Effects of Geometric Configurations on the Performance of Reverse Flow Diverters in Reverse Flow Mode

The reverse flow diverter (RFD) consisting of a nozzle and a diffuser is a key component in pneumatic pulse jet pumps. We investigated the effects of suction gap and diffuser configurations on RFD performance during the reverse flow mode. Three suction gap configurations were examined: (1) an axisymmetrical cylinder, (2) a cuboid whose bottom plane had no half-circle groove and was level with the diffuser entrance lower border, and (3) a cuboid with a half-circle groove on the bottom plane. Among them, the second one resulted in the highest RFD pumping capacity. The effect of receiver presence before the diffuser was also examined. RFD pumping efficiency was found to be enhanced in the presence of a receiver before the diffuser when the suction gap length is small and the jet outlet velocity at the nozzle exit is high enough. Based on experimental data, a dimensionless performance curve of the suction factor q versus the ratio of Euler numbers in sections out-out and 0-0 Eu out /Eu 0 was derived. This curve is insensitive to suction gap configurations.

Compact Pneumatic Pulse-Jet Pump with Venturi-Like Reverse Flow Diverter

A compact pneumatic pulse-jet pump with a Venturi-like reverse flow diverter,which consists of a nozzle and diffuser,is designed for lifting and transporting a hazardous fluid through a narrow mounting hole.The pumping performance for a liquid mixture or a liquid-solid mixture is examined in terms of the effects of liquid viscosity,particle mass concentration,lifting height,and compression pressure.Results reveal that the pumping performance of the compact pneumatic pulse-jet pump is controlled by jet inertia and the flow resistance of the riser tube positioned after the diffuser.The capacity of the compact pneumatic pulse-jet pump increases with compression pressure and decreases with liquid viscosity.However,even for a liquid mixture with a high viscosity of 7.38 mPa·s,a pumping capacity of 170.7 L·h-1 was observed.For a liquid mixture,two dimensionless indices of performance were found to be the ratio of Euler numbers Euout/EuDV and the suction factor q.As the liquid-solid mixture was lifted to elevation of 6.74 m by the compact pump,the particle size distributions of the liquid-solid mixture in the tank and from the riser tube outlet were determined by a particle size analyzer and found to coincide well.

Computational methods applied to analyze the hemodynamic effects of flow-diverter devices in the treatment of cerebral aneurysms:Current status and future directions

Flow diverter(FD)devices have been widely employed to treat cerebral aneurysms.Despite the well-documented clinical benefits,considerable inter-patient variability in clinical outcome has been reported,which implies the necessity of patient-specifically evaluating hemodynamic changes following FD treatment,especially those associated with posttreatment intra-aneurysmal thrombus formation or complications.Computational fluid dynamics(CFD)methods,owing to the advantages in hemodynamic quantification,cost,and flexibility over traditional in vivo measurement or in vitro experiment methods,have increasingly become a major means for addressing hemodynamic problems related to FD treatment.Relevant CFD-based studies have extensively demonstrated that the results of hemodynamic computation can reasonably explain the clinical outcomes in different patient cohorts and provide useful insights for guiding the selection or optimization of FD devices.Nevertheless,CFD models are inherently unable to predict FD implantation-induced mechanical changes in the walls of aneurysm and its parent artery.In addition,the boundary conditions of most existing CFD models were not fully personalized for purpose of simplicity or due to the difficulty of measuring flow velocity in nearaneurysm regions,which may however considerably compromise the fidelity of the models in reproducing in vivo hemodynamics.To address these issues,the following studies would be expected:(1)perform fluid structure interaction simulations to explore the associations between wall stress/tension and posttreatment adverse vascular remodeling or aneurysm rupture,and(2)develop geometrical multiscale models based on available in vivo data to generate patient-specific boundary conditions for CFD models localized to aneurysm regions.

