Fig. 2

a B0 inhomogeneity causes the entire z-spectrum to be shifted, causing a mismatch between the assumed and actual 0 ppm position. Dense sampling (red dots) around the expected water frequency allows the frequency shift α to be derived (often performed with a low power short-duration RF), which may be used to shift back the z-spectrum; b the MTR_asym curve may be derived after the B0 field correction, and CEST effects are observed around τ ppm as indicated by the peak in MTR_asym