Finite element modeling of endovascular coiling and flow diversion enables hemodynamic prediction of complex treatment strategies for intracranial aneurysm - PubMed (original) (raw)

Finite element modeling of endovascular coiling and flow diversion enables hemodynamic prediction of complex treatment strategies for intracranial aneurysm

Robert J Damiano et al. J Biomech. 2015.

Abstract

Endovascular interventions using coil embolization and flow diversion are becoming the mainstream treatment for intracranial aneurysms (IAs). To help assess the effect of intervention strategies on aneurysm hemodynamics and treatment outcome, we have developed a finite-element-method (FEM)-based technique for coil deployment along with our HiFiVS technique for flow diverter (FD) deployment in patient-specific IAs. We tested four clinical intervention strategies: coiling (1-8 coils), single FD, FD with adjunctive coils (1-8 coils), and overlapping FDs. By evaluating post-treatment hemodynamics using computational fluid dynamics (CFD), we compared the flow-modification performance of these strategies. Results show that a single FD provides more reduction in inflow rate than low packing density (PD) coiling, but less reduction in average velocity inside the aneurysm. Adjunctive coils add no additional reduction of inflow rate beyond a single FD until coil PD exceeds 11%. This suggests that the main role of FDs is to divert inflow, while that of coils is to create stasis in the aneurysm. Overlapping FDs decreases inflow rate, average velocity, and average wall shear stress (WSS) in the aneurysm sac, but adding a third FD produces minimal additional reduction. In conclusion, our FEM-based techniques for virtual coiling and flow diversion enable recapitulation of complex endovascular intervention strategies and detailed hemodynamics to identify hemodynamic factors that affect treatment outcome.

Keywords: Flow diverter; Flow diverter with adjunctive coils; Treatment outcome; Virtual coiling; Virtual stenting.

Copyright © 2015 Elsevier Ltd. All rights reserved.

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Conflict of interest statement

Conflict of Interest Statement

Damiano: None. Ma: None. Xiang: Awardee for the American Society for Quality Biomedical Division Dr. Richard J. Schlesinger grant and principal investigator of Brain Aneurysm Foundation grant. Siddiqui: Financial interests- Hotspur, Intratech Medical, StimSox, Valor Medical; Consultant- Codman & Shurtleff, Concentric Medical, ev3/Covidien Vascular Therapies, GuidePoint Global Consulting, Penumbra; Speakers’ bureau’s- Codman & Shurtleff, Genentech; Advisory board- Codman & Shurtleff; Honoraria- Abbot Vascular, Codman & Shurtleff, Genentech, Neocure Group LLC. Snyder: Consultant to, member of the speakers’ bureau, and has received honoraria from Toshiba. Member of the speakers’ bureau for and has received honoraria from ev3/Covidien and The Stroke Group. Meng: Principal Investigator of NIH grant (R01NS064592).

Figures

Fig. 1

Fig. 1

Workflow for coil deployment, including three main components: pre-processing, FEM simulation, and post-processing. Device deployment results enable hemodynamic analysis.

Fig. 2

Fig. 2

Workflow for deploying overlapping flow diverters. After (1) running HiFiVS to implant the 1st FD, we (2) isolated the parent vessel and scaled it down by a distance of 1~2 FD wire diameters to fit entirely inside the 1st deployed FD. Then, we ran a second HiFiVS simulation to (3) deploy the 2nd FD in the scaled-down vessel lumen. Finally, we (4) superimposed the two intermediate deployed FD simulation results, (5) removed the scaled-down vessel and ran one or more FEM simulations to allow the 2nd FD to expand into the 1st FD.

Fig. 3

Fig. 3

FEM modeling and CFD results for coiling (coils only) and flow diversion with adjunctive coils (coils + FD). 1C–8C represents 1–8 coils with packing density from 3.7–29.6% (each coil adds 3.7%) A and B. Deployment results. Each successively deployed coil is depicted with a unique color for clarity and to help visualize changes in their configurations with deployment of successive coils. C and D. Blood streamlines. Each vessel inlet was seeded with 100 streamlines for consistency. The flow was from right to left. E and F. Velocity magnitude contours. The white gaps represent the intersection of the aneurysm mid-plane with the coils. G and H. Wall shear stress contours. They reveal zones of low WSS at the apex of the aneurysm sac as the number of coils deployed increases in both intervention strategies.

Fig. 4

Fig. 4

FEM modeling and CFD results for a single flow diverter and overlapping flow diverters. A. FEM modeling results for 1, 2 and 3 flow diverters. Successively deployed flow diverters are colored by blue, green, and magenta. B. Blood streamline results for untreated aneurysm and treatment by 1, 2 and 3 FDs. Each vessel inlet was seeded with 100 streamlines for consistency. The flow was from right to left. C. Velocity magnitude contours on the aneurysm mid-plane D. Wall shear stress distributions.

Fig. 5

Fig. 5

Hemodynamic quantities for coils only, FD only, and coils + FD, relative to the untreated case (with a hemodynamic baseline of 100%). A. Inflow rate. B. Aneurysm-averaged velocity. C. Aneurysm-averaged wall shear stress. Aneurysm-averaged values are volumetrically-averaged in the aneurysm sac. Each coiling scenario (1C–8C) corresponds to a packing density ranging from 3.7%–29.6%.

Fig. 6

Fig. 6

Hemodynamic quantities (inflow rate, aneurysm-averaged velocity, and aneurysm-averaged wall shear stress) for overlapping flow diverters, relative to the untreated case. A general decrease of inflow rate, aneurysm-averaged velocity, and aneurysm-averaged wall shear stress was observed with successively deployed flow diverters, but the decrease is minimal from 2 FDs to 3 FDs.

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