title: Determination of respiratory motion for distal esophagus cancer using four-dimensional computed tomography.
abstract: OBJECTIVE
  To investigate the motion characteristics of distal esophagus cancer primary tumors using four-dimensional computed tomography (4D CT).
  
  
  METHODS
  Thirty-one consecutive patients treated for esophagus cancer who received respiratory-gated 4D CT imaging for treatment planning were selected. Deformable image registration was used to map the full expiratory motion gross tumor volume (GTV) to the full-inspiratory CT image, allowing quantitative assessment of each voxel's displacement. These displacements were correlated with patient tumor and respiratory characteristics.
  
  
  RESULTS
  The mean (SE) tidal volume was 608 (73) mL. The mean GTV volume was 64.3 (10.7) mL on expiration and 64.1 (10.7) mL on inspiration (no significant difference). The mean tumor motion in the x-direction was 0.13 (0.006) cm (average of absolute values), in the y-direction 0.23 (0.01) cm (anteriorly), and in the z-direction 0.71 (0.02) cm (inferiorly). Tumor motion correlated with tidal volume. Comparison of tumor motion above vs. below the diaphragm was significant for the average net displacement (p = 0.014), motion below the diaphragm was greater than above. From the cumulative distribution 95% of the tumors moved less than 0.80 cm radially and 1.75 cm inferiorly.
  
  
  CONCLUSIONS
  Primary esophagus tumor motion was evaluated with 4D CT. According to the results of this study, when 4D CT is not available, a radial margin of 0.8 cm and axial margin of +/-1.8 cm would provide tumor motion coverage for 95% of the cases in our study population.
authors.affiliation: Division of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Yaremko
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Guerrero
authors.forename: Mary F
authors.initials: MF
authors.lastname: McAleer
authors.forename: M Kara
authors.initials: MK
authors.lastname: Bucci
authors.forename: Josue
authors.initials: J
authors.lastname: Noyola-Martinez
authors.forename: Linda T
authors.initials: LT
authors.lastname: Nguyen
authors.forename: Peter A
authors.initials: PA
authors.lastname: Balter
authors.forename: Rudy
authors.initials: R
authors.lastname: Guerra
authors.forename: Ritsuko
authors.initials: R
authors.lastname: Komaki
authors.forename: Zhongxing
authors.initials: Z
authors.lastname: Liao
mesh_terms: D000465:Algorithms; D004938:Esophageal Neoplasms / Q000000981:diagnostic imaging*; D006801:Humans; D009068:Movement; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012119:Respiration; D013990:Tidal Volume; D014057:Tomography, X-Ray Computed / Q000379:methods*; D047368:Tumor Burden