title: Aortic dissection simulation models for clinical support: fluid-structure interaction vs. rigid wall models.
abstract: BACKGROUND
  The management and prognosis of aortic dissection (AD) is often challenging and the use of personalised computational models is being explored as a tool to improve clinical outcome. Including vessel wall motion in such simulations can provide more realistic and potentially accurate results, but requires significant additional computational resources, as well as expertise. With clinical translation as the final aim, trade-offs between complexity, speed and accuracy are inevitable. The present study explores whether modelling wall motion is worth the additional expense in the case of AD, by carrying out fluid-structure interaction (FSI) simulations based on a sample patient case.
  
  
  METHODS
  Patient-specific anatomical details were extracted from computed tomography images to provide the fluid domain, from which the vessel wall was extrapolated. Two-way fluid-structure interaction simulations were performed, with coupled Windkessel boundary conditions and hyperelastic wall properties. The blood was modelled using the Carreau-Yasuda viscosity model and turbulence was accounted for via a shear stress transport model. A simulation without wall motion (rigid wall) was carried out for comparison purposes.
  
  
  RESULTS
  The displacement of the vessel wall was comparable to reports from imaging studies in terms of intimal flap motion and contraction of the true lumen. Analysis of the haemodynamics around the proximal and distal false lumen in the FSI model showed complex flow structures caused by the expansion and contraction of the vessel wall. These flow patterns led to significantly different predictions of wall shear stress, particularly its oscillatory component, which were not captured by the rigid wall model.
  
  
  CONCLUSIONS
  Through comparison with imaging data, the results of the present study indicate that the fluid-structure interaction methodology employed herein is appropriate for simulations of aortic dissection. Regions of high wall shear stress were not significantly altered by the wall motion, however, certain collocated regions of low and oscillatory wall shear stress which may be critical for disease progression were only identified in the FSI simulation. We conclude that, if patient-tailored simulations of aortic dissection are to be used as an interventional planning tool, then the additional complexity, expertise and computational expense required to model wall motion is indeed justified.
authors.affiliation: Mechanical Engineering, University College London, Torrington Place, London, WC1E 7JE, UK. mona.alimohammadi.10@ucl.ac.uk.
authors.forename: Mona
authors.initials: M
authors.lastname: Alimohammadi
authors.affiliation: Mechanical Engineering, University College London, Torrington Place, London, WC1E 7JE, UK. joseph.sherwood@imperial.ac.uk.|Bioengineering, Imperial College London, South Kensington Campus, London, SW7 2BP, UK. joseph.sherwood@imperial.ac.uk.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Sherwood
authors.affiliation: Mechanical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK. morad.karimpour08@imperial.ac.uk.
authors.forename: Morad
authors.initials: M
authors.lastname: Karimpour
authors.affiliation: Vascular Unit, University College Hospital, 235 Euston Road, London, NW1 2BU, UK. o.agu@ucl.ac.uk.
authors.forename: Obiekezie
authors.initials: O
authors.lastname: Agu
authors.affiliation: Mechanical Engineering, University College London, Torrington Place, London, WC1E 7JE, UK. s.balabani@ucl.ac.uk.
authors.forename: Stavroula
authors.initials: S
authors.lastname: Balabani
authors.affiliation: Mechanical Engineering, University College London, Torrington Place, London, WC1E 7JE, UK. v.diaz@ucl.ac.uk.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Díaz-Zuccarini
mesh_terms: D000784:Aortic Dissection / Q000503:physiopathology*; D001011:Aorta / Q000503:physiopathology* / Q000648:ultrastructure; D001013:Aorta, Thoracic / Q000503:physiopathology* / Q000648:ultrastructure; D017545:Aortic Aneurysm, Thoracic / Q000503:physiopathology*; D001019:Aortic Rupture / Q000473:pathology / Q000503:physiopathology; D001027:Aortography; D003198:Computer Simulation; D005260:Female; D018056:Hemorheology; D006801:Humans; D008875:Middle Aged; D008955:Models, Cardiovascular; D009038:Motion; D057285:Precision Medicine; D033081:Shear Strength; D014057:Tomography, X-Ray Computed; D017539:Tunica Intima / Q000503:physiopathology; D014783:Viscosity