title: A comparative study of target volumes based on18F-FDG PET-CT and ten phases of 4DCT for primary thoracic squamous esophageal cancer.
abstract: OBJECTIVE
  To investigate the correlations in target volumes based on18F-FDG PET/CT and four-dimensional CT (4DCT) to detect the feasibility of implementing PET in determining gross target volumes (GTV) for tumor motion for primary thoracic esophageal cancer (EC).
  
  
  METHODS
  Thirty-three patients with EC sequentially underwent contrast-enhanced 3DCT, 4DCT, and18F-FDG PET-CT thoracic simulation. The internal gross target volume (IGTV)10was obtained by combining the GTV from ten phases of 4DCT. The GTVs based on PET/CT images were defined by setting of different standardized uptake value thresholds and visual contouring. The difference in volume ratio, conformity index (CI), and degree of inclusion (DI) between IGTV10and GTVPETwas compared.
  
  
  RESULTS
  The images from 20 patients were suitable for further analysis. The optimal volume ratio of 0.95±0.32, 1.06±0.50, 1.07±0.49 was at standardized uptake value (SUV)2.5, SUV20%, or manual contouring. The mean CIs were from 0.33 to 0.54. The best CIs were at SUV2.0(0.51±0.11), SUV2.5(0.53±0.13), SUV20%(0.53±0.12), and manual contouring (0.54±0.14). The mean DIs of GTVPETin IGTV10were from 0.60 to 0.90, and the mean DIs of IGTV10in GTVPETranged from 0.35 to 0.78. A negative correlation was found between the mean CI and different SUV (P=0.000).
  
  
  CONCLUSIONS
  None of the PET-based contours had both close spatial and volumetric approximation to the 4DCT IGTV10. Further evaluation and optimization of PET as a tool for target identification are required.
authors.affiliation: Department of Radiation Oncology (Chest Section), Shandong Cancer Hospital and Institute, Jinan, Shandong Province, People's Republic of China.
authors.forename: Yanluan
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Department of Radiation Oncology (Chest Section), Shandong Cancer Hospital and Institute, Jinan, Shandong Province, People's Republic of China.
authors.forename: Jianbin
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Radiation Oncology (Chest Section), Shandong Cancer Hospital and Institute, Jinan, Shandong Province, People's Republic of China.
authors.forename: Peng
authors.initials: P
authors.lastname: Zhang
authors.affiliation: Department of Radiation Oncology (Chest Section), Shandong Cancer Hospital and Institute, Jinan, Shandong Province, People's Republic of China.
authors.forename: Yingjie
authors.initials: Y
authors.lastname: Zhang
keywords: 18F-FDG PET/CT; contour; esophageal cancer; four-dimensional computed tomography; tumor motion