Fast Approximate Quantification of Endovascular Stent Graft Displacement Forces in the Bovine Aortic Arch Variant

Figures

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  Figure 1.. Aortic arch classification. Aortic arch classification in types I, II, and III and subdivision in the Ishimaru’s zones, ie, zones 0 (Z0), 2 (Z2) and 3 (Z3).

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  Figure 2.. Study workflow and displacement forces computation. Patient-specific 3D geometry (a) used to simulate pulsatile aortic blood flow through CFD analysis (b); blood pressure and shearing stresses acting on the aortic wall surface (c) were extracted to compute displacement forces (d). Assuming a mean blood pressure acting on the aortic wall (e), we defined a novel fast-approximate quantification of aortic displacement forces (f). CFD, computational fluid dynamics; CT, computed tomography; DF, displacement force.

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  Figure 3.. Fast-approximate magnitude quantification of displacement force |DFfast| (a) and equivalent surface traction |ESTfast| (b), distinguishing between arch type and zones, in the healthy CILCA subjects.

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  Figure 4.. Magnitude and direction of the aortic shape vector S (a) for each analyzed healthy CILCA anatomy within the corresponding arch type subgroup; (b) direction cosines along the left-right ( α ), anterior-posterior ( β ) and superior-inferior ( γ ) anatomical directions computed for each healthy and aneurysmatic (c) anatomy with CILCA arch configuration.

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  Figure 5.. Sensitivity of S to grid space-resolution: variation of the shape vector S , in terms of magnitude| S | and direction cosines (α, β, γ) at different levels of spatial resolution (expressed in terms of the characteristic triangle dimension RC) of the aortic surface grid employed for the computation of displacement forces according to the fast-approximate method.

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  Figure 6.. CFD-derived magnitude of (a) displacement force |DFCFD| and (b) equivalent surface traction |ESTCFD| , distinguishing between arch type and zones, in the healthy CILCA subjects. CFD, computational fluid dynamics.

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  Figure 7.. Pairwise comparison in terms of (a) |DF| and (b) |EST| results between fast-approximate approach and CFD gold-standard techniques, in all the simulated aortic anatomies. CFD, computational fluid dynamics; DF, displacement force; EST, equivalent surface traction.

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  Figure 8.. Bland-Altman plot (a) of the differences between |DFfast| and |DFCFD| gold-standard; (b) |DF| correlation between fast-approximate and CFD methods; (c) Bland-Altman plots of percentage |DF| differences within each landing zone; (d) angle (δ) between the same DF vector computed according to fast-approximate approach and CFD analysis, respectively. CFD, computational fluid dynamics; DF, displacement force.

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  Figure 9.. Repartition of displacement force magnitude between |DFCFD,p| and |DFCFD,τ| according to (a) blood pressure and (b) wall shear stress contributions, respectively. CFD, computational fluid dynamics; DF, displacement force.

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  Figure 10.. Impact of the dimension (ie, in terms of radius) of vessel branching on the computation of the shape vector S in a straight cylindric surface (a) and in a curved pipe (b).