Computational Hemodynamic Evaluation of Two Clinical Flow-Diverter Treatment Strategies: Overlapping Stents vs. Dense Compaction of a Single Stent

2014 ◽  
Author(s):  
Robert Damiano ◽  
Jianping Xiang ◽  
Adnan Siddiqui ◽  
Hui Meng
Keyword(s):  
Treatment Strategies ◽  
Flow Diverter ◽  
Hemodynamic Effect ◽  
Coverage Rate ◽  
Patient Specific ◽  
Test Cases ◽  
Strongly Correlated ◽  
Aneurysm Neck ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Diverters

We employed computational fluid dynamics (CFD) and finite element method (FEM) to investigate the hemodynamic effect of two flow-diversion strategies of cerebral aneurysm treatment: overlapping stents and dense compaction of a single stent. Three representative patient-specific aneurysms were used as test cases, and flow diverters were virtually deployed into the models. Aneurysmal hemodynamic modification by flow diverters is strongly correlated with the metal coverage rate across the aneurysm neck, and not uniquely determined by FD deployment strategies. Fusiform aneurysms may be more favorable for achieving dense compaction for increased metal coverage rate than saccuclar aneurysms. To induce high flow reduction, the overlapping strategy may be more suitable for sidewall aneurysms, and the dense compaction strategy for fusiform aneurysms.

Simulating Coil Embolization Treatments of Intracranial Aneurysms Using Computational Fluid Dynamics

2019 ◽  
Author(s):  
Nikhil Tulshibagwale ◽  
Stephen P. Gent
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Coil Embolization ◽  
Fluid Velocity ◽  
Volume Flow ◽  
Patient Specific ◽  
Test Cases ◽  
Aneurysm Neck ◽  
Test Models ◽  
Computational Fluid Dynamics Cfd

In this study, a commercially available computational fluid dynamics (CFD) program was used to simulate coil embolization techniques, standard coiling (SC) and stent-assisted coiling (SAC), in simplified vessels that are representative of vessels found in the brain. The test models included a curved vessel, ranging from 3mm to 4mm in diameter. The vessel was afflicted with a spherical aneurysm, ranging from 8mm to 16mm in diameter. The four test cases were simulated without treatment, with SC treatment, and with SAC treatment, for a total of twelve simulations. The parameters of interest were blood volume flow into aneurysm, fluid velocity, wall shear stress (WSS), and vorticity. Results of the simulations indicate, on average, SC and SAC reduced volume flow into the aneurysm by 50% and to over 60%, respectively. Both SC and SAC appeared to reduce distal neck WSS. Both treatments reduced average overall dome WSS by approximately 76%. Average aneurysm neck velocity was reduced by both treatments; SC reduced neck velocity by 69% and SAC reduced neck velocity by 75%. Information on SC and SAC efficacy in idealized scenarios could assist medical professionals determining viable approaches for patient-specific cases and lays foundation for future CFD studies exploring coil embolization treatments.

scholarly journals Mechanism of Action and Biology of Flow Diverters in the Treatment of Intracranial Aneurysms

Neurosurgery ◽  
2019 ◽  
Vol 86 (Supplement_1) ◽  
pp. S13-S19 ◽  
Author(s):  
Krishnan Ravindran ◽  
Amanda M Casabella ◽  
Juan Cebral ◽  
Waleed Brinjikji ◽  
David F Kallmes ◽  
...  
Keyword(s):  
Mechanism Of Action ◽  
Flow Diverter ◽  
Parent Artery ◽  
First Line ◽  
Aneurysm Neck ◽  
First Line Therapy ◽  
Preclinical Animal Models ◽  
Computational Analyses ◽  
Flow Diverters ◽  
Present Understanding

Abstract Flow diverters have drastically changed the landscape of intracranial aneurysm treatment and are now considered first-line therapy for select lesions. Their mechanism of action relies on intrinsic alteration in hemodynamic parameters, both at the parent artery and within the aneurysm sac. Moreover, the device struts act as a nidus for endothelial cell growth across the aneurysm neck ultimately leading to aneurysm exclusion from the circulation. In silico computational analyses and investigations in preclinical animal models have provided valuable insights into the underlying biological basis for flow diverter therapy. Here, we review the present understanding pertaining to flow diverter biology and mechanisms of action, focusing on stent design, induction of intra-aneurysmal thrombosis, endothelialization, and alterations in hemodynamics.

