Ascending aortic tissue biomechanics have been shown to reflect the histopathology of aneurysmal tissue and dissection risk. Accurate in vivo assessment of biomechanics may therefore improve current methods of evaluating dissection risk. Five in vivo imaging-based biomechanical parameters were investigated in this thesis as potential indicators of dissection risk:​ distensibility, compliance, arterial stiffness index (ASI), aortic pulse wave velocity (aPWV) and kinetic energy loss (KEL). Patients at higher risk of aortic dissection were identified based on comparison of ex vivo stiffness, energy loss and delamination strength between aneurysm and control populations. aPWV and KEL classified higher vs. lower risk patients with higher accuracy, greater sen- sitivity, and lower coefficient of variation than distensibility, compliance, and ASI. Thus, of the parameters assessed, aPWV and KEL best reflect tissue biomechanics and show potential as in vivo indicators of dissection risk.