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Session: Vascular - II
Session starts: Friday 27 January, 11:30
Presentation starts: 12:45
Room: Room 559

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Mirunalini Thirugnanasambandam (Eindhoven University of Technology)
Esther Maas (Eindhoven University of Technology)
Arjet Nievergeld (Eindhoven University of Technology)
Marc van Sambeek (Catharina Hospital Eindhoven)
Stephane Avril (Ecole des MINES St. Etienne, France)
Richard Lopata (Eindhoven University of Technology)

Abstract:
Assessment of patient-specific behaviour of abdominal aortic aneurysms (AAA) is crucial to evaluating personalized biomechanical rupture risk indices with better accuracy. The ability of 4D ultrasound (US) to assess AAA wall motion, when combined with a novel inverse method, will provide an innovative framework for evaluation of individualized material behaviour of AAAs. 4D-US images were acquired from patients in a supine position over multiple cardiac cycles at an acquisition rate of 4-8 volumes/second. Image volumes were segmented at diastole, and a 3D speckle tracking algorithm was used to track the AAA walls to the systolic configuration. B-spline grids were fitted to the systolic and diastolic geometries of both walls. The displacement at each node of each wall was evaluated based on the minimization of the distance between the systolic and diastolic grids post-co-registration. Displacement of the nodes in the bulk of the AAA wall were evaluated using a weighted linear interpolation of the displacement vectors of their inner and outer wall neighbours. The smoothed 3D displacement field was input to the modified virtual field method (mVFM) [1], which iteratively evaluated the optimized material parameters based on a virtual work-based cost function. Thus, an automated framework for computationally inexpensive estimation of patient-specific material properties was formulated. The aforementioned technique was implemented, validated in-silico, and applied to multiple patient-specific AAAs. An uncoupled Neo-Hookean formulation was used to describe AAA wall material behaviour. With an initial guess of c10 = 1.24.105 Pa, optimal c10 values were predicted in three different regions (healthy abdominal aorta, anterior and posterior AAA sac) within 10 iterations using the 4D US+mVFM framework. The anterior AAA sac and the healthy abdominal aorta had the highest and lowest shear modulus, respectively. In the future, personalized material parameters will be evaluated while using sophisticated constitutive models. References: [1] Mei Y et al. J Elast, 145, 265-194 (2021).