Cardiac active PVS: a metric derived from dynamic T2-weighted EPI for brain effective perivascular space characterization

Motivation: Perivascular space (PVS) is the anatomical basis of glymphatic system. Except for these enlarged PVS, there still lacks a method to characterize the structural-MRI-invisible PVS. Goal(s): To develop a neuroimaging method to characterize the PVS actively driven by the cardiac cycle. Approach: A strongly T2-weighted EPI (TE=130ms) was dynamically acquired with simultaneously recorded cardiac output. The cardiac-active PVS (caPVS) is defined as the EPI signal intensity fluctuation over a cardiac cycle. Results: We found caPVS decreases rather than increases in aging. Furthermore, the MRI-visible enlarged PVS didn't show a significant cardiac-cycle dependence. Impact: Our proposed method provides with a new way to characterize these MRI-invisible but cardiac-active PVS density, which is a highly promising biomarker to evaluate the glymphatic system in future.