Regional metabolite levels of the normal posterior fossa studied by protonchemical shift imaging

MR spectroscopy of the posterior fossa is pitted with numerous technical di fficulties. It is, however, of great clinical interest in the study of the degenerative diseases and tumors of this area. We have developed a method t o perform 2D CSI of this area, by using a sagittal slice and a careful posi tioning of outer volume saturation. We performed this acquisition in 30 hea lthy volunteers to determine the normal metabolic ratios in five voxels of this area (mesencephalon, pons, medulla oblongata, vermis, cerebellar white matter). The main technical difficulty was magnetic field inhomogeneity in the lower brainstem generated by dental alloys. However, 88% of the voxels were of sufficient quality to be analyzed. The statistically significant r egional variations were a higher NAA/Cr ratio in the pons than in the medul la oblongata, higher Cho/Cr in the pons than in the mesencephalon and highe r Cho/Cr in the cerebellar white matter than in the vermis. We conclude tha t 2D CSI of the brainstem, although technically delicate can be performed i n most patients. (C) 2001 Elsevier Science B.V. All rights reserved.