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This was a presentation given in my Biomedical FE class.
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An aneurysm is defined as: A cardiovascular disease characterized by a saclike widening of an artery resulting from weakening of the artery wall
Intracranial aneurysms(ICA) have a prevalence of 2%-6.5%
Common places for ICAs are the cerebral artery, internal carotid artery, basilar artery, and the anterior communicating artery
Cerebral blood pressure is autoregulated Currently doctors use diameter as a measure of severity
1. http://wordnetweb.princeton.edu/perl/webwn?s=aneurysm 2. Chien A, Castro MA, Tateshima S, et al. Quantitative hemodynamic analysis of brain aneurysms at different locations. AJNR Am J Neuroradiol. 2009;30:1507‐1512.
Relate acute increases in blood pressure with mechanical stress and strain values within an intracranial aneurysm.
http://en.wikipedia.org/wiki/File:Circle_of_Willis_en.svg
Einc: .65MPa 12.2MPa 12.2MPa
ν=.499 Shell Elements, thickness=.086mm Pressure Control-122 mm Hg Aerobic exercise-163 mm Hg Valsalva-250 mm Hg
Elastic/Isotropic materialMiddle cerebral blood pressure during a Valsalva manouver in the standing position, Frank Pott, et al., J Applied PhysiologyPhysical exercise increases middle cerebral artery blood flow velocity, Gunnar Hellstrom, Nils Gunnar Wahlgren, Neurosurgery Rev.The static elastic properties of the arterial wall, D. H. Bergel, J. Physiology
Obtain aneurysm as .dat file and convert to .stl Load into IA-FEMes 1.0 Create block structure Mesh seed-> length=.25 Mesh-> shell elements Add ELSETS & BCs Export to ABAQUS Manually enter pressure values Run ABAQUS and complete post processing
Valsalva
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pa Max VonMises
max at 3407
Lowering maximum stress threshold shows greater detail in values which further deviate from the maxima
Regions of high stress have a strong correlation with regions of greater contour
Valsalva
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max at 3407
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Risk of intracranial aneurysm rupture varies greatly from patient to patient. There is not enough information known to use stress/strain as an indication for rupture. However, there tends to be a concentration of stress near areas of large contour.
Diameter of the aneurysm is likely the simplest/most effective method of assessing aneurysm risk of rupture in a clinical setting