Through progress in medical imaging, image analysis and finite element (FE) meshing tools it is now possible to extract patient-specific geometries from medical images of, e.g., abdominal aortic aneurysms (AAAs), and thus to study clinically relevant problems via FE simulations. Medical imaging is most often performed in vivo, and hence the reconstructed model geometry in the problem of interest will represent the in vivo state, e.g., the AAA at physiological blood pressure. However, classical continuum mechanics and FE methods assume that constitutive models and the corresponding simulations start from an unloaded, stress-free reference condition. Two problems exist when applying such classical approaches to patient-specific simulations of arteries: (i) the in vivo determined 'initial' geometry is not an unloaded reference configuration, and (ii) the unloaded tissue itself is residually stressed. Computational methods of prestressing the model so that, e.g., the initial (image derived) geometry is in equilibrium with the known loads, overcome the first problem. The second problem, that of in vivo residual stresses in patient-specific simulations, has still not been satisfactorily addressed in the biome-chanics literature. We propose a pragmatic method to incorporate experimentally-determined 3D residual stresses (stretches) into general patient-specific FE simulations of arteries which include the layered (intima, media, adventitia) structure of arterial wall.
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