title: Optimization of scan initiation timing after11C-methionine administration for the diagnosis of suspected recurrent brain tumors.
abstract: OBJECTIVE
  11C-Methionine (MET) positron emission tomography (PET) imaging is a valuable technique for the evaluation of primary and recurrent brain tumors. Many studies have used MET-PET for data acquisition starting at 20 min after the tracer injection, while others have used scan initiation times at 5-15 min postinjection. No previous studies have identified the best acquisition timing during MET-PET imaging for suspected recurrent brain tumors. Here we sought to determine the optimal scan initiating timing after MET administration for the detection of recurrent brain tumors.
  
  
  METHODS
  Twenty-three consecutive patients with suspected recurrent brain tumors underwent MET-PET examinations. Brain PET images were reconstructed from the four serial data sets (10-15, 15-20, 20-25, and 25-30 min postinjection) that were obtained using the list-mode acquisition technique. We determined the maximal standardized uptake values (SUVmax) of the target lesions and the target-to-normal-tissue ratios (TNRs), calculated as the SUVmax to the SUVmean of a region of interest placed on the normal contralateral frontal cortex. Target lesions without significant MET uptake were excluded.
  
  
  RESULTS
  Thirty-one lesions from 23 patients were enrolled. There were no significant differences in MET SUVmax or TNR values among the PET images that were reconstructed with the data extracted from the four phases postinjection.
  
  
  CONCLUSIONS
  The MET uptake in the suspected recurrent brain tumors was comparable among all data extraction time phases from 10 to 30 min postinjection. The scan initiation time of MET-PET at 10 min after the injection is allowable for the detection of recurrent brain tumors. The registration identification number of the original study is 1002.
authors.affiliation: Department of Diagnostic Imaging and Nuclear Medicine, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan.
authors.forename: Reiko
authors.initials: R
authors.lastname: Nakajima
authors.affiliation: Department of Diagnostic Imaging and Nuclear Medicine, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan. abe.koichiro@twmu.ac.jp.
authors.forename: Koichiro
authors.identifier: http://orcid.org/0000-0003-0549-9122
authors.initials: K
authors.lastname: Abe
authors.affiliation: Department of Diagnostic Imaging and Nuclear Medicine, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Momose
authors.affiliation: Department of Diagnostic Imaging and Nuclear Medicine, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Fukushima
authors.affiliation: Department of Diagnostic Imaging and Nuclear Medicine, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Matsuo
authors.affiliation: Department of Diagnostic Imaging and Nuclear Medicine, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Kimura
authors.affiliation: Department of Diagnostic Imaging and Nuclear Medicine, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan.
authors.forename: Chisato
authors.initials: C
authors.lastname: Kondo
authors.affiliation: Department of Diagnostic Imaging and Nuclear Medicine, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan.
authors.forename: Shuji
authors.initials: S
authors.lastname: Sakai
mesh_terms: D000328:Adult; D000368:Aged; D001921:Brain / Q000000981:diagnostic imaging; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000628:therapy; D002250:Carbon Radioisotopes / Q000008:administration & dosage*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008297:Male; D008715:Methionine / Q000008:administration & dosage*; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging*; D000072078:Positron Emission Tomography Computed Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000008:administration & dosage*; D012189:Retrospective Studies; D013997:Time Factors; D047368:Tumor Burden
chemical_list: D002250:Carbon Radioisotopes; D019275:Radiopharmaceuticals; D008715:Methionine
keywords: 11C-Methionine; Maximal standardized uptake value; Positron emission tomography; Recurrent brain tumor; Target-to-normal-tissue ratio