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Research Papers

Studies on Design Optimization of Coronary Stents

[+] Author and Article Information
K. Srinivas1

Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japank.srinivas.usyd.edu.au

T. Nakayama, M. Ohta, S. Obayashi

Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan

T. Yamaguchi

Department of Bioengineering and Robotics, Graduate School of Engineering, Tohoku University, Aoba 1, Sendai 980-8579, Japan

1

Corresponding Author. Permanent address: School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, NSW 2006, Australia.

J. Med. Devices 2(1), 011004 (Mar 10, 2008) (7 pages) doi:10.1115/1.2885145 History: Received February 27, 2007; Revised January 29, 2008; Published March 10, 2008

The stent design itself seems to be one of the factors responsible for restenosis. As a remedy, the present work attempts to perform a design optimization of coronary stents from a hemodynamic point of view. For the purpose, we have applied the principles of modern exploration of design space restricting ourselves to two-dimensional considerations. Width, thickness, and spacing of the struts of the stent formed the design variables. The objectives chosen for optimization were the vorticity generated, length of recirculation zone, and the reattachment distance in between the struts. Both semicircular and rectangular cross sections of stents were included. Starting with the range of design variables, sample stent cases were generated using Latin hypercube sampling. Objective functions were calculated for each of these by computing the two-dimensional flow using software FLUENT under the assumption of a steady, Newtonian flow considering a model stent with three struts. This was followed by Kriging to construct a response surface, which gives the relationship between the objectives and the design variables. The procedure gave nondominated fronts, which consist of optimized designs. Stents with minimum vorticity, with minimum recirculation distance, and the ones with maximum reattachment length in between struts were generated. The procedure is capable of producing the optimum set of design variables to achieve the prescribed objectives.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Geometry of the test case

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Figure 2

Schematic showing length of recirculation zone L and reattachment distance DR

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Figure 3

Boundary conditions for computation

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Figure 4

Geometry of stent with semicircular struts

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Figure 5

Nondominated front for stent with semicircular struts. Stent A has least vorticity, B has highest shear stress past S3, and C is a compromise stent.

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Figure 6

Streamlines in region of interest for stents with semicirculat struts, A–C; note the absence of recirculation in each of them

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Figure 7

Comparison of shear stress past the stents with semicircular struts. Shear stress past S3 is highest for B

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Figure 8

Geometry of stent with rectangular struts

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Figure 9

Nondominated front in Δω−L space for stent with rectangular struts. A has least vorticity, B has the least recirculation length, and C is a compromise stent.

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Figure 10

Nondominated front in Δω-RDI space for stent with rectangular struts. D has least vorticity, E has the highest reattachment length, and F is a compromise stent.

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Figure 11

Streamlines in region of interest for stents with rectangular struts, A–F

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