title: L-(methyl-11C) methionine positron emission tomography for target delineation in resected high-grade gliomas before radiotherapy.
abstract: OBJECTIVE
  Using magnetic resonance imaging (MRI), residual tumor cannot be differentiated from nonspecific postoperative changes in operated patients with brain gliomas. The higher specificity and sensitivity of L-(methyl-11C)-labeled methionine positron emissions tomography (MET-PET) in gliomas has been demonstrated in previous studies and is the rationale for the integration of this investigation in gross tumor volume delineation. The goal of this trial was to quantify the affect of MET-PET vs. with MRI in gross tumor volume definition for radiotherapy planning of high-grade gliomas.
  
  
  METHODS
  The trial included 39 patients with resected malignant gliomas. MRI and MET-PET data were coregistered based on mutual information. The residual tumor volume on MET-PET and the volume of tissue abnormalities on T1-weighted MRI (gadolinium [Gd] enhancement) and T2-weighted MRI (hyperintensity areas) were compared using MET-PET/MRI fusion images.
  
  
  RESULTS
  The MET-PET vs. Gd-enhanced T1-weighted MRI analysis was performed on 39 patients. In 5 patients (13%), MET uptake corresponded exactly with Gd enhancement, and in 29 (74%) of 39 patients, the region of MET uptake was larger than that of the Gd enhancement. In 27 (69%) of the 39 patients, the Gd enhancement area extended beyond the MET enhancement. MET uptake was detected up to 45 mm beyond the Gd enhancement. MET-PET vs. T2-weighted MRI was investigated in 18 patients. MET uptake did not correspond exactly with the hyperintensity areas on T2-weighted MRI in any patient. In 9 (50%) of 18 patients, MET uptake extended beyond the hyperintensity area on the T2-weighted MRI, and in 18 (100%), at least some hyperintensity on the T2-weighted MRI was located outside the MET enhancement area. MET uptake was detected up to 40 mm beyond the hyperintensity area on T2-weighted MRI.
  
  
  CONCLUSIONS
  In operated patients with brain gliomas, the size and location of residual MET uptake differs considerably from abnormalities found on postoperative MRI. Because postoperative changes cannot be differentiated from residual tumor by MRI, MET-PET, with a greater specificity for tumor tissue, can help to outline the gross tumor volume with greater accuracy.
authors.affiliation: Department of Radiation Oncology, Klinikum Rechts der Isar, Technical University of Munich, Munich, Germany. anca-ligia.grosu@lrz.tum.de
authors.forename: Anca-Ligia
authors.initials: AL
authors.lastname: Grosu
authors.forename: Wolfgang A
authors.initials: WA
authors.lastname: Weber
authors.forename: Eva
authors.initials: E
authors.lastname: Riedel
authors.forename: Branislav
authors.initials: B
authors.lastname: Jeremic
authors.forename: Carsten
authors.initials: C
authors.lastname: Nieder
authors.forename: Martina
authors.initials: M
authors.lastname: Franz
authors.forename: Hartmut
authors.initials: H
authors.lastname: Gumprecht
authors.forename: Ruprecht
authors.initials: R
authors.lastname: Jaeger
authors.forename: Markus
authors.initials: M
authors.lastname: Schwaiger
authors.forename: Michael
authors.initials: M
authors.lastname: Molls
mesh_terms: D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000532:radiotherapy / Q000601:surgery; D005260:Female; D005682:Gadolinium; D005910:Glioma / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000532:radiotherapy / Q000601:surgery; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008715:Methionine / Q000031:analogs & derivatives*; D008875:Middle Aged; D018365:Neoplasm, Residual / Q000000981:diagnostic imaging / Q000473:pathology; D049268:Positron-Emission Tomography / Q000379:methods
chemical_list: D008715:Methionine; D005682:Gadolinium; C038344:methionine methyl ester