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## Numerical investigation for the effect of blood flow rate and asymmetric bifurcation angle on the anterior circulation aneurysm formation. ASME-JSME-KSME Joint Fluids Engineering Conference (2011)

Citations: | 1 - 0 self |

### Citations

57 |
Pulsatile Flow in the Human Left Coronary Artery Bifurcation Average Conditions,’’
- He, Ku
- 1996
(Show Context)
Citation Context ...th other cases because of an effect of high WSS at ACA which is accompanied with the large flow rate and flow circulation. Oscillatory Shear Index (OSI) Oscillatory Shear Index (OSI) is an index which is formulated to account for the cyclic variation of the wall shear stress vector from its average direction. OSI represents an amount of the shear stress acting on the luminal surface because of cross flow or reverse flow velocity components during pulsatile flow. High OSI according to a fluctuation of Wall Shear Stress (WSS) correlates with a dysfunction of endothelial cells of the blood vessel[25]. A damage of the endothelial cells can cause an aneurysm initiation then OSI is a significant index and is defined as: FIGURE 6. SPATIAL WALL SHEAR STRESS GRADIENT (SWSSG) WITH VARIOUS FLOW RATE RATIOS FIGURE 5. SPATIAL WALL SHEAR STRESS GRADIENT (SWSSG) WITH VARIOUS I-A ANGLES Copyright © 2011 by KSME5 Downloaded From: https://proceedings.asmedigitalcollection.asme.org on 06/29/2019 Terms of Use: http://www.asme.org/about-asme/terms-of-use (a) Case 2 (b) Case 5 (c) Case 8 0 0 1 OSI 1 2 T w T w dt dt (7) In this research, we tried to verify a location of aneurysm f... |

17 |
Complex hemodynamics at the apex of an arterial bifurcation induces vascular remodeling resembling cerebral aneurysm initiation”.
- Meng, Wang, et al.
- 2007
(Show Context)
Citation Context ...low in the aneurysm using idealized models and grouped real aneurysm models. In research on a formation of aneurysm, Brown N.[6] suggested a mathematical model for geometry changes of bifurcation artery that can affect occurrence of the aneurysm. Singh P. K.[7] investigated that smoking and hypertension make the blood viscosity high, and an area of high wall shear stress(WSS) increases. This can cause an initiation of intracranial aneurysm. Ingebrigsten T.[8] carried out that the bifurcation angle of artery in the circle of Willis is a factor which can predict the presence of aneurysm. Meng H.[9] showed that the arterial wall at an apex of bifurcation is injured when the WSS and Wall Shear Stress Gradient (WSSG) is high, and the aneurysm can occur at the apex of bifurcation artery. Copyright © 2011 by KSME Proceedings of the ASME-JSME-KSME 2011 Joint Fluids Engineering Conference AJK-Fluids2011 July 24-29, 2011, Hamamatsu, Shizuoka, JAPAN AJK2011- 00 1 Downloaded From: https://proceedings.asmedigitalcollection.asme.org on 06/29/2019 Terms of Use: http://www.asme.org/about-asme/terms-of-use Shimogonya Y.[10] and Mantha A.[11] suggested indices which can predict the formation of aneurys... |

13 | Hemodynamics in a cerebral artery before and after the formation of an aneurysm.
- Mantha, Karmonik, et al.
- 2006
(Show Context)
Citation Context ...s a factor which can predict the presence of aneurysm. Meng H.[9] showed that the arterial wall at an apex of bifurcation is injured when the WSS and Wall Shear Stress Gradient (WSSG) is high, and the aneurysm can occur at the apex of bifurcation artery. Copyright © 2011 by KSME Proceedings of the ASME-JSME-KSME 2011 Joint Fluids Engineering Conference AJK-Fluids2011 July 24-29, 2011, Hamamatsu, Shizuoka, JAPAN AJK2011- 00 1 Downloaded From: https://proceedings.asmedigitalcollection.asme.org on 06/29/2019 Terms of Use: http://www.asme.org/about-asme/terms-of-use Shimogonya Y.[10] and Mantha A.[11] suggested indices which can predict the formation of aneurysm, Gradient Oscillatory Number(GON) and Aneurysm Formation Indicator(AFI), by numerical study using the geometry of patients’ blood vessels. The main reason of the aneurysm formation is the hemodynamics characteristics excluding the congenital deformity. Accordingly, the blood flow pattern is an important factor for the presence of aneurysm. In particular, to analyze hemodynamics of cerebral aneurysm, it is needed to consider overall flow characteristics of intracranial artery. Circle of Willis, one of cerebral arteries, is a ring-li... |

