title: Correlation of primary middle and distal esophageal cancers motion with surrounding tissues using four-dimensional computed tomography.
abstract: OBJECTIVE
  To investigate the correlation of gross tumor volume (GTV) motion with the structure of interest (SOI) motion and volume variation for middle and distal esophageal cancers using four-dimensional computed tomography (4DCT).
  
  
  METHODS
  Thirty-three patients with middle or distal esophageal carcinoma underwent 4DCT simulation scan during free breathing. All image sets were registered with 0% phase, and the GTV, apex of diaphragm, lung, and heart were delineated on each phase of the 4DCT data. The position of GTV and SOI was identified in all 4DCT phases, and the volume of lung and heart was also achieved. The phase relationship between the GTV and SOI was estimated through Pearson's correlation test.
  
  
  RESULTS
  The mean peak-to-peak displacement of all primary tumors in the lateral (LR), anteroposterior (AP), and superoinferior (SI) directions was 0.13 cm, 0.20 cm, and 0.30 cm, respectively. The SI peak-to-peak motion of the GTV was defined as the greatest magnitude of motion. The displacement of GTV correlated well with heart in three dimensions and significantly associated with bilateral lung in LR and SI directions. A significant correlation was found between the GTV and apex of the diaphragm in SI direction (r left=0.918 and r right=0.928). A significant inverse correlation was found between GTV motion and varying lung volume, but the correlation was not significant with heart (r LR=-0.530, r AP=-0.531, and r SI=-0.588) during respiratory cycle.
  
  
  CONCLUSIONS
  For middle and distal esophageal cancers, GTV should expand asymmetric internal margins. The primary tumor motion has quite good correlation with diaphragm, heart, and lung.
authors.affiliation: Department of Radiation Oncology.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.affiliation: Department of Radiation Oncology.
authors.forename: Jianbin
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Radiation Oncology.
authors.forename: Yingjie
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Radiation Oncology.
authors.forename: Qian
authors.initials: Q
authors.lastname: Shao
authors.affiliation: Department of Radiation Oncology.
authors.forename: Min
authors.initials: M
authors.lastname: Xu
authors.affiliation: Department of Radiation Oncology.
authors.forename: Bing
authors.initials: B
authors.lastname: Guo
authors.affiliation: Department of Big Bore CT Room, Shandong Cancer Hospital Affiliated to Shandong University, Shandong Academy of Medical Sciences, Jinan, Shandong, People's Republic of China.
authors.forename: Dongping
authors.initials: D
authors.lastname: Shang
keywords: 4D-CT; displacement correlation; esophageal neoplasms; gross tumor volume