We have studied 14 patients with different grades of astrocytomas using 'H NMR spectroscopy in vivo . Typically, astrocytomas exhibited a low N-acetylaspartate peak, a prominent signal from choline groupcontaining compounds, and lactate in the 'H NMR spectra in vivo . The uncorrected choline/creatine + phosphocreatine peak area ratios were higher in tumors than in normal brain tissue . Absolute concentration of cholinecontaining compounds (1 .74 ± 0.09 mmol/L) in the normal brain tissue was not different in any grade of astrocytoma, but total creatine concentration in healthy brain (7 .49 --0.30 mmol/L) was higher than that in grade IV astrocytomas (4 .84 ± 0.89 mmol/L). Relaxation constants of choline-containing compounds did not differ in tumors from those determined in normal brain. Perchloric acid extracts of biopsy samples from 35 astrocytomas and 13 samples of normal temporal white matter were analyzed with 'H NMR . Total concentration of choline-containing compounds did not differ between controls and any grade of astrocytoma when the quantification was done in vitro. It is interesting that phosphorylcholine concentration was about twofold greater in grade IV astrocytomas than in controls or other grades of astrocytomas . We conclude that high phosphorylcholine in grade IV astrocytomas may be an indicator of degree of malignancy . The proportional changes within the group of choline-containing compounds observed in vitro were not reflected in the NMR properties of choline signal in vivo . Key Words: Human astrocytoma-'H NMR spectroscopy-N-Acetylaspartate-Choline-Creatine-Phosphorylcholine-Human brain.

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