Hemodynamic analysis for endovascular treatment in small unruptured intracranial aneurysms:a matched comparison study of flow diverter versus LVIS

Background:We compared the treatment of small unruptured intracranial aneurysms(UIAs)with flow diverter and LVIS-assisted coiling to determine the effects of hemodynamic changes caused by different stent and coil packing in endovascular treatment.Methods:Fifty-one UIAs in 51 patients treated with pipeline embolization device(PED)were included in this study and defined as the PED group.We matched controls 1:1 and enrolled 51 UIAs who were treated with LVIS stent,which were defined as the LVIS group.Computational fluid dynamics were performed to assess hemodynamic alterations between PED and LVIS.Clinical analysis was also performed between these two groups after the match.Results:There was no difference in procedural complications between the two groups(P=0.558).At the first angiographic follow-up,the complete occlusion rate was significantly higher in the LVIS group compared with that in the PED group(98.0%vs.82.4%,P=0.027).However,during the further angiographic follow-up,the complete occlusion rate in the PED group achieved 100%,which was higher than that in the LVIS group(98.0%).Compared with the LVIS group after treatment,cases in the PED group showed a higher value of velocity in the aneurysm(0.03±0.09 vs.0.01±0.01,P=0.037)and WSS on the aneurysm(2.32±5.40 vs.0.33±0.47,P=0.011).Consequently,the reduction ratios of these two parameters also showed statistical differences.These parameters in the LVIS group showed much higher reduction ratios.However,the reduction ratio of the velocity on the neck plane was comparable between two groups.Conclusions:Both LVIS and PED were safe and effective for the treatment of small UIAs.However,LVIS-assisted coiling produced greater hemodynamic alterations in the aneurysm sac compared with PED.The hemodynamics in the aneurysm neck may be a key factor for aneurysm outcome.

Pipeline versus Tubridge in the treatment of unruptured posterior circulation aneurysms

Background To compare the safety and efficacy of pipeline embolization device(PED)and Tubridge flow diverter(TFD)for unruptured posterior circulation aneurysms.Methods Posterior aneurysm patients treated with PED or TFD between January,2019,and December,2021,were retrospectively reviewed.Patients’demographics,aneurysm characteristics,treatment details,complications,and follow-up information were collected.The procedural-related complications and angiographic and clinical outcome were compared.Results A total of 107 patients were involved;PED was applied for 55 patients and TFD for 52 patients.A total of 9(8.4%)procedural-related complications occurred,including 4(7.3%)in PED group and 5(9.6%)in TFD group.During a mean of 10.3-month angiographic follow-up for 81 patients,complete occlusion was achieved in 35(85.4%)patients in PED group and 30(75.0%)in TFD group.The occlusion rate of PED group is slightly higher than that of TFD group.A mean of 25.0-month clinical follow-up for 107 patients showed that favorable clinical outcome was achieved in 53(96.4%)patients in PED group and 50(96.2%)patients in TFD group,respectively.No statistical difference was found in terms of procedural-related complications(p=0.737),occlusion rate(p=0.241),and favorable clinical outcome(0.954)between groups.Conclusions The current study found no difference in complication,occlusion,and clinical outcome between PED and TFD for unruptured PCAs.

Giant serpentine aneurysm of the internal cerebral artery and mandibular aneurysm: a case report

Background:Giant serpentine aneurysms(GSA)originate from saccular or spindle aneurysm,dissimilar from dissected aneurysm,that are defined as partially thrombosed giant aneurysms with tortuous internal vascular channel.The clinical and neuroradiologic characteristics are clarified and the mechanism of formation and the efficacy of double stent implantation in GSA are discussed.Case presentation:An 18-year-old man presented himself with a GSA arising from the internal cerebral artery(ICA).In addition,a mandibular aneurysm(MA)arose from the external cerebral artery(ECA).Success was achieved in treating GSA through endovascular treatment with double stents implanted in the parent artery,which were LEO stent and Tubridge flow diverter.After 1 year of follow-up,three-dimensional reconstruction of blood vessels revealed the disappearance of the serpentine access of GSA,which was found to be replaced with a roughly normal vascular structure.Conclusions:Double stent implantation has provided a feasible treatment option for giant serpentine internal carotid aneurysms and eliminated the possibility of causing collateral circulation occlusion.Therefore,it represents a simple and suitable treatment method for anatomical structure and operation.