11 |
Can temporal fluctuation in spatial wall shear stress gradient initiate a cerebral aneurysm? A proposed novel hemodynamic index, the gradient oscillatory number(GON)”.
- Shimogonya, Ishikawa, et al.
- 2009
(Show Context)
Citation Context ...circle of Willis is a factor which can predict the presence of aneurysm. Meng H.[9] showed that the arterial wall at an apex of bifurcation is injured when the WSS and Wall Shear Stress Gradient (WSSG) is high, and the aneurysm can occur at the apex of bifurcation artery. Copyright © 2011 by KSME Proceedings of the ASME-JSME-KSME 2011 Joint Fluids Engineering Conference AJK-Fluids2011 July 24-29, 2011, Hamamatsu, Shizuoka, JAPAN AJK2011- 00 1 Downloaded From: https://proceedings.asmedigitalcollection.asme.org on 06/29/2019 Terms of Use: http://www.asme.org/about-asme/terms-of-use Shimogonya Y.[10] and Mantha A.[11] suggested indices which can predict the formation of aneurysm, Gradient Oscillatory Number(GON) and Aneurysm Formation Indicator(AFI), by numerical study using the geometry of patients’ blood vessels. The main reason of the aneurysm formation is the hemodynamics characteristics excluding the congenital deformity. Accordingly, the blood flow pattern is an important factor for the presence of aneurysm. In particular, to analyze hemodynamics of cerebral aneurysm, it is needed to consider overall flow characteristics of intracranial artery. Circle of Willis, one of cerebral arte... |

9 |
A review on in vitro studies of hemodynamic characteristics in terminal and lateral aneurysm models”.
- Liou, Liou
- 1999
(Show Context)
Citation Context ... aneurysms occur at a bifurcation of circle of Willis. It is reported that 5,276 cases of intracranial aneurysm occur at internal carotid artery (38%), anterior cerebral artery (31%), and middle cerebral artery (20%) [1]. It is known that the cause of the cerebral aneurysm is congenital deformity of the tunica media and the blood pressure that injures the arterial wall [2]. Many numerical and clinical researches are performed for causes, growth, and rupture of aneurysm. Especially, studies for growth and rupture of aneurysm were mainly carried out because of the risk of the rupture. Liou T. M.[3] conducted an experimental study on changes of flow pattern and pressure in the aneurysm for various bifurcation angles and flow rate ratios. Ford M. D.[4] showed that the flow type is sensitive to inflow momentum which is affected by the angle of the aneurysm bulb relative to the parent artery. Gyorgy P.[5] carried out a study for the effect of geometrical parameters on the blood flow in the aneurysm using idealized models and grouped real aneurysm models. In research on a formation of aneurysm, Brown N.[6] suggested a mathematical model for geometry changes of bifurcation artery that can aff... |

7 |
Experimental Investigation of Branch Flow Ratio, Angle, and Reynolds Number Effects on the Pressure and Flow Fields in Arterial Branch Models,"
- Cho, Back, et al.
- 1985
(Show Context)
Citation Context ...ll and noslip condition was applied to the wall. The governing equations included the continuity equation and the momentum conservation equation, and these are shown as: ( ) 0v t (1) ( ) ( ) ( )v vv p t (2) where v is the vector of fluid velocity, and is the shear stress tensor. To consider blood rheology characteristics, the constitutive equations for non-Newtonian fluid were required. Eq. (3) indicated the second invariant of shear stress tensor. (3) Shear rate is represented as Eq. (4). 1 2 ij ji i j (4) We used the Carreau viscosity model[16] which is known as a suitable for rheological characteristics of blood and the viscosity of the blood formed as: 1 2 2 0 ( ) 1 ( ) n (5) where is the zero-shear viscosity( 0.00345 Pa s ), 0 is the infinite shear viscosity( 0.056 Pa s ), is the time constant( 0.313 s ), and n is the power law index( 0.356 ). Boundary Conditions For the blood pulsation, a velocity profile at the ICA was applied from the experimental study for the blood flow[17]. The profile is shown in Fig. 2. In order to consider the varying blood flow rate, the outlet condition using flow... |

