Signal modulation in H-1 magnetic resonance spectroscopy using contrast agents: Proton relaxivities of choline, creatine, and N-acetylaspartate

The effect of gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) on th e proton relaxation properties of choline, creatine and N-acetylaspartate h as been assessed quantitatively, The compounds studied, either directly or indirectly as chemical constituents of other compounds, contribute to proto n MR spectroscopy observable metabolite resonances, The longitudinal and tr ansverse Gd-DTPA proton relaxivities of the methyl groups of choline, creat ine, and N-acetylaspartate have been determined at 1.5 T. The longitudinal relaxivity of lactate has also been measured, Longitudinal and transverse r elaxivity values were found to vary in the order N-acetylaspartate < creati ne < choline, Using choline as an example, the maximum possible signal enha ncement predicted in vivo in the presence of 0.5 mM Gd-DTPA (using a T-1-we ighted sequence, TR = 888 msec, TE = 20 msec) was found to be approximately 100 %, For a T-2-weighted sequence (TR = 3000 msec, TE = 270 msec) a maxim um signal toss of 53 % was calculated. The present study indicates why the use of contrast agents in spectroscopic investigations may lead to signific ant changes in signal intensities. (C) 1999 Wiley-Liss, Inc.