MRI-based flow dynamics analysis in patients with cerebral aneurysm

Object: Flow dynamics are considered to have profound effects on the development and rupture of cerebral aneurysms. The present study used magnetic resonance imaging (MRI)-based flow dynamics analysis to investigate patients with cerebral aneurysms using 4 dimensional analysis (3 geometrical dimensions + chronological changes) to compare the findings of flow dynamics analysis with the intraoperative findings. Methods: MRI-based flow dynamics analysis was performed preoperatively in 6 patients with cerebral aneurysms, 3 with middle cerebral artery aneurysm and 3 with anterior communicating artery aneurysm. Flow dynamics data collection was carried out by the two dimensional fast card phase contrast method with a conventional MRI scanner (GE Signa 1.5 Tesla), combined with ECG gating. The data was analyzed using commercially available software (Flow visualization and analysis: Flova, Artech). Wall shear stress (WSS) was calculated and its change related to cardiac cycle was obtained as a color map. The preoperative findings were directly compared to the intraoperative findings. Results: Intraoperative findings showed that all aneurysms had areas of thin walls which were exposed to low levels of WSS. However, 1 of the 6 patients had multiple thin-wall areas in one aneurysm, one of which was exposed to low levels of WSS and the others to high levels of WSS. Quantification of WSS was available in 2 cases, which showed the thin-wall lesion was exposed to low WSS (around 1.0 Pa) and the thick-wall lesion was exposed to high WSS (over 3.0 Pa). Conclusion: MRI-based flow dynamics analysis is less invasive for patients and easy to perform. For better understanding of the natural history and risk of rupture of cerebral aneurysms, further study is needed.