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Several studies have compared phase contrast magnetic resonance imaging (PC‐MRI) with arterial spin labeling (ASL) in the same cohort of subjects. However, these earlier comparisons included subjects across a wide age range, which can contribute to increased intersubject variability. We compared the range and variability of CBF based on PC‐MRI and ASL in a group of young subjects. We also explored whether the comparison between PC‐MRI and ASL was dependent on sex. Thirty young subjects (17 females) were recruited in this study. The CBF from PC‐MRI (CBFPC) was calculated as the total blood flow normalized to brain parenchyma mass. The CBF from ASL (CBFASL) was quantified based on the perfusion kinetic model. The ratio between CBFASL and CBFPC was calculated. Females exhibited significantly higher CBF using both PC‐MRI (p < 0.05) and ASL (p < 0.005) compared with males. The disparity in CBF between sexes was more prominent in ASL measurements. A significant correlation was observed between CBFPC and CBFASL values (r = 0.47, p < 0.01), and CBFASL tended to be lower than CBFPC values (p < 0.001). This difference between CBFASL and CBFPC was more pronounced in males, as evidenced by the smaller CBFASL/CBFPC ratio in males (p < 0.05). The measurement of global CBF with PC‐MRI and ASL are correlated, but CBFASL exhibits lower values than CBFPC. As the underestimation of CBFASL is prominent in males, ASL amplifies the sexual dimorphism in CBF compared with PC‐MRI. [ABSTRACT FROM AUTHOR]

Cerebrovascular reactivity (CVR) is a specific indicator of autoregulatory efficiency. Studies have demonstrated that CVR depends on the baseline vascular dilation status between groups. Within the brain, there also exist spatial variations in both the resting cerebral blood flow (CBF) and CVR across different cerebral regions. However, the relationship between the regional CBF and CVR remains unclear. Hence, the primary goal of this study was to investigate the relationship between the resting CBF using pseudocontinuous arterial spin labeling (pCASL) technique and CVR using blood oxygenation level‐dependent (BOLD) technique across different cerebral regions. Eleven male and 14 female young volunteers were recruited in this study. Each subject was asked to perform the breath‐holding challenge to evaluate CVR at 3 T. The resting CBF was measured using pCASL in each subject. The relationships between CBF and CVR across the lobes were evaluated using the Spearman's rank test. The results showed that, for both sexes, the frontal lobe had the maximal resting perfusion but minimal vascular response to hypercapnia, whereas the occipital lobe had the lowest baseline CBF but maximal reactivity to hypercapnia, suggesting low and high autoregulatory efficiencies at high and low resting CBF in the brain, respectively. Sex‐related differences were observed in CBF but not in CVR. These findings may be of clinical interest in the assessment of cerebrovascular reserve and regional‐dependent vascular diseases. [ABSTRACT FROM AUTHOR]