Stented Aneurysm Research Articles

CT and 3D-ultrasound registration for spatial comparison of post-EVAR abdominal aortic aneurysm measurements: A cross-sectional study

ObjectiveThe aim of the present study is to provide a methodology to register volumes of stented abdominal aortic aneurysm, imaged by 3D-US and CT modalities. After registration, the method enables to compare the spatial location of measurements and AAA size in a common coordinate system. MethodsThe study is cross-sectional and compares volumes acquired within a few days, in order to eliminate changes due to the evolution of AAA shape after treatment. The key element is to rely on stent alignment to register the CT and 3D-US volumes, providing access to a patient-specific common spatial coordinate system. In parallel, 3D segmentations are performed and used to extract multi-planar reconstructions at the locations of maximum diameter in each modality. The positions of the planes extracted in each modality, and the AAA diameters are finally compared in the common coordinate system. ResultsResults are validated on a database of 52 patients. After registrations, results show a mean inter-planar distance of 6.4 ± 4.5 mm and a mean inter-planar angle of 10.2°±6.7 between CT and 3D-US multi-planar reconstructions. Bland–Altman comparisons of diameter measurements in the CT, US and non-registered volumes are respectively 5.1 ± 2.8, 3.9 ± 2.8, 4.6 ± 3.0 mm. ConclusionThe proposed approach provides both visual and quantitative validations of measurements extracted from multi-modality images of the same pathology, in terms of spatial relationship and diameters. SignificanceThe present work provides additional confidence in the use of 3D-US without CT for the follow-up of patients with abdominal aortic aneurysms after endovascular treatment.

Combination Superficial Temporal Artery-Middle Cerebral Artery Bypass and M2-M2 Reanastomosis With Trapping of a Stented Distal Middle Cerebral Artery Aneurysm: 3-Dimensional Operative Video.

Distal middle cerebral artery (MCA) aneurysms often have non-saccular morphology and cannot be clipped, requiring revascularization and trapping instead. Combination bypasses are needed when 2 arteries exit the aneurysm, and extracranial-intracranial and intracranial-intracranial bypasses can be used. This video demonstrates a combination bypass used to treat a previously stented distal MCA aneurysm with both a superficial temporal artery (STA)-to-MCA bypass and an M2-to-M2 reanastomosis. This 56-yr-old man presented with distal left-sided MCA aneurysm 2 years earlier and attempted stent-assisted coiling was aborted after the aneurysm was perforated with stenting alone. Follow-up angiography demonstrated progressive aneurysm enlargement, and he was referred for surgery. The patient consented for the procedure and a pterional craniotomy extended posteriorly exposed the distal Sylvian fissure and efferent M4-cortical arteries. After splitting the Sylvian fissure, the "flash fluorescence" technique with indocyanine green (ICG) videoangiography identified an M4 recipient artery from the deeper of 2 exiting branches for STA-MCA bypass.1 The aneurysm was then trapped, and inflow and the more superficial outflow arteries were anastomosed end to end (M2-M2 in-situ bypass). A platelet plug that developed at the reanastomosis site was broken apart with mechanical manipulation, and ICG videoangiography demonstrated patency of both bypasses. The patient recovered without any neurological deficits, and postoperative computed tomography angiography confirmed bypass patency. Combination bypasses are needed when unclippable bifurcation aneurysms require revascularization. Careful intraoperative evaluation of patency of the bypass is imperative and helps identifying and addressing any potential early bypass occlusion.

Suppression of Wall Shear Stress inside Intracranial Aneurysms by Simple Stents

The effect of a simple bare-metal stent on suppression of wall shear stress inside a spherical intracranial aneurysm model was experimentally investigated by two dimensional particle image velocimetry in vitro . The flow model simulated an intracranial aneurysm induced both at the side wall and at the apex of bifurcation between the anterior cerebral artery and the anterior communicating artery. Wall shear stress was investigated using both stented and non-stented models to assess the simple bare metal stent characteristics. The flow behavior inside the stented aneurysm sac was unusual and wall shear stress was much smaller inside the aneurysm sac. For both models, the maximum and the temporal and spatial averaged wall shear stress in the stented model is reduced by at least 50 % from those in the non-stented model. Stent placement effectively suppresses the temporal and spatial variations, and the magnitude of wall shear stress. Consequently, there is an effective possibility that would retard the progress of cerebral aneurysms by even simple stent.

