EXPRESS: Quantification of arterial hemodynamics in steno-occlusive disease using time-resolved MRI-based angiography.

BackgroundIntracranial steno-occlusive disease (SOD) assessment benefits from hemodynamic imaging, but comprehensive evaluation often relies on contrast- or radiation-based techniques. Arterial spin labeling (ASL) provides a non-invasive alternative for quantifying tissue-level perfusion and cerebrovascular reactivity, yet does not capture upstream arterial flow dynamics. As a result, non-invasive assessment of macrovascular hemodynamics for SOD remains limited. This study evaluates whether quantitative 4D-MRA provides complementary arterial information beyond established ASL-derived metrics.MethodsTwelve SOD patients (7 women; age 42.3±25.8 years) underwent multi-delay ASL and 4D-MRA before and after acetazolamide. Cerebrovascular reactivity (CVR), arterial transit time (ATT), macrovascular ATT (mATT), and labeled blood volume (LBV) were quantified. Associations and vasodilatory responses were assessed using linear mixed-effects models.ResultsAt baseline, mATT correlated with ATT (β=0.66±0.08, p<0.001). Both decreased following acetazolamide (mATT: 1.07±0.03s to 1.01±0.03s, p=0.029; ATT: 1.63±0.07s to 1.40±0.07s, p<0.001). However, changes in mATT and ATT were not associated with CVR. In contrast, CVR was positively associated with ΔLBV (β=8.84, SE=2.43, p=0.01). Case analyses further demonstrated artery-level delayed inflow and vascular steal.ConclusionQuantitative 4D-MRA provides complementary macrovascular information to ASL in SOD. ΔLBV more consistently reflects cerebrovascular reactivity than transit-based metrics and is sensitive to artery-level delayed inflow and vascular steal.