Reduced B0/B1+ sensitivity in velocity-selective inversion ASL using adiabatic refocusing pulses

Motivation: Fourier transform velocity selective inversion (FT-VSI) ASL is sensitive to B0/B1+ inhomogeneities, which can lead to pronounced artifacts in CBF imaging. Goal(s): Reduce B0/B1+ sensitivity and improve performance of FT-VSI by utilizing adiabatic refocusing pulses in lieu of composite refocusing pulses. Approach: Adiabatic hyperbolic secant (sech) pulses with MLEV-8 phase modulation were integrated into the FT-VSI train, replacing the composite pulses. Simulations and phantom acquisitions were performed to evaluate B0/B1+sensitivity and subtraction fidelity. Human CBF data were acquired to compare image quality, tSNR, and artifacts. Results: Adiabatic refocusing markedly improved FT-VSI robustness to B0/B1+ inhomogeneities. CBF maps showed improved tSNR, image quality, and artifact reduction. Impact: A novel VSASL labeling train that uses adiabatic refocusing pulses for velocity selective inversion is introduced and found to dramatically enhance performance by improving accuracy, increasing tSNR, and reducing artifacts in human CBF imaging.