title: Use of PET in the diagnosis of primary CNS lymphoma in patients with atypical MR findings.
abstract: OBJECTIVE
  The diagnosis of primary central nervous system lymphoma (PCNSL) in immunocompetent patients with atypical magnetic resonance (MR) findings such as disseminated lesions or no (non-enhancing) lesion is sometimes difficult because of mimicking other tumorous and non-tumorous diseases. Positron emission tomography (PET) with (18)F-fluorodeoxyglucose (FDG) and (11)C-methionine (MET) can measure the glucose and amino acid metabolism in the lesions and may provide useful information for diagnosing PCNSL in patients with such subtle MR findings.
  
  
  METHODS
  We performed PET studies with FDG and MET in 17 histologically proven PCNSL and compared the uptake of FDG and MET qualitatively and quantitatively in the tumors between 12 typical and 5 atypical MR findings.
  
  
  RESULTS
  All typical PCNSL showed strong uptake of FDG and MET; however, visual analysis of FDG and MET uptake in atypical PCNSL was not very useful for finding lesions in the brain. Semiquantitative FDG and MET uptake values (SUVmax) and quantitative FDG influx rate constant (K ( i )) in the tumors are significantly lower in atypical PCNSL compared with those in typical PCNSL. These values obtained in the lesions with atypical MR findings were also not useful for differentiating PCNSL from other tumorous and non-tumorous diseases. The k (3) values evaluated by FDG kinetic analysis in atypical PCNSL were similar to those obtained in typical PCNSL.
  
  
  CONCLUSIONS
  Visual analysis of FDG and MET uptake in atypical PCNSL was not useful for finding the lesions in the brain. Semiquantitative and quantitative values obtained in the lesions with atypical MR findings were also not useful for differentiating PCNSL from other tumorous and non-tumorous diseases. The k (3) values evaluated by FDG kinetic analysis in atypical PCNSL may provide valuable information in the diagnosis of PCNSL.
authors.affiliation: Department of Neurological Surgery, Kagawa University, Faculty of Medicine, 1750-1 Miki-cho, Kita-gun, Kagawa, 761-0793, Japan. nobu@med.kagawa-u.ac.jp
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Kawai
authors.forename: Shuichi
authors.initials: S
authors.lastname: Okubo
authors.forename: Keisuke
authors.initials: K
authors.lastname: Miyake
authors.forename: Yukito
authors.initials: Y
authors.lastname: Maeda
authors.forename: Yuka
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Nishiyama
authors.forename: Takashi
authors.initials: T
authors.lastname: Tamiya
mesh_terms: D000328:Adult; D000368:Aged; D016543:Central Nervous System Neoplasms / Q000000981:diagnostic imaging*; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008223:Lymphoma / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging; D008297:Male; D008715:Methionine; D008875:Middle Aged; D049268:Positron-Emission Tomography; D012189:Retrospective Studies
chemical_list: D019788:Fluorodeoxyglucose F18; C086242:carbon-11 methionine; D008715:Methionine