H-1 MRS OF HIGH-GRADE ASTROCYTOMAS - MOBILE LIPID-ACCUMULATION IN NECROTIC TISSUE

Sixty-four samples from six grade 4 astrocytomas were investigated ex vivo by H-1 MRS at 360 MHz and subsequently by histopathology to obtai n percentages of viable and necrotic tumour and grey and white matter. MR-visible lipids were detected in 87% of tumour samples. Necrotic fo ci were <3 X 3 X 6 mm3. The means of the intensities/unit weight tissu e of the lipid resonances at 5.33, 2.80, 1.29 and 0.89 ppm were signif icantly higher (p<0.05) for three sets of comparisons: samples with 85 -100% vs 50-75%; with 50-75% vs 10-40% and with 10-40% vs 0-5% necrosi s. For the lipid resonance at 2.04 ppm the difference in the means was significant only for samples with 50-75% compared to those with 85-10 0% necrosis, because for samples with <50% necrosis resonances from gl utamine and possibly small amounts of glutamate, gamma-aminobutyrate a nd N-acetylaspartate anions contribute significantly to the spectral a rea at 2.0 ppm. We conclude that necrotic foci below MRI resolution yi eld the resonances at 1.3 and 0.9 ppm, and contribute to the intense r esonance at 2.0 ppm observed in in vivo H-1 spectra of some high grade astrocytomas.