Optimizing velocity-selective inversion pulses for improved labeling efficiency and robustness

Motivation: Current Fourier Transform-based velocity-selective inversion (VSI) pulses are sensitive to field inhomogeneities, leading to labeling errors or inefficiency. Goal(s): To improve the labeling robustness and efficiency of the VSI pulses for more robust and high-SNR perfusion measurement. Approach: A new design with 6-segment FT-VSI pulse was implemented and tested in healthy subjects using dual-module VSI labeling. Results: Compared with the existing VSI pulse, the new pulse significantly improved the labeling robustness against field inhomogeneities and the overall labeling efficiency, leading to >15% higher ASL signal (p<0.0002) and >20% higher temporal SNR (p<0.009). Impact: This new VSI pulse can effectively improve the labeling robustness against field inhomogeneities, while increasing the labeling efficiency and reducing the SAR. These features are especially beneficial with dm-VSASL implementation and in ultra-high field applications for delay-insensitive ASL perfusion imaging.