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Influence of Parent Artery Segmentation and Boundary Conditions on Hemodynamic Characteristics of Intracranial Aneurysms.

Hua Y, Oh JH, Kim YB - Yonsei Med. J. (2015)

Bottom Line: Hemodynamic factors such as velocity pattern, streamline, wall shear stress, and oscillatory shear index at the systolic time were visualized and compared among the different cases.Hemodynamic factors were significantly affected by the inlet BCs while there was little influence of the outlet BCs.The effect of the outlet length on the hemodynamic factors was similar to that of the inlet length.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Hanyang University, Seoul, Korea.

ABSTRACT

Purpose: The purpose of this study is to explore the influence of segmentation of the upstream and downstream parent artery and hemodynamic boundary conditions (BCs) on the evaluated hemodynamic factors for the computational fluid dynamics (CFD) analysis of intracranial aneurysms.

Materials and methods: Three dimensional patient-specific aneurysm models were analyzed by applying various combinations of inlet and outlet BCs. Hemodynamic factors such as velocity pattern, streamline, wall shear stress, and oscillatory shear index at the systolic time were visualized and compared among the different cases.

Results: Hemodynamic factors were significantly affected by the inlet BCs while there was little influence of the outlet BCs. When the inlet length was relatively short, different inlet BCs showed different hemodynamic factors and the calculated hemodynamic factors were also dependent on the inlet length. However, when the inlet length (L) was long enough (L>20D, where D is the diameter of inlet section), the hemodynamic factors became similar regardless of the inlet BCs and lengths. The error due to different inlet BCs was negligible. The effect of the outlet length on the hemodynamic factors was similar to that of the inlet length.

Conclusion: Simulated hemodynamic factors are highly sensitive to inlet BCs and upstream parent artery segmentation. The results of this work can provide an insight into how to build models and to apply BCs for more accurate estimation of hemodynamic factors from CFD simulations of intracranial aneurysms.

No MeSH data available.


Related in: MedlinePlus

(A) A patient's volumetric flow rate18 for two cardiac cycles. The investigated systolic and diastolic times are about 1.19 s and 1.84 s, respectively. (B) Waveform blood pressure12 for two cardiac cycles for the outlet boundary condition. Note that the second cardiac cycles for both the flow rate and waveform blood pressure are reconstructed from the first ones.
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Figure 2: (A) A patient's volumetric flow rate18 for two cardiac cycles. The investigated systolic and diastolic times are about 1.19 s and 1.84 s, respectively. (B) Waveform blood pressure12 for two cardiac cycles for the outlet boundary condition. Note that the second cardiac cycles for both the flow rate and waveform blood pressure are reconstructed from the first ones.

Mentions: The blood flow was modeled as Newtonian incompressible fluid with a density of 1060 kg/m3 and a viscosity of 4 mPa·s. The blood vessel wall geometries were assumed to be rigid with a no-slip BC. The solver was set on the second-order, high-resolution advection differencing scheme by default. We used the waveform of flow rate Q(t), demonstrated by Kono, et al.,18 to calculate the inlet velocity of BCs (Fig. 2A). Considering the pulse cycle convergence independence, two cardiac cycles were calculated. The first cycle was used to examine solution convergence, and the results of the second cycle were used for analysis. The systolic time on the second cardiac cycle was about 1.19 s, and the diastolic time was about 1.84 s. Both a parabolic velocity distribution based on Womersley solution and a flat (plug flow) velocity distribution were defined across the inlet sections. The parabolic Womersley velocity profile was calculated according to the predefined procedure19 and applied to the inlet by User-Defined Function (UDF). For the plug flow BC, the average velocity of the inlet entrance section was derived by dividing the flow rate Q(t) with the inlet cross-sectional area, and UDF was then used to apply the resulting flat velocity profile to the inlet.


Influence of Parent Artery Segmentation and Boundary Conditions on Hemodynamic Characteristics of Intracranial Aneurysms.

Hua Y, Oh JH, Kim YB - Yonsei Med. J. (2015)

(A) A patient's volumetric flow rate18 for two cardiac cycles. The investigated systolic and diastolic times are about 1.19 s and 1.84 s, respectively. (B) Waveform blood pressure12 for two cardiac cycles for the outlet boundary condition. Note that the second cardiac cycles for both the flow rate and waveform blood pressure are reconstructed from the first ones.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4541663&req=5

Figure 2: (A) A patient's volumetric flow rate18 for two cardiac cycles. The investigated systolic and diastolic times are about 1.19 s and 1.84 s, respectively. (B) Waveform blood pressure12 for two cardiac cycles for the outlet boundary condition. Note that the second cardiac cycles for both the flow rate and waveform blood pressure are reconstructed from the first ones.
Mentions: The blood flow was modeled as Newtonian incompressible fluid with a density of 1060 kg/m3 and a viscosity of 4 mPa·s. The blood vessel wall geometries were assumed to be rigid with a no-slip BC. The solver was set on the second-order, high-resolution advection differencing scheme by default. We used the waveform of flow rate Q(t), demonstrated by Kono, et al.,18 to calculate the inlet velocity of BCs (Fig. 2A). Considering the pulse cycle convergence independence, two cardiac cycles were calculated. The first cycle was used to examine solution convergence, and the results of the second cycle were used for analysis. The systolic time on the second cardiac cycle was about 1.19 s, and the diastolic time was about 1.84 s. Both a parabolic velocity distribution based on Womersley solution and a flat (plug flow) velocity distribution were defined across the inlet sections. The parabolic Womersley velocity profile was calculated according to the predefined procedure19 and applied to the inlet by User-Defined Function (UDF). For the plug flow BC, the average velocity of the inlet entrance section was derived by dividing the flow rate Q(t) with the inlet cross-sectional area, and UDF was then used to apply the resulting flat velocity profile to the inlet.

Bottom Line: Hemodynamic factors such as velocity pattern, streamline, wall shear stress, and oscillatory shear index at the systolic time were visualized and compared among the different cases.Hemodynamic factors were significantly affected by the inlet BCs while there was little influence of the outlet BCs.The effect of the outlet length on the hemodynamic factors was similar to that of the inlet length.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Hanyang University, Seoul, Korea.

ABSTRACT

Purpose: The purpose of this study is to explore the influence of segmentation of the upstream and downstream parent artery and hemodynamic boundary conditions (BCs) on the evaluated hemodynamic factors for the computational fluid dynamics (CFD) analysis of intracranial aneurysms.

Materials and methods: Three dimensional patient-specific aneurysm models were analyzed by applying various combinations of inlet and outlet BCs. Hemodynamic factors such as velocity pattern, streamline, wall shear stress, and oscillatory shear index at the systolic time were visualized and compared among the different cases.

Results: Hemodynamic factors were significantly affected by the inlet BCs while there was little influence of the outlet BCs. When the inlet length was relatively short, different inlet BCs showed different hemodynamic factors and the calculated hemodynamic factors were also dependent on the inlet length. However, when the inlet length (L) was long enough (L>20D, where D is the diameter of inlet section), the hemodynamic factors became similar regardless of the inlet BCs and lengths. The error due to different inlet BCs was negligible. The effect of the outlet length on the hemodynamic factors was similar to that of the inlet length.

Conclusion: Simulated hemodynamic factors are highly sensitive to inlet BCs and upstream parent artery segmentation. The results of this work can provide an insight into how to build models and to apply BCs for more accurate estimation of hemodynamic factors from CFD simulations of intracranial aneurysms.

No MeSH data available.


Related in: MedlinePlus