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Research Papers

Optimization of Strut Placement in Flow Diverter Stents for Four Different Aneurysm Configurations

[+] Author and Article Information
Hitomi Anzai

Institute of Fluid Science,
2-1-1 Katahira, Aoba-ku, Sendai,
Miyagi 980-8577, Japan
e-mail: anzai@biofluid.ifs.tohoku.ac.jp

Jean-Luc Falcone

University of Geneva,
7 route de Drize,
Carouge CH-1227, Switzerland
e-mail: Jean-Luc.Falcone@unige.ch

Bastien Chopard

University of Geneva,
7 route de Drize,
Carouge CH-1227, Switzerland
e-mail: Bastien.Chopard@unige.ch

Toshiyuki Hayase

Institute of Fluid Science,
Tohoku University,
2-1-1 Katahira, Aoba-ku, Sendai,
Miyagi 980-8577, Japan
e-mail: hayase@ifs.tohoku.ac.jp

Makoto Ohta

Institute of Fluid Science,
Tohoku University,
2-1-1 Katahira, Aoba-ku, Sendai,
Miyagi 980-8577, Japan
e-mail: ohta@biofluid.ifs.tohoku.ac.jp

Contributed by the Bioengineering Division of ASME for publication in the Journal of Biomechanical Engineering. Manuscript received June 18, 2013; final manuscript received April 2, 2014; accepted manuscript posted April 11, 2014; published online May 6, 2014. Assoc. Editor: Francis Loth.

J Biomech Eng 136(6), 061006 (May 06, 2014) (7 pages) Paper No: BIO-13-1266; doi: 10.1115/1.4027411 History: Received June 18, 2013; Revised April 02, 2014; Accepted April 11, 2014

A modern technique for the treatment of cerebral aneurysms involves insertion of a flow diverter stent. Flow stagnation, produced by the fine mesh structure of the diverter, is thought to promote blood clotting in an aneurysm. However, apart from its effect on flow reduction, the insertion of the metal device poses the risk of occlusion of a parent artery. One strategy for avoiding the risk of arterial occlusion is the use of a device with a higher porosity. To aid the development of optimal stents in the view point of flow reduction maintaining a high porosity, we used lattice Boltzmann flow simulations and simulated annealing optimization to investigate the optimal placement of stent struts. We constructed four idealized aneurysm geometries that resulted in four different inflow characteristics and employed a stent model with 36 unconnected struts corresponding to the porosity of 80%. Assuming intracranial flow, steady flow simulation with Reynolds number of 200 was applied for each aneurysm. Optimization of strut position was performed to minimize the average velocity in an aneurysm while maintaining the porosity. As the results of optimization, we obtained nonuniformed structure as optimized stent for each aneurysm geometry. And all optimized stents were characterized by denser struts in the inflow area. The variety of inflow patterns that resulted from differing aneurysm geometries led to unique strut placements for each aneurysm type.

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Figures

Grahic Jump Location
Fig. 3

Streamlines through the aneurysm neck (left: no stent, center: initial stent, right: optimal stent). (a) Straight. (b) U-1. (c) U-3. (d) U-5.

Grahic Jump Location
Fig. 4

Contour images of the velocity perpendicular to the neck and stent structure. (left: no stent, center: initial stent, right: optimal stent) white circle with dotted line indicates the area where the streamlines enter from the parent artery. (a) Straight. (b) U-1. (c) U-3. (d) U-5.

Grahic Jump Location
Fig. 5

Histogram of velocity component perpendicular to the neck. (a) Straight. (b) U-1. (c) U-3. (d) U-5.

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Fig. 2

Schematic of the stent model

Grahic Jump Location
Fig. 1

Idealized sidewall aneurysms. (a) Straight. (b) U-1. (c) U-3. (d) U-5.

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