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Research Papers

Comparison Among Different High Porosity Stent Configurations: Hemodynamic Effects of Treatment in a Large Cerebral Aneurysm

[+] Author and Article Information
Breigh N. Roszelle

Daniel Felix Ritchie School of Engineering
and Computer Science,
Department of Mechanical
and Materials Engineering,
University of Denver,
Clarence M. Knudson Hall,
2390 South York Street #200,
Denver, CO 80208
e-mail: breigh.roszelle@du.edu

Priya Nair, M. Haithem Babiker, Justin Ryan

School of Biological
and Health Systems Engineering,
Arizona State University,
Tempe, AZ 85287

L. Fernando Gonzalez

Department of Neurological Surgery,
Jefferson Medical College,
Philadelphia, PA 19107

David Frakes

School of Biological
and Health Systems Engineering,
Arizona State University,
Tempe, AZ 85287;
School of Electrical,
Computer, and Energy Engineering,
Arizona State University,
Tempe, AZ 85287

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1Corresponding author.

Contributed by the Bioengineering Division of ASME for publication in the Journal of Biomechanical Engineering. Manuscript received September 2, 2013; final manuscript received December 11, 2013; accepted manuscript posted December 16, 2013; published online February 5, 2014. Editor: Victor H. Barocas.

J Biomech Eng 136(2), 021013 (Feb 05, 2014) (9 pages) Paper No: BIO-13-1403; doi: 10.1115/1.4026257 History: Received September 02, 2013; Revised December 11, 2013; Accepted December 16, 2013

Whether treated surgically or with endovascular techniques, large and giant cerebral aneurysms are particularly difficult to treat. Nevertheless, high porosity stents can be used to accomplish stent-assisted coiling and even standalone stent-based treatments that have been shown to improve the occlusion of such aneurysms. Further, stent assisted coiling can reduce the incidence of complications that sometimes result from embolic coiling (e.g., neck remnants and thromboembolism). However, in treating cerebral aneurysms at bifurcation termini, it remains unclear which configuration of high porosity stents will result in the most advantageous hemodynamic environment. The goal of this study was to compare how three different stent configurations affected fluid dynamics in a large patient-specific aneurysm model. Three common stent configurations were deployed into the model: a half-Y, a full-Y, and a crossbar configuration. Particle image velocimetry was used to examine post-treatment flow patterns and quantify root-mean-squared velocity magnitude (VRMS) within the aneurysmal sac. While each configuration did reduce VRMS within the aneurysm, the full-Y configuration resulted in the greatest reduction across all flow conditions (an average of 56% with respect to the untreated case). The experimental results agreed well with clinical follow up after treatment with the full-Y configuration; there was evidence of thrombosis within the sac from the stents alone before coil embolization was performed. A computational simulation of the full-Y configuration aligned well with the experimental and in vivo findings, indicating potential for clinically useful prediction of post-treatment hemodynamics. This study found that applying different stent configurations resulted in considerably different fluid dynamics in an anatomically accurate aneurysm model and that the full-Y configuration performed best. The study indicates that knowledge of how stent configurations will affect post-treatment hemodynamics could be important in interventional planning and demonstrates the capability for such planning based on novel computational tools.

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Figures

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Fig. 1

Illustrations of three different stent configurations: (a) half-Y, (b) crossbar, and (c) full-Y

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Fig. 2

Computational model of the patient-specific aneurysm

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Fig. 3

Image sequence showing the simulated deployment of two Neuroform stents in a full-Y configuration. The final FE simulation result (pane 8) was used in a fluid dynamic simulation.

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Fig. 4

Reductions in VRMS for all flow conditions explored. The percentages shown in each column are the reductions in VRMS with respect to the untreated case.

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Fig. 5

Velocity vector flow patterns within the aneurysm for each stent deployment configuration at 4 ml/s steady flow

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Fig. 6

Velocity vector flow patterns within the aneurysm for each stent deployment configuration at 4 ml/s pulsatile flow

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Fig. 7

Fluid dynamic simulation results showing 3D streamtraces for the untreated case (a) and the full-Y configuration (b) at 4 ml/s steady flow

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Fig. 8

Simulated WSS contour plots for the untreated case (a) and the full-Y configuration (b). Contour plots are shown for the posterior view of the aneurysm (view 1—(a) and (b)) and the anterior view (view 2—(c) and (d)).

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Fig. 9

Simulated contour plot of the WSSG gradient for the untreated case (a) and the full-Y configuration (b). Contour plots are shown for the posterior view of the aneurysm (view 1—(a) and (b)) and anterior view (view 2—(c) and (d)).

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Fig. 10

Digital subtraction angiography images of the large aneurysm at different stages of treatment: (a) immediately after stent treatment, (b) one month after stent treatment, before coiling (note the partial occlusion of the sac), and (c) one year after stent assisted coiling

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Fig. 11

Comparison of VRMS reductions associated with all three stent configurations in both the patient-specific anatomical model and a previously examined idealized model

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