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Session: Poster session 2 (Odd numbers)
Session starts: Friday 27 January, 10:00
Presentation starts: 10:00

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Arjet Nievergeld (Eindhoven University of Technology)
Judith Fonken (Eindhoven University of Technology)
Esther Maas (Eindhoven University of Technology)
Marc van Sambeek (Catharina hospital Eindhoven)
Richard Lopata (Eindhoven University of Technology)

Abstract:
Introduction An abdominal aortic aneurysm (AAA) is a localized dilatation of the aorta, which in case of rupture has a mortality rate of 80%. Current clinical guidelines of intervention are based on AAA diameter, which has been proven to be an inadequate criterion. Biomechanical models can improve rupture risk prediction in a more patient-specific way, using e.g. CT or ultrasound (US) imaging [1, 2]. US is safer compared to CT and adds temporal information for mechanical characterization of the AAA. It is hypothesized that the intraluminal thrombus (ILT) lowers the wall stress and therefore should be included in rupture risk assessment [3]. The objective of this study is to show feasibility to use the acquired time-varying geometry of the lumen and vessel wall for mechanical characterization of both ILT and AAA wall, for future patient-specific modelling of the AAA, including ILT. Materials and Methods An in-house developed semi-automatic segmentation method was used to segment the lumen, ILT, and vessel wall out of 3D+t US images. Despite the low contrast, the lumen diameter-time curve showed a clear blood pressure induced pulsatility in 22 out of 26 patients. Those diameter-time curves were used to calculate the ILT systolic-diastolic volume change, and both lumen and vessel distensibility [4]. Results The ILT volume change (median -0.57%) was within the IQR range of Kontopodis et al. [5]. The median distensibility of the lumen (5.9 MPa-1) and vessel wall (2.8 MPa-1) are lower than the ones found in Molacek et al. (lumen 12 - 30 MPa-1, vessel 5 – 13 MPa-1)[4]. Discussion and Conclusions The compressibility was in agreement with literature showing that ILT can be considered as incompressible. The under-estimation in distensibility might result from the low frame rate of (3D+t) US (3.2-7.3 Hz), since this might cause an under-estimation in systolic diameter and over-estimation of the diastolic diameter (Figure 1). Despite this limitation, a higher distensibility was found for the lumen, compared to the vessel. This observation is in agreement with Molacek et al. [5]. Future research will focus on incorporating these mechanical properties in personalized biomechanical models to improve AAA rupture risk assessment. References 1. Van Disseldorp et al, Eur J Vasc Endovasc Surg, 59: 81-91, 2020 2. Kok et al, J Vasc Surg 61: 1175-1185, 2015 3. Domonkos et al. , Int. Angiol.38: 39-45, 2019 4. Molacek et al. Ann Vasc Surg 2011;25:1036-1042 5. Kontopodis et al. Theor Biol Med Model. 2013;10(1):1-9 Acknowledgements: This work was supported by e/MTIC MEDICAID project.