Flow visualization of recurrent aneurysms after coil embolization by 3D phase-contrast MRI.

Flow patterns in cerebral aneurysms are clinically important. Information on inflow patterns into aneurysms is especially helpful in preventing a recurrence after coil embolization. Computational fluid dynamics (CFD) simulations of patient-specific cerebral aneurysms are feasible and provide information on flow patterns. However, flow visualization by CFD simulations is challenging for recurrent aneurysms after coil embolization because coils make it difficult to obtain precise geometry of the recurrent aneurysms. In this study, we assessed the feasibility of flow visualization of recurrent aneurysms using 3D phase-contrast magnetic resonance imaging (PC-MRI). Time-of-flight magnetic resonance angiography and 3D PC-MRI were performed in eight cases of recurrent aneurysms after coil embolization. We attempted to visualize flow inside the aneurysms using data of 3D PC-MRI and evaluated the visualization. Additionally, CFD simulations were performed in a single case. Inflow into aneurysms was visualized in all eight cases (100%). Flow patterns inside aneurysms were visualized in six cases (75%), and these were associated with a large size of recurrent aneurysms (mean size, 10.3 mm for visualized cases vs. 4.8 mm for unvisualized cases; p = 0.046, Mann-Whitney test). Flow patterns were similar between PC-MRI and CFD simulations. PC-MRI was faster and easier for observing inflow patterns than CFD simulations. This is the first study to demonstrate that flow visualization of recurrent aneurysms by 3D PC-MRI is feasible. This technique may be more practical and easier than CFD simulations, and may provide clinically helpful information.