 2006. 34(7): p. 1098-1106.
(14) Raghavan, M.L., et al., Regional distribution of wall thickness and failure properties of human abdominal aortic aneurysm. Journal of biomechanics, 2006. 39(16): p. 3010-3016.
(15) J. Thubrikar, M.L., F. Robicsek, J. Al-Soudi, B. Fowler, M, Mechanical properties of abdominal aortic aneurysm wall. Journal of medical engineering & technology, 2001. 25(4): p. 133-142.
(16) Raghavan, M.L., M.W. Webster, and D.A. Vorp, Ex vivo biomechanical behavior of abdominal aortic aneurysm: assessment using a new mathematical model. Annals of biomedical engineering, 1996.
(5): p. 573-582.
(17) Van den Hengel, W.K. and F. van de Vosse, Abdominal aortic wall thickness and compliance. 2008.
(18) Truijers, M., et al., Wall stress analysis in small asymptomatic, symptomatic and ruptured abdominal aortic aneurysms. European Journal of Vascular and Endovascular Surgery, 2007. 33(4): p. 401-407.
(19) Fillinger, M.F., et al., In vivo analysis of mechanical wall stress and abdominal aortic aneurysm rupture risk. Journal of vascular surgery, 2002. 36(3): p. 589-597.
(20) Haller, C., et al., Sequential based analysis of Intima-Media Thickness (IMT) in common carotid artery studies. Atherosclerosis, 2007. 195(2): p. e203-e209.
(21) McGloughlin, T.M., et al., A finite element analysis rupture index (FEARI) as an additional tool for abdominal aortic aneurysm rupture prediction. 2009.
(22) Doyle, B.J., A. Callanan, and T.M. McGloughlin, A comparison of modelling techniques for computing wall stress in abdominal aortic aneurysms. Biomedical engineering online, 2007. 6(1): p. 38.
(23) Doyle, B.J., et al., Vessel asymmetry as an additional diagnostic tool in the assessment of abdominal aortic aneurysms. Journal of vascular surgery, 2009. 49(2): p. 443-454.
(24) Schurink, G., et al., Thrombus within an aortic aneurysm does not reduce pressure on the aneurysmal wall. Journal of Vascular Surgery, 2000. 31(3): p. 501-506.
