title: Patient specific stress and rupture analysis of ascending thoracic aneurysms.
abstract: 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.
authors.affiliation: Center for Biomedical and Healthcare Engineering, Ecole Nationale Supérieure des Mines de Saint-Etienne, CIS-EMSE, CNRS:UMR5146, LCG, Saint Etienne, France. Electronic address: olfa.trabelsi@emse.fr.
authors.forename: Olfa
authors.initials: O
authors.lastname: Trabelsi
authors.affiliation: Center for Biomedical and Healthcare Engineering, Ecole Nationale Supérieure des Mines de Saint-Etienne, CIS-EMSE, CNRS:UMR5146, LCG, Saint Etienne, France.
authors.forename: Frances M
authors.initials: FM
authors.lastname: Davis
authors.affiliation: Dipartimento di Chimica, Materiali e Ingegneria Chimica "Giulio Natta", Politecnico di Milano, Milan, Italy.
authors.forename: Jose F
authors.initials: JF
authors.lastname: Rodriguez-Matas
authors.affiliation: Center for Biomedical and Healthcare Engineering, Ecole Nationale Supérieure des Mines de Saint-Etienne, CIS-EMSE, CNRS:UMR5146, LCG, Saint Etienne, France; Hôpital Nord, Cardiovascular Surgery Service, CHU de Saint Etienne, F-42055 Saint-Etienne, France.
authors.forename: Ambroise
authors.initials: A
authors.lastname: Duprey
authors.affiliation: Center for Biomedical and Healthcare Engineering, Ecole Nationale Supérieure des Mines de Saint-Etienne, CIS-EMSE, CNRS:UMR5146, LCG, Saint Etienne, France.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Avril
mesh_terms: D000368:Aged; D017545:Aortic Aneurysm, Thoracic / Q000000981:diagnostic imaging / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D004867:Equipment Design; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D012189:Retrospective Studies; D012306:Risk; D018570:Risk Assessment; D012421:Rupture; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed
keywords: Aneurysm rupture; Ascending thoracic aortic aneurysm; Finite element analysis; Patient specific material properties; Rupture risk; Wall stress