Rare case of diffuse spinal arachnoiditis following a complicated vertebral artery dissection

Spinal arachnoiditis (SA) is an extremely rare and delayed complication of subarachnoid hemorrhage (SAH). Little is known about its underlying pathogenesis and subsequent clinical course. A middle-aged patient presented with the worst headache of her life and a grade 3 SAH of the basal-cisterns and posterior fossa was identified on Computed Tomography scans (CT). Angiography revealed a ruptured dissecting aneurysm of the left vertebral artery (VA-V4), as well as an unruptured left Anterior Cerebral Artery (ACA-A1) aneurysm. The VA aneurysm was treated with flow diversion. The patient re-ruptured the stented aneurysm, another telescoping pipeline was placed. The patient developed polymicrobial ventriculitis, and returned several months later complaining of paraparesis and left sided weakness. Magnetic Resonance Imaging (MRI) revealed diffuse thecal dural thickening from the cervicomedullary junction to the sacrum. Loculations, diffuse edema and cord compression were noticed along the inferior surface of the cerebellum, and the cervico-thoracic spine with a T4–T6 syrinx. The patient underwent a posterior (T4–T8) spinal fusion and (T5–T7) decompression with arachnoid-cyst fenestration and placement of a subarachnoid-pleural shunt. On latest follow-up, the patient is weaning off the thoraco-lumbosacral orthosis and ambulating with a cane. SA is often a complicated two-staged disease in which a “free interval phase” separates the initial inflammatory reaction (IIR) from the late adhesive phase. Posterior fossa bleeding, warranting prolonged surveillance, additional bleeding and ventriculitis might augment the risk and the severity of arachnoiditis.

Brachial artery thrombosis due to a giant, stented arteriovenous fistula aneurysm in a renal transplant patient

Brachial artery thrombosis due to a giant, stented arteriovenous fistula aneurysm in a renal transplant patient

Endoleak Assessment Using Computational Fluid Dynamics and Image Processing Methods in Stented Abdominal Aortic Aneurysm Models.

Endovascular aortic aneurysm repair (EVAR) is a predominant surgical procedure to reduce the risk of aneurysm rupture in abdominal aortic aneurysm (AAA) patients. Endoleak formation, which eventually requires additional surgical reoperation, is a major EVAR complication. Understanding the etiology and evolution of endoleak from the hemodynamic perspective is crucial to advancing the current posttreatments for AAA patients who underwent EVAR. Therefore, a comprehensive flow assessment was performed to investigate the relationship between endoleak and its surrounding pathological flow fields through computational fluid dynamics and image processing. Six patient-specific models were reconstructed, and the associated hemodynamics in these models was quantified three-dimensionally to calculate wall stress. To provide a high degree of clinical relevance, the mechanical stress distribution calculated from the models was compared with the endoleak positions identified from the computed tomography images of patients through a series of imaging processing methods. An endoleak possibly forms in a location with high local wall stress. An improved stent graft (SG) structure is conceived accordingly by increasing the mechanical strength of the SG at peak wall stress locations. The presented analytical paradigm, as well as numerical analysis using patient-specific models, may be extended to other common human cardiovascular surgeries.

Wall stress in media layer of stented three-layered aortic aneurysm at different intraluminal thrombus locations with pulsatile heart cycle

At the point when the aorta ruptures suddenly, as opposed to as the after-effect of injury, it is for the most part in aortic aneurysm. Aortic aneurysm rupture happens when the wall stress surpasses the strength of the vascular tissue. Intraluminal thrombus (ILT) may have advantages as it can absorb tension and decrease aortic aneurysm wall stress. This study aims to investigate the presence and growth effects of ILT on the wall stress in a stented aneurysm in one heart cycle. A virtual stented aneurysm model with ILT was made to study the flow and wall dynamics using fluid–structure interaction (FSI) analysis. Wall stresses at the center line of media layer of aorta thickness were calculated by two-dimensional axisymmetric finite element analysis. Calculations were executed as thrombus elastic modulus increased from 0.1 to 2 MPa and calculations were repeated as thrombus depth was increased in 10% increment until thrombus filled the whole aneurysm cavity. The von Mises stresses were compared in three sections, namely proximal, aneurysm and distal sections in the abdominal aorta. The wall stress showed its maximum value during a peak flow and pressure and gradually decreased as the pressure and velocity of blood reduced in all three aforementioned sections. As the intraluminal thrombus depth increased from 10% to 100%, the wall stress in distal, proximal and centre of aneurysm during one heart cycle was decreased. Furthermore, increasing the elastic modulus of thrombus from 10% to 100% triggered a reduction in wall stress in proximal, centre of intraluminal thrombus and distal regions during one heart cycle. The achievements of this study may have implications not only for understanding the wall stress in ILT, but also for providing more detailed information about aortic aneurysm with intraluminal thrombus and can help surgeons to do their best.

