title: Comparative evaluation of target volumes defined by deformable and rigid registration of diagnostic PET/CT to planning CT in primary esophageal cancer.
abstract: BACKGROUND
  To evaluate the geometrical differences of target volumes propagated by deformable image registration (DIR) and rigid image registration (RIR) to assist target volume delineation between diagnostic Positron emission tomography/computed tomography (PET/CT) and planning CT for primary esophageal cancer (EC).
  
  
  METHODS
  Twenty-five patients with EC sequentially underwent a diagnostic F-fluorodeoxyglucose (F-FDG) PET/CT scan and planning CT simulation. Only 19 patients with maximum standardized uptake value (SUVmax) ≥ 2.0 of the primary volume were available. Gross tumor volumes (GTVs) were delineated using CT and PET display settings. The PET/CT images were then registered with planning CT using MIM software. Subsequently, the PET and CT contours were propagated by RIR and DIR to planning CT. The properties of these volumes were compared.
  
  
  RESULTS
  When GTVCT delineated on CT of PET/CT after both RIR and DIR was compared with GTV contoured on planning CT, significant improvements using DIR were observed in the volume, displacements of the center of mass (COM) in the 3-dimensional (3D) direction, and Dice similarity coefficient (DSC) (P = 0.003; 0.006; 0.014). Although similar improvements were not observed for the same comparison using DIR for propagated PET contours from diagnostic PET/CT to planning CT (P > 0.05), for DSC and displacements of COM in the 3D direction of PET contours, the DIR resulted in the improved volume of a large percentage of patients (73.7%; 68.45%; 63.2%) compared with RIR. For diagnostic CT-based contours or PET contours at SUV2.5 propagated by DIR with planning CT, the DSC and displacements of COM in 3D directions in the distal segment were significantly improved compared to the upper and middle segments (P > 0.05).
  
  
  CONCLUSIONS
  We observed a trend that deformable registration might improve the overlap for gross target volumes from diagnostic PET/CT to planning CT. The distal EC might benefit more from DIR.
authors.affiliation: Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Jinan, Shandong, China.
authors.forename: Yanluan
authors.initials: Y
authors.lastname: Guo
authors.forename: Jianbin
authors.initials: J
authors.lastname: Li
authors.forename: Peng
authors.initials: P
authors.lastname: Zhang
authors.forename: Qian
authors.initials: Q
authors.lastname: Shao
authors.forename: Min
authors.initials: M
authors.lastname: Xu
authors.forename: Yankang
authors.initials: Y
authors.lastname: Li
mesh_terms: D000368:Aged; D000465:Algorithms; D061827:Dimensional Measurement Accuracy; D004938:Esophageal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000494:pharmacology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D000072078:Positron Emission Tomography Computed Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000494:pharmacology; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods*; D047368:Tumor Burden
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18