Investigation of control scans in pseudo-continuous arterial spin labeling (pCASL): Strategies for improving sensitivity and reliability of pCASL

Purpose: To investigate the performance of control scans in pseudo-continuous ASL (pCASL) and propose strategies for improving sensitivity and reliability of pCASL.

Methods: The labeling efficiencies of pCASL with conventional control scan and distal control scan were investigated at various radiofrequency (RF) duration/spacing of 0.5/1-2/4 ms, mean slice-selection gradients (G_SS ) of 1 and 0 mT/m, and total labeling durations of 1.5-3 s, through Bloch equation simulations and in vivo experiments. In addition, the feasibility of three-dimensional (3D) pCASL with the distal control scan and control scan with no RF preparation was demonstrated in a wide brain area, by suppressing the magnetization transfer (MT) effects with high G_SS while maintaining the G_SS /mean G_SS ratio.

Results: The distal control scan provided pCASL signals approximately 40% higher and more robust to variations in the labeling conditions than those from the conventional control scan. The distal and no RF control scans with high G_SS provided uniform pCASL signals in approximately 8-cm-thick imaging region with MT contributions <10% of the perfusion signals.

Conclusions: pCASL perfusion signals can be enhanced (∼40%) and become more stable by using the distal or no RF control scan, which can be applied in a wide area by increasing G_SS while maintaining G_SS /mean G_SS . Magn Reson Med 78:917-929, 2017. © 2016 International Society for Magnetic Resonance in Medicine.