Classification of biopsy-confirmed brain tumors using single-voxel MR spectroscopy

Our purpose was to develop a classification scheme and method of presentation of in vivo single-voxel proton spectroscopic data from astrocytomas that most closely match the classification scheme determined from biopsy specimens. Since in vivo proton spectroscopy is noninvasive, it may be an attractive alternative to intracranial biopsy.

Single-voxel spectra were acquired using the point-resolved spectroscopic pulse sequence as part of the Probe spectroscopy package on a G.E. 1.5-T Signa scanner. Subjects consisted of 27 patients with biopsy-confirmed brain tumors (13 with glioblastoma multiforme, six with anaplastic astrocytoma, and eight with low-grade astrocytoma). The patients were divided into groups based on the histologic subtype of their tumor for different treatment protocols.

Metabolic peak areas were normalized for each metabolite (choline, creatine, N-acetylaspartate, lactate) to the area of the unsuppressed water peak and to the area of the creatine peak. Kruskal-Wallis nonparametric analysis of variance (ANOVA) tests showed statistically significant differences among the tumor groups for all the area ratios. The lactate/water ratio could be used to distinguished all three tumor groups, whereas the choline/water ratio distinguished low-grade astrocytomas from the two high-grade groups. Both the choline and lactate ratios could be used to separate the high-grade from the low-grade tumors.

Specific relative metabolic peak area ratios acquired from regions of contrast-enhancing brain tumor can be used to classify astrocytomas as to histopathologic grade.