The effects of stent porosity on the endovascular treatment of intracranial aneurysms located near a bifurcation

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Computational fluid dynamics study of bifurcation aneurysms treated with pipeline embolization device: side branch diameter study

An intracranial aneurysm, abnormal swelling of the cerebral artery, may lead to undesirable rates of mortality and morbidity upon rupture. Endovascular treatment involves the deployment of a flow-diverting stent that covers the aneurysm orifice, thereby reducing the blood flow into the aneurysm and mitigating the risk of rupture. In this study, computational fluid dynamics analysis is performed on a bifurcation model to investigate the change in hemodynamics with various side branch diameters. The condition after the deployment of a pipeline embolization device is also simulated. Hemodynamic factors such as flow velocity, pressure, and wall shear stress are studied. Aneurysms with a larger side branch vessel might have greater risk after treatment in terms of hemodynamics. Although a stent could lead to flow reduction entering the aneurysm, it would drastically alter the flow rate inside the side branch vessel. This may result in side-branch hypoperfusion subsequent to stenting. In addition, two patient-specific bifurcation aneurysms are tested, and the results show good agreement with the idealized models. Furthermore, the peripheral resistance of downstream vessels is investigated by varying the outlet pressure conditions. This quantitative analysis can assist in treatment planning and therapeutic decision-making.published_or_final_versio

Note on the nonlinear electrokinetic effects in mircochannel flowexact analytical solutions for sinh-Poisson equation

Session AM Microfluids - General I: Electrokinetic: Abstract ID: BAPS.2010.DFD.AM.3Electrokinectic effects are important phenomena for fluid flow in microchannels, especially in mechanical systems involving movable micromechanical devices. Electrokinectic effects arise from electric double layer, which is a layer of charges attached to the dielectric surfaces as a result of the interaction of charges between ionized solution and dielectric surfaces. Electric potential inside the flow field is governed by the nonlinear Poisson-Boltzmann equation. Owing to the difficulty in solving the nonlinear equation, Debye-Hückel approximation, having an assumption of small electric potential, is a common approach to solve the linearized problem. In the present work, exact analytical expressions are obtained for the fully nonlinear sinh - Poisson equation without invoking the linear approximation. These solutions give insight on treating flow problems when Debye-Hückel approximation does not hold. Selected examples of solutions for a rectangular cell with zero homogenous boundary conditions applied on three wall surfaces are used for comparisons between the fully nonlinear and the linearized cases. Significant discrepancies are observed if the potential is not small, hence the present nonlinear theory is essential to better describe the physics involved.link_to_OA_fulltextThe 63rd Annual Meeting of the American Physical Society's Division of Fluid Dynamics (DFD 2010), Long Beach, CA., 21-23 November 2010. In Bulletin of the American Physical Society, 201

Computer fluid dynamics study of intracerebral aneurysms after flow-diverter treatment

Free Paper III – AneurysmBACKGROUND: The introduction of flow-diverters such as the Pipeline embolization device in recent years has widened the scope of endovascular therapeutic options of intracerebral aneurysms, particularly in those with difficult morphology such as wide-necked aneurysm. It limits blood flow into the aneurysmal sac thus facilitating obliteration, and allows preservation of flow into nearby vascular side-branches. The initial results are promising with obliteration rates in the range of 80-90%. However, the intra-aneurysmal and side-branches fluid dynamics before and after stent placement is not well understood. The geometrical risk factors for treatment failure and complications are also unclear. We aim to study the fluid dynamics related to the use of such flow-diverters using computational and actual models. METHOD: Using computational and 3-dimentional manufacturing techniques we created idealized and actual models of intracerebral aneurysms based on clinical data. Various parameters of flow dynamics are measured by USG and computational calculation prior and after Pipeline embolization device placement. RESULTS: We present data on the flow dynamics difference after flow-diverters treatment in intra-cerebral aneurysm models. Differences in the number of stents deployed, the influence of blood pressure, aspect ratio and other variables will be analyzed

Exact solutions for domain walls in coupled complex Ginzburg-Landau equations

The complex Ginzburg-Landau equation (CGLE) is a ubiquitous model for the evolution of slowly varying wave packets in nonlinear dissipative media. A front (shock) is a transient layer between a plane-wave state and a zero background. We report exact solutions for domain walls, i.e., pairs of fronts with opposite polarities, in a system of two coupled CGLEs, which describe transient layers between semi-infinite domains occupied by each component in the absence of the other one. For this purpose, a modified Hirota bilinear operator, first proposed by Bekki and Nozaki, is employed. A novel factorization procedure is applied to reduce the intermediate calculations considerably. The ensuing system of equations for the amplitudes and frequencies is solved by means of computer-assisted algebra. Exact solutions for mutually-locked front pairs of opposite polarities, with one or several free parameters, are thus generated. The signs of the cubic gain/loss, linear amplification/attenuation, and velocity of the coupled-front complex can be adjusted in a variety of configurations. Numerical simulations are performed to study the stability properties of such fronts. © 2011 The Physical Society of Japan.link_to_subscribed_fulltex

Wall-less flow phantoms with tortuous vascular geometries: design principles and a patient-specific model fabrication example

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Targeting JAK/STAT pathway in acute myeloid leukemia (AML): a potential therapeutic strategy and its link to WNT pathway

Young Investigator Award - Biomedicine: abstract no. A5

Blood flow in intracranial aneurysms treated with Pipeline embolization devices: computational simulation and verification with Doppler ultrasonography on phantom models

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Effect of sorafenib treatment in FLT3-ITD+ acute myeloid leukemia: mechanism of non-responsive and emergence of novel clones

Young Investigator Award - Biomedicine: abstract no. A5