Towards an improvement in aneurysm assessment: coupling 3D reconstruction tools with engineering know-how

Purpose: Currently, abdominal aortic aneurysms (AAAs), which are a permanent dilation of the aorta, are treated surgically when the maximum transverse diameter surpasses 5.0cm. AAA rupture occurs when the locally acting wall stress exceeds the locally acting wall strength. There is a need to review the current diameter-based criterion, and so it may be clinically useful to develop an additional tool to aid the surgical decision-making process. A Finite Element Analysis Rupture Index (FEARI) was developed. 3D reconstructions were also performed to aid endovascular aneurysm repair (EVAR). Methods: Patient-specific AAAs were reconstructed using Mimics v12 and analysed for use with the FEARI. Previous experimental work on determination of ultimate tensile strengths (UTS) from AAA tissue samples was implemented in this study. By combining peak wall stress along with average regional UTS, a new approach to the estimation of patient-specific rupture risk has been developed. A further 4 AAA cases were reconstructed and analysed in Mimics v12 to determine stent-graft sizes and plan EVAR. Results: A detailed examination of these cases utilising the FEARI analysis suggested that there was a possibility that some of the AAAs may have been less prone to rupture than previously considered. 3D reconstructions as a surgical guidance tool proved to be very effective in accurate device sizing and pre-surgical planning. Conclusions: It is proposed that FEARI, used alongside other rupture risk factors, may improve the current surgical decision-making process. The use of FEARI as an additional tool for rupture prediction may provide a useful adjunct to the diameterbased approach in surgical decision-making. 3D reconstructions aid surgeons in planning EVAR, in particular in the case of extreme cases of aneurismal disease.