title: Characterization of FDG-PET images after stereotactic body radiation therapy for lung cancer.
abstract: OBJECTIVE
  The purpose was to characterize (18)F-fluorodeoxyglucose-positron emission tomography (FDG-PET) findings after stereotactic body radiation therapy (SBRT) for lung cancer.
  
  
  METHODS
  This was a retrospective review of 32 FDG-PET scans from 23 patients who underwent SBRT for lung cancer and who showed no evidence of local recurrence. The FDG uptake by lesions was assessed visually using a 3-point scale (0, none or faint; 1, mild; or 2, moderate to intense), and the demarcation (ill- or well-defined) was evaluated. For semi-quantitative analysis, the maximum standardized uptake value (SUVmax) was calculated.
  
  
  RESULTS
  Grade 2 intensity was observed in 70%, 33%, 30%, and 0% of PET scans performed <6, 6-12, 12-24, and >24 months, respectively, after SBRT; well-defined demarcation was observed in 80%, 33%, 40%, and 17%, respectively, and the respective means of the SUVmax were 4.9, 2.6, 3.0, and 2.3. The SUVmax was significantly higher for scans performed at <6 months than at 6-12 or >24 months.
  
  
  CONCLUSIONS
  FDG uptake tended to be intense and well-defined at early times after SBRT, especially within 6 months, and was faint and ill-defined at later periods. Moderate to intense FDG uptake observed soon after SBRT does not always indicate a residual tumour.
authors.affiliation: Department of Radiation Oncology and Image-Applied Therapy, Kyoto University, Sakyo-ku, Kyoto, Japan. ymatsuo@kuhp.kyoto-u.ac.jp
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Matsuo
authors.forename: Yuji
authors.initials: Y
authors.lastname: Nakamoto
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Nagata
authors.forename: Keiko
authors.initials: K
authors.lastname: Shibuya
authors.forename: Kenji
authors.initials: K
authors.lastname: Takayama
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Norihisa
authors.forename: Masaru
authors.initials: M
authors.lastname: Narabayashi
authors.forename: Takashi
authors.initials: T
authors.lastname: Mizowaki
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Saga
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Higashi
authors.forename: Kaori
authors.initials: K
authors.lastname: Togashi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hiraoka
mesh_terms: D000230:Adenocarcinoma / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D011859:Radiography; D012189:Retrospective Studies
chemical_list: D019788:Fluorodeoxyglucose F18