The clinical usefulness of
L-methyl-11C-methionine positron emission tomography (11C-MET PET) and
thallium-201 single photon emission computed tomography (201T1 SPECT) for distinguishing
glioma recurrence from radiation-induced changes was evaluated. Ten patients with lesions highly suggestive of recurrent
glioma on magnetic resonance imaging underwent 11C-MET PET and 201T1 SPECT studies. Two patients were examined twice, so a total of 12 studies were performed. The clinical diagnoses were five recurrent
gliomas and seven radiation
necrosis. The five recurrent
gliomas appeared as increased uptakes on both 11C-MET PET and 201T1 SPECT scans. Four of the seven radiation
necrosis lesions also appeared as increased uptakes on the 201T1 SPECT scans. In contrast, only one radiation
necrosis appeared as increased uptake on the 11C-MET PET scans. There was no significant difference in 201T1 SPECT indices between radiation
necrosis and
tumor recurrence, but the ratio of the differential absorption ratio of
tumor tissue to that of the homologous contralateral gray matter in PET of recurrent
glioma was significantly higher than that of radiation
necrosis. 11C-MET PET is superior to 201T1 SPECT for the differentiation of
tumor recurrence from radiation
necrosis and delineation of the extent of the
tumor.