High levels of 18F-FDG uptake in aortic aneurysm wall are associated with high wall stress.

Abstract

Functional imaging using positron emission tomography (PET) showed increased metabolic activities in the aneurysm wall prior to rupture, whereas separate studies using finite element analysis techniques found the presence of high wall stresses in aneurysms that subsequently ruptured. This case series aimed to evaluate the association between wall stress and levels of metabolic activities in aneurysms of the descending thoracic and abdominal aorta. Five patients with aneurysms in the descending thoracic aorta or abdominal aorta were examined using positron emission tomography-computed tomography (PET-CT). Patient-specific models of the aortic aneurysms were reconstructed from CT scans, and wall tensile stresses at peak blood pressure were calculated using the finite element method. Predicted wall stresses were qualitatively compared with measured levels of 18F-fluoro-2-deoxy-glucose (18F-FDG) uptakes in the aneurysm wall. The distribution of wall stress in the aneurysm wall was highly non-uniform depending on the individual geometry. Predicted high wall stress regions co-localised with areas of positive 18F-FDG uptake in all five patients examined. In the two ruptured cases, the locations of rupture corresponded well with regions of elevated metabolic activity and high wall stress. These preliminary observations point to a potential link between high wall stress and accelerated metabolism in aortic aneurysm wall and warrant further large population-based studies.