In Vitro Performance Assessment of Distal Protection Devices for Carotid Artery Stenting: Effect of Physiological Anatomy on Vascular Resistance

2007 ◽  
Vol 14 (5) ◽  
pp. 712-724 ◽  
Author(s):  
Gail M. Siewiorek ◽  
Mark H. Wholey ◽  
Ender A. Finol
Keyword(s):  
Carotid Artery ◽  
Pressure Gradient ◽  
Vascular Resistance ◽  
Flow Rate ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Physiological Anatomy ◽  
Protection Devices ◽  
Distal Protection

Purpose: To assess in vitro the performance of 5 distal protection devices (DPDs) by evaluating the capture efficiency, pressure gradient, volume flow rate, and vascular resistance in the internal carotid artery (ICA). Methods: The time-averaged mean peak velocity in the common carotid artery and a blood-mimicking solution were used to simulate physiological conditions in a silicone carotid phantom representing average human carotid artery geometry with a 70% symmetrical ICA stenosis. Five milligrams of dyed 200-μm nominal diameter polymer microspheres (larger than the pore size of the devices, except Spider RX, which was tested with 300-μm-diameter particles) were injected into the ICA. The percentages of particles missed after injection and lost during device retrieval were measured for the 5 devices (Spider RX, FilterWire EZ, RX Accunet, Angioguard XP, and Emboshield). The normalized pressure gradient, fraction of the volume flow rate, and vascular resistance in the ICA were calculated. Results: Spider RX captured the most particles (missing 0.06%, p<0.05) and yielded the smallest normalized pressure gradient increase (4.2%), the largest volume flow rate fraction (0.40), and the smallest vascular resistance in the ICA (272 mmHg/L·min−1, a 5.4% increase with respect to initial conditions). Angioguard XP captured the fewest particles (missing 36.3%, p<0.05 except Emboshield) and resulted in the largest normalized pressure gradient increase (37%) in the ICA. RX Accunet produced the smallest volume flow rate fraction in the ICA (0.30) and the largest vascular resistance in the ICA (470 mmHg/L·min−1, an 82.2% increase). Emboshield migrated ∼6 cm distal to the original position after particle injection. FilterWire EZ lost the fewest particles during retrieval (0.45%, p<0.05 except Accunet RX and Spider RX) and had the best overall performance with 200-μm emboli (p<0.05 except Accunet RX). Conclusion: None of the devices tested completely prevented embolization. Overall, Spider RX had the best performance and is conjectured to have the best wall apposition of the devices tested. Vascular resistance should be considered a key filter design parameter for performance testing since it represents a quantitative estimation of the “slow-flow phenomenon.” Our findings should be extrapolated cautiously to help interventionists choose the best device.

EVOLUTION OF CHAIN STRUCTURE OF ELECTRORHEOLOGICAL FLUIDS IN FLOW MODEL

2002 ◽  
Vol 16 (17n18) ◽  
pp. 2697-2703 ◽  
Author(s):  
X. P. ZHAO ◽  
X. Y. GAO ◽  
D. J. GAO
Keyword(s):  
Pressure Gradient ◽  
Flow Rate ◽  
Volume Flow Rate ◽  
Chain Structure ◽  
Volume Flow ◽  
Electrorheological Fluids ◽  
Relative Pressure ◽  
Dynamic Simulations ◽  
Er Fluids ◽  
The Relationship

The movement of particles in electrorheological (ER) fluids is analyzed by means of molecular dynamic simulations. We found that the velocity profile of particles can be divided into two zones. One zone near electrodes where particles' velocity profiles change periodically like "breathing type" is called transition zone. The other in the middle of two electrodes where particles move smoothly like a plug is called "plug zone". In addition, the relationship between volume flow rate and relative pressure gradient is simulated out. Factors such as volume flow rate, critical electric field, critical pressure gradient and response time of shutting up were also analyzed respectively.

Effects of heat transfer and the endoscope on Jeffrey fluid peristaltic flow in tubes

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
A.M. Abd-Alla ◽  
S.M. Abo-Dahab ◽  
M.A. Abdelhafez ◽  
Esraa N. Thabet
Keyword(s):  
Heat Transfer ◽  
Pressure Gradient ◽  
Flow Rate ◽  
Analytical Solutions ◽  
Volume Flow Rate ◽  
Peristaltic Flow ◽  
Volume Flow ◽  
Jeffrey Fluid ◽  
Temperature Profiles ◽  
Content Type

PurposeThis article aims to describe the effect of an endoscope and heat transfer on the peristaltic flow of a Jeffrey fluid through the gap between concentric uniform tubes.Design/methodology/approachThe mathematical model of the present problem is carried out under long wavelength and low Reynolds number approximations. Analytical solutions for the velocity, temperature profiles, pressure gradient and volume flow rate are obtained.FindingsThe results indicate that the effect of the wave amplitude, radius ratio, Grashof number, the ratio of relaxation to retardation times and the radius are very pronounced in the phenomena. Also, a comparison of obtaining an analytical solution against previous literatures shows satisfactory agreement.Originality/valueAnalytical solutions for the velocity, temperature profiles, pressure gradient and volume flow rate are obtained. Numerical integration is performed to analyze the pressure rise and frictional forces on the inner and outer tubes.