7 |
Relationship between variations in the circle of Willis and flow rates in internal carotid and basilar arteries determined by means of magnetic resonance imaging with semiautomated lumen segmentation: Reference data from 105 healthy volunteers”.
- Tanaka, Fujita, et al.
- 2006
(Show Context)
Citation Context ...ty of the blood formed as: 1 2 2 0 ( ) 1 ( ) n (5) where is the zero-shear viscosity( 0.00345 Pa s ), 0 is the infinite shear viscosity( 0.056 Pa s ), is the time constant( 0.313 s ), and n is the power law index( 0.356 ). Boundary Conditions For the blood pulsation, a velocity profile at the ICA was applied from the experimental study for the blood flow[17]. The profile is shown in Fig. 2. In order to consider the varying blood flow rate, the outlet condition using flow rate ratio for ACA and MCA was applied. The ratio of flow rate was 0.5:0.5, 0.25:0.75[18], and 0.15:0.85[16], and this is listed in Tab. 1. Methods of Numerical Simulations The CFD simulations for hemodynamics were performed with the commercial CFD software, FLUENT V6.3, using the User-Defined Function(UDF) for Carreau viscosity model and velocity inlet profile. In this study, the second-order scheme was used for discretization of the governing equations, because of the simulation accuracy. For unsteady simulations, the PISO algorithm was used and each time step was 0.001 s. To meet the numerical stability, the number of time steps was set to 1000, in other words, it was 2 cardiac... |

6 | Intracranial aneurysms: Flow analysis of their origin and progression”.
- Gonzalez, Cho, et al.
- 1992
(Show Context)
Citation Context ...s, because of the simulation accuracy. For unsteady simulations, the PISO algorithm was used and each time step was 0.001 s. To meet the numerical stability, the number of time steps was set to 1000, in other words, it was 2 cardiac cycles. The solution time for each case was about 4 hours on a 4-node, parallel, and 2.0 GHz Xeon system. RESULTS AND DISCUSSION Averaged Wall Shear Stress (AWSS) High or low Wall Shear Stress(WSS) can render damage to the intima. High WSS increase the possibility of the initial aneurysm formation and rupture, and the growth of aneurysm can be stimulated by low WSS[7,19]. Especially, there is a region of high WSS at the apex of bifurcation artery[20]. In this study, we calculate WSS at the peak systole and Averaged Wall Shear Stress(AWSS) for 1 cardiac cycle. AWSS is defined as: FIGURE 2. PULSATILE INLET VELOCITY PROFILE [17] Copyright © 2011 by KSME3 Downloaded From: https://proceedings.asmedigitalcollection.asme.org on 06/29/2019 Terms of Use: http://www.asme.org/about-asme/terms-of-use (a) Case 4 (b) Case 5 (c) Case 6 0 1 AWSS T w dt T (6) (a) Case 2 (b) Case 5 (c) Case 8 Figure 3 is a distribution of AWSS with various I-A angles when the flow rate ra... |

5 |
On the effect of parentaneurysm angle on flow patterns in basilar tip aneurysms: Towards a surrogate geometric marker of intra-aneurismal hemodynamics”.
- Ford, Lee, et al.
- 2008
(Show Context)
Citation Context ...erior cerebral artery (31%), and middle cerebral artery (20%) [1]. It is known that the cause of the cerebral aneurysm is congenital deformity of the tunica media and the blood pressure that injures the arterial wall [2]. Many numerical and clinical researches are performed for causes, growth, and rupture of aneurysm. Especially, studies for growth and rupture of aneurysm were mainly carried out because of the risk of the rupture. Liou T. M.[3] conducted an experimental study on changes of flow pattern and pressure in the aneurysm for various bifurcation angles and flow rate ratios. Ford M. D.[4] showed that the flow type is sensitive to inflow momentum which is affected by the angle of the aneurysm bulb relative to the parent artery. Gyorgy P.[5] carried out a study for the effect of geometrical parameters on the blood flow in the aneurysm using idealized models and grouped real aneurysm models. In research on a formation of aneurysm, Brown N.[6] suggested a mathematical model for geometry changes of bifurcation artery that can affect occurrence of the aneurysm. Singh P. K.[7] investigated that smoking and hypertension make the blood viscosity high, and an area of high wall shear str... |