Phototherapy Enhanced Exclusion of Aneurysms From the Cerebral Circulation

2013 ◽  
Author(s):  
Baruch B. Lieber ◽  
Chander Sadasivan ◽  
David J. Fiorella ◽  
Henry H. Woo
Keyword(s):  
Thrombus Formation ◽  
A Priori ◽  
Flow Diverter ◽  
Experimental Models ◽  
Neointimal Formation ◽  
Fresh Blood ◽  
Aneurysm Neck ◽  
The Past ◽  
Neointimal Proliferation ◽  
Flow Diverters

Accumulated experience using flow diverters in humans suggests that complete cure of the aneurysm is usually a protracted process that can last up to twelve months [1]. While it is well established that a properly designed flow diverter serves as a scaffold for neointimal proliferation, the process of its formation over the aneurysm neck is delayed until the aneurysm cavity itself is occluded by a thrombus, negating flow of fresh blood through the neck, and thus allowing the neointimal formation to bridge the aneurysm neck. The notion that induction of some injury to the luminal surface of the aneurysmal tissue, particularly to the endothelium, may result in a healing response that is faster than just placing a flow diverter and waiting for thrombus formation within the aneurysm has been tried in the past using various experimental models. Some of the injuries to the aneurysm tissue that have been tried in the past include mechanical scraping, thermal heating and UV irradiation. All these attempts, while showing that hastening the thrombus formation is feasible, have not resulted in any success due to the fact that the processes that were tried suffered from lack of proper control to be implemented in actual aneurysmal tissue that is weakened and diseased a priori.

scholarly journals Acute thrombus formation on phosphorilcholine surface modified flow diverters

2017 ◽  
Vol 10 (4) ◽  
pp. 406-411 ◽  
Author(s):  
Miklos Marosfoi ◽  
Frederic Clarencon ◽  
Erin T Langan ◽  
Robert M King ◽  
Olivia W Brooks ◽  
...  
Keyword(s):  
Thrombus Formation ◽  
Rabbit Model ◽  
Flow Diverter ◽  
Side Branch ◽  
Clot Formation ◽  
Neck Size ◽  
Aneurysm Neck ◽  
Before And After ◽  
Surface Modified ◽  
Flow Diverters

PurposeThromboembolic complications remain a limitation of flow diverting stents. We hypothesize that phosphorilcholine surface modified flow diverters (Pipeline Flex with Shield Technology, sPED) would have less acute thrombus formation on the device surface compared with the classic Pipeline Embolization device (cPED).MethodsElastase-induced aneurysms were created in 40 rabbits and randomly assigned to receive cPED or sPED devices with and without dual antiplatelet therapy (DAPT) (four groups, n=10/group). Angioplasty was performed to enhance apposition and create intimal injury for a pro-thrombotic environment. Both before and after angioplasty, the flow diverter was imaged with intravascular optical coherence tomography. The outcome measure was the number of predefined segments along the implant relative to the location of the aneurysm with a minimum of 0 (no clot formation) and maximum of 3 (all segments with thrombus). Clot formation over the device at ostia of branch arteries was assessed as either present or absent.ResultsFollowing angioplasty, the number of flow diverter segments with clots was significantly associated with the flow diverter (p<0.0001), but not with DAPT (p=0.3872) or aneurysm neck size (p=0.8555). The incidence rate for clots with cPED was 1.72 times more than with sPED. The clots on the flow diverter at the location corresponding to side branch ostia was significantly lower with sPED than with cPED (OR 0.180; 95% CI 0.044 to 0.734; p=0.0168), but was not associated with DAPT (p=0.3198).ConclusionIn the rabbit model, phosphorilcholine surface modified flow diverters are associated with less thrombus formation on the surface of the device.

scholarly journals In-silico trial of intracranial flow diverters replicates and expands insights from conventional clinical trials

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ali Sarrami-Foroushani ◽  
Toni Lassila ◽  
Michael MacRaild ◽  
Joshua Asquith ◽  
Kit C. B. Roes ◽  
...  
Keyword(s):  
Clinical Trials ◽  
In Silico ◽  
Flow Diverter ◽  
Patient Specific ◽  
Success Rates ◽  
Virtual Experiments ◽  
Flow Reduction ◽  
The Cost ◽  
Flow Diverting Stent ◽  
Flow Diverters