Repression of wall shear stress inside cerebral aneurysm at bifurcation of anterior cerebral artery by stents.

The effect of a simple bare metal stent on repression of wall shear stress inside a model cerebral aneurysm was experimentally investigated by two-dimensional particle image velocimetry in vitro. The flow model simulated a cerebral aneurysm induced at the apex of bifurcation between the anterior cerebral artery and the anterior communicating artery. Wall shear stress was investigated using both stented and non-stented models to assess the simple stent characteristics. The flow behavior inside the stented aneurysm sac was unusual and wall shear stress was much smaller inside the aneurysm sac. Stent placement effectively repressed the temporal and spatial variations and the magnitude of wall shear stress. Hence, there is an effective possibility that would retard the progress of cerebral aneurysms by even simple stent.

Hemodynamic investigation of intraluminal thrombus effect on the wall stress in a stented three-layered aortic aneurysm model under pulsatile flow

PurposeAortic aneurysms occurs when the wall stress exceeds the strength of the vascular tissue. Intraluminal Thrombus (ILT) may absorb tension and reduce the aortic aneurysm wall stress. The purpose of this study is to test the hypothesis that the presence and growth of ILT alters the wall stress in a stented aneurysm. MethodA virtual stented aneurysm model with ILT is created to study the flow and wall dynamics by means of Fluid-Structure Interaction (FSI) analysis. Wall stresses are determined by two-dimensional axisymmetric finite element analysis. Calculations are performed as thrombus elastic modulus increased from 0.1 to 2 MPa and calculations are repeated as thrombus depth is increased in 10% increment until thrombus fills the entire aneurysm cavity. ResultsThe blood flow velocity, pressure, and maximum wall stresses are compared to the aforementioned models. The maximum stress reduction of 46% occurs at the time of peak flow and 28% at the time of peak pressure when thrombus elastic modulus increases from 0.1 to 2 MPa. In addition, as the thrombus depth increased from 10% to 100 %, the wall stress at the time of peak flow and peak pressure decreased almost 25% and 20%. ConclusionsThe findings of this study may have implications not only for understanding the wall stress in ILT but also for providing more detailed information about aortic aneurysm with intraluminal thrombus.

Preliminary Study on the Comparable Flow Pattern between Stented and Non-Stented Aneurysm at Hypertension Condition

The presence of the vortex formation associated with high pressure gradient has aggravated the rupture at the aneurismal wall. In order to decrease the possibility of aneurysm to be rupture, device like wire-mesh called stent was inserted at the aneurysm bulge. This study was focused on investigates the hemodynamic factor especially pressure distribution toward the failure of the aneurismal wall. Computational fluid dynamics method has used to identify the influence of the hemodynamic factor at the aneurysm. The results of this study shown the slightly decrease of the pressure distribution after the insertion of the bare metallic stent (BMS). The results on non-stented aneurysm was depicted the strong vortex was dominated the entire region of aneurysm. The strength of the vortex also was seems very weak after the insertion of this stent. The flow visualization between stented and non-stented aneurysm has given a good features in deep understanding of hemodynamic effect on the aneurismal wall. From the observed, the insertion of the stent manages to reduce the stress that exerted to aneurismal wall as well as decreased the strength of the vortex formation.

Fluid structure interaction simulation in three-layered aortic aneurysm model under pulsatile flow: Comparison of wrapping and stenting

One treatment method for aortic aneurysm is the invasive insertion of a stent into the aneurysm. Another method is wrapping the aneurysm using newly developed expanded polytetrafluoroethylene (PTFE) material. A virtual stented aneurysm model and a wrapped aneurysm model were created to study the flow and wall dynamics by means of fluid-structure interaction analyses. The flow velocity and pressure distribution as well as the deformation and wall stress were investigated. Stenting significantly changed the blood flow pattern and the vortexes in the aneurysm. Wrapping increased the thickness of the aneurysm wall and increased the strength of the vessel wall. The maximum von Mises stress in the stented model was found to be 220,494Pa and 228,218Pa at the time of peak flow and peak pressure, respectively. This was reduced by 37.8% and 36.7% to 137,200 and 144,354Pa, respectively, in the wrapped model. Our results provide information that may improve the understanding of the biomechanics of stenting and wrapping.

