title: PET/CT of skull base meningiomas using 2-18F-fluoro-L-tyrosine: initial report.
abstract: Precise delineation of the shape of skull base meningiomas is critical for their treatment and follow-up but is often difficult using conventional imaging such as CT and MRI. We report our results with PET/CT and 2-(18)F-fluoro-L-tyrosine ((18)F-TYR), a marker of amino acid transport, as part of the yearly follow-up of irradiated patients.
  
  
  METHODS
  Eleven patients (mean age, 56.5 y) with skull base meningiomas (n=13 lesions) previously irradiated were included. All patients received 300 MBq of (18)F-TYR and were imaged after 30 min of uptake, using a dedicated PET/CT system. The images were first visually examined, and regions of interest (ROI) were then placed over the transaxial PET slice showing the highest uptake. Another ROI was placed over the normal parietal cortex. Tumor-to-cortex activity ratios were obtained by dividing the maximum pixel value in the tumor ROI by the maximum pixel value in the cortex ROI. The PET/CT images were compared with the MR images obtained as part of routine follow-up.
  
  
  RESULTS
  Accumulation of the tracer was higher in all meningiomas than in the surrounding tissue. The tumor-to-cortex activity ratio was 2.53 +/- 0.35 (range, 1.3-6). Nonneoplastic tissue such as hyperemic cavernous sinus did not take up the radionuclide and was therefore easily distinguished from the meningioma. The (18)F-TYR anomalies completely overlapped with the MR image in 54% of the tumors, extended beyond the MRI lesion in 38% of the tumors, and were smaller in 8% of the tumors.
  
  
  CONCLUSIONS
  Meningiomas of the skull base are clearly visualized using (18)F-TYR PET/CT, even after irradiation. In addition to MRI, (18)F-TYR PET/CT images may contribute to the evaluation, delineation, and follow-up of these tumors.
authors.affiliation: Department of Radiotherapy, C.H.U. of Liège, Liège, Belgium. irutten@chu.ulg.ac.be
authors.forename: Isabelle
authors.initials: I
authors.lastname: Rutten
authors.forename: Jean-Evrard
authors.initials: JE
authors.lastname: Cabay
authors.forename: Nadia
authors.initials: N
authors.lastname: Withofs
authors.forename: Christian
authors.initials: C
authors.lastname: Lemaire
authors.forename: Joel
authors.initials: J
authors.lastname: Aerts
authors.forename: Veronique
authors.initials: V
authors.lastname: Baart
authors.forename: Roland
authors.initials: R
authors.lastname: Hustinx
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D008297:Male; D008577:Meningeal Neoplasms / Q000175:diagnosis*; D008579:Meningioma / Q000175:diagnosis*; D008875:Middle Aged; D010865:Pilot Projects; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D019292:Skull Base Neoplasms / Q000175:diagnosis*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014443:Tyrosine / Q000031:analogs & derivatives*
chemical_list: D019275:Radiopharmaceuticals; D014443:Tyrosine; C060489:2-fluorotyrosine