International Society for Magnetic Resonance in Medicine
Abstract
Inhomogenous Magnetization Transfer (ihMT), the differential response to irradiation at single and dual frequency offsets, is sensitive to myelination. Quantification of ihMT in terms of MT saturation (MTsat), the percent reduction of Mz, corrects for underlying T1 and B1+ and allows comparing different implementations to optimize multi-parameter mapping (MPM) protocols. ihMTsat in white matter is roughly one twentieth of MTsat, merely 0.2 p.u. at 5kHz and 100% SAR at 3T. Noise propagation demands acquisition at 1.5mm resolution, large-array coils, and smaller offsets than suggested previously. Inverse MT ratios are highly correlated to ihMTs but obscure the true effect size
