Xiang He1, Jie Luo2, Dmitriy A. Yablonskiy2, Kyongtae Ty Bae1
1Department of Radiology, University of Pittsburgh, Pittsburgh, PA, United States; 2Mallinckrodt Institute of Radiology, Washington University in St Louis, St Louis, MO, United States
We investigated the effect of chemical exchange on water MR frequency through Bloch equation simulation and by in-vivo brain CEST experiment. Bloch equation simulation predicted a very small contribution from slow exchange amide (NH) group proton. The predicted contribution from faster exchange hydroxyl (OH) group, if measured with CEST approach, would also be small. Both statements were confirmed by in-vivo experiment, which found undetectable absolution frequency shift and little change on relative GM/WM frequency contrast by CEST. The effect by hydroxyl groups can only be detected by CEST if the phase evolution profile can be acquired with sub-millisecond echo time.