To prevent rupture of aortic aneurysms (locally dilated and weakened walls), a stent graft (metal wire-frame sealed with synthetics) can be placed inside the aorta (Figure 1). This procedure is referred to as endovascular aortic aneurysm repair (EVAR). Sealing and fixation of the stent graft to the aortic wall is crucial for successful outcome and failure hereof is often a reason for reintervention. Reinterventions are a burden for EVAR, both for the well-being of patients and for health care costs. The pulsatile blood flow challenges the sealing and fixation, yet knowledge on the interaction with the stent graft is limited.
Figure 1 . Schematic representation of an EVAR intervention in an infra-renal abdominal aortic aneurysm. Reproduced with permission from Droc et. al. 
Our objective is to provide insight in both the heartbeat-induced interaction between stent graft and adjacent vessels and configurational changes over time. With this research, we aim to identify parameters that aid the prediction of stent graft failure. This would allow for patient specific follow-up schemes and early identification of problems. In addition, stent graft manufacturers may optimize their designs based on this knowledge.
About the project
ECG-gated computed tomography (CT) enables motion analysis of implanted stent grafts. In 2011, Klein et al. developed algorithms to estimate stent graft motion by means of segmentation and image registration. In this project, Klein’s method is further developed, validated and applied to clinical data in order to investigate the dynamic behavior of stent grafts and their interaction with aortic wall during the cardiac cycle and over time. In collaboration with the Medisch Spectrum Twente hospital, the LSPEAS trial is conducted. Patients included is the trial receive ECG-gated CT scans at standardized time points until two years of follow-up. In 2017, the LSPEAS F-EVAR national multicenter trial was launched. Patients with complex abdominal aneurysms who undergo fenestrated EVAR are included. Motion and configurational changes of stented branch vessels are investigated.
Figure 2. Example of a pre-operative CTA scan in which the aortic lumen is clearly visible (left) and a post-operative dynamic CT scan (right), in which the proximal part of the stent was segmented after applying an image registration algorithm. Colors represent three-dimensional displacement of points on the stent.
On the 31st of August 2015, Maaike Koenrades has won the Twente Graduate School Research Honours PhD Award for writing and presenting a research proposal to obtain external funding for this project. A 2-minutes movie has been published in which she explains her research.
 Droc, I., B. Calinescu, and D. Raithel, Abdominal Aortic Aneurysms - Actual Therapeutic Strategies. 2012: INTECH Open Access Publisher.