Intellectual Merit: Abdominal aortic aneurysms (AAAs) represent permanent, localized swellings of the aorta that occur where the diseased vessel is weakened. AAA rupture accounts for 14,000 deaths in the US annually. A growing body of literature has developed in recent years concerned with methods for quantitatively evaluating the distribution and magnitude of stress in patient-specific models of the aneurysm wall, since mechanical stress is thought to be the cause of rupture. However, the role of blood flow in creating wall stress has not been addressed to date. Accordingly, the research objective of this award is to develop a combined experimental-computational physiologic wall stress analysis (PWSA) procedure that evaluates wall stress distributions and maxima in models accurately replicating the shape, non-uniform thickness and mechanical properties of individual patient AAAs. To accomplish this aim, AAA wall tissue samples will be collected from patients undergoing surgical repair. The mechanical properties of those samples will be measured, and an elastic material replicating the diseased wall stiffness will be used to fabricate a model replicating the shape of the patient lesion. Wall pressure in this model will be measured under flow conditions emulating the patient aorta. The measured wall pressure data will then be used as loading in a corresponding computational evaluation of stress levels within the wall. Broader Impact: Establishment of a protocol for accurate assessment of AAA wall stress using patient-specific information has the potential to significantly impact clinical AAA management. The proposed studies will provide the first quantitative measurements of pressure distributions using aneurysm phantoms with both realistic geometries and patient-derived mechanical properties, as well as the first quantitative evaluation of wall stress based entirely on patient properties. Furthermore, the project will permit us to continue to engage undergraduate as well as graduate students in our ongoing research efforts, expanding the research training, educational experience and opportunities available to the students involved. Moreover, we will take full advantage of infrastructure in place at Tufts University for recruiting and retaining women and underrepresented minorities in research. These include undergraduate outreach programs in Computer Science, Biomedical Engineering and robotics. In addition, the Tufts University School of Medicine has conducted a highly successful NIH-funded minority outreach program for over ten years, permitting underrepresented undergraduates to spend summers at Tufts involved in biomedical science research. Research-driven training activities generated through this project will engage students in cross-disciplinary computational thinking, thus providing critical training for future scientists and engineers.
