Impact of Postlabeling Delay on Arterial Spin-Labeling MRI-Based Measures of Cerebral Blood Flow in a Simultaneous PET/MRI Study of Aging

Single-PLD ASL with 1800 msec PLD demonstrated the best balance of reliability and agreement with [¹⁵O]water PET, suggesting it may be an effective choice for studying CBF in aging and AD populations. While multiple-PLD ASL offered comparable performance, it did not confer notable benefits compared with the best-performing single-PLD under similar acquisition time constraints. These findings underscore the importance of PLD selection in ASL protocols in older or cognitively impaired cohorts and highlight the value of assessing intermediate-term reliability in longitudinal studies.