Combined MR imaging and numerical simulation of flow in realistic arterial bypass graft models.
We report methods for (a) transforming a three-dimensional geometry acquired by magnetic resonance angiography (MRA) in vivo, or by imaging a model cast, into a computational surface representation, (b) use of this to construct a three dimensional numerical grid for computational fluid dynamic (CFD) studies, and (c) use of the surface representation to produce a stereo-lithographic replica of the real detailed geometry, at a scale convenient for detailed magnetic resonance imaging (MRI) flow studies. This is applied to assess the local flow field in realistic geometry arterial bypass grafts. Results from a parallel numerical simulation and MRI measurement of flow in an aorto-coronary bypass graft with various inlet flow conditions demonstrate the strong influence of the graft inlet waveform on the perianastomotic flow field. A sinusoidal and a multi harmonic coronary flow waveform both with a mean Reynolds number (Re) of 100 and a Womersley parameter of 2.7 were applied at the graft inlet. A weak axial flow separation region just distal to the toe was found in sinusoidal flow near end deceleration (Re = 25). At the same location and approximately the same point in the cycle (Re = 30) but in coronary flow, the axial flow separation was stronger and more spatially pronounced. No axial flow separation occurred in steady flow for Re = 100. Numerical predictions indicate a region in the vicinity of the suture line (where there is a local narrowing of the graft) with a wall shear magnitude in excess of five times that associated with fully developed flow at the graft inlet.
Papaharilaou
Y
Y
Biomedical Flow Group, Aeronautics Department, Imperial College of Science, Technology and Medicine, Prince Consort Road, London, UK.
Doorly
D J
DJ
Sherwin
S J
SJ
Peiro
J
J
Griffith
C
C
Cheshire
N
N
Zervas
V
V
Anderson
J
J
Sanghera
B
B
Watkins
N
N
Caro
C G
CG
D003198:Computer Simulation; D001026:Coronary Artery Bypass; D023921:Coronary Stenosis / Q000503:physiopathology / Q000601:surgery; D003331:Coronary Vessels / Q000503:physiopathology*; D006801:Humans; D018810:Magnetic Resonance Angiography; D008955:Models, Cardiovascular; D012039:Regional Blood Flow