title: Biomechanical analysis of an aortic aneurysm model and its clinical application to thoracic aortic aneurysms for defining "saccular" aneurysms.
abstract: BACKGROUND
  We aimed to develop a simple structural model of aortic aneurysms using computer-assisted drafting (CAD) in order to create a basis of definition for saccular aortic aneurysms.
  
  
  RESULTS
  We constructed a simple aortic aneurysm model with 2 components: a tube similar to an aorta and an ellipse analogous to a bulging aneurysm. Three parameters, including the vertical and horizontal diameters of the ellipse and the fillet radius, were altered in the model. Using structural analysis with the finite element method, we visualized the distribution of the maximum principal stress (MPS) in the aortic wall and identified the area(s) of prominent stress. We then selected patients with thoracic aortic aneurysms in whom the aneurysm expansion rates were followed up and applied the theoretical results to the raw imaging data. The maximum MPS drastically increased at areas where the aspect ratio (vertical/horizontal) was <1, indicating that "horizontally long" hypothetical ellipses should be defined as "saccular" aneurysms. The aneurysm expansion rate for the patients with thoracic aneurysms conforming to these parameters was significantly high. Further, "vertically long" ellipses with a small fillet might be candidates for saccular aneurysms; however, the clinical data did not support this.
  
  
  CONCLUSIONS
  Based on the biomechanical analysis of a simple aneurysm model and the clinical data of the thoracic aortic aneurysms, we defined "horizontally long" aortic aneurysms with an aspect ratio of <1 as "saccular" aneurysms.
authors.affiliation: Division of Vascular Surgery, Department of Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan (T.A., K.H., Y.N., K.S., T.W.).
authors.forename: Takafumi
authors.initials: T
authors.lastname: Akai
authors.affiliation: Division of Vascular Surgery, Department of Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan (T.A., K.H., Y.N., K.S., T.W.).
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Hoshina
authors.affiliation: Department of Mechanical Engineering, Graduate School, Shibaura Institute of Technology, Tokyo, Japan (S.Y., H.T.).
authors.forename: Sota
authors.initials: S
authors.lastname: Yamamoto
authors.affiliation: Department of Mechanical Engineering, Graduate School, Shibaura Institute of Technology, Tokyo, Japan (S.Y., H.T.).
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Takeuchi
authors.affiliation: Division of Vascular Surgery, Department of Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan (T.A., K.H., Y.N., K.S., T.W.).
authors.forename: Youkou
authors.initials: Y
authors.lastname: Nemoto
authors.affiliation: Interfaculty Initiative in Information Studies/Institute of Industrial Science, The University of Tokyo, Tokyo, Japan (M.O.).
authors.forename: Marie
authors.initials: M
authors.lastname: Ohshima
authors.affiliation: Division of Vascular Surgery, Department of Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan (T.A., K.H., Y.N., K.S., T.W.).
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Shigematsu
authors.affiliation: Vascular Center, Sanno Hospital and Sanno Medical Center, Tokyo, Japan (T.M.).
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Miyata
authors.affiliation: Division of Cardiac Surgery, Department of Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan (H.Y., M.O.).
authors.forename: Haruo
authors.initials: H
authors.lastname: Yamauchi
authors.affiliation: Division of Cardiac Surgery, Department of Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan (H.Y., M.O.).
authors.forename: Minoru
authors.initials: M
authors.lastname: Ono
authors.affiliation: Division of Vascular Surgery, Department of Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan (T.A., K.H., Y.N., K.S., T.W.).
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Watanabe
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000783:Aneurysm / Q000000981:diagnostic imaging / Q000503:physiopathology; D017542:Aneurysm, Ruptured / Q000517:prevention & control; D017545:Aortic Aneurysm, Thoracic / Q000000981:diagnostic imaging* / Q000503:physiopathology; D001027:Aortography / Q000379:methods; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D018450:Disease Progression; D006801:Humans; D021621:Imaging, Three-Dimensional; D008955:Models, Cardiovascular; D008991:Monitoring, Physiologic; D015588:Observer Variation; D018570:Risk Assessment; D012494:Sampling Studies; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: aortic aneurysm; principal stress; saccular