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FIG 5. Images obtained at the first follow-up evaluation (after radiation therapy and chemotherapy) include an axial T1-weighted Gd-enhanced MR image and multivoxel MR spectra in a male patient with an anaplastic (malignant) astrocytoma in the left thalamus. Selected proton MR spectra (1–8) illustrate that tumor spectral patterns were detected beyond the contrast-enhancing region and that regions of tumor corresponded to necrotic spectral patterns. Spectrum 1 shows a pattern that is characteristic of normal tissue, because all three biologically important metabolites (NAA, Cho, tCr) are detected. The voxel corresponding to spectrum 2 includes enhancing tissue and shows increased Cho and prominent NAA levels; this spectral pattern is characteristic of mixed tumor and normal tissue. Spectrum 3 shows a spectral pattern with only Cho and lipids (L) values; this is consistent with tumor and necrosis and corresponds to both enhancing and nonenhancing tissue. Spectrum 4 shows extensive necrosis (prominent lipids), along with some normal and tumor tissue (Cho and NAA peaks). Spectrum 5 shows primarily necrosis (predominantly lipid) and, possibly, some tumor. Voxels corresponding to spectra 6 and 7 show minimal enhancement, whereas the voxel that corresponds to spectrum 8 includes areas of enhancement. Spectra 6–8 show tumor spectral patterns (prominent Cho and tCr) and correspond to regions of contrast enhancement (spectrum 8) and beyond (spectra 6 and 7).
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