AbstractThe cost of clinical trials is ever-increasing. In-silico trials rely on virtual populations and interventions simulated using patient-specific models and may offer a solution to lower these costs. We present the flow diverter performance assessment (FD-PASS) in-silico trial, which models the treatment of intracranial aneurysms in 164 virtual patients with 82 distinct anatomies with a flow-diverting stent, using computational fluid dynamics to quantify post-treatment flow reduction. The predicted FD-PASS flow-diversion success rates replicate the values previously reported in three clinical trials. The in-silico approach allows broader investigation of factors associated with insufficient flow reduction than feasible in a conventional trial. Our findings demonstrate that in-silico trials of endovascular medical devices can: (i) replicate findings of conventional clinical trials, and (ii) perform virtual experiments and sub-group analyses that are difficult or impossible in conventional trials to discover new insights on treatment failure, e.g. in the presence of side-branches or hypertension.

scholarly journals Hemodynamic Investigation of the Effectiveness of a Two Overlapping Flow Diverter Configuration for Cerebral Aneurysm Treatment

2021 ◽  
Vol 8 (10) ◽  
pp. 143
Author(s):  
Yuya Uchiyama ◽  
Soichiro Fujimura ◽  
Hiroyuki Takao ◽  
Takashi Suzuki ◽  
Motoharu Hayakawa ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Cerebral Aneurysms ◽  
Flow Diverter ◽  
Cfd Simulations ◽  
Qualitative And Quantitative ◽  
Pressure Loss Coefficient ◽  
Computational Fluid Dynamics Cfd ◽  
Simulation Results ◽  
Wide Neck ◽  
Flow Diverters

Flow diverters (FDs) are widely employed as endovascular treatment devices for large or wide-neck cerebral aneurysms. Occasionally, overlapped FDs are deployed to enhance the flow diversion effect. In this study, we investigated the hemodynamics of overlapping FDs via computational fluid dynamics (CFD) simulations. We reproduced the arterial geometry of a patient who had experienced the deployment of two overlapping FDs. We utilized two stent patterns, namely the patterns for one FD and two overlapping FDs. We calculated the velocity, mass flow rate, wall shear stress, and pressure loss coefficient as well as their change rates for each pattern relative to the no-FD pattern results. The CFD simulation results indicated that the characteristics of the blood flow inside the aneurysm were minimally affected by the deployment of a single FD; in contrast, the overlapping FD pattern results revealed significant changes in the flow. Further, the velocity at an inspection plane within the aneurysm sac decreased by up to 92.2% and 31.0% in the cases of the overlapping and single FD patterns, respectively, relative to the no-FD pattern. The simulations successfully reproduced the hemodynamics, and the qualitative and quantitative investigations are meaningful with regard to the clinical outcomes of overlapped FD deployment.

Abstract WP90: The Role of Haemodynamics in a Bifurcation Vessel Narrowing or Occlusion After Aneurysm Treatment with Flow Diverter Stents

Stroke ◽  
2017 ◽  
Vol 48 (suppl_1) ◽  
Author(s):  
Ana Paula Narata ◽  
Fernando Silva ◽  
Ignacio Larrabide ◽  
Cecile Perrault ◽  
Charles Sennoga ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Flow Diverter ◽  
Outcome Data ◽  
Patient Specific ◽  
Anatomical Data ◽  
Radiological Images ◽  
Endothelial Response ◽  
Computational Fluid Dynamics Cfd ◽  
Possible Cause

Background and Purpose: Treatment of intracranial aneurysms at bifurcations with flow-diverter stents (FDS) can lead to occlusion/narrowing of the distal vessels. This study investigated the role played by haemodynamics within different bifurcation types treated with FDS. Materials and Methods: Radiological images, demographic and outcome data were acquired for 25 bifurcating aneurysm treated with FDS. Statistical analysis was used to correlate the event of occlusion/narrowing with anatomical data. Computational Fluid Dynamics (CFD) study was performed on idealized and patient-specific anatomies to identify possible cause-effect mechanisms mediated by haemodynamics. Results: Statistical analysis identified marked correlation between asymmetric bifurcation and occlusion/narrowing (diameters ratio=DR=1 symmetric, <1 asymmetric). CFD predictions in both idealized and patient-specific anatomies showed that wall shear stress (WSS) in the jailed vessel is mostly affected when FDS are deployed in non-symmetric bifurcations (DR<0.65), and least affected when deployed in symmetric anatomies (DR = 1.00). Conclusion: Analysis of the anatomical data showed statistically significant correlations between occlusion/narrowing and bifurcation asymmetry characterized by DR<0.7. Similarly, CFD results showed that FDS have the highest impact on haemodynamics when deployed in bifurcations with higher degrees of anatomical asymmetry (DR<0.65) with strong changes induced on the WSS fields. This suggests a higher risk associated to FDS-treatment of asymmetric bifurcation together with a possible FDS-induced pathway leading to occlusion/narrowing of arteries and mediated by haemodynamics and endothelial response.

