Proton Magnetic Resonance Spectroscopy at 3T-Evaluation of Metabolic Profile of Human Brain Lesions

Brain MR imaging at 3T has been increasingly used in clinical practice since a great deal of effort has been invested in research into high magnetic fields to overcome the difficulties of successively working with stronger fields. Theoretically the signal to noise ratio (SNR) of a 3T MR scanner will be double that of a 1.5T one which is advantageous for MR spectroscopy as this technique has always required the strongest possible magnetic field strength. However, the relationship between the magnetic field used and the spectra obtained is very complex depended on several other data acquisition parameters not only field strength. Single-voxel at short echo time (TE=35msec) and multivoxel at long echo time (TE=144msec) spectra were recorded for 46 patients with several brain lesions using PRESS pulse sequence. Spectra were compared in terms of resolution as it varies among changes of data acquisition parameters such as NEX (Number of Excitations), NSA (Number of Signals Averaging) and field homogeneity. Spectra exhibited significantly improved resolution as field homogeneity was improved and NEX as well as NSA were increased. MRS metabolic profiles at 3T gave valuable clinical information when differentiating among brain lesions and tumour stages. However, in some cases, differences among tumour grade and lesion type were subtle, rendering tumour classification a difficult issue.