Comparison of Water Exchange Rate in Young and Elderly Adults with Diffusion Prepared and Multi-Echo Arterial Spin Labeling MRI

Motivation: Blood-brain barrier (BBB) water exchange rate (Kw) has emerged as a candidate biomarker for neuropsychiatric and neurodegenerative disorders. Goal(s): Currently, two arterial spin labeling (ASL) methods —diffusion-prepared (DP) and multi-echo (ME) ASL —exist to assess regional Kw in humans. Approach: Our study applies the two sequences in a young and elderly cohort to characterize regional Kw in two groups to understand the effect of brain aging on BBB function. Results: DP and ME ASL exhibit opposing directions of Kw in the same participants with ME ASL showing more focal Kw changes in the temporal lobe and surrounding regions across the two age groups. Impact: Our study provides novel biological information about water exchange rate (Kw) in different brain regions to understand aging-related changes in blood-brain barrier physiology and advances the understanding of how Kw imaging measures differ between arterial spin labeling methods.