U7 - A Novel Computational Framework for Structural and Hemodynamic Modeling of Intrasaccular Flow Disruption Treatment in Wide-Necked Intracranial Aneurysms

Friday, October 10, 2025

10:00 AM - 11:00 AM PDT

Location: Exhibit Hall F, G & H

Presenting Author(s)

Sumit Kumar, PhD

Postdoctoral Researcher
Brigham and Women's Hospital, Harvard Medical School
Boston, United States

Co-Author(s)

Sumit Kumar, PhD

Postdoctoral Researcher
Brigham and Women's Hospital, Harvard Medical School
Boston, United States
Sam Boxwell

PhD Researcher
University of Galway, Ireland
WS

William J Smith, MD

Neurosurgery Resident Fellow
Massachusetts General Hospital, United States
Farhad R. Nezami

Assistant Professor
Harvard Medical School
Boston, Massachusetts, United States

Last Author(s)

Farhad R. Nezami

Assistant Professor
Harvard Medical School
Boston, Massachusetts, United States

Primary Investigator(s)

Farhad R. Nezami

Assistant Professor
Harvard Medical School
Boston, Massachusetts, United States

Co-Author(s)

AP

Aman Patel

Introduction: : An intracranial aneurysm (IA) is a prevalent vascular abnormality of the cerebral artery wall, affecting 5-11% of the US population [1]. Preventing IA rupture through early intervention is crucial, as rupture is the leading cause of hemorrhagic stroke accounting for 500,000 deaths worldwide each year [2]. The risk of rupture is primarily determined by IA anatomy, including shape, size and location. Wide-necked IAs are associated with high rupture risk, present greater treatment challenges, and require advanced treatment techniques compared to narrow-neck IAs [1].
Intrasaccular devices, such as the Woven EndoBridge (WEB – Terumo Neuro, Aliso Viejo, CA, USA), have emerged as effective treatments for wide-necked IAs. These devices consist of a nitinol braided mesh designed to disrupt intra-aneurysmal flow and provide a scaffold for endothelialization [3]. However, complications such as recanalization and sub-total embolization have been reported [3]. These issues are intrinsically linked to anatomical and procedural factors including device sizing, positioning, and pre-/post-treatment hemodynamics.
Patient-specific computational modelling, including finite element (FE) and computational fluid dynamics (CFD) approaches, have shown promise for planning and optimizing neurovascular procedures [4]. Such tools offer the potential to systemically evaluate numerous intrasaccular flow disruption treatments, quantifying how device sizing and positioning affect post-treatment hemodynamics. However, a comprehensive structural-hemodynamic framework for this purpose remains underdeveloped.
The objective of this study is to develop, verify, and validate a structural-hemodynamic computational framework for simulating intrasaccular flow disruption treatment in wide-necked IAs leveraging both in vitro experiments and clinical data.

Materials and

Methods: : A retrospective, patient-specific model of a wide-necked IA was reconstructed from pre-treatment computed tomography (CT) scans using 3D Slicer (Figure 1a,b).
To analyze pre-treatment hemodynamics, we performed CFD simulations using ANSYS Fluent. Following mesh independence testing, the patient-specific IA model was discretized with approximately 3 million hexahedral cells. A transient flow analyses was performed using a physiological, time-dependent velocity waveform from prior IA studies [5]. Blood was modeled as Newtonian and incompressible with a density of 1060 kg/m3 and viscosity of 0.0035 kg/ms.
Following pre-treatment CFD, we developed a FE model of the WEB device using Abaqus/Explicit (v2023, Simulia). The device model comprised 144 braided nitinol wires, modeled as a superelastic, phase-transforming material [6], with platinum end caps (Figure 2a). Prior to deployment, we conducted a number of verification and validation tests, including a simulation of radial force to calibrate the nitinol material model (Figure 2b).
The patient-specific IA model was meshed with S4R elements and modeled as hyperelastic and isotropic [7]. To simulate device deployment, we crimped the device into a rigid catheter, by applying a displacement to the bottom platinum cap (Figure 2c). Once the catheter was positioned at the base of the wide-neck cerebral aneurysm, we applied a controlled displacement to the top platinum cap, which allowed the WEB device to expand within the IA model. For crimping and deployment, general contact with "hard" behavior was defined between the device, rigid catheter, and aneurysm surfaces.