Non-Newtonian Effect on Hemodynamic Characteristics of Blood Flow in Stented Cerebral Aneurysm

AbstractStent placement is considered as a promising and minimally invasive technique to prevent rupture of aneurysm and favor coagulation mechanism inside the aneurysm. Many scholars study the effect of the stent on blood flow in cerebral aneurysm by numerical simulations, and usually regard blood as the Newtonian fluid, blood, however, is a kind of non-Newtonian fluid in practice. The main purpose of the present paper is to investigate the effect of non-Newtonian behavior on the hemodynamic characteristics of blood flow in stented cerebral aneurysm with lattice Boltzmann method. The Casson model is used to describe the blood non-Newtonian character, which is one of the most popular models in depicting blood fluid. In particular, hemodynamic characteristics derived with Newtonian and non-Newtonian models are studied, and compared in detail. The results show that the non-Newtonian effect gives a great influence on hemodynamic characteristics of blood flow in stented cerebral aneurysm, especially in small necked ones.

Fluid-structure interaction based study on the physiological factors affecting the behaviors of stented and non-stented thoracic aortic aneurysms

Endovascular aneurysm repair (EVAR) is considered as a promising alternative technique for the treatment of aortic aneurysm. However, complications often occur after EVAR. In this paper, the influence of the physiological factors on the biomechanical behaviors of stented and non-stented thoracic aortic aneurysm (TAA) were presented. Representative TAA models with different intraluminal thrombus (ILT) volume before and after stent-graft (SG) implantation were built. Fluid-structure interaction effect was taken into account. The relative sliding between the SG wall and the aortic wall was allowed. Results showed that the cardiac cycle and ILT volume should be given much more consideration than previously thought in future investigations on TAA compliance. The time-averaged longitudinal displacement of SG necks were not uniformly distributed along circumferential direction of the aortic wall. Drag force increased with the increase of the cardiac cycle and decreased with the decrease of ILT volume. Computational results of TAA wall stress, sac and lumen pressure indicated that patient with faster heart rate might be at great risk of aneurysm rupture. The stress absorption effect of the SG was influenced by both ILT and cardiac cycle, which was also found to have strong impact on flow pattern. We believe that this study will bring new insights into further researches on the relevant issues and provide mechanics-based implications for clinical management of EVAR for TAA patient.

Non-Newtonian and flow pulsatility effects in simulation models of a stented intracranial aneurysm

Three models of different stent designs implanted in a cerebral aneurysm, originating from the Virtual Intracranial Stenting Challenge '07, are meshed and the flow characteristics simulated using commercial computational fluid dynamics (CFD) software in order to investigate the effects of non-Newtonian viscosity and pulsatile flow. Conventional mass inflow and wall shear stress (WSS) output are used as a means of comparing the CFD simulations. In addition, a WSS distribution is presented, which clearly discriminates in favour of the stent design identified by other groups. It is concluded that non-Newtonian and pulsatile effects are important to include in order to avoid underestimating wss, to understand dynamic flow effects, and to discriminate more effectively between stent designs.

A Rapid and Computationally Inexpensive Method to Virtually Implant Current and Next-Generation Stents into Subject-Specific Computational Fluid Dynamics Models

Computational modeling is often used to quantify hemodynamic alterations induced by stenting, but frequently uses simplified device or vascular representations. Based on a series of Boolean operations, we developed an efficient and robust method for assessing the influence of current and next-generation stents on local hemodynamics and vascular biomechanics quantified by computational fluid dynamics. Stent designs were parameterized to allow easy control over design features including the number, width and circumferential or longitudinal spacing of struts, as well as the implantation diameter and overall length. The approach allowed stents to be automatically regenerated for rapid analysis of the contribution of design features to resulting hemodynamic alterations. The applicability of the method was demonstrated with patient-specific models of a stented coronary artery bifurcation and basilar trunk aneurysm constructed from medical imaging data. In the coronary bifurcation, we analyzed the hemodynamic difference between closed-cell and open-cell stent geometries. We investigated the impact of decreased strut size in stents with a constant porosity for increasing flow stasis within the stented basilar aneurysm model. These examples demonstrate the current method can be used to investigate differences in stent performance in complex vascular beds for a variety of stenting procedures and clinical scenarios.

