In vivo single-voxel proton MR spectroscopy in intracranial cystic masses.

PURPOSE Our objective was to evaluate the proton MR spectroscopic pattern of the cystic contents of various intracranial masses and to report characteristic spectral patterns that may be helpful in the differential diagnosis of these lesions.

METHODS We evaluated 40 proton MR spectra obtained from cystic contents of various intracranial cystic masses in 39 patients, including gliomas (n = 14), metastases (n = 3), abscesses (n = 8), cysticercosis (n = 4), epidermoids (n = 3), and others (n = 7). Proton MR spectroscopy was performed on a 1.5-T MR unit using a point-resolved spectroscopic sequence with a 2 x 2 x 2 cm3 volume of interest. Assignment of the resonance peaks was based on previous studies.

RESULTS Adequate proton MR spectroscopic data were obtained in 35 cases (88%). In most gliomas and metastases, only a lactate resonance was observed. There was a trend toward a higher lactate peak in high-grade gliomas. A few tumors, including malignant gliomas and metastases, showed lipid signal combined with lactate signal. In abscesses, there were various combinations of lactate, acetate, succinate, amino acids (including valine, alanine, and/or leucine), and/or unassigned resonances. In cysticercosis, resonances of lactate, succinate, alanine, acetate, and/or unassigned resonances were observed. Three epidermoid cysts showed only lactate signal. There were no identifiable resonances from the arachnoid and porencephalic cysts.

CONCLUSION Only lactate is commonly observed in a variety of intracranial cystic masses, except for abscess and cysticercosis, in which resonances of acetate, succinate, amino acids, and/or unassigned metabolites can be seen in addition to a lactate peak.