title: A finite element updating approach for identification of the anisotropic hyperelastic properties of normal and diseased aortic walls from 4D ultrasound strain imaging.
abstract: Computational analysis of the biomechanics of the vascular system aims at a better understanding of its physiology and pathophysiology and eventually at diagnostic clinical use. Because of great inter-individual variations, such computational models have to be patient-specific with regard to geometry, material properties and applied loads and boundary conditions. Full-field measurements of heterogeneous displacement or strain fields can be used to improve the reliability of parameter identification based on a reduced number of observed load cases as is usually given in an in vivo setting. Time resolved 3D ultrasound combined with speckle tracking (4D US) is an imaging technique that provides full field information of heterogeneous aortic wall strain distributions in vivo. In a numerical verification experiment, we have shown the feasibility of identifying nonlinear and orthotropic constitutive behaviour based on the observation of just two load cases, even though the load free geometry is unknown, if heterogeneous strain fields are available. Only clinically available 4D US measurements of wall motion and diastolic and systolic blood pressure are required as input for the inverse FE updating approach. Application of the developed inverse approach to 4D US data sets of three aortic wall segments from volunteers of different age and pathology resulted in the reproducible identification of three distinct and (patho-) physiologically reasonable constitutive behaviours. The use of patient-individual material properties in biomechanical modelling of AAAs is a step towards more personalized rupture risk assessment.
authors.affiliation: Department of Biological Sciences, Goethe University Frankfurt am Main, Germany; Department of Mechanical Engineering, University Siegen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Wittek
authors.affiliation: Department of Vascular and Endovascular Surgery, Goethe University Frankfurt am Main, Germany.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Derwich
authors.affiliation: University Heart Centre, Philipps University Marburg, Germany.
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Karatolios
authors.affiliation: Department of Mechanical Engineering, University Siegen, Germany.
authors.forename: Claus Peter
authors.initials: CP
authors.lastname: Fritzen
authors.affiliation: University Heart Centre, Philipps University Marburg, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Vogt
authors.affiliation: Department of Vascular and Endovascular Surgery, Goethe University Frankfurt am Main, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Schmitz-Rixen
authors.affiliation: Department of Biological Sciences, Goethe University Frankfurt am Main, Germany. Electronic address: c.blase@bio.uni-frankfurt.de.
authors.forename: Christopher
authors.initials: C
authors.lastname: Blase
mesh_terms: D016880:Anisotropy; D001011:Aorta / Q000000981:diagnostic imaging / Q000473:pathology* / Q000502:physiology*; D001696:Biomechanical Phenomena; D004548:Elasticity; D020342:Finite Element Analysis; D006801:Humans; D008955:Models, Cardiovascular; D015203:Reproducibility of Results; D013314:Stress, Mechanical; D014463:Ultrasonography
keywords: 3D ultrasound; AAA; Constitutive parameter identification; Full field strain imaging; In vivo