Compliance of Abdominal Aortic Aneurysms before and after Stenting with Tissue Doppler Imaging: Evolution during Follow-Up and Correlation with Aneurysm Diameter

Usual imaging after endovascular aneurysm repair (EVAR) of abdominal aortic aneurysm (AAA) consists of AAA diameter monitoring and endoleak detection. Among additional predictor parameters previously proposed to help clinicians in better identifying subgroups of AAA still at risk of rupture, AAA wall motion after EVAR has been studied, but its value was not clearly established. Tissue Doppler imaging (TDI) is an ultrasonographic modality which allows wall motion measurements along an arterial segment. The aim of the current study was to analyze AAA wall motion with TDI before and after EVAR and to describe its evolution in patients with more than 1 month of follow-up. Twenty-five consecutive patients undergoing EVAR between February 2005 and June 2007 gave informed consent to be prospectively investigated with the TDI system before EVAR and at each visit during follow-up. The mean (SD) follow-up was 13.7 (9.7) months. Maximum mean segmental dilation (MMSD), segmental compliance, dilation at maximum diameter, pressure strain elastic modulus (Ep), and stiffness were compared between three periods (before stenting, before discharge, and at last follow-up), and their relation with AAA diameter was analyzed. A significant decrease in AAA compliance was immediately observed after successful EVAR and remained stable during later follow-up. On the other hand, AAA diameter progressively decreased along time and was statistically lower at the last control compared to the initial value. MMSD, segmental compliance, and dilation at maximum diameter were positively related to AAA diameter. This means that the larger the AAA diameter after stenting, the higher the value for these parameters can be expected. On the contrary, percentage of AAA diameter decrease and percentage of MMSD decrease were not related after successful EVAR. There was no parallelism between loss in compliance and diameter decrease along time, and there is not a unique pattern of AAA diameter and compliance evolution after EVAR. Even if comparison between patients without and with endoleak was weak due to the small sample of the latter group (five patients with endoleak), compliance tended to be greater in case of endoleak. AAA wall motion after successful EVAR reflects complex interactions between all the components of the stented aneurysm which evolve over time, including true compliance of the aneurysm wall itself; intra-aneurysm sac pressure with possible different effects for peak, mean, and pulse pressures; remodeling of the thrombus; stiffness characteristics of the graft; and systemic pressure. Combining simultaneous MMSD records with actual intrasaccular pressure measurements in patients with and without endoleak would improve our understanding of the clinical pulsatility mechanism within AAA after EVAR.

Vascular device interaction with the endothelium

Cerebral stents and Intra Aortic Balloon Pumps (IABP) are examples of mechanical devices that are inserted into arteries to restore flows to clinically healthy states. The stent and the IABP ‘correct’ the arterial flow by static dilation and by cyclical occlusion respectively. As this presentation shows, these functions are effectively modelled by current engineering practice. As interventions however, by their very nature they involve physical contact between a non-biological structure and the sensitive endothelial surface. The possible damage to the endothelium is not currently well addressed and we also consider this issue. Cerebral stents generally have two primary clinical objectives: to mechanically dilate a stenosed artery and to have minimal detrimental impact upon local blood flow characteristics. These objectives are well served at the arterial scale as these devices are evidently effective in opening up diseased arteries and restoring vital flows. However, at the near-wall micro-scale the picture is less satisfactory, as thin stent wires apply stresses to the endothelium and glycocalyx and the local flow is disturbed rather than being ideally streamlined. This causes further interaction with this endothelium topography. Wall Shear Stress (WSS) is the measure commonly used to indicate the interaction between fluid and wall but it is a broad brush approach that loses fidelity close to the wall. We will present simulation results of blood flow through a stented cerebral saccular aneurysm under these limitations of WSS. The Intra Aortic Balloon Pump (IABP) is a widely used temporary cardiac assist device. The balloon is usually inserted from the iliac artery, advanced in the aorta until it reaches the desired position; with its base just above the renal bifurcation and the tip approximately 10cm away from the aortic valve. The balloon is inflated and deflated every(1:1), every other(1:2) or every second (1:3) cardiac cycle. Balloon inflation, which takes place during early diastole, causes an increase in the pressure of the aortic root which leads to an increase in coronary flow. Balloon deflation which takes place during late diastole achieves one of the main IABP therapeutic effects by reducing left ventricular afterload. Unavoidably, the balloon contacts the inner wall of the aorta with every inflation/deflation cycle. This repeated event and possible contact with atherosclerotic plaque have been reported to be responsible for balloon rupture. However, there has not been a methodical study to investigate the mechanical effects of balloon-wall interaction. For example, during inflation the balloon approaches the endothelium as it displaces a volume of blood proximally and distally. This squeezing process generates shear stresses, which hasn’t yet been quantified. Similarly, when the balloon moves away from the endothelium during deflation, it generates micro pressure differences that may impose stretching (pulling) stresses on the endothelium cells. Both of the above cases indicate that a very high spatial resolution is required in order to fully understand the process of interaction between device and endothelium, and to interpret the effects at the cellular level.

