Intraluminal thrombus (ILT) is a fibrin structure which might affect rupture characteristics and be observed 80% of abdominal aortic aneurysms (AAA). Disturbed hemodynamics inside AAA might affect ILT formation, that are generally quantified by wall shear stress (WSS) parameters in literature. Together with WSS parameters, vortex structures observed inside arterial systems can also be counted as indicators of disturbed hemodynamics, and might contribute the generation of ILT. To understand the effect of disturbed hemodynamics on ILT formation, blood flow through AAAs can be simulated by using computational methods. In computational models, setting up inlet boundary conditions (BC) and fluid properties are very important steps which affect the reliability and accuracy of the hemodynamic assessment. The aim of this study is understanding the effect of inlet boundary conditions and rheology model selection on predicting the WSS parameters and vortex structures, and determining a correlation between those hemodynamic parameters. To understand the effect of inlet different BCs on hemodynamic parameters, Womersley, Parabolic and Plug velocity profiles, with different entrance lengths, L_(ent )=D,3D and 11D, are examined. Results reveal that Parabolic profile even with a short entrance length can be utilized instead of complex Womersley profile. To investigate the effect of inlet flow waveform pattern on rheology model selection, three waveform patterns, Base, Case 1 and 2, are tested for eight viscous shear thinning models, along with the viscoelastic Oldroyd-B and Newtonian models. Newtonian model might obtain different OSI and ECAP distributions from shear-thinning models even for high mean flow rates, albeit the differences introduced by elasticity might be negligible. Also, vortex transport mechanism might affect the rheology model selection. To observe the correlation between WSS parameters and vortex structures, time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), endothelial cell activation potential (ECAP) and relative residence time (RRT) distributions and contours of time-averaged (λ_ci ) ̅-criterion, Q ̅-criterion and (λ_2 ) ̅-criterion are plotted. Regions with high |(λ_ci ) ̅ |,|(λ_2 ) ̅ | and |Q ̅ | are correlated with high TAWSS and low OSI, ECAP and RRT. To conclude, vortex identification methods have the potential to be utilized to predict ILT accumulation and rupture sites.


Characterization of wall shear stress in abdominal aortic aneurysm phantom using particle image velocimetry
Türk, Semih; Yavuz, Mehmet Metin; Department of Mechanical Engineering (2021-9)
Abdominal Aortic Aneurysm (AAA) is defined as the enlargement of the largest artery in the abdominal cavity, the abdominal aorta. The vascular rupture begins to pose a risk after a certain enlargement, and the rupture is described as one of the most critical emergencies in medicine. The disease is labeled as the 14th disease with the highest mortality rate. Thus, predicting the progression of the disease is vitally important. Hence, researchers are trying to identify and standardize all biological and mecha...
Characterization of vortex ring in abdominal aortic aneurysm phantom using particle image velocimetry
Gökçek, Kerem Tuğ; Yavuz, Mehmet Metin; Department of Mechanical Engineering (2021-9)
Abdominal aortic aneurysm (AAA) is the permanent enlargement of the abdominal artery that may even rupture at the end, and it is a critical medical situation with a high mortality rate. Although there are some approaches to model its enlargement and rupture, a complete understanding is far from over. A vortex ring is generated during physiological flow pattern, and its evolution should be analyzed in detail to understand its effect on the flow field. The aim of this study is to investigate and characterize ...
Computational analysis for non-invasive detection of stenosis in peripheral arteries
Salman, Huseyin Enes; Yazıcıoğlu, Yiğit (Elsevier BV, 2019-08-01)
Atherosclerosis usually affects the entire cardiovascular system, including peripheral blood vessels. Peripheral arterial stenosis may indicate possible serious vascular disorders related to more vital organs. If peripheral arterial stenosis can be discerned at an early stage, it can serve as a warning sign to take precautions, such as using more invasive diagnostic techniques or adopting a healthier life style. In this study, peripheral regions, such as the thigh, upper arm, and neck are modelled consideri...
Defining a master curve of abdominal aortic aneurysm growth and its potential utility of clinical management
Akkoyun, Emrah; Gharahi, Hamidreza; Kwon, Sebastian T.; Zambrano, Byron A.; Rao, Akshay; Acar, Aybar Can; Lee, Whal; Baek, Seungik (2021-09-01)
The maximum diameter measurement of an abdominal aortic aneurysm (AAA), which depends on orthogonal and axial cross-sections or maximally inscribed spheres within the AAA, plays a significant role in the clinical decision making process. This study aims to build a total of 21 morphological parameters from longitudinal CT scans and analyze their correlations. Furthermore, this work explores the existence of a “master curve” of AAA growth, and tests which parameters serve to enhance its predictability for cli...
Biomechanical Investigation of Disturbed Hemodynamics-Induced Tissue Degeneration in Abdominal Aortic Aneurysms Using Computational and Experimental Techniques
Salman, Huseyin Enes; Ramazanlı, Burcu; Yavuz, Mehmet Metin; Yalcin, Huseyin Cagatay (2019-05-31)
Abdominal aortic aneurysm (AAA) is the dilatation of the aorta beyond 50% of the normal vessel diameter. It is reported that 4-8% of men and 0.5-1% of women above 50 years of age bear an AAA and it accounts for similar to 15,000 deaths per year in the United States alone. If left untreated, AAA might gradually expand until rupture; the most catastrophic complication of the aneurysmal disease that is accompanied by a striking overall mortality of 80%. The precise mechanisms leading to AAA rupture remains unc...
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