Time-resolved TOF MR angiography in mice using a prospective 3D radial double golden angle approach

Abstract

Purpose: To develop an undersampled anatomical, three-dimensional (3-D) time-resolved magnetic resonance angiography (MRA) method for small animals based on time-of-flight (TOF) effect and radial sampling. Methods: Mouse carotid arteries and Circle of Willis images were acquired on a 7T scanner with an electrocardiogram (ECG)-triggered sequence. Preliminary experiments were used to generate an approximately uniform distribution of radial projections with a first golden angle and to produce anatomical TOF images. A second golden angle ratio between consecutive projections of cine acquisitions was added to make it possible to use a temporal filter during reconstruction of time-resolved angiography. A decreasing number of projections were tested, and their impact on signal-to-noise ratio (SNR) and spatial resolution was assessed. Results: In anatomical MRA, the undersampled radial approach efficiently allows fast acquisition of mouse angiogram in 3D (22 sec). It was also only slightly sensitive to motion and flow artifacts. The time-resolved sequence can be performed with only 2,500 projections per cine and a temporal resolution under 4 ms in a relatively short acquisition time (less than 5 min). Conclusion: This technique simultaneously provided high 3D isotropic spatial resolution and excellent temporal resolution with a good SNR level, allowing blood flow to be visualized in a restricted acquisition time.