An ascending
thoracic aortic aneurysm (
ATAA) is a serious medical condition which, more often than not, requires surgery.
Aneurysm diameter is the primary clinical criterion for determining when surgical intervention is necessary but, biomechanical studies have suggested that the diameter criterion is insufficient. This manuscript presents a method for obtaining the patient specific wall stress distribution of the
ATAA and the retrospective
rupture risk for each patient. Five human ATAAs and the preoperative dynamic CT scans were obtained during elective surgeries to replace each patient's
aneurysm with a synthetic graft. The material properties and
rupture stress for each tissue sample were identified using bulge inflation tests. The dynamic CT scans were used to generate patient specific geometries for a finite
element (FE) model of each patient's
aneurysm. The material properties from the bulge inflation tests were implemented in the FE model and the wall stress distribution at four different pressures was estimated. Three different
rupture risk assessments were compared: the maximum diameter, the
rupture risk index, and the overpressure index. The peak wall stress values for the patients ranged from 28% to 94% of the
ATAA's failure stress. The
rupture risk and overpressure indices were both only weakly correlated with diameter (ρ=-0.29, both cases). In the future, we plan to conduct a large experimental and computational study that includes asymptomatic patients under surveillance, patients undergoing elective surgery, and patients who have experienced
rupture or dissection to determine if the
rupture risk index or maximum diameter can meaningfully differentiate between the groups.