5 |
A mathematical model for the formation of cerebral aneurysms”.
- Brown
- 1991
(Show Context)
Citation Context ...ture of aneurysm were mainly carried out because of the risk of the rupture. Liou T. M.[3] conducted an experimental study on changes of flow pattern and pressure in the aneurysm for various bifurcation angles and flow rate ratios. Ford M. D.[4] showed that the flow type is sensitive to inflow momentum which is affected by the angle of the aneurysm bulb relative to the parent artery. Gyorgy P.[5] carried out a study for the effect of geometrical parameters on the blood flow in the aneurysm using idealized models and grouped real aneurysm models. In research on a formation of aneurysm, Brown N.[6] suggested a mathematical model for geometry changes of bifurcation artery that can affect occurrence of the aneurysm. Singh P. K.[7] investigated that smoking and hypertension make the blood viscosity high, and an area of high wall shear stress(WSS) increases. This can cause an initiation of intracranial aneurysm. Ingebrigsten T.[8] carried out that the bifurcation angle of artery in the circle of Willis is a factor which can predict the presence of aneurysm. Meng H.[9] showed that the arterial wall at an apex of bifurcation is injured when the WSS and Wall Shear Stress Gradient (WSSG) is hig... |

5 |
Histopathology of cerebral aneurysms".
- Stehbens
- 1963
(Show Context)
Citation Context ... the stagnation point in ACA for all cases. This is because WSS is elevated in the surrounding area of the stagnation point. Meng H.[9] observed the remodeling of the blood vessel and divided the bifurcation artery into three regions with different flow characteristics called by impinging, acceleration, and recovery region. Destructive remodeling of the vessel wall is shown in an acceleration region where increased WSS appears and positive SWSSG occurs. Internal Elastic Lamina (IEL) disruption and Smooth Muscle Cells (SMCs) contributes to medial thinning[9] and can make the blood vessel expand[22,23]. The stagnation point of the blood flow moves slightly toward ACA with small I-A angle, and there is a little difference owing to the similar location of high WSS region. Negative WSSG region appears after the acceleration region since a flow velocity through the bifurcated artery and the velocity gradient near the vessel wall decreases and it causes a decline of WSS. This region can be called recovery region and remodeling of the vessel wall may not occur in recovery region according to Meng H.[9]. Maximum positive and negative SWSSG in case 2 appears highly in comparison with other cases be... |

4 |
Bifurcation geometry and the presence of cerebral artery aneurysms”.
- Ingebrigtsen, Morgan, et al.
- 2004
(Show Context)
Citation Context ...of the aneurysm bulb relative to the parent artery. Gyorgy P.[5] carried out a study for the effect of geometrical parameters on the blood flow in the aneurysm using idealized models and grouped real aneurysm models. In research on a formation of aneurysm, Brown N.[6] suggested a mathematical model for geometry changes of bifurcation artery that can affect occurrence of the aneurysm. Singh P. K.[7] investigated that smoking and hypertension make the blood viscosity high, and an area of high wall shear stress(WSS) increases. This can cause an initiation of intracranial aneurysm. Ingebrigsten T.[8] carried out that the bifurcation angle of artery in the circle of Willis is a factor which can predict the presence of aneurysm. Meng H.[9] showed that the arterial wall at an apex of bifurcation is injured when the WSS and Wall Shear Stress Gradient (WSSG) is high, and the aneurysm can occur at the apex of bifurcation artery. Copyright © 2011 by KSME Proceedings of the ASME-JSME-KSME 2011 Joint Fluids Engineering Conference AJK-Fluids2011 July 24-29, 2011, Hamamatsu, Shizuoka, JAPAN AJK2011- 00 1 Downloaded From: https://proceedings.asmedigitalcollection.asme.org on 06/29/2019 Terms of Use: ... |

