title: An automated voxel-based method for calculating the reference value for a brain tumour metabolic index using18F-FDG-PET and11C-methionine PET.
abstract: OBJECTIVE
  The tumour-to-normal ratio (T/N) is a representative index reflecting brain tumour activity by18F-fluorodeoxyglucose (FDG) and11C-methionine (MET) PET. We proposed a new automated method of calculating the normal reference value (N-value) for use as the denomination of T/N. This method uses voxel-based analysis of FDG- and MET-PET images. We compared the results of this method with those of the standard region-of-interest (ROI) method.
  
  
  METHODS
  Data sets were obtained from 32 patients with newly diagnosed glioma and 13 patients with recurrent brain tumour. Our methods were as follows: (1) FDG-PET and MET-PET images were co-registered. (2) The areas where the FDG uptake was higher than a set threshold were selected. (3) For the corresponding areas of MET-PET images, mode and mean voxel values were calculated as tentative MET N-values. (4) Applying the same coordinates to FDG-PET, the voxel values were averaged and used as tentative FDG N-values. (5) The threshold of FDG-PET and whether to use the mode or the mean voxel values were computationally optimized using learning data sets. (6) Applying the optimal threshold and either the mode or mean, N-values of FDG and MET were finally determined.
  
  
  RESULTS
  N-values determined by our automated method showed excellent agreement with those determined by a manual ROI method (ICC(2,1) > 0.78). These values were significantly correlated with mean manual N-values (p < 0.001).
  
  
  CONCLUSIONS
  Our new method shows sufficiently good agreement with the standard method and can provide a more objective metabolic index.
authors.affiliation: Division of Nuclear medicine, Department of Radiology, Graduate School of Medicine, The University of Tokyo, 3-1 Hongo 7-Chome, Bunkyo-ku, Tokyo, 113-8655, Japan. tmiwako-tky@umin.ac.jp.
authors.forename: Miwako
authors.initials: M
authors.lastname: Takahashi
authors.affiliation: Division of Nuclear medicine, Department of Radiology, Graduate School of Medicine, The University of Tokyo, 3-1 Hongo 7-Chome, Bunkyo-ku, Tokyo, 113-8655, Japan.|QMS Group, Quality Assurance Dept., FUJIFILM RI Pharma Co., Ltd., 14-1 Kyobashi 2-Chome Chuo-ku, Tokyo, 104-0031, Japan.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Soma
authors.affiliation: Department of Neurosurgery, Graduate School of Medicine, The University of Tokyo, 3-1 Hongo 7-Chome, Bunkyo-ku, Tokyo, 113-8655, Japan.
authors.forename: Akitake
authors.initials: A
authors.lastname: Mukasa
authors.affiliation: Division of Nuclear medicine, Department of Radiology, Graduate School of Medicine, The University of Tokyo, 3-1 Hongo 7-Chome, Bunkyo-ku, Tokyo, 113-8655, Japan.
authors.forename: Keitaro
authors.initials: K
authors.lastname: Koyama
authors.affiliation: Division of Nuclear medicine, Department of Radiology, Graduate School of Medicine, The University of Tokyo, 3-1 Hongo 7-Chome, Bunkyo-ku, Tokyo, 113-8655, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Arai
authors.affiliation: Division of Nuclear medicine, Department of Radiology, Graduate School of Medicine, The University of Tokyo, 3-1 Hongo 7-Chome, Bunkyo-ku, Tokyo, 113-8655, Japan.
authors.forename: Toshimitsu
authors.initials: T
authors.lastname: Momose
mesh_terms: D000328:Adult; D000465:Algorithms; D001932:Brain Neoplasms / Q000000981:diagnostic imaging*; D002250:Carbon Radioisotopes / Q000737:chemistry*; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000737:chemistry*; D005910:Glioma / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D008715:Methionine / Q000737:chemistry*; D008875:Middle Aged; D010363:Pattern Recognition, Automated; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000737:chemistry; D012016:Reference Values
chemical_list: D002250:Carbon Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; C086242:carbon-11 methionine; D008715:Methionine
keywords: Brain tumour; FDG-PET; MET-PET; Tumour-to-normal ratio; Voxel-based analysis