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Research Papers

Hemodynamic Characterization of Geometric Cerebral Aneurysm Templates Treated With Embolic Coils

[+] Author and Article Information
Priya Nair

School of Biological and Health Systems Engineering,
Arizona State University,
501 E Tyler Mall,
BLDG ECG RM #334,
Tempe, AZ 85287
e-mail: priyanair@asu.edu

Brian W. Chong

School of Biological and Health Systems Engineering,
Arizona State University,
501 E Tyler Mall,
BLDG ECG RM #334,
Tempe, AZ 85287;
Mayo Clinic Hospital,
Phoenix AZ 85054
e-mail: Brian.W.Chong@asu.edu

Aprinda Indahlastari

School of Biological and Health Systems Engineering,
Arizona State University,
501 E Tyler Mall,
BLDG ECG RM #334,
Tempe, AZ 85287
e-mail: Aprinda.Indahlastari@asu.edu

Justin Ryan

School of Biological and Health Systems Engineering,
Arizona State University,
501 E Tyler Mall,
BLDG ECG RM #334,
Tempe, AZ 85287;
Phoenix Children's Hospital,
Phoenix, AZ 85006
e-mail: jrryan@asu.edu

Christopher Workman

School of Biological and Health Systems Engineering,
Arizona State University,
501 E Tyler Mall,
BLDG ECG RM #334,
Tempe, AZ 85287
e-mail: cworkma2@asu.edu

M. Haithem Babiker

Endovantage,
Scottsdale, AZ 85257
e-mail: haithem.babiker@endovantage.com

Hooman Yadollahi Farsani

School for Engineering of Matter,
Transport, and Energy,
Arizona State University,
Tempe, AZ 85287
e-mail: hyadolla@asu.edu

Carlos E. Baccin

Centro de NeuroAngiografia (CNA),
Hospital Beneficencia Portuguesa de São Paulo,
São Paulo, SP 01323-900, Brazil
e-mail: edubaccin@hotmail.com

David Frakes

School of Biological and Health Systems Engineering,
Arizona State University,
501 E Tyler Mall,
BLDG ECG RM #334,
Tempe, AZ 85287;
School of Electrical, Computer, and Energy Engineering,
Arizona State University,
Tempe, AZ 85287
e-mail: dfrakes@asu.edu

1Corresponding author.

Manuscript received August 4, 2015; final manuscript received November 5, 2015; published online January 27, 2016. Editor: Victor H. Barocas.

J Biomech Eng 138(2), 021011 (Jan 27, 2016) (8 pages) Paper No: BIO-15-1390; doi: 10.1115/1.4032046 History: Received August 04, 2015; Revised November 05, 2015

Embolic coiling is one of the most effective treatments for cerebral aneurysms (CAs), largely due to the hemodynamic modifications that the treatment effects in the aneurysmal environment. However, coiling can have very different hemodynamic outcomes in aneurysms with different geometries. Previous work in the field of biofluid mechanics has demonstrated on a general level that geometry is a driving factor behind aneurysmal hemodynamics. The goal of this study was to relate two specific geometric factors that describe CAs (i.e., dome size (DS) and parent-vessel contact-angle (PV-CA)) and one factor that describes treatment (i.e., coil packing density (PD)) to three clinically relevant hemodynamic responses (i.e., aneurysmal root-mean-square velocity (Vrms), aneurysmal wall shear stress (WSS), and cross-neck flow (CNF)). Idealized models of basilar tip aneurysms were created in both virtual and physical forms to satisfy two-level multifactorial experimental designs. Steady and pulsatile flow hemodynamics were then evaluated in the virtual models using computational fluid dynamics (CFD) (before and after virtual treatment with finite element (FE) embolic coil models), and hemodynamics were also evaluated in the physical models using particle image velocimetry (PIV) (before and after treatment with actual embolic coils). Results showed that among the factors considered, PD made the greatest contributions to effects on hemodynamic responses in and around the aneurysmal sac (i.e., Vrms and WSS), while DS made the greatest contributions to effects on hemodynamics at the neck (i.e., CNF). Results also showed that while a geometric factor (e.g., PV-CA) may play a relatively minor role in dictating hemodynamics in the untreated case, the same factor can play a much greater role after coiling. We consider the significance of these findings in the context of aneurysmal recurrence and rupture, and explore potential roles for the proposed methods in endovascular treatment planning.

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References

Figures

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Fig. 1

An anatomical basilar tip aneurysm

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Fig. 3

Computational IBTA templates (top) pre- and (bottom) post-treatment with embolic coils

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Fig. 2

Two-level full-factorial design including two geometric factors: DS and PV-CA. Numbers outside the parenthesis indicate the model numbers, and the numbers within are the DS (in mm) and PV-CA (in deg).

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Fig. 4

WSS distribution in the idealized BTA templates pre- and post-treatment at a 3 ml/s steady inflow rate

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Fig. 5

Effect of increasing DS (change from black to red) on CNF keeping PV-CA constant. The solid and patterned boxes represent changes in untreated and treated aneurysms, respectively.

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Fig. 6

Aneurysmal Vrms calculated in IBTA-1 under steady (solid boxes) and pulsatile (patterned boxes) inflow conditions, before and after treatment with embolic coils

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Fig. 7

Percentage contributions of DS, PV-CA and PD on (a) RMS velocity magnitude, (b) WSS, and (c) CNF

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Fig. 8

Percentage contributions of DS and PV-CA on untreated (solid boxes) and treated (patterned boxes) aneurysmal (a) RMS velocity magnitude, (b) WSS, and (c) CNF

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Fig. 9

CFD to PIV comparison of CNF in untreated (solid boxes) and treated (patterned boxes) IBTA models at a 3 ml/s steady inflow rate

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Fig. 10

CFD (left) and PIV (right) velocity vector distribution plots, color-coded by velocity magnitude, in IBTA-4 at a 3 ml/s steady inflow rate

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Fig. 11

WSS distributions in an anatomical bifurcation aneurysm model, before and after treatment, at a steady inflow rate of 3 ml/s

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