Results, Conclusions, and Discussions:: Pre-treatment CFD simulations revealed a primary jet, with the velocity of 0.8 m/s, separating at the arterial junction between the branching vessels and IA (Figure 1c). However, within the sac, multiple low-velocity vortices (between 0.1 to 0.3 m/s) were observed, consistent with type II IA flow patterns commonly observed in wide-necked IAs [8].
FE modelling of radial force testing showed a maximum radial force of 0.55 N at 1mm compression of the WEB device (Figure 2b). Experimental testing of the WEB device is underway to better calibrate nitinol material properties.
The deployment simulation (Figure 2c) demonstrated complete apposition of the WEB device to the patient-specific IA wall. Ongoing work aims to validate the deployment mechanics and final morphology with recorded, retrospective treatment angiography. We are also implementing a centerline-based approach for FE catheter tracking and deployment to more accurately replicate clinical deployment mechanics.
Once validated, we will conduct post-treatment hemodynamic simulations to identify changes in IA flow. This approach will then be applied to a retrospective cohort of 50+ WEB-treated patients from Massachusetts General Hospital to assess the impact of procedural strategies, particularly device sizing and positioning, on post-treatment hemodynamics.

Acknowledgements and/or References (Optional): : [1] Lee, K. S., Zhang, J. J., Nguyen, V., Han, J., Johnson, J. N., Kirollos, R., & Teo, M. (2022). The evolution of intracranial aneurysm treatment techniques and future directions. Neurosurgical Review, 45(1), 1-25.
[2] Brain Aneurysm Foundation. (2025). Statistics and Facts. https://www.bafound.org/statistics-and-facts/
[3] Asnafi, S., Rouchaud, A., Pierot, L., Brinjikji, W., Murad, M. H., & Kallmes, D. F. (2016). Efficacy and safety of the Woven EndoBridge (WEB) device for the treatment of intracranial aneurysms: a systematic review and meta-analysis. American Journal of Neuroradiology, 37(12), 2287-2292.
[4] Luraghi, G., Rodriguez Matas, J. F., Dubini, G., Berti, F., Bridio, S., Duffy, S., ... & INSIST investigators. (2021). Applicability assessment of a stent-retriever thrombectomy finite-element model. Interface Focus, 11(1), 20190123.
[5] Mut, F., Chung, B. J., Chudyk, J., Lylyk, P., Kadirvel, R., Kallmes, D. F., & Cebral, J. R. (2019). Image‐based modeling of blood flow in cerebral aneurysms treated with intrasaccular flow diverting devices. International journal for numerical methods in biomedical engineering, 35(6), e3202.
[6] Armfield, D., Boxwell, S., Mcnamara, L., Cook, S., Conway, S., Celikin, M., & Cardiff, P. (2024). Effect of bioprosthetic leaflet anisotropy on stent dynamics of Transcatheter Aortic Valve Replacement devices. Journal of the Mechanical Behavior of Biomedical Materials, 157, 106650.
[7] Parshin, D. V., Lipovka, A. I., Yunoshev, A. S., Ovsyannikov, K. S., Dubovoy, A. V., & Chupakhin, A. P. (2019). On the optimal choice of a hyperelastic model of ruptured and unruptured cerebral aneurysm. Scientific Reports, 9(1), 15865.
[8] Mantilla, D., Berod, A., Ortiz, A. F., Vera, D. D., Nicoud, F., & Costalat, V. (2025). Heterogeneous model to evaluate CFD in intracranial bifurcation aneurysms treated with the WEB device to predict angiographic outcome. Interventional Neuroradiology, 31(3), 315-323.