Role of molecular imaging with positron emission tomographic in aortic aneurysms

Aortic aneurysms (AA) are often asymptomatic before the occurrence of acute, potentially fatal complications including dissection and/or rupture. Beyond aortic size, the ability to assess aortic wall characteristics and processes contributing to aneurysm development may allow improved selection of patients who may benefit from prophylactic surgical intervention. Current risk stratification for aneurysms relies upon routine noninvasive imaging of aortic size without assessing the underlying pathophysiologic processes, including features such as inflammation, which may be associated with aneurysm development and progression. The use of molecular imaging modalities with positron emission tomographic (PET) scan allows characterization of aortic wall inflammatory activity. Elevated uptake of Fuorine-2-deoxy-D-glucose (FDG), a radiotracer with elevated avidity in highly-metabolic cells, has been correlated with the development and progression of both abdominal and thoracic AA in a number of animal models and clinical studies. Other novel PET radiotracers targeting matrix metalloproteinases (MMPs), mitochondrial translocator proteins (TSPO) and endothelial cell adhesion molecules are being investigated for clinical utility in identifying progression of disease in AA. By further defining the activation of molecular pathways in assessing aortic regions at risk for dilatation, this imaging modality can be integrated into future clinical decision-making models.