Evaluation of Two Fast Virtual Stenting Algorithms for Intracranial Aneurysm Flow Diversion

2020 ◽  
Vol 17 (1) ◽  
pp. 58-70 ◽  
Author(s):  
Saeb R. Lamooki ◽  
Vincent M. Tutino ◽  
Nikhil Paliwal ◽  
Robert J. Damiano ◽  
Muhammad Waqas ◽  
...  
Keyword(s):  
A Priori ◽  
Flow Diverter ◽  
Post Treatment ◽  
Patient Specific ◽  
Clinical Tool ◽  
Neck Size ◽  
Aneurysm Neck ◽  
Flow Modification ◽  
Stent Expansion ◽  
Stent Geometry

Background: Endovascular treatment of intracranial aneurysms (IAs) by flow diverter (FD) stents depends on flow modification. Patient-specific modeling of FD deployment and computational fluid dynamics (CFD) could enable a priori endovascular strategy optimization. We developed a fast, simplistic, expansion-free balls-weeping algorithm to model FDs in patientspecific aneurysm geometry. However, since such strong simplification could result in less accurate simulations, we also developed a fast virtual stenting workflow (VSW) that explicitly models stent expansion using pseudo-physical forces. Methods: To test which of these two fast algorithms more accurately simulates real FDs, we applied them to virtually treat three representative patient-specific IAs. We deployed Pipeline Embolization Device into 3 patient-specific silicone aneurysm phantoms and simulated the treatments using both balls-weeping and VSW algorithms in computational aneurysm models. We then compared the virtually deployed FD stents against experimental results in terms of geometry and post-treatment flow fields. For stent geometry, we evaluated gross configurations and porosity. For post-treatment aneurysmal flow, we compared CFD results against experimental measurements by particle image velocimetry. Results: We found that VSW created more realistic FD deployments than balls-weeping in terms of stent geometry, porosity and pore density. In particular, balls-weeping produced unrealistic FD bulging at the aneurysm neck, and this artifact drastically increased with neck size. Both FD deployment methods resulted in similar flow patterns, but the VSW had less error in flow velocity and inflow rate. Conclusion: In conclusion, modeling stent expansion is critical for preventing unrealistic bulging effects and thus should be considered in virtual FD deployment algorithms. Also endowed with its high computational efficiency and superior accuracy, the VSW algorithm is a better candidate for implementation into a bedside clinical tool for FD deployment simulation.

scholarly journals Particle Image Velocimetry Measurements of the Flow-Diverting Effects of a New Generation of the eCLIPs Implant for the Treatment of Intracranial Bifurcation Aneurysms

2020 ◽  
Vol 10 (23) ◽  
pp. 8639
Author(s):  
Sina G. Yazdi ◽  
Daniel Mercier ◽  
Renee Bernard ◽  
Adam Tynan ◽  
Donald R. Ricci
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Flow Diverter ◽  
Flow Diversion ◽  
Similar Reduction ◽  
Adequate Treatment ◽  
Aneurysm Neck ◽  
Image Velocimetry ◽  
New Generation ◽  
Flow Diverters

Flow diverters (FDs) for the endovascular treatment of intracranial aneurysms are effective for sidewall aneurysms, but their use at a bifurcation is problematic because FDs only partially cover the aneurysm neck and impede flow into a daughter branch; they are thus not employed routinely in this anatomy. eCLIPs was developed as a non-tubular implant to completely cover the neck of an aneurysm and serve as a coil retention device necessary for the adequate treatment of wide-neck bifurcation aneurysms. eCLIPs has shown some flow diversion effects in bifurcation anatomy but not equal to those exhibited by clinically accepted flow diverters in sidewall anatomy. A new generation of eCLIPs implant, the eCLIPs bifurcation flow diverter (eBFD), with higher metal coverage, was developed to achieve a similar flow diversion as a Pipeline Embolization Device (PED), a prototypical FD. Particle image velocimetry was used to capture the fluid dynamics and velocity reduction within silicone aneurysm replicas. A circulatory mimicking loop was developed to circulate the flow through the silicone models. All generations of eCLIPs implants had some flow-diverting effect, with increasing metal coverage density of the implant proportionately increasing the flow diversion effect. The eBFD, with a metal density of 35%, showed greater flow diversion than PED, with 30% metal density, for bifurcation anatomy. The eBFD showed similar reduction of flow in a bifurcation anatomy to PED in a sidewall, both sufficient to permit early thrombosis of the aneurysm. Thus, the eBFD can potentially provide sufficient flow diversion for the treatment of bifurcation aneurysms to avoid adjunctive coiling.

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