Biomechanical Analysis of Aortic Aneurysm Failure to Find Out the Important Factors

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The aim of this project are to obtain mechanical properties of aneurysmal wall in vitro, to noninvasively measure the three dimensional shape of aneurysms for patients from MRI images, and to make models to predict the dangerous regions for aneurysm failure from the motion and stress analyses of aneurysmal wall. The following results were obtained.1. The specimen excised form the aneurysmal region of patients was used for the biaxial tensile testing. The machine was newly developed in our laboratory. The diseased specimen from aneurysm was stiffer than normal tissues. The specimens with the higher elastic moduli were the higher anisotropic mechanical properties.2. Three dimensional finite element model was successfully composed from MRI images for human thoracic aortas. In this model, the aortic wall was assumed to be thin membrane, isotropic, large linear deformation between diastolic and systolic pressures. The stress concentration was found in the frontal and dosal sides of aortic arch where aneurysm formation is frequently observed. Further, the location and shapes of the aneurysm had important and significant effects on the highest stress values and the stress distribution.3. The strain and stress were calculated around the aneurysm of patients by measuring the deformation of aortic wall in MRI images. The results showed us that the strain was large around the frontal walls of aortic arch in healthy normal person. In aneurysmal patients, the large deformation to the outer wall side around the aneurysms was observed.According to the present results, we will develop the new system to rapidly construct the finite element model from the MRI images and study more precise mechanical properties of aneurysmal walls.