Detecting magnetization exchange between human brain tissue and CSF compartments using selective parenchyma spin labeling and CSF imaging

Motivation: While challenging in humans, measuring fluid exchange between the brain parenchyma tissue and CSF compartments is essential for understanding the role of CSF-mediated metabolic waste clearance in neurodegeneration. Goal(s): We demonstrate the feasibility of detecting such fluid exchange in human brains, unaffected by CSF-flow and partial-volume artifacts. Approach: Free-water spins inside parenchyma were selectively saturated and labeled by magnetization transfer, and subsequent partial saturations were quantified within CSF compartments. Results: We found 3.6% saturation in subarachnoid space (SAS), significant saturation difference between SAS and lateral ventricles (1.3%), and higher saturations in slow-flowing, narrow compartments (e.g. SAS and longitudinal fissure) than larger ventricle spaces. Impact: We demonstrated feasibility of detecting fluid exchange between brain parenchyma and CSF compartments in human brains through selective parenchyma saturation and CSF saturation quantification. Measuring such exchange is important for understanding the role of CSF-mediated metabolic waste clearance in neurodegeneration.