The differential diagnosis between brain tumors recurrence and early neuroinflammation or late radionecrosis is still an unsolved problem. The new emerging magnetic resonance imaging, computed tomography, and positron emission tomography diagnostic modalities still lack sufficient accuracy. In the last years, a great effort has been made to develop radiotracers able to detect specific altered metabolic pathways or tumor receptor markers. Our research project aims to evaluate irradiation effects on radiopharmaceutical uptake and compare the kinetic of the fluorinate tracers. T98G glioblastoma cells were irradiated at doses of 2, 10, and 20 Gy with photons, and 18F-DOPA and 18F-FET tracer uptake was evaluated. Activity and cell viability at different incubation times were measured. 18F-FET and 18F-DOPA are accumulated via the LAT-1 transporter, but 18F-DOPA is further incorporated, whereas 18F-FET is not metabolized. Therefore, time-activity curves (TACs) tend to plateau with 18F-DOPA and to a rapid washout with 18F-FET. After irradiation, 18F-DOPA TAC resembles the 18F-FET pattern. 18F-DOPA activity peak we observed at 20 min might be fictitious, because earlier time points have not been evaluated, and a higher activity peak before 20 min cannot be excluded. In addition, the activity retained in the irradiated cells remains higher in comparison to the sham ones at all time points investigated. This aspect is similar in the 18F-FET TAC but less evident. Therefore, we can hypothesize the presence of a second intracellular compartment in addition to the amino acidic pool one governed by LAT-1, which could explain the progressive accumulation of 18F-DOPA in unirradiated cells.

• Klíčová slova
• 18F-DOPA, 18F-FET, T98G cells, glioblastoma, photon irradiation, radionecrosis,
• Publikační typ
• časopisecké články MeSH

In this study, we have compared four 68Ga-labeled peptides (three Arg-Gly-Asp (RGD) peptides and substance-P) with two 18F-tracers clinically approved for tumor imaging. We have studied in vitro and in vivo characteristics of selected radiolabeled tracers in a glioblastoma multiforme tumor model. The in vitro part of the study was mainly focused on the evaluation of radiotracers stability under various conditions. We have also determined in vivo stability of studied 68Ga-radiotracers by analysis of murine urine collected at various time points after injection. The in vivo behavior of tested 68Ga-peptides was evaluated through ex vivo biodistribution studies and PET/CT imaging. The obtained data were compared with clinically used 18F-tracers. 68Ga-RGD peptides showed better imaging properties compared to 18F-tracers, i.e., higher tumor/background ratios and no accumulation in non-target organs except for excretory organs.

• Klíčová slova
• 18F-FDG, 18F-FLT, PET, RGD peptides, biodistribution, gallium-68, glioblastoma multiforme,
• MeSH
• glioblastom diagnostické zobrazování   metabolismus   MeSH
• lidé MeSH
• myši SCID MeSH
• nádorové buněčné linie MeSH
• nádory mozku diagnostické zobrazování   metabolismus   MeSH
• oligopeptidy chemie   MeSH
• PET/CT MeSH
• počítačová rentgenová tomografie MeSH
• pozitronová emisní tomografie metody   MeSH
• radiofarmaka chemie   MeSH
• radioizotopy fluoru MeSH
• radioizotopy galia chemie   MeSH
• tkáňová distribuce MeSH
• transplantace nádorů MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• arginyl-glycyl-aspartic acid MeSH Prohlížeč
• Fluorine-18 MeSH Prohlížeč
• oligopeptidy MeSH
• radiofarmaka MeSH
• radioizotopy fluoru MeSH
• radioizotopy galia MeSH