Orientation-independent magnetization transfer measurement of white matter in brain

Motivation: Quantitative magnetization transfer (MT) imaging of white matter in human brain exhibits orientation dependence, potentially confounding its clinical application. Goal(s): This study demonstrates that Macromolecular Proton Fraction Mapping based on Spin-Lock (MPF-SL) has significantly reduced orientation sensitivity than saturation-pulse based MT imaging in the human brain. Approach: Two healthy human volunteers underwent MRI exams at two different head orientations, including MPF-SL, saturation-pulse based MT imaging and diffusion tensor imaging (DTI). The DTI was performed to determine the orientation of white matter fiber with respect to static magnetic field B0. Results: The MPF-SL technique yields significantly reduced orientation sensitivity than saturation-pulse based approach. Impact: The MPF-SL technique provides a potential solution for orientation-independent magnetization transfer measurement of white matter in human brain.