title: Voxel-based analysis of dual-time-point 18F-FDG PET images for brain tumor identification and delineation.
abstract: We have investigated dual-time-point (18)F-FDG PET for the detection and delineation of high-grade brain tumors using quantitative criteria applied on a voxel basis.
  
  
  METHODS
  Twenty-five patients with suspected high-grade brain tumors and inconclusive MRI findings underwent (11)C-methionine PET and dual-time-point (18)F-FDG PET. Images from each subject were registered and spatially normalized. Parametric maps of standardized uptake value (SUV) and tumor-to-normal gray matter (TN) ratio for each PET image were obtained. Tumor diagnosis was evaluated according to 4 criteria comparing standard and delayed (18)F-FDG PET images: any SUV increase, SUV increase greater than 10%, any TN increase, and TN increase greater than 10%. Voxel-based analysis sensitivity was assessed using (11)C-methionine as a reference and compared with visual and volume-of-interest analysis for dual-time-point PET images. Additionally, volumetric assessment of the tumor extent that fulfills each criterion was compared with the volume defined for (11)C-methionine PET.
  
  
  RESULTS
  The greatest sensitivity for tumor identification was obtained with any increase of TN ratio (100%), followed by a TN increase greater than 10% (96%), any SUV increase (80%), and an SUV increase greater than 10% (60%). These values were superior to visual analysis of standard (18)F-FDG (sensitivity, 40%) and delayed (18)F-FDG PET (sensitivity, 52%). Volume-of-interest analysis of dual-time-point PET reached a sensitivity of only 64% using the TN increase criterion. Regarding volumetry, voxel-based analysis with the TN ratio increase as a criterion, compared with (11)C-methionine PET, detected 55.4% of the tumor volume, with the other criteria detecting volumes lower than 20%. Nevertheless, volume detection presented great variability, being better for metastasis (78%) and glioblastomas (56%) than for anaplastic tumors (12%). A positive correlation was observed between the volume detected and the time of acquisition of the delayed PET image (r = 0.66, P < 0.001), showing volumes greater than 75% when the delayed image was obtained at least 6 h after (18)F-FDG injection.
  
  
  CONCLUSIONS
  Compared with standard (18)F-FDG PET studies, quantitative dual-time-point (18)F-FDG PET can improve sensitivity for the identification and volume delineation of high-grade brain tumors.
authors.affiliation: Department of Nuclear Medicine, Clínica Universidad de Navarra, Pamplona, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: Prieto
authors.forename: Josep María
authors.initials: JM
authors.lastname: Martí-Climent
authors.forename: Inés
authors.initials: I
authors.lastname: Domínguez-Prado
authors.forename: Puy
authors.initials: P
authors.lastname: Garrastachu
authors.forename: Ricardo
authors.initials: R
authors.lastname: Díez-Valle
authors.forename: Sonia
authors.initials: S
authors.lastname: Tejada
authors.forename: José Javier
authors.initials: JJ
authors.lastname: Aristu
authors.forename: Iván
authors.initials: I
authors.lastname: Peñuelas
authors.forename: Javier
authors.initials: J
authors.lastname: Arbizu
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001921:Brain / Q000000981:diagnostic imaging; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D002648:Child; D005260:Female; D019788:Fluorodeoxyglucose F18; D005909:Glioblastoma / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008715:Methionine; D008875:Middle Aged; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D055815:Young Adult
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; C086242:carbon-11 methionine; D008715:Methionine