title: Uptake and tracer kinetics of O-(2-(18)F-fluoroethyl)-L-tyrosine in meningiomas: preliminary results.
abstract: OBJECTIVE
  O-(2-[(18)F]Fluoroethyl)-L-tyrosine ((18)F-FET) is a well-established PET tracer for the imaging of cerebral gliomas, but little is known about (18)F-FET uptake in meningiomas. The aim of this study was to explore (18)F-FET kinetics and tumour-to-background contrast in meningiomas of various histologies.
  
  
  METHODS
  A group of 24 patients with suspected cerebral meningioma on MRI/CT had an additional dynamic (18)F-FET PET scan prior to surgery. Time-activity curves (TAC) of (18)F-FET uptake in the tumours and tumour-to-brain ratios (TBR) for early (3 - 14 min after injection) and late (18)F-FET uptake (20 - 40 min after injection) were analysed and compared with histological subtypes and WHO grade. (18)F-FET uptake in critical structures in the skull base was also evaluated in terms of tumour-to-tissue (T/Tis) ratio.
  
  
  RESULTS
  TBR of (18)F-FET uptake in meningiomas was significantly higher in the early phase than in the late phase (3.5 ± 0.8 vs. 2.2 ± 0.3; P < 0.001). The difference in TBR between low-grade meningiomas (WHO grade I, 18 patients) and high-grade meningiomas (WHO grade II or III, 6 patients) was significant in the late phase of (18)F-FET uptake (2.1 ± 0.2 vs. 2.5 ± 0.2, P = 0.003) while there was no significant difference in the early phase. ROC analysis showed that TBR of (18)F-FET uptake in the late phase had significant power to differentiate low-grade from high-grade meningiomas (AUC 0.87 ± 0.18, sensitivity 83 %, specificity 83 %, optimal cut-off 2.3; P < 0.01). Evaluation of TAC yielded three different curve patterns of (18)F-FET PET uptake. Combination of TBR (cut-off value 2.3) and TAC pattern slightly improved the differentiation of high-grade from low-grade meningiomas (accuracy 92 %; P = 0.001). Analysis of background radioactivity in the skull base indicated that (18)F-FET uptake may be helpful in distinguishing meningioma tissue in the late phase. T/Tis ratios were >1.2 in all patients for the periorbita, sphenoidal sinus, pituitary gland, tentorium, bone and brain, in more than 90 % of patients for the mucosa and dura, but in only 63 % of patients for the cavernous sinus.
  
  
  CONCLUSIONS
  (18)F-FET PET may provide additional information for noninvasive grading of meningiomas and possibly for the discrimination of tumour in critical areas of the skull base. A further evaluation of (18)F-FET PET in meningiomas appears to be justified.
authors.affiliation: Department of Neurosurgery, Heinrich Heine University, Düsseldorf, Germany, janfcornelius@yahoo.com.
authors.forename: Jan F
authors.initials: JF
authors.lastname: Cornelius
authors.forename: Gabriele
authors.initials: G
authors.lastname: Stoffels
authors.forename: Christian
authors.initials: C
authors.lastname: Filß
authors.forename: Norbert
authors.initials: N
authors.lastname: Galldiks
authors.forename: Philipp
authors.initials: P
authors.lastname: Slotty
authors.forename: Marcel
authors.initials: M
authors.lastname: Kamp
authors.forename: Mustafa
authors.initials: M
authors.lastname: el Khatib
authors.forename: Daniel
authors.initials: D
authors.lastname: Hänggi
authors.forename: Michael
authors.initials: M
authors.lastname: Sabel
authors.forename: Jörg
authors.initials: J
authors.lastname: Felsberg
authors.forename: Hans Jakob
authors.initials: HJ
authors.lastname: Steiger
authors.forename: Heinz H
authors.initials: HH
authors.lastname: Coenen
authors.forename: Nadim J
authors.initials: NJ
authors.lastname: Shah
authors.forename: Karl-Josef
authors.initials: KJ
authors.lastname: Langen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007700:Kinetics; D008297:Male; D008577:Meningeal Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D008579:Meningioma / Q000000981:diagnostic imaging* / Q000473:pathology; D008875:Middle Aged; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics
chemical_list: C117289:O-(2-fluoroethyl)tyrosine; D019275:Radiopharmaceuticals; D014443:Tyrosine