CEST MRI has been used for quantitative assessment of dilute metabolites and/or pH in ischemic tissue and in tumors. However, conventional asymmetry analysis (MTRasym) may be confounded by concomitant effects such as RF spillover, semisolid macromolecular MT and NOE effects. Therefore, decoupling multiple contributions is essential for elucidating the origins of in vivo CEST contrast for improved quantification. Here we used an Image Downsampling Expedited Adaptive Least-squares (IDEAL) fitting algorithm which is not strongly constrained by image SNR and initial values for fitting. It provides a closer estimation of MTRasym that calculated from acquired data than voxel-wise multi-pool Lorentzian fitting and unravels the major contributors to CEST contrasts between white and gray matters as well as to the CEST changes after global ischemia.