Understanding inhomogeneous MT (ihMT) in multi-parameter mapping of human brain: Towards larger ihMT, higher resolution, and influence of T1d

Inhomogenous Magnetization Transfer (ihMT), the differential response to irradiation at single and dual frequency offsets, is more complex than MT approaches. Expressing ihMT in terms of MT-saturation (ihMTsat) is a first step to quantification as it corrects for underlying T and B . Larger ihMTsat was observed for smaller frequency offsets, which is explained using MTsat as proxy for bound pool saturation. For longer TR, ihMTsat increased faster than MTsat indicating recovery of dipolar order as ihMTsat increased super-linearly to 1.1pu in WM and 0.2pu in GM at TR=52ms. ihMTsat mapping in vivo was performed at 1.3mm isotropic resolution