scholarly journals Hemodynamic Study of Flow Remodeling Stent Graft for the Treatment of Highly Angulated Abdominal Aortic Aneurysm

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Siang Lin Yeow ◽  
Hwa Liang Leo
Keyword(s):  
Shear Stress ◽  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Wall Shear Stress ◽  
Stent Graft ◽  
Thrombus Formation ◽  
Flow Recirculation ◽  
Aortic Neck ◽  
Abdominal Aortic ◽  
Wall Shear

This study investigates the effect of a novel flow remodeling stent graft (FRSG) on the hemodynamic characteristics in highly angulated abdominal aortic aneurysm based on computational fluid dynamics (CFD) approach. An idealized aortic aneurysm with varying aortic neck angulations was constructed and CFD simulations were performed on nonstented models and stented models with FRSG. The influence of FRSG intervention on the hemodynamic performance is analyzed and compared in terms of flow patterns, wall shear stress (WSS), and pressure distribution in the aneurysm. The findings showed that aortic neck angulations significantly influence the velocity flow field in nonstented models, with larger angulations shifting the mainstream blood flow towards the center of the aorta. By introducing FRSG treatment into the aneurysm, erratic flow recirculation pattern in the aneurysm sac diminishes while the average velocity magnitude in the aneurysm sac was reduced in the range of 39% to 53%. FRSG intervention protects the aneurysm against the impacts of high velocity concentrated flow and decreases wall shear stress by more than 50%. The simulation results highlighted that FRSG may effectively treat aneurysm with high aortic neck angulations via the mechanism of promoting thrombus formation and subsequently led to the resorption of the aneurysm.

scholarly journals Comprehensive mechanical & metabolic imaging of abdominal aortic aneurysm with 4D flow/ FDG PET on an integrated PETMRI: a feasibility study

2021 ◽  
Vol 22 (Supplement_3) ◽  
Author(s):  
S Wan ◽  
J Steeden ◽  
M Rega ◽  
L Hoy ◽  
D Walls ◽  
...  
Keyword(s):  
Shear Stress ◽  
Abdominal Aortic Aneurysm ◽  
Image Quality ◽  
Aortic Aneurysm ◽  
Wall Shear Stress ◽  
Fdg Pet ◽  
Metabolic Imaging ◽  
Research Centre ◽  
Abdominal Aortic ◽  
Wall Shear

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): NIHR Biomedical Research Centre, University College London Hospitals. Background A number of non-invasive imaging derived parameters have been implicated in the development and progression of abdominal aortic aneurysm, although the mechanism, and relationships of many of these are yet to be precisely determined.  Mechanical parameters can now be studied using 4D phase contrast magnetic resonance (PCMR), and inflammatory cellular activity can be detected with FDG PET. Purpose It may be postulated that inflammation of the aortic wall may be the intermediary at the tissue level linking mechanical wall shear stress (WSS) to aneurysm progression. It may be feasible to study 4D PCMR and FDG PET at the same patient visit on a PETMRI platform, with the potential to enhance temporal and spatial co-registration and improving the understanding of any relationship between these two parameters.  Our study aims to assess feasibility of studying these on an integrated PETMRI system. Methods 7 patients with known aortic aneurysm were recruited in a vascular ultrasound screening follow up clinic.  During a single visit following 6 hours fasting, all patients underwent FDG injection and 60 minutes uptake period.  With quiet breathing, list mode PET acquisition and concurrent 4D PCMR was acquired using stacks of spiral acquisition, with ECG trace information for retrospective gating.  Images from the 4D PCMR and FDG PET were assessed qualitatively for image quality and visual matching. Results All 7 patients completed the study.  Overall image quality was adequate to good.  There is qualitatively a good concordance with impression of positive correlation between wall shear stress and inflammatory signal (see attached image). Conclusion We have demonstrated feasibility of combined assessment of mechanical and metabolic imaging parameters using an integrated PETMRI system.  Initial findings show there to be a broad concordance of wall shear stress and inflammatory signal in the abdominal aneurysm.

scholarly journals Combining Volumetric and Wall Shear Stress Analysis from CT to Assess Risk of Abdominal Aortic Aneurysm Progression

