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Session: Arteries
Session starts: Thursday 24 January, 10:30
Presentation starts: 10:45
Room: Lecture room 536

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Ronald van den Berg (Erasmus Medical Center)
Stéphane Avril (Ecole des Mines de Saint-Etienne)
Frank Gijsen (Erasmus Medical Center)
Ali Akyildiz (Erasmus Medical Center)

Abstract:
Fatal cardiovascular events are majorly caused by atherosclerotic plaque rupture, a biomechanical event that occurs when local plaque stresses exceed strength. Plaque stresses can be assessed by computational (finite element, FE) models and accurate plaque material parameters are a must for accurate plaque stress computations[1]. Current techniques for material parameter estimation, such as inverse FE modelling[2], have large computational costs (hours or days). This study aims to develop and validate an approach to much faster obtain plaque properties by employing the virtual fields method (VFM)[3]. VFM employs the virtual work principle and utilizes full-field deformation measurements of the investigated structure. Energy balance equations, obtained by prescribing kinematically admissible virtual fields, are solved for unknown material stiffness parameters. In this study, firstly full-field displacement maps of atherosclerotic plaque for physiological intraluminal pressure were computed with three FE plaque models, based on histological slides of human carotids. Computed full-field deformation maps were then used as input for the developed VFM approach. VFM-estimated plaque stiffness values were finally compared against the ground truth values prescribed in FE models to validate the approach. In the single-component cases of an idealized and a realistic plaque; VFM-estimated plaque stiffness was <1% different from the ground-truth value(200 kPa). For more complex, three component plaque case; soft and calcified region stiffness values were 13% and 3% off from ground-truth(10&1000 kPa, respectively), yet plaque stiffness was still <1% off. Even when a mean noise of 15% was added to the deformation input, the developed VFM approach satisfactorily estimated the plaque stiffness, where the difference was only 5%. VFM estimation procedures took <30 seconds. In this study, VFM was used for atherosclerotic plaques for the first time. Study results demonstrate the potential of VFM for plaque stiffness estimation if full-field deformation data is available. The short computational time required and the possibility to use it with clinically measured deformation data make the developed method a great potential method of assessing plaque tissue stiffness in-vivo. Near-future plan is employing the developed VFM approach on existing ultrasound full-field deformation data from ex-vivo inflation experiments with atherosclerotic porcine iliac arteries and human coronaries[2].