PURPOSE: To assess the metabolite ratios in gliomas to determine whether the metabolic information obtained by using by using in vivo single vexel 1H magnetic resonance spectroscopy(MRS) can be used as a marker for the grading of malignancy.
MATERIALS AND METHODS: A total of 28 1H MR spectra from brain tumors in 27 patients with pathologically-proven gliomas were recorded. Seven patients had low grade gliomas (grade II astrocytoma in three, oligodendroglioma in three and mixed glioma in one), six had anaplastic gliomas (grade III astrocytoma in three and oligodendroglioma in three), and 14 had glioblastoma multiformes (grade IV), 1H MRS was performed on a 1.5T MRunit using PRESS sequence with a TR of 2000ms, a TE of 270 or 135ms and a voxel size of cm for all spectra. Relative lactate levels, NAA/Cho, NAA/Cr and Cho/Cr ratios were measured based on the peak heights of each resonance and compared among gliomas.
RESULTS: Most tumors demonstrated decreased NAA, elevated Cho and lactate. Relatively high lactate and Cho levels and markedly decreased NAA level were more frequently observed in the high grade gliomas than in low grade gliomas. Marked elevation of lactate level in the solid component of the tumor was mostly observed in high grade gliomas. In a patient with gliomatosis cerebri, 1H MRS demonstrated a spectral pattern of tumor in filtration in an area that on MR images was apparently normal. However, NAA/Cr, NAA/Cho and Cho/Cr ratios did not significantly correlate, however, with the histologic grading of malignancy. Because of the partial volume effect, the heterogeneity of tumors containing solid and cystic or necrotic components within avoxel limited the interpretation of 1H MRS data for the grading of malignancy.
CONCLUSION: The results suggest that in some patients in vivo single voxel 1H MRS may be useful for grading the malignancy of gliomas and evaluating the exact extent of tumors. In solid gliomas, the relative level of lactate appears to be a good markerfor the grading of malignancy.
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