Radiology ◽  
2020 ◽  
Vol 295 (3) ◽  
pp. 722-729
Author(s):  
Olivier Meyrignac ◽  
Laurence Bal ◽  
Charline Zadro ◽  
Adrien Vavasseur ◽  
Anou Sewonu ◽  
...  
Keyword(s):  
Shear Stress ◽  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Wall Shear Stress ◽  
Stress Analysis ◽  
Abdominal Aortic ◽  
Wall Shear

Steady Flow in Abdominal Aortic Aneurysm Models

1993 ◽  
Vol 115 (4A) ◽  
pp. 418-423 ◽  
Author(s):  
R. Budwig ◽  
D. Elger ◽  
H. Hooper ◽  
J. Slippy
Keyword(s):  
Shear Stress ◽  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Laminar Flow ◽  
Wall Shear Stress ◽  
Steady Flow ◽  
Recirculation Zone ◽  
Abdominal Aortic ◽  
Onset Of Turbulence ◽  
Wall Shear

Steady flow in abdominal aortic aneurysm models has been examined for four aneurysm sizes over Reynolds numbers from 500 to 2600. The Reynolds number is based on entrance tube diameter, and the inlet condition is fully developed flow. Experimental and numerical methods have been used to determine: (i) the overall features of the flow, (ii) the stresses on the aneurysm walls in laminar flow, and (iii) the onset and characteristics of turbulent flow. The laminar flow field is characterized by a jet of fluid (passing directly through the aneurysm) surrounded by a recirculating vortex. The wall shear stress magnitude in the recirculation zone is about ten times less than in the entrance tube. Both wall shear stress and wall normal stress profiles exhibit large magnitude peaks near the reattachment point at the distal end of the aneurysm. The onset of turbulence in the model is intermittent for 2000 < Re < 2500. The results demonstrate that a slug of turbulence in the entrance tube grows much more rapidly in the aneurysm than in a corresponding length of uniform cross section pipe. When turbulence is present in the aneurysm the recirculation zone breaks down and the wall shear stress returns to a magnitude comparable to that in the entrance tube.

scholarly journals Low wall shear stress predominates at sites of abdominal aortic aneurysm rupture

2016 ◽  
Vol 63 (6) ◽  
pp. 1613-1619 ◽  
Author(s):  
April J. Boyd ◽  
David C.S. Kuhn ◽  
Richard J. Lozowy ◽  
Gordon P. Kulbisky
Keyword(s):  
Shear Stress ◽  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Wall Shear Stress ◽  
Aneurysm Rupture ◽  
Abdominal Aortic Aneurysm Rupture ◽  
Abdominal Aortic ◽  
Wall Shear

scholarly journals In-Vitro Simulation of the Blood Flow in an Axisymmetric Abdominal Aortic Aneurysm

2019 ◽  
Vol 9 (21) ◽  
pp. 4560
Author(s):  
Espa ◽  
Moroni ◽  
Boniforti
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Wall Shear Stress ◽  
Particle Tracking ◽  
Classical Particle ◽  
Abdominal Aortic ◽  
Wall Shear

We investigated the blood flow patterns and the hemodynamics associated with an abdominal aortic aneurysm detected in an in vitro measurement campaign performed in a laboratory model of an aneurysm with rigid walls and an axisymmetric shape. Experiments were run in steady flow conditions and by varying the Reynolds number in the range 410 < Re < 2650. High spatial and temporal resolution 2D optical measurements of the velocity field were obtained through a particle tracking technique known as Hybrid Lagrangian Particle Tracking. Conversely to classical Particle Image Velocimetry, both the fluid particle trajectories and the instantaneous and time-averaged velocity fields are provided without constraints on the grid size and very close to the vessel boundary. All the most relevant quantities needed to investigate the flow features were evaluated, and in particular, we focused on the wall shear stress distribution both in the healthy aortic portion and within the aneurysm. Results show that the recirculation zone in correspondence of the cavity moves downstream, and this displacement is found to increase with Re. Very low wall shear stress values are recovered in correspondence of the aneurysmal cavity, while a sharp peak occurs in correspondence of the reattachment point. In agreement with the literature data, the peak value is found to decrease with Re and to be about equal to twice the upstream value.

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