In vivo observation of lactate methyl proton magnetization transfer in ratC6 glioma

Magnetic resonance spectroscopy (MRS) measurements of the lactate methyl pr oton in rat brain C6 glioma tissue acquired in the presence of an off-reson ance irradiation field, analyzed using coupled Bloch equation formalism ass uming two spin pools, demonstrated the occurrence of magnetization transfer . Quantitative analysis revealed that a very small fraction of lactate (f = 0.0012) is rotationally immobilized despite a large magnetization transfer effect. Off-resonance rotating frame spin-lattice relaxation studies demon strated that deuterated lactate binds to bovine serum albumin and the prote ins present in human plasma, thereby providing a possible physical basis fo r the observed magnetization transfer effect. These results demonstrate tha t partial or complete saturation of the motionally restricted lactate pool (as well as other metabolites) by the application of an off-resonance irrad iation field, such as that used for water presaturation, can lead to a subs tantial decrease in resonance intensity by way of magnetization transfer ef fects, resulting in quantitation errors. (C) 1999 Wiley-Liss, Inc.