Improving Pseudo-continuous ASL Efficiency at 7 Tesla Using Gapless Multi-echo EPI

Motivation: Arterial spin labeling (ASL) at 7 Tesla is often SAR-constrained compared to at 3 Tesla, leading to lower labeling capacity and hence lower SNR. Goal(s): To boost the SNR of ASL at 7T by both increasing labeled-blood volume and improving imaging efficiency. Approach: Longer labeling duration and higher flip angles are used together with gapless multi-echo 2D EPI readout. A T2*-informed algorithm is used to combine echoes to optimize SNR. Results: Higher-SNR perfusion images were obtained for a given scan time. Results were tested at several spatial resolutions on multiple subjects. Impact: The gapless multi-echo EPI readout, along with the proposed processing method, significantly improves the overall efficiency of arterial spin labeling at 7 Tesla, which can make ASL faster, more robust, and more accessible at ultra-high fields.