Fast acceleration of ASL-based time-resolved magnetic resonance angiography by acquisition of control and labeled images in the same shot (fast ACTRESS): An optimization study.

PURPOSE: To establish an optimized sequence design for fast acceleration of arterial spin labeling (ASL)-based time-resolved magnetic resonance angiography (MRA) by acquisition of control and labeled images in the same shot (fast ACTRESS) and a scan time of <1min, for the evaluation of intracranial vessels.

MATERIALS AND METHODS: Ten healthy volunteers with no unilateral symptomatic arterial stenosis, who underwent 3-tesla MRI, were investigated. Imaging parameters for the fast ACTRESS sequence were set with an acquisition time of 45s. During post-processing, the first phase in the multi-phase readout, which was defined as the control image, was subtracted from each of the other phases. Thus, four-dimensional (4D)-MRA images of each phase were obtained. The maximum intensity projection was used for the reconstruction of 4D-MRA images and time-to-signal intensity curves (TIC) obtained for each vessel. The area under the curve (AUC), peak time, and maximum signal intensity were obtained from TIC. The different labeling types were broadly divided into six groups: L1, L2, L3, L4, L5, and L6 according to the actual number of labeling pulse.

RESULTS: A total of 5040 regions of interest were evaluated. The peak SI of L3, except for those in the A2 segment of the anterior cerebral artery, was significantly higher than that of L5. However, there were no significant differences between L4 and L5. Although the AUCs of L3 and L4 for anterior circulation were relatively higher than that of the other subgroups, the AUC of L3 was significantly higher than that of L4.

CONCLUSION: The fast ACTRESS was optimized and indicated that the labeling type of L3 was the most appropriate for the well visualization of intracranial arteries. The fast ACTRESS sequence was useful to acquire well-delineated images of intracranial vessels in ˂1min.