Figure 1.

Direct saturation Z-spectra in various voxels of an axial-oblique slice. (a, c–g) The direct saturation signal magnitude is plotted as a function of RF offset frequency with respect to the scanner reference frequency (ω_ref) at 0ppm. (b) The resonance frequency map (field map) is calculated from the minimum of the direct saturation spectra using Lorentzian lineshape fitting. The colored dots in Z-spectra denote the experimental data points, and the black lines denote the fitted lineshape.