The water exchange across the blood-CSF barrier in human choroid plexus detected by relaxation-exchange MRI (REXI)

Motivation: The lack of non-invasive imaging methods for assessing choroid plexus function has limited our understanding of the blood-cerebrospinal fluid barrier (BCSFB). Goal(s): Our objective was to measure the trans-barrier water exchange rate (kBCSFB) in human choroid plexus (CP) using MRI. Approach: We adapted our new imaging method, i.e., relaxation-exchange magnetic resonance imaging (REXI) for the human brain, conducted methodological validation, and measured age-related changes in kBCSFB. Results: REXI showed good repeatability in measuring the kBCSFB in the CP (Intraclass correlation coefficient = 0.88) and detected a 56% decrease in kBCSFB from the young group (~ 23 years) to the mild-aged group (~ 55 years). Impact: Considering the growing importance of neurofluids and CP, REXI provides with a new and contrast-agent-free technique to measure the water exchange across BCSFB and serves as a promising neuroimaging tool for evaluating CP function in future clinical studies.