PROTON MAGNETIC-RESONANCE SPECTROSCOPY IN PATIENTS WITH GLIAL TUMORS - A MULTICENTER STUDY

The authors represent a cooperative group of 15 institutions that exam ined the feasibility of using metabolic features observed in vivo with H-1-magnetic resonance (MR) spectroscopy to characterize brain tumors of the glial type. The institutions provided blinded, centralized MR spectroscopy data processing along with independent central review of MR spectroscopy voxel placement, composition and contamination by brai n, histopathological typing using current World Health Organization cr iteria, and clinical data. Proton H-1-MR spectroscopy was performed us ing a spin-echo technique to obtain spectra from 8-cc voxels in the tu mor and when feasible in the contralateral brain. Eighty-six cases wer e assessable, 41 of which had contralateral brain spectra. Glial tumor s had significantly elevated intensities of choline signals, decreased intensities of creatine signals, and decreased intensities of N-acety laspartate compared to brain. Choline signal intensities were highest in astrocytomas and anaplastic astrocytomas, and creatine signal inten sities were lowest in glioblastomas. However, whether expressed relati ve to brain or as intratumoral ratios, these metabolic characteristics exhibited large variations within each subtype of glial turner. The r esulting overlaps precluded diagnostic accuracy in the distinction of low- and high-grade tumors. Although the extent of contamination of th e H-1-MR spectroscopy voxel by brain had a marked effect on metabolite concentrations and ratios, selection of cases with minimal contaminat ion did not reduce these overlaps. Thus, each type and grade of tumor is a metabolically heterogeneous group. Lactate occurred infrequently and in all grades. Mobile lipids, on the other hand, occurred in 41% o f high-grade tumors with higher mean amounts found in glioblastomas. T his result, coupled with the recent demonstration that intratumoral mo bile lipids correlate with microscopic tumor cell necrosis, leads to t he hypothesis that mobile lipids observed in vivo in H-1-MR spectrosco py may correlate independently with prognosis of individual patients.