Volume Flow Rate of Common Carotid Artery Measured by Doppler Method and Color Velocity Imaging Quantification (CVI-Q)

2006 ◽  
Vol 16 (1) ◽  
pp. 34-38 ◽  
Author(s):  
Pornpatr Likittanasombut ◽  
Patrick Reynolds ◽  
Dana Meads ◽  
Charles Tegeler
Keyword(s):  
Carotid Artery ◽  
Flow Rate ◽  
Common Carotid Artery ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Doppler Method ◽  
Velocity Imaging

Permeability and Porosity of Embolic Protection Filters: An Experimental Study

2008 ◽  
Author(s):  
Gail M. Siewiorek ◽  
Ender A. Finol
Keyword(s):  
Carotid Artery ◽  
Flow Rate ◽  
Optimization Approach ◽  
Embolic Protection ◽  
High Resolution Images ◽  
Computational Fluid Dynamics Simulations ◽  
Protection Devices ◽  
Distal Perfusion ◽  
Dynamics Simulations

Endovascular therapies are an evolving form of treatment for stenosed atherosclerotic blood vessels. In particular, stenting and angioplasty of the carotid artery has recently gained more attention. Due to risk of periprocedural distal embolization, cerebral protection devices such as embolic protection filters (EPFs), which maintain distal perfusion during the intervention, have been developed to capture embolized plaque particles. This investigation studied in vitro the effects of a deployed EPF on flow rate in the internal carotid artery. The pseudopermeability of each device was calculated by maintaining a constant pressure gradient during its deployed state and after injection of emboli by adjusting the flow rate. High resolution images were used to calculate the porosity of each device. Experimentally-determined permeability and porosity can be used in computational fluid dynamics simulations as a design optimization approach to determine the optimal pore size for each EPF.

Experimental and Computational Evaluation of Embolic Protection

2010 ◽  
Author(s):  
Gail M. Siewiorek ◽  
Ender A. Finol
Keyword(s):  
Carotid Artery ◽  
The Body ◽  
Cerebral Vasculature ◽  
Treatment Alternative ◽  
Computational Evaluation ◽  
Protection Devices ◽  
Distal Protection ◽  
Distal Perfusion ◽  
Viable Treatment

Carotid artery stenting (CAS), an endovascular treatment for severe carotid artery occlusive disease, is increasingly considered a complimentary procedure to carotid endarterectomy. One reason for the acceptance of CAS as a viable treatment alternative is cerebral protection devices (CPDs), which can reduce the embolic load in the cerebral vasculature. One particular type of CPD, distal protection filters (DPFs), are a popular choice due to their ability to allow distal perfusion peri-procedurally while filtering and removing plaque emboli from the body. This investigation studied one FDA-approved DPF, RX Accunet, using both in vitro and computational methods.

Novel epoxy/anhydride alternatives for biological electron microscopy: Physical and performance characteristis of embed 812 and LX 112 in combination with NSA/NMA/DMAE

1989 ◽  
Vol 47 ◽  
pp. 1000-1001
Author(s):  
Joe A. Mascorro ◽  
Gerald S. Kirby
Keyword(s):  
Electron Microscopy ◽  
Flow Rate ◽  
Succinic Anhydride ◽  
Volume Flow Rate ◽  
Mass Density ◽  
Uranyl Acetate ◽  
Volume Flow ◽  
Base Resin ◽  
And Performance ◽  
Acid Anhydrides

Embedding media based upon an epoxy resin of choice and the acid anhydrides dodecenyl succinic anhydride (DDSA), nadic methyl anhydride (NMA), and catalyzed by the tertiary amine 2,4,6-Tri(dimethylaminomethyl) phenol (DMP-30) are widely used in biological electron microscopy. These media possess a viscosity character that can impair tissue infiltration, particularly if original Epon 812 is utilized as the base resin. Other resins that are considerably less viscous than Epon 812 now are available as replacements. Likewise, nonenyl succinic anhydride (NSA) and dimethylaminoethanol (DMAE) are more fluid than their counterparts DDSA and DMP- 30 commonly used in earlier formulations. This work utilizes novel epoxy and anhydride combinations in order to produce embedding media with desirable flow rate and viscosity parameters that, in turn, would allow the medium to optimally infiltrate tissues. Specifically, embeding media based on EmBed 812 or LX 112 with NSA (in place of DDSA) and DMAE (replacing DMP-30), with NMA remaining constant, are formulated and offered as alternatives for routine biological work.Individual epoxy resins (Table I) or complete embedding media (Tables II-III) were tested for flow rate and viscosity. The novel media were further examined for their ability to infilftrate tissues, polymerize, sectioning and staining character, as well as strength and stability to the electron beam and column vacuum. For physical comparisons, a volume (9 ml) of either resin or media was aspirated into a capillary viscocimeter oriented vertically. The material was then allowed to flow out freely under the influence of gravity and the flow time necessary for the volume to exit was recored (Col B,C; Tables). In addition, the volume flow rate (ml flowing/second; Col D, Tables) was measured. Viscosity (n) could then be determined by using the Hagen-Poiseville relation for laminar flow, n = c.p/Q, where c = a geometric constant from an instrument calibration with water, p = mass density, and Q = volume flow rate. Mass weight and density of the materials were determined as well (Col F,G; Tables). Infiltration schedules utilized were short (1/2 hr 1:1, 3 hrs full resin), intermediate (1/2 hr 1:1, 6 hrs full resin) , or long (1/2 hr 1:1, 6 hrs full resin) in total time. Polymerization schedules ranging from 15 hrs (overnight) through 24, 36, or 48 hrs were tested. Sections demonstrating gold interference colors were collected on unsupported 200- 300 mesh grids and stained sequentially with uranyl acetate and lead citrate.

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