Numerical Evaluation of MR-Measurement-Integrated Simulation of Unsteady Hemodynamics in a Cerebral Aneurysm

Detailed and accurate information of hemodynamics is essential for clarification and advanced diagnosis of circulatory diseases. In order to reproduce complicated real flow field, the concept of flow observer, which integrates measurement and computation by feedback process, have been proposed. By applying the method to the MR (Magnetic Resonance) measurement, we propose MR-measurement-integrated (MR-MI) simulation: the difference between the Phasecontrast MRI (PC MRI) data and the computational result of three-dimensional velocity vector field is fed back to the numerical simulation. The objective in this study is to evaluate the MR-MI simulation by numerical experiment dealing with an unsteady blood flow in a cerebral aneurysm. In the numerical experiment, we first defined a standard solution with velocity profiles obtained by PC MRI measurement at boundaries as a model of real blood flow. Then, MR-MI simulation was carried out by assuming a uniform velocity profile at the upstream boundary and pressure zero and free flow conditions at the downstream boundaries. During the computation, a feedback signal being proportional to the difference between the standard solution and the computational result was applied at each grid point in the aneurysm. As the result, the MR-MI simulation reproduced the standard solution in the aneurysm owing to the feedback process. The error derived from the inaccurate boundary conditions decreased to 22% in one cardiac cycle, comparing to the ordinary simulation. Consequently, the MR-MI simulation accurately provided the wall shear stress distribution on the cerebral aneurysm as hemodynamic information.