2 |
Effects of smoking and hypertension on wall shear stress and oscillatory shear index at the site of intracranial aneurysm formation”.
- Singh, Marzo, et al.
- 2010
(Show Context)
Citation Context ... of flow pattern and pressure in the aneurysm for various bifurcation angles and flow rate ratios. Ford M. D.[4] showed that the flow type is sensitive to inflow momentum which is affected by the angle of the aneurysm bulb relative to the parent artery. Gyorgy P.[5] carried out a study for the effect of geometrical parameters on the blood flow in the aneurysm using idealized models and grouped real aneurysm models. In research on a formation of aneurysm, Brown N.[6] suggested a mathematical model for geometry changes of bifurcation artery that can affect occurrence of the aneurysm. Singh P. K.[7] investigated that smoking and hypertension make the blood viscosity high, and an area of high wall shear stress(WSS) increases. This can cause an initiation of intracranial aneurysm. Ingebrigsten T.[8] carried out that the bifurcation angle of artery in the circle of Willis is a factor which can predict the presence of aneurysm. Meng H.[9] showed that the arterial wall at an apex of bifurcation is injured when the WSS and Wall Shear Stress Gradient (WSSG) is high, and the aneurysm can occur at the apex of bifurcation artery. Copyright © 2011 by KSME Proceedings of the ASME-JSME-KSME 2011 Join... |

2 |
Computational simulation of autoregulatory brain circulation using
- Kim
- 2005
(Show Context)
Citation Context ..., by numerical study using the geometry of patients’ blood vessels. The main reason of the aneurysm formation is the hemodynamics characteristics excluding the congenital deformity. Accordingly, the blood flow pattern is an important factor for the presence of aneurysm. In particular, to analyze hemodynamics of cerebral aneurysm, it is needed to consider overall flow characteristics of intracranial artery. Circle of Willis, one of cerebral arteries, is a ring-like structure of blood vessels which is found beneath the hypothalamus, and distributes oxygen-rich arterial blood to the cerebral mass[12]. Moorhead K. T.[13] suggested one-dimensional and threedimensional model for circle of Willis and captured autoregulated cerebrovascular flow. Although blood flow in the cerebral arteries is different from other arteries, there is little research for the cerebral aneurysm considering blood flow pattern of circle of Willis. In addition, the analysis for the formation and causes of cerebral aneurysm is limited to the retrospective study from the clinical research. Thus, this paper provides hemodynamic data for aneurysm formation by analyzing blood flow pattern and predicts a location of cerebra... |

2 |
Embolus trajectory through a physical replica of the major cerebral arteries”.
- Chung, Hague, et al.
- 2010
(Show Context)
Citation Context ...or. (3) Shear rate is represented as Eq. (4). 1 2 ij ji i j (4) We used the Carreau viscosity model[16] which is known as a suitable for rheological characteristics of blood and the viscosity of the blood formed as: 1 2 2 0 ( ) 1 ( ) n (5) where is the zero-shear viscosity( 0.00345 Pa s ), 0 is the infinite shear viscosity( 0.056 Pa s ), is the time constant( 0.313 s ), and n is the power law index( 0.356 ). Boundary Conditions For the blood pulsation, a velocity profile at the ICA was applied from the experimental study for the blood flow[17]. The profile is shown in Fig. 2. In order to consider the varying blood flow rate, the outlet condition using flow rate ratio for ACA and MCA was applied. The ratio of flow rate was 0.5:0.5, 0.25:0.75[18], and 0.15:0.85[16], and this is listed in Tab. 1. Methods of Numerical Simulations The CFD simulations for hemodynamics were performed with the commercial CFD software, FLUENT V6.3, using the User-Defined Function(UDF) for Carreau viscosity model and velocity inlet profile. In this study, the second-order scheme was used for discretization of the governing equations, because of the simulatio... |

2 |
Shear stress in cerebral arteries carrying saccular aneurysms”.
- Rossitti
- 1998
(Show Context)
Citation Context ... was used and each time step was 0.001 s. To meet the numerical stability, the number of time steps was set to 1000, in other words, it was 2 cardiac cycles. The solution time for each case was about 4 hours on a 4-node, parallel, and 2.0 GHz Xeon system. RESULTS AND DISCUSSION Averaged Wall Shear Stress (AWSS) High or low Wall Shear Stress(WSS) can render damage to the intima. High WSS increase the possibility of the initial aneurysm formation and rupture, and the growth of aneurysm can be stimulated by low WSS[7,19]. Especially, there is a region of high WSS at the apex of bifurcation artery[20]. In this study, we calculate WSS at the peak systole and Averaged Wall Shear Stress(AWSS) for 1 cardiac cycle. AWSS is defined as: FIGURE 2. PULSATILE INLET VELOCITY PROFILE [17] Copyright © 2011 by KSME3 Downloaded From: https://proceedings.asmedigitalcollection.asme.org on 06/29/2019 Terms of Use: http://www.asme.org/about-asme/terms-of-use (a) Case 4 (b) Case 5 (c) Case 6 0 1 AWSS T w dt T (6) (a) Case 2 (b) Case 5 (c) Case 8 Figure 3 is a distribution of AWSS with various I-A angles when the flow rate ratio is constant for 0.25:0.75. A shear stress stagnation point where AWSS is low,... |

