Study of Extracted Geometry Effect on Patient-Specific Cerebral Aneurysm Model with Different Threshold Coefficient (Cthres)

Abstract

The recent diagnostic assessment of cerebrovascular disease makes use of computational fluid dynamics (CFD) to quantify blood flow and determine the hemodynamics factors contributing to the disease from patient-specific models. However, compliant and anatomical patient-specific geometries are generally reconstructed from the medical images with different threshold values subjectively. Therefore, this paper tends to present the effect of extracted geometry with different threshold coefficient, Cthres by using a patient-specific cerebral aneurysm model. A set of medical images, digital subtraction angiography (DSA) images from the real patient diagnosed with internal carotid artery (ICA) aneurysm was obtained. The threshold value used to extract the patient-specific cerebral aneurysm geometry was calculated by using a simple threshold determination method. Several threshold coefficients, Cthres such as 0.2, 0.3, 0.4, 0.5 and 0.6 were employed in the image segmentation creating three-dimensional (3D) realistic arterial geometries that were then used for CFD simulation. As a result, we obtained that the volume of patient-specific cerebral aneurysm geometry decreases as the threshold coefficient, Cthres increases. There is dislocation of artery attached to the ICA aneurysm geometry occurred at a high threshold coefficient, Cthres. Besides, the physical changes also bring remarkable physiological effect on the wall shear stress (WSS) distribution and velocity flow field at patient-specific cerebral aneurysm geometry reconstructed with different threshold coefficient, Cthres.

Study of Bio-Fluid Dynamics in Carotid Artery System Using Numerical Methods

“…Because of the different geometric profiles of ICA branching in three models, the flow velocity is higher in ICA than in ECA in case (b) and (c), while in case (c), the flow is equally distributed with slightly higher magnitude in ICA than in ECA. Due to the higher curvature of ICA than ECA in bifurcation models, the flow separation occurs mainly in the outer wall of ICA with the increased flow towards the inner wall of ICA as clinically observed [12,22,23]. At peak systole along the center line of geometry, 50% magnitude of peak velocity value is observed in CCA of all three models.…”

“…The blood flow in the current vascular study is found to be to be non-Newtonian, incompressible and laminar [5,8,12]. The blood flow behavior is assumed to be laminar as it is considered under resting time of the cardiac cycle [20].…”

“…Change in velocity is monitored for change in grid size at CCA, ECA and ICA. The grid test evaluation finds that velocity and pressure are normalized with the number of elements 420000 for case-a, 390000 for case-b, and 410000 for case-c. [12,19]. In the current study, µ∞ and µ0 is considered to be 0.00345 Pas and 0.056 Pas respectively as found in equation 3.…”

“…However, with the increasing trend of better computational capability, numerical methods are cheaper, valuable and extremely efficient substitute source for several researchers to in domain of bio fluid dynamics as compared to expensive experimental techniques [10,11]. The numerical approach using CFD has been extensively practiced in the biofluid dynamics in virtue of lower computational cost [12,13]. Besides, the analysis of haemodynamics, the importance of Computational Fluid Dynamics (CFD) has been largely used in understanding the haemodynamics of the carotid bifurcation system and to visualise the blood flow changes due to the carotid artery geometric variations.…”