Enhancement of MT and CEST Contrast Via Heuristic Fitting of Z-Spectra

Moritz Wilhelm Zaiss¹, Benjamin Schmitt¹, Bram Stieltjes, Peter Bachert¹

Magnetizations transfer processes are quantified by the evaluation of z-spectra. A superposition of Lorentzian line shape functions, a solution of Bloch equations, is discussed as a heuristic but parametric model for z-spectrum fitting. Numerical, phantom and in vivo studies demonstrate the functionality of this method which is less dependent on exact knowledge of the system and provides enhanced contrast through parameter maps compared to standard asymmetry analysis. The heuristic fit is also less dependent on B₀ inhomogeneities and its parameters can be assigned to physical parameters such as concentration and transfer rates, which are markers for tumour activity.