title: Cine computed tomography without respiratory surrogate in planning stereotactic radiotherapy for non-small-cell lung cancer.
abstract: OBJECTIVE
  To determine whether cine computed tomography (CT) can serve as an alternative to four-dimensional (4D)-CT by providing tumor motion information and producing equivalent target volumes when used to contour in radiotherapy planning without a respiratory surrogate.
  
  
  METHODS
  Cine CT images from a commercial CT scanner were used to form maximum intensity projection and respiratory-averaged CT image sets. These image sets then were used together to define the targets for radiotherapy. Phantoms oscillating under irregular motion were used to assess the differences between contouring using cine CT and 4D-CT. We also retrospectively reviewed the image sets for 26 patients (27 lesions) at our institution who had undergone stereotactic radiotherapy for Stage I non-small-cell lung cancer. The patients were included if the tumor motion was >1 cm. The lesions were first contoured using maximum intensity projection and respiratory-averaged CT image sets processed from cine CT and then with 4D-CT maximum intensity projection and 10-phase image sets. The mean ratios of the volume magnitude were compared with intraobserver variation, the mean centroid shifts were calculated, and the volume overlap was assessed with the normalized Dice similarity coefficient index.
  
  
  RESULTS
  The phantom studies demonstrated that cine CT captured a greater extent of irregular tumor motion than did 4D-CT, producing a larger tumor volume. The patient studies demonstrated that the gross tumor defined using cine CT imaging was similar to, or slightly larger than, that defined using 4D-CT.
  
  
  CONCLUSIONS
  The results of our study have shown that cine CT is a promising alternative to 4D-CT for stereotactic radiotherapy planning.
authors.affiliation: Department of Imaging Physics, University of Texas M.D. Anderson Cancer Center, Houston, TX, USA.
authors.forename: Adam C
authors.initials: AC
authors.lastname: Riegel
authors.forename: Joe Y
authors.initials: JY
authors.lastname: Chang
authors.forename: Sastry S
authors.initials: SS
authors.lastname: Vedam
authors.forename: Valen
authors.initials: V
authors.lastname: Johnson
authors.forename: Pai-Chun Melinda
authors.initials: PC
authors.lastname: Chi
authors.forename: Tinsu
authors.initials: T
authors.lastname: Pan
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000601:surgery; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery; D009068:Movement; D019047:Phantoms, Imaging; D016634:Radiosurgery; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012119:Respiration; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*; D047368:Tumor Burden