title: Evaluation of primary brain tumors with FLT-PET: usefulness and limitations.
abstract: OBJECTIVE
  The purpose of this report was to investigate the potential of positron emission tomography using F-18 fluorodeoxythymidine (FLT-PET) in evaluating primary brain tumors.
  
  
  METHODS
  FLT-PET was performed in 25 patients with primary brain tumors. FLT uptake in the lesion was semiquantitatively evaluated by measuring the maximal standardized uptake value (SUVmax) and the tumor-to-normal tissue ratio (TNR). SUVmax and TNR were compared with the histologic grade and the expression of the proliferation marker (Ki-67).
  
  
  RESULTS
  FLT uptake in normal brain parenchyma was very low, resulting in the visualization of brain tumors with high contrast. Both SUVmax and TNR significantly correlated with the malignant grade of brain gliomas, in which high SUVmax/TNR was obtained for high-grade gliomas. Patients with primary lymphoma also showed SUVmax/TNR equivalent to glioblastoma. There was a positive correlation between SUVmax/TNR and the Ki-67 index. In contrast, spuriously high SUVmax and TNR were obtained in 3 of 6 patients with suspected recurrent tumors (2 patients with recurrent grade 2 glioma and one patient with postoperative granuloma), all of which showed lesion enhancement on MRI after Gd administration.
  
  
  CONCLUSIONS
  FLT-PET can be used to evaluate the malignant grade and proliferation activity of primary brain tumors, especially malignant brain tumors. However, the presence of benign lesions showing blood-brain barrier disruption cannot be distinguished from malignant tumors and needs to be carefully evaluated.
authors.affiliation: Department of Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Saga
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Kawashima
authors.forename: Norio
authors.initials: N
authors.lastname: Araki
authors.forename: Jun A
authors.initials: JA
authors.lastname: Takahashi
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Nakashima
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Higashi
authors.forename: Natsuo
authors.initials: N
authors.lastname: Oya
authors.forename: Takahiro
authors.initials: T
authors.lastname: Mukai
authors.forename: Masato
authors.initials: M
authors.lastname: Hojo
authors.forename: Nobuo
authors.initials: N
authors.lastname: Hashimoto
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Manabe
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hiraoka
authors.forename: Kaori
authors.initials: K
authors.lastname: Togashi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000000981:diagnostic imaging*; D001932:Brain Neoplasms / Q000000981:diagnostic imaging*; D002648:Child; D015224:Dideoxynucleosides; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D015224:Dideoxynucleosides; D019275:Radiopharmaceuticals; C002854:alovudine