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Session: Poster session II
Session starts: Thursday 24 January, 16:00

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Daniel Rutten (TU Delft / Erasmus MC)
Ronald van den Berg (TU Delft / Erasmus MC)
Frank Gijsen (Erasmus Medical Centre)
Ali Akyildiz (Erasmus Medical Centre)

Abstract:
The leading cause of death worldwide is acute cardiovascular event precipitated by atherosclerotic plaque rupture1. Rupture occurs when the structural integrity of plaque tissue is compromised by an overwhelming mechanical load. Plaque biomechanics are therefore key to predicting rupture. Seminal studies demonstrated colocalisation of rupture loci and mechanical stress concentrations in plaque-models2,3. Subsequent research has mostly consisted of improving modelling techniques and the acquisition of (imaging-)data. However, there has been little-to-no investigation into the rupturepredictive power of alternative mechanical metrics. This study performs colocalisation-analyses for a comprehensive selection of mechanical metrics in order to identify appropriate metrics for rupture prediction and improve our fundamental understanding of rupture mechanisms. A total of ten stress, strain, and energy metrics were selected for isotropic and anisotropic FEMs based on a unique histopathological dataset of ruptured carotid plaques (n=30)4. The plaques had undergone minimal morphological change during rupture, allowing accurate replication of pre-rupture geometry. Segmentation of the histology images produced plaque geometries for isotropic FEMS. In addition, histology images were put through a custom-made image-processing tool capable of detecting intra-plaque collagen fibres. Local fibre orientations and dispersions were implemented using the Holzapfel-Gasser-Ogden constitutive model, creating a second set of histology-based, heterogeneous and anisotropic FEMs. Colocalisation analyses of rupture sites with selected metrics were performed in the isotropic and anisotropic FEMs. Ten of the twelve ruptures (83%) analysed showed colocalisation with at least one metric. Two metrics had sensitivity below 50% and the average sensitivity of the metrics was 58% (64% without the two <50% metrics). Although isotropic and anisotropic metrics had comparable performance overall, anisotropic fibre-shear strain had the highest sensitivity (75%). Furthermore, it was the only predictor for one rupture. The success of anisotropic fibre-shear strain supports the previously-posited delamination-based damage mode4. Furthermore, reliable strain-based predictors may promote the application of biomechanical results in clinical settings, since strain measurements are possible with recent advancements in ultrasound and MR imaging. Planned analysis of the remainder of the dataset is expected to strengthen these results.