A patient-specific study of blood flow in a cerebral aneurysm using medical images

Cerebral aneurysm disease causes intracranial hemorrhage by rupturing, which can eventually, lead to organ failure or death. For this reason, it is important to anticipate the reasons for rupturing of a cerebral aneurysm from biomechanical point of view. Investigating this disease may even help the physicians to find treatments and predict the patient’s situation. This research was conducted to understand risks of development and rupture of a patient-specific cerebral aneurysm.

In a computational simulation, fluid-structure interaction method has been used for a patient-specific case. Also, considering the speed of the systole as the initial condition of the problem, the blood fluid domain has been solved in three types of fluid mathematical models (Newtonian, non-Newtonian Carreau, and non-Newtonian power-law). Then, the pressure results on the wall have been transmitted to ANSYS software, version 15.0 (ANSYS Inc., Canonsburg, PA, USA) and the structure has been solved based on three material models (linear elastic, hyperplastic Neo-Hookean and hyperplastic Mooney-Rivlin, with 5 parameters). The study was done in University of Tehran, Iran, from October 2016 to September 2018.

Shear stress, pressure, flow velocity, wall displacement and von-Mises stress have been extracted from the simulations. The average wall displacement of the aneurysm was 1.8 mm. Also, no significant difference was found in the amount of arterial wall displacement, with constant wall material model and different blood models. However, a significant difference has been observed in the case of considering constant blood model and different wall material models in the value of displacement.

With regard to the amount of displacement of the aneurysm wall in this particular patient, with the geometry and location of the specific aneurysm, the brain nerves 3 and 6 were under stress and exposed to damage. The minimum shear stress was in the aneurysm neck, which stimulates the endothelial cells in the area of aneurysm. In addition, the blood model didn’t had a significant effect on the displacement calculations, while the wall material model played a more decisive role.