title: Computational fluid dynamics simulation of a-v fistulas: from MRI and ultrasound scans to numeric evaluation of hemodynamics.
abstract: OBJECTIVE
  A-v anastomosis entails dramatic changes in hemodynamic conditions, which may lead to major alterations to the vessels involved; primarily dilatations and devastating stenoses. Wall shear stress is thought to play a key role in the remodeling of the vessels exposed to abnormal levels and oscillating wall shear stress. In this study we sought to develop a framework suitable for thorough in vivo analyses of wall shear stress and vessel morphology of a-v fistulas in patients.
  
  
  METHODS
  Using ultrasound and magnetic resonance imaging (MRI) transverse image stacks from six patient a-v fistulas were obtained. From the image stacks three-dimensional geometries of the patient fistulas were created using dedicated segmentation software. Geometries of three a-v fistulas were imported into finite element software in order to perform fluid flow simulations of blood flows and frictional forces on the vessel walls in the a-v fistulas. Boundary conditions for the simulations were obtained using both a MRI phase contrast and an ultrasound Doppler technique.
  
  
  RESULTS
  The segmentation of the six fistulas of very different age and morphology (two end-to-side and four side-to-side) showed the ability of the approach to create geometries of various fistula morphologies. Simulations of the three fistulas showed an instant picture of the present status of the exposure to different levels of wall shear stress and the morphological status in the vessel remodeling process.
  
  
  CONCLUSIONS
  The study demonstrated the capability of the CFD framework to analyze patient a-v fistulas on a regular basis using both MRI and ultrasound-based approaches.
authors: MR-center, Aarhus University Hospital, Skejby, Aarhus N, Denmark. niemann@mr.au.dk
authors: Anders Koustrup
authors: AK
authors: Niemann
authors: Samuel
authors: S
authors: Thrysoe
authors: Jens Vinge
authors: JV
authors: Nygaard
authors: John Michael
authors: JM
authors: Hasenkam
authors: Steffen Ellebaek
authors: SE
authors: Petersen
mesh_terms: D001166:Arteriovenous Shunt, Surgical / Q000009:adverse effects; D001783:Blood Flow Velocity; D003198:Computer Simulation; D020342:Finite Element Analysis; D017276:Friction; D006439:Hemodynamics; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008955:Models, Cardiovascular; D009716:Numerical Analysis, Computer-Assisted; D012039:Regional Blood Flow; D013314:Stress, Mechanical; D013997:Time Factors; D018608:Ultrasonography, Doppler; D034941:Upper Extremity / Q000098:blood supply*