Probing Glymphatic Exchange Between CSF and Tissue Using Long-TE Arterial Spin Labeling: Simplified Model and Shorter Scan Time

Motivation: There is currently not a clinically feasible imaging technique for the evaluation of glymphatic function. Goal(s): We proposed a new framework to measure a simple index, CSF signal fraction in ASL, which only requires 10 minutes of scan time using a single delay and two echoes. Approach: Compared to standard pCASL, the proposed sequence used enhanced background suppression, complex control and label subtraction, and a T2-preparation module with a long effective TE(eTE). Results: The parametric map had a variability of approximately 5%. An eTE of ≥480ms and a PLD of ≥2500ms are suitable for CSF fraction mapping. Impact: In this study, we developed a framework to measure CSF signal fraction in ASL MRI, which may provide a physiological index to evaluate tissue CSF dynamics and brain waste clearance system.