RaPPiD: A Region-Specific MRI Metric for Assessing Glymphatic Function and Its Relation to Sleep Quality and Cardiovascular Health

Motivation: The glymphatic system plays a vital role in clearing waste from the brain, yet current imaging techniques lack regional specificity, overlooking crucial cortical areas and subcortical white matter (sWM). Goal(s): Develop a metric, RaPPiD to measure glymphatic function within defined brain regions, linking it to sleep quality. Approach: Using T2 MRI and multi-shell diffusion-weighted imaging, we isolated water diffusivity in periarterial spaces , calculating RaPPiD as a ratio of perpendicular to parallel PAS diffusivity in nine functional sWM ROIs. Results: RaPPiD successfully identified region-specific associations, with lower RaPPiD in FPN and limbic regions correlating with higher PSQI scores. Impact: This study's development of RaPPiD enables precise, region-specific assessment of glymphatic function, advancing understanding of brain waste clearance. Clinicians may use RaPPiD to identify glymphatic impairments linked to sleep and cardiovascular health, guiding potential interventions and research in neurodegenerative disease.