Thoracic aortic aneurysms (TAA) predispose patients to increased risk of sudden death due to aortic rupture or dissection. The purpose of this study is to understand what factors predict enlargement of thoracic aortic aneurysms in subjects with a genetic form of abnormal connective tissue called Marfan syndrome. This abnormal connective tissue commonly affects the aorta and can make the aorta stiff and inflamed. We also want to study the potential clinical utility of image based predictors of enlargement before actual anatomical enlargement. In order to do this, we will perform positron emission tomography (PET) scans using radiopharmaceuticals (drug molecules containing radioactive atoms).

In each subject, we plan to perform two PET scans using [18F]-Fluorodeoxyglucose (FDG), and [11C]-PK11195 (PK). Both these PET scans have the potential to identify the areas of inflammation associated with the thoracic aortic enlargement. As part of the each PET scan, we will also obtain a low-dose, non-diagnostic computed tomography (CT) scan, which is needed to help process the PET data. Two MRI scans, both clinically indicated test, will be performed one year apart (timing is decided by the clinical physician). Central blood pressure and carotid tonometry (carotid probe waveform detection) measurements will be made prior to or after the baseline MRI.

FDG is Food and Drug Administration (FDA) approved PET drug for routine clinical studies in patients with cancer or diseases of brain and heart. The FDG-PET/CT scan allows us to visualize inflammatory activity within the blood vessel wall. However, FDG is not specifically approved by the FDA for blood vessel examinations or to image inflammation in the blood vessels. [11C]-PK11195 is an investigational new drug (IND) and not approved by FDA for routine clinical imaging studies. However, this new IND drug (study drug) has been administered to several thousand patients worldwide and has shown to be quite safe. The [11C]-PK11195 agent binds to macrophages at the site of inflammation, and allows us to visualize inflammatory activity within the blood vessel wall.