Effects of cerebral perfusion and total intracranial blood supply in small vessel disease: a comparative study between multi-delay arterial spin labeling and 4D phase-contrast magnetic resonance imaging

BACKGROUND AND PURPOSE: Chronic hypoperfusion is considered a central mechanism in cerebral small vessel disease (CSVD). However, the results of studies on CBF vary across the imaging method, with phase-contrast MRI (PC-MRI) reflecting large vessel blood flow and arterial spin labeling (ASL) capturing tissue perfusion. We aimed to investigate the relationship between CSVD and CBF as measured by these two methods. MATERIALS AND METHODS: 94 subjects from community and neurology clinics were enrolled. Global CBF was measured using 4D flow by summing the blood flow in the bilateral internal carotid arteries and the basilar artery, then normalizing by brain volume and density (ntCBFPC). Mean CBF was measured in the whole brain using multi-delay ASL (wbCBFASL). CSVD imaging markers, including white matter hyperintensities (WMH), lacunes, perivascular spaces (PVS), and microbleeds, were assessed in each subject, and a CSVD summary score was calculated to reflect the overall CSVD burden. Free water (FW) and tissue fractional anisotropy (tFA) were used to evaluate the microstructural integrity of white matter. Cognitive performance was assessed using neuropsychological tests. Associations between the two CBF measures, all CSVD imaging markers, and cognition were assessed while controlling for potential confounding variables. RESULTS: Lower ntCBFPC (OR, 0.933; 95% CI: 0.884, 0.984; p = 0.01) and wbCBFASL (OR, 0.914; 95% CI: 0.842, 0.992; p = 0.03) were associated with higher BG-PVS scores. Lower ntCBFPC (OR, 0.798; 95% CI: 0.683, 0.932; p = 0.004) and wbCBFASL (OR, 0.767; 95% CI: 0.636, 0.926; p = 0.006) were associated with the presence of lacune. Only wbCBFASL correlated with white matter injury: higher PWMH Fazekas score (OR, 0.868; 95% CI: 0.791, 0.951; p = 0.003), larger WMH volume (β, -0.252, p = 0.02), higher FW (β, -0.314, p = 0.001), and lower tFA (β, 0.254, p = 0.02). No significant associations existed between ntCBFPC and WMH or diffusion imaging markers. Only ntCBFPC was positively associated with MMSE (β, 0.210, p = 0.04). CONCLUSIONS: CBF measured by ASL demonstrates stronger CSVD associations than those derived from PC-MRI, suggesting that microcirculation impairment, rather than global blood flow, contributes more significantly to CSVD.