Erin Leigh MacMillan1, Daniel Guo Quae Chong1, Wolfgang Dreher2, Anke Henning3, Chris Boesch1, Roland Kreis1
1Department of Clinical Research, University of Bern, Bern, Switzerland; 2Dept. Chemistry, University of Bremen, Bremen, Germany; 3Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
MRS without water suppression can detect exchangeable proton resonances, particularly downfield of water. Employing a two-acquisition scheme with alternating up- or down-field metabolite inversion prior to PRESS, both the metabolite and water spectra were obtained from the human brain in-vivo. The experiment was performed with and without a water inversion prepulse with varying inversion times (TI). The magnetization transfer curves were fit with a Bloch-McConnell two-site exchange model to determine exchange rates, with initial estimates yeilding lifetimes (1/Kmw) ranging from 90ms to >2s, which offer information about pH and chemical microenvironments, and may aid in the understanding of CEST effects.