Cerebral blood volume mapping using hyperoxia and oxygenation-sensitive MRI is robust to O2-induced hypocapnia

Motivation: Cerebral Blood Volume (CBV) is a critical parameter for clinical diagnosis and neuroscientific applications (e.g. quantitative BOLD-fMRI), yet traditional CBV-mapping MRI is limited by contrast-agent injection. A non-invasive alternative is hyperoxia (HOX) based BOLD-fMRI. Goal(s): This study examines HOX-induced hypocapnia (reduced CO2-levels) as a potential confounder in HOX-CBV-mapping. Approach: We acquired dual-echo pseudo-continuous Arterial Spin Labeling (de-pCASL) data from 15 volunteers while administering 100% O2 and recording end-tidal (et) O2 and etCO2. Temporal dynamics were also evaluated within different HOX-periods. Results: Hyperoxia moderately decreased etCO2 and CBF, while HOX-CBV remained stable across time periods, confirming reliable non-invasive CBV estimation using HOX-fMRI. Impact: This study supports hyperoxia (HOX) BOLD-fMRI as promising for non-invasive CBV-mapping. Despite moderate HOX-induced hypocapnia, CBV remained stable. Thus HOX-CBV may enhance neuroscientific research, especially for quantitative BOLD-fMRI. Also, it may facilitate clinical imaging in patients with contrast-agent contraindications.