The behavior of wall shear stress (WSS) was previously reported in a deformable aneurysm model using fluid-structure interactions. However, these findings have not been validated. In the present study, we examined the effect of elasticity (i.e., deformation) on wall shear stress inside a cerebral aneurysm at the apex of a bifurcation using particle image velocimetry in vitro. The flow model simulated a human patient-specific aneurysm at the apex of the bifurcation of the middle cerebral artery. Flow characteristics by wall elasticity were examined for both elastic and non-deformable aneurysm models with pulsatile blood flow. The absolute temporally-and spatially-averaged WSS along the bleb wall was smaller in the elastic model than that in the non-deformable model. This small WSS may be related to attenuation of the WSS. Further, the WSS gradient had a finite value near the stagnation point of the aneurysm dome. Finally, the WSS gradient near the stagnation point was slightly smaller in the elastic model than that in the non-deformable model. These data suggest that elasticity of the aneurysm wall can affect the progression and rupture of aneurysms via hemodynamic stress.

The mortality and morbidity rate due to the severe effect of intracranial aneurysm (IA) is increasing, which has driven research trend on aneurysm rupture risk. By understanding the nature and causes of the aneurysm rupture, preventive measures could be taken in avoiding rupture besides recommending proper treatments such as endovascular coiling. However, the presence of flow recirculation causes the aneurysm wall to degenerate and weakened. The weakened wall is due to the haemodynamic factors such as velocity, wall shear stress (WSS), time average WSS (TAWSS), OSI and RRT, which were analysed in this study. In the present study, the flow model simulated a human patient-specific aneurysm at the apex of the bifurcation in the middle cerebral artery (MCA) in the transient state. Experimental results of full-scale models were collected on a median, side plane to study the flow behaviour and validation to the numerical simulation settings, which resulted in good agreement with only 8% difference. The simulation results obtained showed several interesting findings. The jet flow into the aneurysm led to complex vortex formation due to impinging flow behaviour within the aneurysm dome. Additionally, the area that recorded low velocity was at 30% of low TAWSS with only 1% of OSI that was more than 0.3, while the OSI critical value and 0.27% area exceeded RRT threshold, which caused the large oscillating blood flow direction and activated the atherosclerosis progression. These results suggest that the jet flow into the dome may cause further damage to the wall of the MCA aneurysm, which will help in providing an insight towards completing a guidance system assessment of rupture risk for medical practitioners in future work.

Aortic cannula is one of major factors leading to adverse events such as thrombosis and atherosclerosis development during open heart surgery, due to oxygenated blood outflow with high velocity jet from heart lung machine (HLM) when exiting the cannula tip into the ascending aorta. It was discovered, and validated by several researchers that blood flow out of the left ventricle into the aorta is spiral in nature. In this study, a novel design in which internal profile of the cannula was made to induce spiral flow were tested by way of numerical simulation, and compared against existing commercial cannula. Three designs were tested, which differed in number of groove employed. Among the cannula model designs, cannula design with 4 grooves yielded the lowest value of maximum wall shear stress at testing tube with 3.778 (Pa) and highest value of area weighted helicity density at 11.829 m/s, 40 mm from cannula tips. Overall, spiral cannula models showed high potential in inducing spiral flow, while the effect on blood hemolysis is acceptable.

Patent ductus arteriosus (PDA) complication can pose several problems to neonates. Practices that use commonly available stents for neonates have been shown to generate others problems such as re-stenosis and thrombosis formation. Thus, there is a need to introduce a specialized stent for PDA application. In this study, initial effort to design a PDA stent has been started. Investigations were focused on the effect of flow dynamics to the failure of the stent inserted into the PDA. Load effects on stent were modeled using finite element modeling software. Unsteady flow effects including both systolic and diastolic conditions were used to mimic physiological conditions. Stress distributions on the stents struts are analyzed to determine critical area of high stress. Several types of stent including slotted stents and diamond shape stent were used for comparisons. The materials of stents are stainless steels 316L and CobaltChromium L605. The results show that blood flow only contributes to 10 -15 percent of the total stress required for the stent to fail. Distribution of the stresses was found to be highest in the area of joints of the struts for all types studied. The ratio of the maximum stress experienced by the struts to the minimum was roughly double. Comparing all the stresses experienced by the stents, the slotted stent was found to the most susceptible to least favorable.Index Terms -stent, computational fluid dynamics, patent ductus arteriosus (PDA), biomechanics, and medical device

Spiral flow-inducing cannula has been shown in previous research to exhibit a considerable effect on flow hemodynamic. However, there is still room for improvement. In this study, several design variations were tested to determine which variants were the best in terms of flow reduction. Computational Fluid Dynamics (CFD) software was used to simulate flow within a spiral flow-inducing cannula with several variations from chamber width and angle differences. The variants were compared against each other by using several flow parameters and a selection method was employed to determine which model was the best. It was found that a variant that has the widest chamber (14 mm) and biggest angle opening (70°) from the chamber to the cannula tube was the best in several parameters, and as such was chosen as the best variant. When compared with the standard straight cannula, the reduction in flow output was recorded to be 30% which is deemed significantly. In conclusion, spiral flow cannula recorded better hemodynamic effects with lower outflow velocity and wall shear stress value.