Risk for Abdominal Aortic Aneurysms Determined by Molecular Imaging

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Based on new research published in the October issue of The Journal of Nuclear Medicine, numerous nascent identified markers could offer worthy insight to forecast the risk of rupture abdominal aortic aneurysms (AAA).

Imaging with positron emission tomography/computed tomography (PET/CT) has demonstrated that thick white blood cells in the outermost connective tissue in the vascular wall, increased C-reactive protein and a loss of smooth muscle cells in the middle layer of the vascular wall are all components that may allude to future AAA rupture.

An abdominal aneurysm puts stress on the wall of the aorta, which can cause it to rupture. Rupture of AAA is the 13th leading cause of death in western society and leads to considerable morbidity and mortality in the aging population. AAA is normally asymptomatic, so the accurate prediction of rupture is vital to positively impact public health.

In order to set potential markers that could be indicative of AAA rupture, the researchers performed 18F-FDG PET/CT scans on 18 patients with AAA initially diagnosed by ultrasound. Ten of the patients had no uptake of the 18F-FDG, while eight had positive uptake of the radiopharmaceutical. Biopsies were then taken from each of the patients; patients with positive 18F-FDG uptake had tissue removed from both the site of the positive uptake and a distant negative site of the aortic wall.risk for abdominal aortic

"Our approach allows us for the first time to our knowledge to analyze spots of high 18F-FDG uptake and compare them to a distant inactive zone of the same aneurysm. We further compared these biopsies to fragments collected in patients with negative 18F-FDGuptake. This strategy allowed for the discrimination of biologic alterations associated with 18F-FDGuptake that would help identify relevant biologic markers predictive of rupture. 18F-FDG Uptake Assessed by PET/CT in Abdominal Aortic Aneurysms Is Associated with Cellular and Molecular Alterations Prefacing Wall Deterioration and Rupture,” said lead author of the study, Audrey Courtois, PhD.

The tissue from the area of positive 18F-FDG uptake were catagorized by an increased number of inflammatory cells in the outermost connective tissue, a high level of C-reactive protein and a significant reduction in smooth muscle cells, as opposed to the biopsies from areas of no uptake. Moreover, an increase in several matrix metalloproteinases enzymes was noted in the tissue with positive 18F-FDG uptake.

"These data suggest that a PET scan with positive 18F-FDG uptake provide diagnostic support to proceed without delay to aneurysm surgery, despite a person's age or operative risk. However, the absence of FDG uptake at the level of the aneurismal aortic wall can help us make a safe decision to avoid unnecessary surgery and decrease the burden of health care costs," said Courtois.

"This 18F-FDG PET/CT study, with an arterial phase CT, allows us to fully characterize the disease, including the conventional risk factors such as the size of the aneurysm. Although much of the current research is being conducted in the field of oncology, the current study further strengthens 18F-FDG PET/CT as a decisive tool in the management of inflammatory disorders,” she added.