Comparison of velocity-selective arterial spin labeling schemes

Purpose In velocity-selective (VS) arterial spin labeling, strategies using multiple saturation modules or using VS inversion (VSI) pulse can provide improved SNR efficiency compared to the original labeling scheme using one VS saturation (VSS) module. Their performance improvement, however, has not been directly compared. Methods Different VS labeling schemes were evaluated by Bloch simulation for their SNR efficiency, eddy current sensitivity, and robustness against B-1 and B-0 variation. These schemes included dual-module double-refocused hyperbolic secant and symmetric 8-segment B-1-insensitive rotation (sBIR8-) VSS pulses, the original and modified Fourier transform-based VSI pulses. A subset of the labeling schemes was examined further in phantom and in vivo experiments for their eddy current sensitivity and SNR performance. An additional sBIR8-VSS with a built-in inversion (sBIR8-VSS-inversion) was evaluated for the effects of partial background suppression to allow a fairer comparison to VSI. Results According to the simulations, the sBIR8-VSS was the most robust against field imperfections and had similarly high SNR efficiency (dual-module, dual-sBIR8-VSS) compared with the best VSI pulse (sinc-modulated, sinc-VSI). These were confirmed by the phantom and in vivo data. Without additional background suppression, the sinc-VSI pulses had the highest temporal SNR, closely followed by the sBIR8-VSS-inversion pulse, both benefited from partial background suppression effects. Conclusion Dual-sBIR8-VSS and sinc-VSI measured the highest SNR efficiency among the VS labeling schemes. Dual-sBIR8-VSS was the most robust against field imperfections, whereas sinc-VSI may provide a higher SNR efficiency if its immunity to field imperfections can be improved.

Automated summary

Among the velocity-selective (VS) labeling schemes, dual-sBIR8-VSS and sinc-VSI measured the highest SNR efficiency. Dual-sBIR8-VSS was the most robust against field imperfections, while sinc-VSI may provide a higher SNR efficiency if its immunity to field imperfections can be improved. Both were confirmed by phantom and in vivo data, with sinc-VSI pulses showing the highest temporal SNR due to partial background suppression effects.