查看文章

Chemical exchange saturation transfer (CEST) is a contrast mechanism that exploits exchange‐based magnetization transfer (MT) between solute and water protons. CEST effects compete with direct water saturation and conventional MT processes, and generally can only be quantified through an asymmetry analysis of the water saturation spectrum (Z‐spectrum) with respect to the water frequency, a process that is exquisitely sensitive to magnetic field inhomogeneities. Here it is shown that direct water saturation imaging allows measurement of the absolute water frequency in each voxel, allowing proper centering of Z‐spectra on a voxel‐by‐voxel basis independently of spatial B₀ field variations. Optimal acquisition parameters for this “water saturation shift referencing” (WASSR) approach were estimated using Monte Carlo simulations and later confirmed experimentally. The optimal ratio of the WASSR sweep …