Uniform Magnetization Transfer contrast at 7T with Direct Saturation Control

Conventional RF pulse design methods optimize for rotation of the magnetization. However, in systems with Magnetization Transfer (MT) with a semisolid pool, the dynamics do not follow the Bloch equations; saturation of the semisolid depends on |B₁⁺|², making it particularly sensitive to B₁⁺ inhomogeneities. This work employs a novel pulse design framework termed ‘Direct Saturation Control’ (DSatC) to directly consider semisolid saturation. We use this to design composite pulses with spatially uniform semisolid saturation using parallel transmition at 7T, where B₁⁺ is intrinsically highly inhomogeneous. In-vivo results show much more homogeneous MT contrast when using DSatC.