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Differential Uptake of O-(2-18F-Fluoroethyl)-L-Tyrosine, L-3H-Methionine, and 3H-Deoxyglucose in Brain Abscesses

2007; Society of Nuclear Medicine and Molecular Imaging; Volume: 48; Issue: 12 Linguagem: Inglês

10.2967/jnumed.107.046615

1535-5667

Dagmar Salber, Gabriele Stoffels, D. Pauleit, Ana‐Maria Oros‐Peusquens, N. Jon Shah, Peter Klauth, K. Hamacher, H.H. Coenen, Karl‐Josef Langen,

Glioma Diagnosis and Treatment

The amino acid O -(2- 18 F-fluoroethyl)-l-tyrosine ( 18 F-FET) has been shown to be a useful tracer for brain tumor imaging. Experimental studies demonstrated no uptake of 18 F-FET in inflammatory cells but increased uptake has been reported in single cases of human brain abscesses. To explore this inconsistency, we investigated the uptake of 18 F-FET in comparison with that of l-[methyl- 3 H]methionine ( 3 H-MET) and d- 3 H-deoxyglucose ( 3 H-DG) in brain and calf abscesses in rats. Methods: Abscesses were induced in the brain ( n = 9) and calf ( n = 5) of Fisher CDF rats after inoculation of Staphylococcus aureus . Five days later, 18 F-FET and 3 H-MET ( n = 10) or 18 F-FET and 3 H-DG ( n = 4) were injected intravenously. One hour after injection the rats were sacrificed, and the brain or calf muscle was investigated using dual-tracer autoradiography. Lesion-to-background ratios (L/B) and standardized uptake values (SUVs) were calculated. The autoradiograms were compared with histology and immunostaining for glial fibrillary acidic protein (GFAP), CD68 for macrophages, and CD11b for microglia. Results: 18 F-FET uptake in the area of macrophage infiltration and activated microglia at the rim of the brain abscesses was low (L/B, 1.5 ± 0.4). In contrast, high uptake was observed for 3 H-MET as well as for 3 H-DG (L/B, 4.1 ± 1.1 for 3 H-MET vs. 3.1 ± 1.5 for 3 H-DG; P < 0.01 vs. 18 F-FET). Results for calf abscesses were similar. In the vicinity of the brain abscesses, slightly increased uptake was noted for 18 F-FET (L/B, 1.8 ± 0.3) and 3 H-MET (L/B, 1.8 ± 0.4), whereas 3 H-DG distribution was normal (L/B, 1.2 ± 0.2). Anti-GFAP immunofluorescence showed a diffuse astrocytosis in those areas. Conclusion: Our results demonstrate that there is no accumulation of 18 F-FET in macrophages and activated microglia in experimental brain abscesses, whereas 3 H-MET and 3 H-DG exhibit high uptake in these cells. Thus, the specificity of 18 F-FET for gliomas may be superior to that 3 H-MET and 3 H-DG. Increased 18 F-FET uptake in human brain abscesses appears to be related to reactive astrocytosis.