title: Potential of [18F]-fluoromisonidazole positron-emission tomography for radiotherapy planning in head and neck squamous cell carcinomas.
abstract: OBJECTIVE
  Positron-emission tomography (PET) with [(18)F]-fluoromisonidazole (FMISO) permits consideration of radiotherapy dose escalation to hypoxic volumes in head and neck cancers (HNC). However, the definition of FMISO volumes remains problematic. The aims of this study are to confirm that delayed acquisition at 4 h is most appropriate for FMISO-PET imaging and to assess different methods of volume segmentation.
  
  
  METHODS
  A total of 15 HNC patients underwent several FMISO-PET/computed tomography (CT) acquisitions 2, 3 and 4 h after FMISO injection. Three automatic methods of PET image segmentation were tested: fixed threshold, adaptive threshold based on the ratio between tumour-derived and background activities (R(T/B)) and the fuzzy locally adaptive Bayesian (FLAB) method. The hypoxic fraction (HF), which is defined as the ratio between the FMISO and CT volumes, was also calculated.
  
  
  RESULTS
  The R(T/B) for images acquired at 2, 3 and 4 h differed significantly, with mean values of 2.5 (1.7-2.9), 3 (2-4.5) and 3.4 (2.3-6.1), respectively. The mean tumour volume, as defined manually using CT images, was 39.1 ml (1.2-116 ml). After 4 h, the mean FMISO volumes were 18.9 (0.1-81), 9.5 (0.9-33.1) and 12.5 ml (0.9-38.4 ml) with fixed threshold, adaptive threshold and the FLAB method, respectively; median HF values were 0.47 (0.1-1.93), 0.25 (0.11-0.75) and 0.35 (0.14-1.05), respectively. FMISO volumes were significantly different.
  
  
  CONCLUSIONS
  The best contrast is obtained at the 4-hour acquisition time. Large discrepancies were found between the three tested methods of volume segmentation.
authors.affiliation: Department of Radiotherapy, Institut Bergonié, 229, cours de l'Argonne, 33076, Bordeaux Cedex, France, b.henriques@bordeaux.unicancer.fr.
authors.forename: B
authors.initials: B
authors.lastname: Henriques de Figueiredo
authors.forename: T
authors.initials: T
authors.lastname: Merlin
authors.forename: H
authors.initials: H
authors.lastname: de Clermont-Gallerande
authors.forename: M
authors.initials: M
authors.lastname: Hatt
authors.forename: D
authors.initials: D
authors.lastname: Vimont
authors.forename: P
authors.initials: P
authors.lastname: Fernandez
authors.forename: F
authors.initials: F
authors.lastname: Lamare
mesh_terms: D000368:Aged; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D005240:Feasibility Studies; D005260:Female; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008920:Misonidazole / Q000031:analogs & derivatives*; D049268:Positron-Emission Tomography / Q000379:methods*; D011379:Prognosis; D019275:Radiopharmaceuticals; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D000077195:Squamous Cell Carcinoma of Head and Neck; D016896:Treatment Outcome; D047368:Tumor Burden
chemical_list: D019275:Radiopharmaceuticals; C031843:fluoromisonidazole; D008920:Misonidazole