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Zusammenfassung:
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/Km¨w) ranging from 90ms to >2s, which offer information about pH and chemical microenvironments, and may aid in the understanding of CEST
