3D imaging of abdominal aortic aneurysms: Techniques and application

Background The advancements in medical imaging technology over the last number of years has revolutionised the management and treatment of all aspects of healthcare. Computed tomography and magnetic resonance imaging have led to the development of reconstruction software that allows internal bodily structures to be easily visualised in 3D. These developments have led to improved surgical planning and treatment. The assessment of abdominal aortic aneurysms (AAA) has benefited greatly from these advancements. There is currently much debate as when to surgically repair these lifethreatening dilations of the aorta and 3D reconstructions of AAAs have led to many new diagnostic tools and rupture-prediction indices. This chapter explores some of the more recent developments in this area. Methods Imaging of patient-specific AAAs opens many possibilities for the surgical-planning and biomechanical examination of the diseased vessel. 3D reconstructions allow for exact measurements and dimensions of stent-grafts to be obtained. These 3D reconstructions also form the basis for all numerical modelling techniques, be it finite element analysis, computational fluid dynamics or fluid-structure interaction. Computational and experimental examination of the wall stress within a particular AAA can reveal important information regarding possible rupture sites, and relationships between wall stress and geometrical factors. 3D imaging has allowed the development of new parameters that may better assess the likelihood of AAA rupture on a patient-specific basis. Postoperative monitoring of the stent-graft also benefits from 3D imaging. The in-vivo pulsatile forces acting on the stent-graft, which contribute to stent-graft migration and may result in sac re-pressurisation, can be numerically determined on a patient-specific basis. The use of 3D reconstructions also allows for improved experimental testing through exact AAA replication and numerical validation models. Results New diagnostic tools and rupture-prediction methods have revealed that similarly sized AAAs may have significantly different rupture potentials. Experimental approaches to AAA assessment have shown that AAAs will rupture at regions of elevated wall stress and not necessarily at areas of maximum diameter. Fluid-structure interaction is a useful tool for assessing post-operative stent-graft performance, as both the haemodynamic forces acting on the stent-graft and wall stress of the aneurysm are of interest. Numerical modelling has also allowed for the design and evaluation of novel stent-graft designs such as the tapered device presented in this chapter. Conclusion 3D imaging has allowed engineers to aid clinicians in the management and treatment of AAAs. 3D reconstructions form the basis for many engineering techniques, both numerical and experimental, and help contribute to the decision to either surgically intervene and repair an AAA, or monitor the expansion of the AAA with regular imaging. There is a need to implement alternative factors in the clinical decision-making process and the methodologies reported in this chapter may be beneficial in future AAA rupture assessment and management.