POSITRON EMISSION TOMOGRAPHY WITH ([C-11] METHYL)-L-METHIONINE, [C-11] D-GLUCOSE, AND [GA-68] EDTA IN SUPRATENTORIAL TUMORS

Sixteen patients with supratentorial tumors were examined with positron emission tomography (PET) using ([11C]methyl)-L-methionine, [11C]D-glucose and [68Ga]EDTA as well as CT [computed tomography]. There were 9 astrocytomas (grade II), 3 oligoastrocytomas (grade II), 2 anaplastic astrocytomas (grade III) and 2 meningiomas. Six patients with low-grade astrocytomas and all 3 patients with oligoastrocytomas had an accumulation of [11C]methionine varying from slightly to intensely increased as compared with normal brain tissue. There was a markedly increased uptake of methionine in the anaplastic astrocytomas. Three of the low-grade astrocytomas had a decreased uptake of [11C]methionine in at least part of the tumor as compared with normal brain tissue. Contrast enhancement on CT or uptake of [68Ga]EDTA was not a prerequisite for increased accumulation of methionine. Uptake of [11C]glucose was lower than or equal to that of normal brain tissue in the low-grade tumors and also in 1 of the 2 anaplastic astrocytomas and in the bulk of the other. In each individual case the methionine uptake tended to be higher, or less decreased, than the glucose uptake. In the low-grade tumors the uptake of methionine and that of glucose were often different, occasionally markedly different, as far as the tumoral-peritumoral areas involved. These differences were even more remarkable in the 2 anaplastic astrocytomas. An increased uptake of methionine was often seen in areas appearing normal on CT. It appears that PET with [11C]glucose has limitations with regard to delineation of the low-grade astrocytomas, whereas PET with [11C]methionine usually better reflects the extent of these tumors and, to a lesser degree, the extent of the high-grade neoplasms. The results of PET with [68Ga]EDTA were similar to those with postcontrast CT in most patients. The 2 meningiomas exhibited a high uptake of all tracers used for PET as well as a marked contrast enhancement on CT. The extent of the meningiomas judged by PET with the various tracers correlated well with the extent assessed by postcontrast CT.