CONTRIBUTION OF MAGNETIC-RESONANCE SPECTROSCOPIC IMAGING AND L-[1-C-11]TYROSINE POSITRON EMISSION TOMOGRAPHY TO LOCALIZATION OF CEREBRAL GLIOMAS FOR BIOPSY

PROTON MAGNETIC RESONANCE spectroscopic imaging (H-1-MRSI) and positro n emission tomography with the tracer L-[1-C-11]tyrosine (C-11-TYR) we re used to localize gliomas for biopsy or resection. This is especiall y helpful in cases of low-grade gliomas, if these lesions are not visu alized by contrast-enhanced computed tomographic and magnetic resonanc e imaging scans. The clues to improved localization are provided by ch anges in tissue metabolite contents, such as elevation of phosphocholi ne, indicating cellular proliferation; decrease of N-acetylaspartate, denoting toss of neurons (as these are replaced by tumor cells); and e levation of lactate, pointing to the prevalence of glycolysis, as obse rved in many tumors. These data on tissue metabolite content have been obtained in vivo in the patient by proton magnetic resonance spectros copy; metabolite maps derived from these data then visualize the distr ibution of the various metabolites over the section of the brain under investigation. Alternatively, localization of a tumor may be achieved by means of positron emission tomography depicting the pattern of upt ake of the amino acid tracer C-11-TYR, as it tends to be incorporated in the process of cellular proliferation and protein biosynthesis. Fiv e cases are presented as examples.