Absolute arterial cerebral blood volume quantification using inflow vascular-space-occupancy with dynamic subtraction magnetic resonance imaging.

In patients with steno-occlusive disease of the internal carotid artery (ICA), cerebral blood flow may be maintained by autoregulatory increases in arterial cerebral blood volume (aCBV). Therefore, characterizing aCBV may be useful for understanding hemodynamic compensation strategies. A new 'inflow vascular-space-occupancy with dynamic subtraction (iVASO-DS)' MRI approach is presented where aCBV (mL blood/100 mL parenchyma) is quantified without contrast agents using the difference between images with and without inflowing blood water signal. The iVASO-DS contrast mechanism is investigated (3.0 T, spatial resolution=2.4 x 2.4 x 5 mm(3)) in healthy volunteers (n=8; age=29+/-5 years), and patients with mild (n=7; age=72+/-8 years) and severe (n=10; age=73+/-8 years) ICA stenoses. aCBV was quantified in right and left hemispheres in controls, and, alongside industry standard dynamic susceptibility contrast (DSC), contralateral (cont), and ipsilateral (ips) to maximum stenosis in patients. iVASO contrast significantly correlated (R=0.67, P<0.01) with DSC-CBV after accounting for transit time discrepancies. Gray matter aCBV (mL/100 mL) was 1.60+/-0.10 (right) versus 1.61+/-0.20 (left) in controls, 1.59+/-0.38 (cont) and 1.65+/-0.37 (ips) in mild stenosis patients, and 1.72+/-0.18 (cont) and 1.58+/-0.20 (ips) in severe stenosis patients. aCBV was asymmetric (P<0.01) in 41% of patients whereas no asymmetry was found in any control. The potential of iVASO-DS for autoregulation studies is discussed in the context of existing hemodynamic literature.