Hemodynamics altered by placing helix stents in an aneurysm at a 45° angle to the curved vessel

Flow visualization, particle image velocimetry and numerical computation have been complementarily performed to study the fluid flow inside a stented lateral aneurysm. The curved afferent vessel had an inner diameter of 5 mm. The diameters of the aneurysmal orifice, neck and fundus were 7 mm, 5 mm and 7.5 mm, respectively, and the distance between the orifice and dome measured 10 mm. Stents with various porosities were examined. A volume-flow rate waveform of the internal carotid artery was reconstructed with a Wormersley number of 4 and Reynolds number ranging from 202 to 384 in a cardiac cycle. Results are presented in terms of the main and secondary flow velocity vector fields, the inflow rates into the aneurysm and the intra-aneurysmal wall shear stress and pressure. Some comparisons of the computed results with the experimental results and the data available from the literature are also made. It is found that the placement of stents for endovascular treatment is more critical for an unstented parent vessel with curvature than without since the maximum inflow rate of the former is 15 times the latter. The critical porosity of 70% below which an inhibition of intra-aneurysmal thrombus formation will not occur is identified for the first time.

Analysis of type I endoleaks in a stented abdominal aortic aneurysm

To improve the performance of endovascular grafts used for the treatment of abdominal aortic aneurysms, we develop a methodology to analyze the phenomena of type I endoleaks in a non-invasive-stented abdominal aorta. As one aspect of this study, an evaluation of the parietal stresses generated by the blood flow is provided. As blood is known to be a shear-thinning, non-Newtonian fluid, we have chosen to use the Phan-Thien and Tanner model, which can be derived from the rheology of polymer solutions. As a second aspect, we develop an axisymmetric finite-element model of the complete system. An explicit finite-element in-house code, is used to simulate the behavior of the system, which is subjected to hydrostatic pressure and to the stresses generated by the blood flow. As the response of the solid is strongly affected by the response of the fluid, and vice versa, the modeling of a coupled fluid–structure interaction is achieved in this work. This study provides an evaluation of the stresses generated by the blood flow on the aorta's wall. The finite-element model allows to identify biomechanical factors that can influence the propensity of an aneurysm treated with an endograft, to exhibit endoleaks. First observations are made concerning the influence of oversizing of the endograft and the influence of friction coefficients between the aorta, endograft and plaque.

Effects of stent porosity on hemodynamics in a sidewall aneurysm model

Computation and experiment have been complementarily performed to study the fluid flow inside a stented lateral aneurysm anchored on the straight parent vessel. The implicit solver was based on the time-dependent incompressible Navier–Stokes equations of laminar flow. Solutions were generated by a cell-center finite-volume method that used second-order upwind and second-order center flux difference splitting for the convection and diffusion term, respectively. The second-order Crank–Nicolson method was used in the time integration term. Experimental techniques used were flow visualization (FV) and particle tracking velocimetry (PTV). Experimentally, the straight afferent vessel had an inner diameter 10 mm. The diameters of the aneurysmal orifice, neck, and fundus were 14, 10, and 15 mm, respectively, and the distance between the orifice and dome measured 20 mm. A 30 mm long helix-shaped stent was tested. Four stent porosities of 100%, 70%, 50%, and 25% were examined. Volume-flow rate waveform of a cerebral artery was considered with a maximum Reynolds number of 250 and Womersley number of 3.9. Results are presented in terms of the pulsatile main and secondary flow velocity vector fields, the volume inflow rates into the aneurysm, and the wall shear stress (WSS) and wall pressure at the aneurysm dome. Some comparisons of computed results with the present FV and PTV results and with the data available from the literature are also made. The maximum flow velocity inside the aneurysm ostium and the WSS in the dome region at the peak flow can, respectively, be suppressed to less than 5% of the parent vessel bulk velocity (or 20% of the unstented case) and 8% of the unstented case if the stent porosity is smaller than 40% (about the porosity of the two-layer stents). In general, the three-layer stents seem not as effective as the two-layer stents in reducing the magnitude of aneurysm inflow rate and WSS.