title: Early static (18)F-FET-PET scans have a higher accuracy for glioma grading than the standard 20-40 min scans.
abstract: OBJECTIVE
  Current guidelines for glioma imaging by positron emission tomography (PET) using the amino acid analogue O-(2-[(18)F]fluoroethyl)-L-tyrosine ((18)F-FET) recommend image acquisition from 20-40 min post injection (p.i.). The maximal tumour-to-background evaluation (TBRmax) obtained in these summation images does not enable reliable differentiation between low and high grade glioma (LGG and HGG), which, however, can be achieved by dynamic (18)F-FET-PET. We investigated the accuracy of tumour grading using TBRmax values at different earlier time points after tracer injection.
  
  
  METHODS
  Three hundred and fourteen patients with histologically proven primary diagnosis of glioma (131 LGG, 183 HGG) who had undergone 40-min dynamic (18)F-FET-PET scans were retrospectively evaluated. TBRmax was assessed in the standard 20-40 min summation images, as well as in summation images from 0-10 min, 5-15 min, 5-20 min, and 15-30 min p.i., and kinetic analysis was performed. TBRmax values and kinetic analysis were correlated with histological classification. ROC analyses were performed for each time frame and sensitivity, specificity, and accuracy were assessed.
  
  
  RESULTS
  TBRmax values in the earlier summation images were significantly better for tumour grading (P < 0.001) when compared to standard 20-40 min scans, with best results for the early 5-15 min scan. This was due to higher TBRmax in the HGG (3.9 vs. 3.3; p < 0.001), while TBRmax remained nearly stable in the LGG (2.2 vs. 2.1). Overall, accuracy increased from 70 % in the 20-40 min analysis to 77 % in the 5-15 min images, but did not reach the accuracy of dynamic analysis (80 %).
  
  
  CONCLUSIONS
  Early TBRmax assessment (5-15 min p.i.) is more accurate for the differentiation between LGG and HGG than the standard static scan (20-40 min p.i.) mainly caused by the characteristic high (18)F-FET uptake of HGG in the initial phase. Therefore, when dynamic (18)F-FET-PET cannot be performed, early TBRmax assessment can be considered as an alternative for tumour grading.
authors.affiliation: Department of Nuclear Medicine, Ludwig-Maximilians-University Munich, Marchioninistr. 15, 81377, Munich, Germany. albert@med.uni-muenchen.de.
authors.forename: Nathalie L
authors.initials: NL
authors.lastname: Albert
authors.affiliation: Department of Nuclear Medicine, Ludwig-Maximilians-University Munich, Marchioninistr. 15, 81377, Munich, Germany.
authors.forename: Isabel
authors.initials: I
authors.lastname: Winkelmann
authors.affiliation: Department of Neurosurgery, Ludwig-Maximilians-University Munich, Marchioninistr. 15, 81377, Munich, Germany.
authors.forename: Bogdana
authors.initials: B
authors.lastname: Suchorska
authors.affiliation: Department of Nuclear Medicine, Ludwig-Maximilians-University Munich, Marchioninistr. 15, 81377, Munich, Germany.
authors.forename: Vera
authors.initials: V
authors.lastname: Wenter
authors.affiliation: Institute for Clinical Radiology, Ludwig-Maximilians-University Munich, Marchioninistr. 15, 81377, Munich, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Schmid-Tannwald
authors.affiliation: Department of Nuclear Medicine, Ludwig-Maximilians-University Munich, Marchioninistr. 15, 81377, Munich, Germany.
authors.forename: Erik
authors.initials: E
authors.lastname: Mille
authors.affiliation: Department of Nuclear Medicine, Ludwig-Maximilians-University Munich, Marchioninistr. 15, 81377, Munich, Germany.
authors.forename: Andrei
authors.initials: A
authors.lastname: Todica
authors.affiliation: Department of Nuclear Medicine, Ludwig-Maximilians-University Munich, Marchioninistr. 15, 81377, Munich, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Brendel
authors.affiliation: Department of Neurosurgery, Ludwig-Maximilians-University Munich, Marchioninistr. 15, 81377, Munich, Germany.
authors.forename: Jörg-Christian
authors.initials: JC
authors.lastname: Tonn
authors.affiliation: Department of Nuclear Medicine, Ludwig-Maximilians-University Munich, Marchioninistr. 15, 81377, Munich, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Bartenstein
authors.affiliation: Division of Nuclear Medicine and Clinical Molecular Imaging, Department of Radiology, University of Tübingen, Otfried-Müller Str. 14, 72076, Tübingen, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: la Fougère
mesh_terms: D003937:Diagnosis, Differential; D005260:Female; D005910:Glioma / Q000000981:diagnostic imaging* / Q000473:pathology*; D006801:Humans; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D049268:Positron-Emission Tomography / Q000592:standards*; D012372:ROC Curve; D012015:Reference Standards; D012189:Retrospective Studies; D014443:Tyrosine / Q000031:analogs & derivatives*
chemical_list: C545932:(18F)fluoroethyltyrosine; D014443:Tyrosine
keywords: 18F-FET-PET; Glioma grading; TBRmax