Comparison of long-labeled pseudo-continuous arterial spin labeling (ASL) features between young and elderly adults: special reference to parameter selection

Background The signal intensity obtained by arterial spin labeling (ASL) depends not only on perfusion signal, but also on arterial transit time (ATT). Although ATT has a more significant effect on accurate regional cerebral blood flow (CBF) calculations, the multiple post-labeling delay (PLD) approach is difficult to use in routine examinations. Purpose To optimize imaging parameters for labeling duration (LD) and PLD and to confirm their validity in long-labeled pseudo-continuous ASL. Material and Methods The perfusion signal was simulated in four LDs and theoretical signal-to-noise ratio efficiency (SNReff) was calculated. Invivo studies were performed on a 3.0T magnetic resonance imaging (MRI) scanner and 15 volunteers were categorized into either the young or elderly adult groups. We compared the differences in CBF values with or without ATT correction. Results Regarding signal simulation, perfusion signal increased with the length of LD. SNReff also improved with LD, but SNReff plateaued at an LD of 3.0s. As for the invivo study, SNR linearly increased along with the LD. The CBF differences with the correction of ATT were larger in the elderly adult group. This trend was most prominent in the longer ATT area in the occipital cortical region. Conclusion A combination of imaging settings of LD=3.5s and PLD=2.0s were suggested as optimal imaging parameters for allowing acceptable CBF quantification and sufficient SNR in both young and elderly individuals.