ERETIC based in vivo 1H MRSI quantification

Purpose/Introduction: Proton MR spectroscopy allows the noninvasive evaluation of in vivo brain metabolites. In children, the measured metabolite concentration can be age dependent. We examined the effect of maturation on the regional distribution of brain metabolite concentrations in different brain regions during the first two decades of life with a multivoxel chemical shift imaging (CSI) technique. Subjects and Methods: 92 healthy children and young adults, aged 3.5months to 20 years, were examined by a two-dimensional 1H MRS-CSI sequence during routine MR imaging. CSI was performed on two axial slices at the level of the head of the caudate nucleus and infratentorial through the middle cerebellar peduncles. Spectra were obtained from voxels of 1,5 cm 3 in regions of the frontal and parietal white matter and the caudate head on both sides, the genu and splenium of the corpus callosum, in the midbrain as well as in the right and left cerebellar hemisphere. In each subject, spectra in these brain regions were selected and the metabolite concentrations were evaluated by LC Model. Results: The concentration of N-acetylaspartate increased in the frontal and parietal white matter and in the region of the right and left caudate head during infancy and childhood, whereas it remained constant in the region of the genu and splenium of the corpus callosum. The concentration of creatine minimally decreased during maturation in the frontal white matter, in the region of the genu and splenium and in the midbrain. It remained constant in the parietal white matter. The concentration of choline containing compounds had the tendency to decrease over time in the region of the caudate head, in the genu and splenium and in the parietal white matter. Because of the small size of the genu and splenium especially in very young children and because of artifacts in the posterior fossa, reliable concentrations in those regions were difficult to establish. Discussion/Conclusion: Using CSI it was possible to determine metabolite concentrations in different regions of the brain in an acceptable time frame as part of routine MR imaging. The obtained data about age dependency will be helpful in future pediatric CSI measurements to decide whether the concentration of one of the main metabolites in different examined areas is within the range of normal values or has to be considered as pathologic