2 |
High wall shear stress gradient suppress morphological response of endothelial cells to fluid flow”.
- Sato, Saito, et al.
- 2009
(Show Context)
Citation Context ... increases. Therefore, a high WSS and high AWSS region comes about, but with a decrease in the blood flow rate through ACA like case 5 and 8, AWSS is not as high as case 2. Spatial Wall Shear Stress Gradient (SWSSG) Endothelial Cells (ECs) elongated and align to the direction of flow after exposure to physiological levels of WSS, and such morphological changes of ECs have been thought to influence functions. Local hemodynamics at regions of high WSS and high Wall Shear Stress Gradient (WSSG) plays a key role in aneurysm formation since WSSG may suppress orientation of ECs to the flow direction[21]. In this research, we realized an importance of WSSG and calculated the Spatial Wall Shear Stress Gradient (SWSSG) from the WSS curve along the upper wall of MCA and ACA. Figure 5 and 6 are a distribution of SWSSG according to IA angle and flow rate ratio, and the high SWSSG region appears around the stagnation point in ACA for all cases. This is because WSS is elevated in the surrounding area of the stagnation point. Meng H.[9] observed the remodeling of the blood vessel and divided the bifurcation artery into three regions with different flow characteristics called by impinging, acceleratio... |

2 |
Genesis of cerebral aneurysms-an update”.
- Krex, Schackert, et al.
- 2001
(Show Context)
Citation Context ... the stagnation point in ACA for all cases. This is because WSS is elevated in the surrounding area of the stagnation point. Meng H.[9] observed the remodeling of the blood vessel and divided the bifurcation artery into three regions with different flow characteristics called by impinging, acceleration, and recovery region. Destructive remodeling of the vessel wall is shown in an acceleration region where increased WSS appears and positive SWSSG occurs. Internal Elastic Lamina (IEL) disruption and Smooth Muscle Cells (SMCs) contributes to medial thinning[9] and can make the blood vessel expand[22,23]. The stagnation point of the blood flow moves slightly toward ACA with small I-A angle, and there is a little difference owing to the similar location of high WSS region. Negative WSSG region appears after the acceleration region since a flow velocity through the bifurcated artery and the velocity gradient near the vessel wall decreases and it causes a decline of WSS. This region can be called recovery region and remodeling of the vessel wall may not occur in recovery region according to Meng H.[9]. Maximum positive and negative SWSSG in case 2 appears highly in comparison with other cases be... |

1 |
Pathology of the cerebral blood vessels”. St Louis,
- Stehbens
- 1972
(Show Context)
Citation Context ...sed a subarachnoid hemorrhage (SAH) which is bleeding into the subarachnoid space. It brings about a decrease of the blood supply that caused by the contraction of cerebral artery. Also, it can cause neurologic deficits and disorders of cognitive functions. In severe cases, the brain is pressed by intracranial hypertension and this can be even deadly for patients. Most of cerebral aneurysms occur at a bifurcation of circle of Willis. It is reported that 5,276 cases of intracranial aneurysm occur at internal carotid artery (38%), anterior cerebral artery (31%), and middle cerebral artery (20%) [1]. It is known that the cause of the cerebral aneurysm is congenital deformity of the tunica media and the blood pressure that injures the arterial wall [2]. Many numerical and clinical researches are performed for causes, growth, and rupture of aneurysm. Especially, studies for growth and rupture of aneurysm were mainly carried out because of the risk of the rupture. Liou T. M.[3] conducted an experimental study on changes of flow pattern and pressure in the aneurysm for various bifurcation angles and flow rate ratios. Ford M. D.[4] showed that the flow type is sensitive to inflow momentum whi... |

