© Pol J Radiol, 2010; 75(2): 22-26 Krukowski P et al – Analysis of the brain proton magnetic resonance… Figure 1. Localization of the posterior cingulate gyrus gray matter (PGM) voxel and example of spectroscopic spectrum. Figure 2. Localization of the parietal white matter (PWM) voxel and example of spectroscopic spectrum. with nA [Hz] – resonance frequency of a metabolite nucleus nW [Hz] – resonance frequency of the nuclei of a model n0 [Hz] – resonance frequency of a spectrometer The chemical shift is most frequently expressed in parts per million (ppm), which makes the graph of the spectrum independent from the applied intensity of the magnetic field. The location of the ‘peaks’ – i.e. signals of specific metabolites – is marked on axis X with a ppm value, while the peak amplitude is roughly proportional to the number of the nuclei generating magnetic resonance signals – i.e. concentration of a given substance in the examined sample. To obtain a HMRS spectrum in vivo, it is necessary to apply so called localisation techniques which consist in data acquisition from one, spatially selected volume of interest (VOI) (Figures 1, 2). The sources of the strongest resonance signals within the brain are: N-acetylaspartate (NAA), creatine (Cr), choline (Cho), myoinositol (mI) and, first of all, water, the signal of which is several hundred times stronger than the signal of the remaining metabolites. In the review of the literature on brain MRS, there are multiple articles concerning the pathological processes. However, the topic of spectrum analysis in healthy indi- viduals (i.e. after the completion of myelinisation), with respect to the differences between the grey and white mat- ter, is rarely introduced. The aim of our study was to analyse the potential changes and differences in the image of the spectroscopic spectrum of the brain tissue, within the white and grey matter, and to create a model of HMRS results, including the differenc- es in the HMRS spectrum of the white and the grey matter. Material and Methods In the group of 194 patients who underwent brain HMRS, 90 individuals in the age ranging from 8 to 80 years were included in the study. The study was conducted prospec- tively: it included logically responsive patients, not revealing any cognitive disturbances, without diseases or injuries of the central nervous system or history of systemic diseases; without neurological symptoms or pathological lesions found on brain MRI. The mean age of the whole group was 43.3 years (SD=17.9). In that group, there were 61 women (from 8 to 80 years old, mean age of 40.4; SD=17.7). All patients underwent MRI examinations (in T1- and T2-weighted images and FLAIR) and brain HMRS with a Signa HDx 1.5 T GE Healthcare unit, with PRESS sequence, using a single voxel method (voxel volume of 8 cm3, i.e. a cube with an edge of 2 cm), at TE of 35 ms and TR of 1500 ms. In every patient, two voxels were subjected to analy- sis: within the grey matter of the posterior cingulated gyrus (PGM) and in the parietal white matter (PWM) (Figures 1, 2). The location of every voxel was supposed to omit bone structures and lateral ventricles. Signal amplitudes were determined automatically on the AW 4.4 workstation with SVS software, for analysis. After estab- lishing signal intensity of N-acetylaspartate (NAA), cre- atine (Cr), choline (Cho), myoinositol (mI) and water, the proportions of these signals were calculated. To evaluate 23