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Aneurysm - a diverticulum the arterial wall due to its stretching

Unsteady hemodynamic simulation of cerebral aneurysms А.А. Cherevko , А. P . Chupakhin , А.А. Yanchenko ( IGiL SB RAS , NSU ). Aneurysm - a diverticulum the arterial wall due to its stretching.

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Aneurysm - a diverticulum the arterial wall due to its stretching

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  1. Unsteady hemodynamic simulation of cerebral aneurysmsА.А.Cherevko, А.P.Chupakhin, А.А.Yanchenko( IGiL SB RAS, NSU)

  2. Aneurysm - a diverticulum the arterial wall due to its stretching Place the appearance of aneurysms: bifurcation of vessels, space anatomical changes structure of vessels, next to the arteriovenous malformation. The reasons of occurrence: structural changes in the arteries, hemodynamic factor, mechanical damage of the vessel wall. Found in 0.3-5% of the adult population, a rare occurrence in children. Aneurysmal wall material differs from the material of a healthy vessel wall.

  3. Endovascular treatment of aneurysms aneurysm Аневризма catheter treatment: embolization stenting riskiness:rupturerecanalization

  4. Aneurysmshemodynamic modeling • Preoperative simulation should be carried out quickly enough - 1-2 days • The most simple and effective model, giving sufficient accuracy • Geometry of aneurysm - tomography data (NNIIPK) • Flow parameters - intravascular pressure and velocity sensor (NNIIPK) • CFD calculations – ANSYS (IGiL, NSU computer cluster) • Stages of work: • Reconstruction of the geometry from the CT scan • Numerical simulation of hemodynamics with fixed walls of the vessel • Simulation of the stress-strain state of the wall using the pressure distribution obtained in the previous stage of the calculation What hemodynamic parameters determine the effectiveness of the operation? What is the safe range of variation of these parameters?

  5. Vessel geometry before after control a year later Progressive rectification of bifurcation

  6. Mathematical Statement of the Problem Blood flow described by the Navier-Stokes equations for three-dimensional motion of an incompressible, viscous Newtonian fluid where v - velocity, p - pressure, ν - the kinematic viscosity, Ω - the internal volume of the computational domain, including the configuration of the vessels in the form of the tee and an aneurysm located at the bifurcation. γ = ∂ Ω - boundary wall of the vessel. Boundary conditions: where vreal and preal - speed and pressure, taken from the sensor during operation. Гin-cross section of the parent vessel tee; Г1out, Г2out - cross sections of child vessels

  7. The computational domain (Before surgery)

  8. Clinical velocity and pressure data

  9. Hydrodynamics

  10. computational grid Used computational grid of tetrahedra. When mesh refinement is 5 times - deviation of pressure is less than 1%, slightly larger deviations (up to 5%) observed in the values ​​of the velocity modulus. Further refinement grid has almost no influence on the result.

  11. streamlines (up to stenting) High speeds, vorticity within the aneurysm.

  12. Streamlines (after stenting) Reducing the area of ​​maximum speed. The appearance of "almost circular" vortex.

  13. Streamlines (control a year later) Weak vorticity, velocity decreased.

  14. WSS (up to stenting) Clearly visible zones of large WSS on bends (not on the cupola!).

  15. WSS (after stenting) Zones of large WSS decreased.

  16. WSS (control a year later) Zone of high stress is very small, almost all within the normal range (1.5-2 Pa).

  17. Energy flux (up to stenting) Loss of energy flux is ~ 9%, which is quite a large value at longer tee is approximately equal to 2 cm

  18. Energy flux (after stenting) After surgery, vascular geometry is restored almost to the health and loss constitute ~ 4%.

  19. Energy flux (control a year later) Energy loss is ~ 1%.

  20. mechanics

  21. wall parameters Unsteady calculation. Aneurysm's zone has a different properties.

  22. Total deformation and von-Mises stress (up to stenting) Maxima concentrated on the aneurysm's cupola. Compared with the stationary calculations: maximum deformations slightly increased. Stress are increased (4.335e5 against 3.0894e5). Localization of maximums is not changed.

  23. Total deformation and von-Mises stress (after stenting) Maximum values ​​decreased slightly. Compared with the stationary calculations: Localization of maximums is not changed.

  24. Total deformation and von-Mises stress (control a year later) The maximum strain decreased by 2 times, the maximum stress at 1/3.

  25. Comparison of simulation results. (Maxima of displacement and von- Mises stress) 1 mmHg = 133.322 Pа

  26. conclusions • Maxima of stresses and displacements in the steady and unsteady calculations based differ in magnitude, but do not differ by location. • To identify "dangerous places" stationary calculation with allocation of area of the aneurysm can be used. • To find the magnitudes of stresses and displacements ​​need to use unsteady calculations with allocation of area of the aneurysm. • Unsteady calculation without separation zone of the aneurysm is not sufficiently accurate

  27. Time costs: Steady calculation: a few minutes Transient calculation: 3 hours for 1 simulation second

  28. Thank you for your attention!

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