Role of short TE H-1-MR spectroscopy in monitoring of post-operation irradiated patients

Post-surgical radiation therapy is a routine procedure in the treatment of primary malignant brain tumors. Along with modest therapeutic effects conve ntional fractionated radiotherapy, in spite of any modifications, produces damage to non-malignant brain tissues lying within the treatment volume, th e extent of which depends on radiation dose. Serial H-1-MRS allows non-inva sive investigation of tissue metabolic profiles. In the present study the r atios of resonance signals assigned to the major H-1-MRS-visible metabolite s (N-acetylaspartate, choline, creatine, inositol, lactate and lipid methyl ene group) were evaluated before, during and after post-surgical fractionat ed radiotherapy in brain regions close to and more distant from the tumor b ed, receiving different radiation exposures (60 and < 40 Gy, respectively). The study group consisted of ten patients (aged 28-51). A MRI/MRS system ( Elscint 2T Prestige) operating at the field strength of 2T and the proton r esonance frequency of 81.3 MHz has been used and the H-1-MR spectra were ac quired using single voxel double-spin-echo PRESS sequence with a short TE. The spectra were post-processed with automatic fitting in the frequency dom ain. It was found that although the metabolite profiles depend on the dose obtained, but other stress factors (like surgery) seem to contribute to the overall picture of the metabolic status of the brain as well. In studies o f early irradiation injuries, an increase of choline related ratios may ser ve rather as cell proliferation indictors than as cell injury ones, whereas the ml/Cr ratio appears as one of the first indicators of local irradiatio n injury. In order to establish the prognostic marker for early radiation d amage, however, it seems necessary to analyze all visible metabolites as we ll. None of the metabolites separately may serve as such an indicator due t o the complexity of tissue metabolism Interestingly, MRI reveals no changes during the therapy process, whereas the metabolite ratios are being affect ed in the course of time, thus supporting the presumption that the H-1-MRS is a valuable method of radiation therapy monitoring. (C) 1999 Elsevier Sci ence Ireland Ltd. All rights reserved.