Measurement of absolute arterial cerebral blood volume in human brain without using a contrast agent

Arterial cerebral blood volume (CBV _a) is a vital indicator of tissue perfusion and vascular reactivity. We extended the recently developed inflow vascular-space-occupancy (iVASO) MRI technique, which uses spatially selective inversion to suppress the signal from blood flowing into a slice, with a control scan to measure absolute CBV _a using cerebrospinal fluid (CSF) for signal normalization. Images were acquired at multiple blood nulling times to account for the heterogeneity of arterial transit times across the brain, from which both CBV _a and arterial transit times were quantified. Arteriolar CBV _a was determined separately by incorporating velocity-dependent bipolar crusher gradients. Gray matter (GM) CBV _a values (n=11) were 2.04±0.27 and 0.76±0.17ml blood/100ml tissue without and with crusher gradients (b=1.8s/mm ²), respectively. Arterial transit times were 671±43 and 785±69ms, respectively. The arterial origin of the signal was validated by measuring its T ₂, which was within the arterial range. The proposed approach does not require exogenous contrast agent administration, and provides a non-invasive alternative to existing blood volume techniques for mapping absolute CBV _a in studies of brain physiology and neurovascular diseases.