title: Reproducibility of O-(2-(18)F-fluoroethyl)-L-tyrosine uptake kinetics in brain tumors and influence of corticoid therapy: an experimental study in rat gliomas.
abstract: OBJECTIVE
  Positron emission tomography (PET) using O-(2-(18)F-fluoroethyl)-L-tyrosine ((18)F-FET) is a well-established method for the diagnostics of brain tumors. This study investigates reproducibility of (18)F-FET uptake kinetics in rat gliomas and the influence of the frequently used dexamethasone (Dex) therapy.
  
  
  METHODS
  F98 glioma or 9L gliosarcoma cells were implanted into the striatum of 31 Fischer rats. After 10-11 days of tumor growth, the animals underwent dynamic PET after injection of (18)F-FET (baseline). Thereafter, animals were divided into a control group and a group receiving Dex injections, and all animals were reinvestigated 2 days later. Tumor-to-brain ratios (TBR) of (18)F-FET uptake (18-61 min p.i.) and the slope of the time-activity-curves (TAC) (18-61 min p.i.) were evaluated using a Volume-of-Interest (VOI) analysis. Data were analyzed by two-way repeated measures ANOVA and reproducibility by the intraclass correlation coefficient (ICC).
  
  
  RESULTS
  The slope of the tumor TACs showed high reproducibility with an ICC of 0.93. A systematic increase of the TBR in the repeated scans was noted (3.7 ± 2.8 %; p < 0.01), and appeared to be related to tumor growth as indicated by a significant correlation of TBR and tumor volume (r = 0.77; p < 0.0001). After correction for tumor growth TBR showed high longitudinal stability with an ICC of 0.84. Dex treatment induced a significant decrease of the TBR (-8.2 ± 6.1 %; p < 0.03), but did not influence the slope of the tumor TAC.
  
  
  CONCLUSIONS
  TBR of (18)F-FET uptake and tracer kinetics in brain tumors showed high longitudinal stability. Dex therapy may induce a minor decrease of the TBR; this needs further investigation.
authors.affiliation: Research Center Jülich, Institute of Neuroscience and Medicine, Jülich, Germany.
authors.forename: Carina
authors.initials: C
authors.lastname: Stegmayr
authors.affiliation: Research Center Jülich, Institute of Neuroscience and Medicine, Jülich, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Schöneck
authors.affiliation: Research Center Jülich, Institute of Neuroscience and Medicine, Jülich, Germany.
authors.forename: Dennis
authors.initials: D
authors.lastname: Oliveira
authors.affiliation: Research Center Jülich, Institute of Neuroscience and Medicine, Jülich, Germany.
authors.forename: Antje
authors.initials: A
authors.lastname: Willuweit
authors.affiliation: Research Center Jülich, Institute of Neuroscience and Medicine, Jülich, Germany.|Department of Nuclear Medicine and Neurology, University of Aachen, Aachen, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Filss
authors.affiliation: Research Center Jülich, Institute of Neuroscience and Medicine, Jülich, Germany.|Department of Neurology, University of Cologne, Cologne, Germany.
authors.forename: Norbert
authors.initials: N
authors.lastname: Galldiks
authors.affiliation: Research Center Jülich, Institute of Neuroscience and Medicine, Jülich, Germany.|Department of Nuclear Medicine and Neurology, University of Aachen, Aachen, Germany.|Jülich-Aachen Research Alliance (JARA) - Section JARA-Brain, Jülich, Germany.
authors.forename: N Jon
authors.initials: NJ
authors.lastname: Shah
authors.affiliation: Research Center Jülich, Institute of Neuroscience and Medicine, Jülich, Germany.|Department of Nuclear Medicine and Neurology, University of Aachen, Aachen, Germany.
authors.forename: Heinz H
authors.initials: HH
authors.lastname: Coenen
authors.affiliation: Research Center Jülich, Institute of Neuroscience and Medicine, Jülich, Germany. k.j.langen@fz-juelich.de.|Department of Nuclear Medicine and Neurology, University of Aachen, Aachen, Germany. k.j.langen@fz-juelich.de.
authors.forename: Karl-Josef
authors.initials: KJ
authors.lastname: Langen
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001932:Brain Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology* / Q000627:therapeutic use; D004195:Disease Models, Animal; D005910:Glioma / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D049268:Positron-Emission Tomography; D051381:Rats; D015203:Reproducibility of Results; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: C117289:O-(2-fluoroethyl)tyrosine; D014443:Tyrosine; D003907:Dexamethasone
keywords: Brain tumors; Dexamethasone treatment; O-(2-[18F]fluoroethyl)-L-tyrosine (FET); PET; Rat glioma model; Reproducibility