1 |
Diagnosis imaging and categorization of intracranial aneurysm”.
- Kim
- 2000
(Show Context)
Citation Context ...ction of cerebral artery. Also, it can cause neurologic deficits and disorders of cognitive functions. In severe cases, the brain is pressed by intracranial hypertension and this can be even deadly for patients. Most of cerebral aneurysms occur at a bifurcation of circle of Willis. It is reported that 5,276 cases of intracranial aneurysm occur at internal carotid artery (38%), anterior cerebral artery (31%), and middle cerebral artery (20%) [1]. It is known that the cause of the cerebral aneurysm is congenital deformity of the tunica media and the blood pressure that injures the arterial wall [2]. Many numerical and clinical researches are performed for causes, growth, and rupture of aneurysm. Especially, studies for growth and rupture of aneurysm were mainly carried out because of the risk of the rupture. Liou T. M.[3] conducted an experimental study on changes of flow pattern and pressure in the aneurysm for various bifurcation angles and flow rate ratios. Ford M. D.[4] showed that the flow type is sensitive to inflow momentum which is affected by the angle of the aneurysm bulb relative to the parent artery. Gyorgy P.[5] carried out a study for the effect of geometrical parameters o... |

1 |
Flow in simplified and real models of intracranial aneurysms”.
- Gyorgy, Adam, et al.
- 2007
(Show Context)
Citation Context ...ca media and the blood pressure that injures the arterial wall [2]. Many numerical and clinical researches are performed for causes, growth, and rupture of aneurysm. Especially, studies for growth and rupture of aneurysm were mainly carried out because of the risk of the rupture. Liou T. M.[3] conducted an experimental study on changes of flow pattern and pressure in the aneurysm for various bifurcation angles and flow rate ratios. Ford M. D.[4] showed that the flow type is sensitive to inflow momentum which is affected by the angle of the aneurysm bulb relative to the parent artery. Gyorgy P.[5] carried out a study for the effect of geometrical parameters on the blood flow in the aneurysm using idealized models and grouped real aneurysm models. In research on a formation of aneurysm, Brown N.[6] suggested a mathematical model for geometry changes of bifurcation artery that can affect occurrence of the aneurysm. Singh P. K.[7] investigated that smoking and hypertension make the blood viscosity high, and an area of high wall shear stress(WSS) increases. This can cause an initiation of intracranial aneurysm. Ingebrigsten T.[8] carried out that the bifurcation angle of artery in the circ... |

1 | 1D and 3D models of auto-regulated cerebrovascular flow”. - Moorhead, Moore, et al. - 2004 |

1 |
Characteristics of aneurysms of the internal carotid artery bifurcation”.
- Sakamoto, Ohba, et al.
- 2006
(Show Context)
Citation Context ...te [1/s ] Infinite shear viscosity [ Pa s ] 0 Zero-shear viscosity [ Pa s ] Time constant [ s ] NUMERICAL DETAILS In order to analyze the blood flow for various bifurcation angles and flow rate ratios, three-dimensional simulations were performed for 9 cases and each case is listed in Tab. 1. Modeling of a Bifurcated Artery The blood vessel for simulation consisted of Internal Carotid Artery (ICA), Anterior Cerebral Artery (ACA), and Middle Cerebral Artery (MCA) in the circle of Willis. The geometry of arteries was formed by referring an average value of results from the clinical study[15]. Figure 1 shows a schematic geometry of the idealized blood vessel. The diameters of ICA, ACA, and MCA were 2.9 mm, 1.9 mm, and 2.5 mm respectively. Numerical simulations were preformed for cases that the bifurcation angle between ICA and ACA is 40.8°, 57.3°, and 73.8°. The computational grid consisted of the hexagonal mesh with O-grid shape using ANSYS ICEM-CFD. The total number of grid cells was about 200,000 and was selected through the grid independence test. TABLE 1. CASES OF NUMERICAL SIMULATION Case I-A angle Flow rate ratio (ACA:MCA) 1 40.8° 0.5:0.5 2 57.3° 3 73.8° 4 40.8° 0.25:0.75 5... |

1 | Pulsatile flow and atherosclerosis in the heman carotid bifurcation. Positive correlation between plaque location and low oscillating shear stress”. - Ku, Giddens, et al. - 1985 |