title: 18F-FDG-PET-based tumor delineation in cervical cancer: threshold contouring and lesion volumes.
abstract: OBJECTIVE
  To evaluate a semi-automated PET-image tumor segmentation algorithm for gross tumor volume (GTV) delineation in patients with locally advanced cervical cancer.
  
  
  METHODS
  Thirty-two patients with locally advanced cervical cancer were retrospectively evaluated. Semi-automated PET-image-based GTV delineation was applied using a previous established algorithm (GTV2SD) and 2 fixed threshold-based methods (GTV40% and GTV50%). GTV2SD was determined as the pixel with the mean value plus 2-standard deviation of the liver intensity, and GTV40% and GTV50% with 40% and 50% of the maximum tumor intensity (Tmax), respectively. The derived volumes were then compared with the GTVs generated manually using MR (GTVMR).
  
  
  RESULTS
  The mean value of GTV2SD, GTV40% and GTV50% was 85.3cc, 16.2cc and 24.1cc, respectively. Good agreement was noticed between GTV2SD and GTVMR (ρ=0.88). GTV40% and GTV50% showed weaker correlation with GTVMR (ρ=0.68 and ρ=0.71, respectively).
  
  
  CONCLUSIONS
  This study provides preliminary evidence that metabolic tumor volume delineation is feasible using computer-generated measurements in (18)F-FDG PET images. Generation of PET-based tumor volumes is affected by the choice of threshold level used. Metabolic tumor bulk calculated using the pixel with the mean value plus 2-standard deviations of the liver intensity (GTV2SD) correlates better with the MR-derived tumor volumes. The method is a simple and clinically applicable approach to generate PET-derived GTV for radiation therapy planning of cervical cancer.
authors: Radiation Oncology Service, National Cancer Institute of Brazil, Rio de Janeiro, Brazil.
authors: F
authors: F
authors: Erlich
authors: C
authors: C
authors: Camisão
authors: A
authors: A
authors: Nogueira-Rodrigues
authors: S
authors: S
authors: Altino
authors: C G
authors: CG
authors: Ferreira
authors: M
authors: M
authors: Mamede
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008875:Middle Aged; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D012189:Retrospective Studies; D047368:Tumor Burden; D002583:Uterine Cervical Neoplasms / Q000175:diagnosis*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18