[Imaging Parameter Optimization of 3D Radial Stack-of-stars MRA with FID Sampling after Treatment of Cerebral Aneurysms with Metallic Devices]

Magnetic resonance angiography (MRA) using ultra-short TE (uTE) is known to be used for the evaluation of cerebral aneurysm after treatment such as clipping and coiling. However, conventional uTE sequences are not appropriate as an additional imaging sequence for 3D time-of-flight (TOF)-MRA because it is not possible to shorten scan time and acquire selective-volume imaging. To solve the problem, we focused on the combination of uTE sampling and 3D radial scan sequences. In this study, we examined the optimal imaging parameters of the proposed uTE-MRA. A simulated blood flow phantom with stents (Enterprise) and titanium clips (YASARGIL) was used for optimizing the TR, flip angle (FA), and radial percentage. The signal intensity in the simulated vessel was measured in each imaging condition, and the ratio of the presence or absence of a stent was evaluated as a relative in-stent signal (RIS). In addition, the diameter of the signal loss of the simulated artery was measured for each imaging condition, and signal loss length (SLL) of a clip was calculated from the average value. The RIS improved with increasing the FA and shortening the TR, but it did not change by changing the radial percentage. The SLL became smaller at the coil as the FA increased, but there was no significant difference between the intersection and the blade. There was also no significant difference between TR and radial percentage. The effective imaging conditions for uTE-MRA to improve the vascular description of the evaluation after treatment of cerebral aneurysms with metallic devices were those with large FA and short TR.