title: A novel PET index, 18F-FDG-11C-methionine uptake decoupling score, reflects glioma cell infiltration.
abstract: The linear correlation between (11)C-methionine PET and tumor cell density is not well conserved at the tumor border in glioma. A novel imaging analysis method, voxelwise (18)F-FDG-(11)C-methionine PET decoupling analysis (decoupling score), was evaluated to determine whether it could be used to quantitatively assess glioma cell infiltration in MRI-nonenhancing T2 hyperintense lesions.
  
  
  METHODS
  Data collection was performed in a prospective fashion. Fifty-four MRI-nonenhancing T2 hyperintense specimens were stereotactically obtained from 23 glioma patients by intraoperative navigation guidance. The decoupling score and tumor-to-normal tissue (T/N) ratio of (11)C-methionine PET were calculated at each location. Correlations between the tumor cell density at these lesions, decoupling score, and T/N ratio of (11)C-methionine PET were then evaluated.
  
  
  RESULTS
  Both the decoupling score and the T/N ratio showed a linear correlation with tumor cell density at these specimens (R(2) = 0.52 and 0.53, respectively). Use of the decoupling score (cutoff = 3.0) allowed the detection of specimens with a tumor cell density of more than 1,000/mm(2), with a sensitivity and specificity of 93.5% and 87.5%, respectively, whereas conventional (11)C-methionine PET (cutoff = 1.2 in T/N ratio) was able to detect with a sensitivity and specificity of 87.0% and 87.5%, respectively. Reconstructed images (decoupling map) using the decoupling score enabled the visualization of glioma lesions that were difficult to visualize by (11)C-methionine PET alone.
  
  
  CONCLUSIONS
  The decoupling score showed better performance in detecting glioma cell infiltration than (11)C-methionine uptake alone, thus suggesting that (18)F-FDG-(11)C-methionine uptake decoupling analysis is a powerful imaging modality for assessing glioma invasion.
authors.affiliation: Department of Neurosurgery, Osaka University Graduate School of Medicine, Osaka, Japan. m-kinoshita@nsurg.med.osaka-u.ac.jp
authors.forename: Manabu
authors.initials: M
authors.lastname: Kinoshita
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Arita
authors.forename: Tetsu
authors.initials: T
authors.lastname: Goto
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Okita
authors.forename: Kayako
authors.initials: K
authors.lastname: Isohashi
authors.forename: Tadashi
authors.initials: T
authors.lastname: Watabe
authors.forename: Naoki
authors.initials: N
authors.lastname: Kagawa
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Fujimoto
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Kishima
authors.forename: Eku
authors.initials: E
authors.lastname: Shimosegawa
authors.forename: Jun
authors.initials: J
authors.lastname: Hatazawa
authors.forename: Naoya
authors.initials: N
authors.lastname: Hashimoto
authors.forename: Toshiki
authors.initials: T
authors.lastname: Yoshimine
mesh_terms: D000328:Adult; D000368:Aged; D001692:Biological Transport; D001921:Brain / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology; D002452:Cell Count; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism*; D005910:Glioma / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D016014:Linear Models; D008279:Magnetic Resonance Imaging; D008297:Male; D008715:Methionine / Q000378:metabolism*; D008875:Middle Aged; D049268:Positron-Emission Tomography
chemical_list: D019788:Fluorodeoxyglucose F18; C086242:carbon-11 methionine; D008715:Methionine