o-(2-fluoroethyl)tyrosine and Myositis

O-(3-[(18)F]fluoropropyl)-L-tyrosine (FPT), an analogue of O-(2-[(18)F]fluoroethyl)-L-tyrosine (FET) as an amino acid tracer for tumor imaging with positron emission tomography (PET), was synthesized and evaluated. FPT was prepared by [(18)F]fluoropropylation of L-tyrosine in a two-step procedure. Biodistribution of FPT was determined in normal mice. FPT, FET and [(18)F]fluorine-2-deoxy-D-glucose (FDG) uptake studies were performed in mice bearing S18 fibrosarcoma and S. aureus-inoculated mice. Also, carcinoma-bearing mice and S. aureus-inoculated mice were imaged using FPT PET imaging compared with FET and FDG PET imaging. Synthesis of FPT was accomplished in about 60 min with an overall radiochemical yield of 25-30% (without decay correction) by manual operation. High uptake and long retention time of FPT and FET in kidney, liver, lung, blood, etc., and low uptake in brain were found. Furthermore, high FPT, FET and FDG uptake in tumor, and almost no FPT and FET uptake in inflammatory tissue, in contrast, high FDG uptake in inflammatory tissue, were observed. In conclusion, FPT is easy to prepare and superior to FDG in the differentiation of tumor and inflammation, and seems to be a potential amino acid tracer like FET for tumors imaging with PET.

Topics: Animals; Fibrosarcoma; Fluorine Radioisotopes; Fluorodeoxyglucose F18; Isotope Labeling; Mice; Myositis; Organ Specificity; Radiopharmaceuticals; Tissue Distribution; Tomography, Emission-Computed; Tyrosine

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.

Topics: Abscess; Animals; Autoradiography; Carbon Radioisotopes; Deoxyglucose; Fluorodeoxyglucose F18; Leg; Leukocytes; Myositis; Radionuclide Imaging; Radiopharmaceuticals; Rats; Reference Values; Staphylococcal Infections; Tyrosine