Determination of effectiveness of flow diverter stents usingcomputational fluid dynamics

A flow diverter (FD) stent, being the latest technology in treating giant aneurysms at carotid arteries, diverts blood flow into the parent arteries by reducing inflow into the aneurysm sac. The deviation in the porosity of the FD when it is implanted into the aneurysm neck can even yield an unsuccessful treatment for a patient emerging a cerebral hemorrhage or a nonstagnant fluid zone in the sac. Therefore, the present multi-disciplinary study aims to understand the effects of wire configuration (which determines the porosity) an FD possesses on the blood flow characteristics inside the aneurysm sac. In this study, clinical images of two female patients who are 67 and 47-year-old, one male patient who is 56, before and just after the FD placement operation were obtained and used to reconstruct the fluid domain for numerical simulations. 72, 64, and 48 wired FD stents separately placed all three patients' artery in the clinic were also placed virtually inside the patients' aneurysm site based on the FD's mesh structure and its change due to the patients' anatomy. Patients who are 47 and 56 years old were treated by 64 wire-braid but different brand FDs while the 67-year-old patient was treated by 72 wire-braid FD in the clinic. Besides, a 48 wire-braid FD was virtually implanted in 67 and 47-year-old patients' aneurysm necks to make comparisons with placed ones in the clinic, separately. These three different FD stent configurations were built, and numerical simulations were done before and after the FD placement cases for each patient. Numerical simulations revealed that the use of 72 or 64 wire-braid FD stents show superior performance compared to 48-wire FD (FD-X) stent for stagnation region formation. Furthermore, velocity and dynamic viscosity plots indicated the possible physical pathways of blood stagnation and thus clotting inside the sac. However, there is no stagnation region for the 56-year-old patient due to that the aneurysm is blister and neighbor to Posterior Cerebral Artery (PCA) inlet. Thus, the blood enters the aneurysm did not stagnate and did continue to flow through PCA, possibly causing a long recovery time for the patient.