Age and gender-related patterns of arterial transit time and cerebral blood flow in healthy adults

Normal aging has been associated with increased arterial transit time (ATT) and reduced cerebral blood flow (CBF). However, age-related patterns of ATT and CBF and their relationship remain unclear. This is partly due to the lengthy scan times required for ATT measurements, which caused previous age-related CBF studies to not fully account for transit time. In this work, we aimed to elucidate age-related ATT and ATT-corrected CBF patterns. We examined 131 healthy subjects aged 19 to 82 years old using two pseudo-continuous arterial spin labeling (PCASL) MRI scans: one to measure fast low-resolution ATT maps with five post-labeling delays and the other to measure high-resolution perfusion-weighted maps with a single post-labeling delay. Both ATT and perfusion-weighed maps were applied with vessel suppression. We found that ATT increases with age in the frontal, temporoparietal, and occipital regions, with a more pronounced elongation in males compared to females in the middle temporal gyrus. ATT-corrected CBF decreases with age in several brain regions, including the anterior cingulate, insula, posterior cingulate, angular, precuneus, supramarginal, frontal, parietal, superior and middle temporal, occipital, and cerebellar regions, while remaining stable in the inferior temporal and subcortical regions. In contrast, without ATT correction, we detected artifactual decreases in the inferior temporal and precentral regions. These findings suggest that ATT provides valuable and independent insights into microvascular deficits and should be incorporated into CBF measurements for studies involving aging populations.