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

PurposeTo investigate the performance of control scans in pseudo-continuous ASL (pCASL) and propose strategies for improving sensitivity and reliability of pCASL. MethodsThe 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. ResultsThe 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. ConclusionspCASL perfusion signals can be enhanced (approximate to 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. (c) 2016 International Society for Magnetic Resonance in Medicine.