TY - JOUR T1 - Differential Uptake of <em>O</em>-(2-<sup>18</sup>F-Fluoroethyl)-<span class="sc">l</span>-Tyrosine, <span class="sc">l</span>-<sup>3</sup>H-Methionine, and <sup>3</sup>H-Deoxyglucose in Brain Abscesses JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 2056 LP - 2062 DO - 10.2967/jnumed.107.046615 VL - 48 IS - 12 AU - Dagmar Salber AU - Gabriele Stoffels AU - Dirk Pauleit AU - Anna-Maria Oros-Peusquens AU - Nadim Jon Shah AU - Peter Klauth AU - Kurt Hamacher AU - Heinz Hubert Coenen AU - Karl-Josef Langen Y1 - 2007/12/01 UR - http://jnm.snmjournals.org/content/48/12/2056.abstract N2 - The amino acid O-(2-18F-fluoroethyl)-l-tyrosine (18F-FET) has been shown to be a useful tracer for brain tumor imaging. Experimental studies demonstrated no uptake of 18F-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 18F-FET in comparison with that of l-[methyl-3H]methionine (3H-MET) and d-3H-deoxyglucose (3H-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, 18F-FET and 3H-MET (n = 10) or 18F-FET and 3H-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: 18F-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 3H-MET as well as for 3H-DG (L/B, 4.1 ± 1.1 for 3H-MET vs. 3.1 ± 1.5 for 3H-DG; P &lt; 0.01 vs. 18F-FET). Results for calf abscesses were similar. In the vicinity of the brain abscesses, slightly increased uptake was noted for 18F-FET (L/B, 1.8 ± 0.3) and 3H-MET (L/B, 1.8 ± 0.4), whereas 3H-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 18F-FET in macrophages and activated microglia in experimental brain abscesses, whereas 3H-MET and 3H-DG exhibit high uptake in these cells. Thus, the specificity of 18F-FET for gliomas may be superior to that 3H-MET and 3H-DG. Increased 18F-FET uptake in human brain abscesses appears to be related to reactive astrocytosis. ER -