Two-phase [11C]L-methionine PET in childhood brain tumors |
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Authors: | L A O'Tuama P C Phillips L C Strauss B C Carson Y Uno Q R Smith R F Dannals A A Wilson H T Ravert S Loats |
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Institution: | Department of Radiology, Johns Hopkins Hospital, Baltimore, Maryland. |
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Abstract: | Thirteen children (1.8-15.8 years of age) with brain tumors were studied with 11C]L-methionine positron emission tomography (METPET). Patients were injected intravenously with tracer before a baseline PET scan was obtained. To assess the sensitivity of 11C]L-methionine uptake to competitive inhibition, 10 patients received oral L-phenylalanine (100 mg/kg); 1 hour later, a second METPET was obtained. Subjective assessment of 11C]L-methionine uptake closely paralleled results of quantitative examination (r = 0.81). 11C]L-methionine uptake in tumor-containing brain was increased in 11 patients (mean ratio of 11C] radioactivity in tumor to normal brain: 1.5 +/- 0.57; range: 1.13-2.98). Increased tracer uptake occurred in ependymomas (3), medulloblastoma (1), and astrocytomas (5), but was less intense in low-grade tumors. L-phenylalanine reduced L-methionine uptake (25-69%) in 70% of studies. L-methionine uptake was not sensitive to competitive inhibition in brain radiation injury. Two-phase METPET is of potential value in difficult clinical situations evident in children with brain tumors, including the differential diagnosis of tumor recurrence and cerebral radiation injury. |
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