title: Evaluation of Elekta 4D cone beam CT-based automatic image registration for radiation treatment of lung cancer.
abstract: OBJECTIVE
  The study was aimed to evaluate the precision of Elekta four-dimensional (4D) cone beam CT (CBCT)-based automatic dual-image registrations using different landmarks for clipbox for radiation treatment of lung cancer.
  
  
  METHODS
  30 4D CBCT scans from 15 patients were studied. 4D CBCT images were registered with reference CT images using dual-image registration: a clipbox registration and a mask registration. The image registrations performed in clinic using a physician-defined clipbox, were reviewed by physicians, and were taken as the standard. Studies were conducted to evaluate the automatic dual registrations using three kinds of landmarks for clipbox: spine, spine plus internal target volume (ITV) and lung (including as much of the lung as possible). Translational table shifts calculated from the automatic registrations were compared with those of the standard.
  
  
  RESULTS
  The mean of the table shift differences in the lateral direction were 0.03, 0.03 and 0.03 cm, for clipboxes based on spine, spine plus ITV and lung, respectively. The mean of the shift differences in the longitudinal direction were 0.08, 0.08 and 0.08 cm, respectively. The mean of the shift differences in the vertical direction were 0.03, 0.03 and 0.03 cm, respectively.
  
  
  CONCLUSIONS
  The automatic registrations using three different landmarks for clipbox showed similar results. One can use any of the three landmarks in 4D CBCT dual-image registration. Advance in knowledge: The study provides knowledge and recommendations for application of Elekta 4D CBCT image registration in radiation therapy of lung cancer.
authors.affiliation: Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: Amy
authors.initials: A
authors.lastname: Harrison
authors.affiliation: Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: Yan
authors.initials: Y
authors.lastname: Yu
authors.affiliation: Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Xiao
authors.affiliation: Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: Maria
authors.initials: M
authors.lastname: Werner-Wasik
authors.affiliation: Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: Bo
authors.initials: B
authors.lastname: Lu
mesh_terms: D056973:Four-Dimensional Computed Tomography / Q000379:methods / Q000592:standards*; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods / Q000592:standards*; D013131:Spine / Q000000981:diagnostic imaging*