Explained variance of cerebrospinal fluid component in resting-state fMRI as a potential biomarker for proportionate perivascular space volume

Motivation: Estimating cerebrospinal fluid (CSF) in perivascular spaces (PVS) is essential to advance understanding of glymphatic clearance of cerebral waste products. Goal(s): This study aimed to explore a novel method for evaluating CSF in PVS in awake subjects, including healthy controls and those with mild cognitive impairment (MCI). Approach: We analyzed the explained variance of CSF components (CSF-derived R2) in resting-state fMRI images to determine the proportionate volume of PVS. Results: We observed a decline in CSF-derived R2 with aging in healthy controls. Conversely, elevated CSF-derived R2 in MCI participants suggests enlargement of PVS, which may implicate altered glymphatic function in cognitive disorders. Impact: The CSF-derived R2 metric from resting-state fMRI images offers a quantifiable assessment of CSF volume in perivascular spaces of the gray matter, holding potential as a biomarker for investigating glymphatic system efficiency.