Magnetic Resonance Elastography in Patients With Abdominal Aortic Aneurysms

Overview

The main objective of this study is to utilize Magnetic Resonance Elastography (MRE) to determine tissue stiffness of abdominal aortic aneurysms (AAA). For patients with AAA, MRE is a more sensitive and superior method of determining the risk for rupture of AAA based on stiffness estimates when compared to the current, crude method of assessing risk based on measurement of the diameter of the aneurysm. The investigators will also validate the stiffness estimates against gold standard i.e. mechanical testing and histopathology only AAA patients undergoing AAA surgery.

Currently, MRE is a clinical tool used to assess hepatic fibrosis at many institutions. MRE is superior to invasive techniques (i.e. biopsies) and mechanical testing in that it is noninvasive and can be performed in vivo under physiologic conditions. MRE could make diagnosing stiffness widely available and could revolutionize the diagnosis and treatment of numerous other diseases affecting stiffness of soft tissues. Aortic wall "stiffness" is a fundamental biomechanical parameter that reflects the structural integrity of normal and aneurysmal aortic tissue. AAAs enlarge over time leading to sudden rupture and death in up to 90% of patients. Surgical or endovascular aneurysm repair (EVAR) is recommended for AAAs \> 5.5 cm in diameter. However, previous studies have reported a high percentage (13%) of smaller AAAs (\<5 cm) go on to rupture, and an even higher percentage (60%) of larger AAAs (\>5 cm) remain stable. Despite the poor prognostic value of aortic diameter, it is still the primary parameter used to time surgical repair. It is known that changes in stiffness of AAA can reveal important information on extra-cellular matrix content; a key factor in the pathophysiological development of AAA and the risk for rupture. A non-invasive, spatially resolved estimate of aortic stiffness may provide a superior determinant of the risk for rupture compared to the currently used anatomical measures. The relationship between non-invasively measured wall stiffness (WS) and the structural integrity of the aortic wall must be further elucidated. Therefore, aortic MRE can be used as a noninvasive tool to estimate the stiffness of AAAs and can provide superior diagnostic and prognostic information in patients with developing AAA disease. Entry to this study is open to men and women aged 18 years and older, and to all racial and ethnic subgroups. Two separate groups of patients with AAA will be recruited. One group will be patients who have been diagnosed with AAA and are monitored to observe the size of the AAA. The other group is comprised of patients who are scheduled for surgical repair of AAA.