18F-FDG and 18F-FET uptake in experimental soft tissue infection

Abstract

The aim of this study was to compare the uptake of (18)F-fluoroethyl- L-tyrosine ((18)F-FET) with that of (18)F-fluorodeoxyglucose ((18)F-FDG) in activated inflammatory white blood cells. Unilateral thigh muscle abscesses were induced in 11 rats by intramuscular inoculation of 0.1 ml of a bacterial suspension ( S. aureus, 1.2 x 10(9) CFU/ml). Four animals were intraperitoneally injected with 130-180 MBq (18)F-FDG, four with 140-170 MBq (18)F-FET and three with a mixture of 140-170 MBq (18)F-FET and 1.8 MBq (14)C-deoxyglucose. Autoradiography (10 microm slice thickness) of the abscess and the contralateral muscle was performed and detailed spatial correlation of autoradiography and histopathology (haematoxylin-eosin staining) was obtained. Regions of interest were placed on the abscess wall and the grey values (digitised image intensities) measured were converted to kBq/cc per kBq injected activity per gram (SUV). Areas with increased (18)F-FDG uptake corresponded to cellular inflammatory infiltrates mainly consisting of granulocytes. The SUV was calculated to be 4.08+/-0.65 (mean+/-SD). The uptake of (18)F-FET in activated white blood cells was not increased: the SUV of the abscess wall, at 0.74+/-0.14, was even below that of contralateral muscle. The low uptake of (18)F-FET in non-neoplastic inflammatory cells promises a higher specificity for the detection of tumour cells than is achieved with (18)F-FDG, since the immunological host response will not be labelled and inflammation can be excluded.

Comparison of the Amino Acid Tracers18F-FET and18F-DOPA in High-Grade Glioma Patients

“…18 F-FET transport in F98 glioma cells, however, is shared by serine, which is a substrate of LAT2 but not of LAT1 (20). At the same time, 18 F-FET shows no uptake in inflammatory tissue where LAT2 is not expressed (31,35). Therefore, it remains unclear whether the different results in both papers can be attributed to the particular tracer uptake or if they were caused by different study methodology.…”

TSPO Imaging in Glioblastoma Multiforme: A Direct Comparison Between 123I-CLINDE SPECT, 18F-FET PET, and Gadolinium-Enhanced MR Imaging

“…In addition to binding to glioma cells, TSPO tracers bind to myeloid cell lines, including glioma-associated microglia and macrophages (18). In contrast, uptake of 18 F-FET is not increased in areas of infiltrating activated macrophages and activated microglia in experimental abscesses (4,19). It may be hypothesized that TSPO-negative but 18 F-FET-positive areas represent primarily reactive astrocytosis, predicting a less aggressive development, but biopsy control confirmation is needed.…”

Comparison of O-(2-18F-Fluoroethyl)-l-Tyrosine and l-3H-Methionine Uptake in Cerebral Hematomas

“…Animal experiments have shown that 18 F-FET, in contrast to 18 F-FDG and 3 H-methyl-L-methionine ( 3 H-MET), exhibits no uptake in inflammatory cells and in inflammatory lymph nodes, promising a higher specificity for the detection of tumor cells (13)(14)(15)(16). Nevertheless, increased uptake of 18 F-FET has been observed in single cases of brain abscesses and in a demyelinating process (17).…”