title: High reproducibility of tumor hypoxia evaluated by 18F-fluoromisonidazole PET for head and neck cancer.
abstract: Tumor hypoxia is well known to be radiation resistant. (18)F-fluoromisonidazole ((18)F-FMISO) PET has been used for noninvasive evaluation of hypoxia. Quantitative evaluation of (18)F-FMISO uptake is thus expected to play an important role in the planning of dose escalation radiotherapy. However, the reproducibility of (18)F-FMISO uptake has remained unclarified. We therefore investigated the reproducibility of tumor hypoxia by using quantitative analysis of (18)F-FMISO uptake.
  
  
  METHODS
  Eleven patients with untreated head and neck cancer underwent 2 (18)F-FMISO PET/CT scans ((18)F-FMISO(1) and (18)F-FMISO(2)) with a 48-h interval prospectively. All images were acquired at 4 h after (18)F-FMISO injection for 10 min. The maximum standardized uptake (SUVmax), tumor-to-blood ratio (TBR), and tumor-to-muscle ratio (TMR) of (18)F-FMISO uptake were statistically compared between the 2 (18)F-FMISO scans by use of intraclass correlation coefficients (ICCs). The hypoxic volume was calculated as the area with a TBR of greater than or equal to 1.5 or the area with a TMR of greater than or equal to 1.25 to assess differences in hypoxic volume between the 2 (18)F-FMISO scans. The distances from the maximum uptake locations of the (18)F-FMISO(1) images to those of the (18)F-FMISO(2) images were measured to evaluate the locations of (18)F-FMISO uptake.
  
  
  RESULTS
  The SUVmax (mean ± SD) for (18)F-FMISO(1) and (18)F-FMISO(2) was 3.16 ± 1.29 and 3.02 ± 1.12, respectively, with the difference between the 2 scans being 7.0% ± 4.6%. The TBRs for (18)F-FMISO(1) and (18)F-FMISO(2) were 2.98 ± 0.83 and 2.97 ± 0.64, respectively, with a difference of 9.9% ± 3.3%. The TMRs for (18)F-FMISO(1) and (18)F-FMISO(2) were 2.25 ± 0.71 and 2.19 ± 0.67, respectively, with a difference of 7.1% ± 5.3%. The ICCs for SUVmax, TBR, and TMR were 0.959, 0.913, and 0.965, respectively. The difference in hypoxic volume based on TBR was 1.8 ± 1.8 mL, and the difference in hypoxic volume based on TMR was 0.9 ± 1.3 mL, with ICCs of 0.986 and 0.996, respectively. The maximum uptake locations of the (18)F-FMISO(1) images were different from those of the (18)F-FMISO(2) images and were within the full width at half maximum of the PET/CT scanner, except in 1 case.
  
  
  CONCLUSIONS
  The values for (18)F-FMISO PET uptake and hypoxic volume in head and neck tumors between the 2 (18)F-FMISO scans were highly reproducible. Such high reproducibility of tumor hypoxia is promising for accurate radiation planning.
authors: Department of Nuclear Medicine, Hokkaido University Graduate School of Medicine, Sapporo 060-8638, Japan.
authors: Shozo
authors: S
authors: Okamoto
authors: Tohru
authors: T
authors: Shiga
authors: Koichi
authors: K
authors: Yasuda
authors: Yoichi M
authors: YM
authors: Ito
authors: Keiichi
authors: K
authors: Magota
authors: Katsuhiko
authors: K
authors: Kasai
authors: Yuji
authors: Y
authors: Kuge
authors: Hiroki
authors: H
authors: Shirato
authors: Nagara
authors: N
authors: Tamaki
mesh_terms: D000328:Adult; D000368:Aged; D005462:Fluorine Radioisotopes; D006258:Head and Neck Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging*; D006801:Humans; D000860:Hypoxia / Q000000981:diagnostic imaging* / Q000473:pathology; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D008920:Misonidazole / Q000031:analogs & derivatives*; D009683:Nuclear Medicine / Q000379:methods; D049268:Positron-Emission Tomography / Q000379:methods*; D011379:Prognosis; D018787:Radiation Oncology / Q000379:methods; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D013997:Time Factors
chemical_list: D005462:Fluorine Radioisotopes; D019275:Radiopharmaceuticals; C031843:fluoromisonidazole; D008920:Misonidazole