IMG-02. USEFUL DIAGNOSIS OF PEDIATRIC CYSTIC BRAIN TUMORS USING MULTIPLE POSITRON EMISSION TOMOGRAPHY STUDIES

OBJECTIVE: Pediatric brain tumors are primarily diagnosed using MRI or CT examination; however, determining the correct diagnosis using only morphological MRI can sometimes be challenging. Positron emission tomography (PET) uses radiotracers for metabolic and molecular imaging. We examined the accumulation of multiple PET (FDG, MET, FLT, and FMISO) studies for diagnosing pediatric cystic brain tumors. METHODS: We performed PET scans for eight pediatric patients (five pilocytic astrocytoma, one pleomorphic xanthoastrocytoma, one diffuse astrocytoma with IDH1 mutation, one ganglioglioma) from April 2010 to December 2019. The resulting studies were compared by measuring the tumor-to-normal lesion (T/N) ratio of FDG, MET, and FLT and the tumor-to-blood value (T/B) ratio of FMISO between each pediatric cystic brain tumor. RESULTS: All pediatric brain tumors showed tumor uptake of FDG, MET, and FLT. We could not examine FMISO PET for one diffuse astrocytoma with IDH1 mutation. The T/N ratios of FDG, MET, and FLT and the T/B ratio of FMISO were 1.07, 2.76, 4.6, and 1.12 for pilocytic astrocytoma; 0.65, 4.6, 7.67, and 1.38 for pleomorphic xanthoastrocytoma; 0.61, 2.14, and 3.82 for diffuse astrocytoma with IDH1 mutation; and 0.79, 1.78, 5, and 1.49 for ganglioglioma, respectively. The T/N ratios of MET and FLT for pleomorphic xanthoastrocytoma were high, but the Ki-67 labeling index was 1%. In the ganglioglioma, the T/N ratio of FLT was high, but the T/N ratio of MET was low. CONCLUSION: Specialized multiple PET accumulation patterns for tumors are useful for discriminating each tumor.