3D MRI of whole-brain water permeability with intrinsic diffusivity encoding of arterial labeled spin (IDEALS)

This work proposes a novel MRI method – Intrinsic Diffusivity Encoding of Arterial Labeled Spin (IDEALS) – for the whole-brain mapping of water permeability in the human brain without an exogenous contrast agent. Quantitative separation of the intravascular and extravascular labeled water MRI signal was achieved in arterial spin labeling experiments with segmented 3D-GRASE acquisition by modulating the relative sensitivity between relaxation, true diffusion, and pseudodiffusion. The intrinsic diffusivity encoding in k-space created different broadening of the image-domain point spread functions for intravascular and extravascular labeled spins, from which blood-brain barrier (BBB) water extraction fraction (Ew) and water permeability surface area product (PSw) were estimated. The feasibility and sensitivity of this method was evaluated in healthy subjects at baseline and after caffeine challenge. The estimated baseline Ew and PSw maps showed contrast among gray matter (GM) and white matter (WM). GM Ew was significantly lower than that of WM (78.8% ± 3.3% in GM vs. 83.9% ± 4.6% in WM; p