Imaging pH using the chemical exchange saturation transfer (CEST) MRI: Correction of concomitant RF irradiation effects to quantify CEST MRI for chemical exchange rate and pH
Three different 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetamide (DOTAM) derivatives bearing as amide N-substituents phenyl, p-methoxyphenyl and p-ethylbenzoate groups were synthesized and the 1H and 17O NMR relaxometric behaviour of the Gd(III)-chelates and chemical exchange saturation transfer (CEST) effect of the Eu(III) complexes were evaluated. The electronic properties of the substituents were shown to strongly influence the coordinated water exchange rate (kex), resulting in five times faster kex for the electron donating phenylmethoxy group compared to the electron withdrawing ethylbenzoate group.
Improved measurement of labile proton concentration-weighted chemical exchange rate (kws) with experimental factor-compensated and T1-normalized quantitative chemical exchange saturation transfer (CEST) MRI