title: Changes in tumour volume and motion during radiotherapy for thoracic oesophageal cancer.
abstract: OBJECTIVE
  Variations of target volume and position were important factors in correction of radiotherapy planning. The purpose was to investigate the changes in volume and motion of oesophageal cancer during radiotherapy using four-dimensional computed tomography (4D-CT).
  
  
  METHODS
  In total, 109 enhanced 4D-CT data sets were acquired for 38 patients throughout treatment. Gross tumour volumes (GTVs) were outlined on each data set. Variations in volume, motion, and position were calculated for GTV and internal GTV (IGTV) during treatment.
  
  
  RESULTS
  GTV (25%, P<0.01) and IGTV (27%, P<0.01) had decreased significantly when measured at the twentieth fraction. Larger intrafractional GTV centre shifts (P<0.01) were observed in the superior-inferior direction (median value of 3.1mm) compared with the right-left and anterior-posterior directions (1.6mm and 1.4mm, respectively). The interfractional shift of the IGTV centre was not significant during radiotherapy. The overlap ratios of the targets decreased for both GTV and IGTV during treatment.
  
  
  CONCLUSIONS
  Variations in GTV and IGTV centre shifts were not significant throughout treatment. However, tumour volume decreased significantly by the twentieth fraction. Finally, changes in oesophageal tumour volume and motion may decrease the overlap ratio for GTV and IGTV during radiotherapy.
authors.affiliation: Department of Thoracic Radiation Oncology, Shandong Cancer Hospital, Jinan, China; Medicine and Life Sciences College of Shandong Academy of Medical Sciences, Jinan University, China.
authors.forename: Jin-Zhi
authors.initials: JZ
authors.lastname: Wang
authors.affiliation: Department of Thoracic Radiation Oncology, Shandong Cancer Hospital, Jinan, China. Electronic address: lijianbin@msn.com.
authors.forename: Jian-Bin
authors.initials: JB
authors.lastname: Li
authors.affiliation: Department of Thoracic Radiation Oncology, Shandong Cancer Hospital, Jinan, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.affiliation: Department of Thoracic Radiation Oncology, Shandong Cancer Hospital, Jinan, China.
authors.forename: Huan-Peng
authors.initials: HP
authors.lastname: Qi
authors.affiliation: Department of Thoracic Radiation Oncology, Shandong Cancer Hospital, Jinan, China.
authors.forename: Zhi-Fang
authors.initials: ZF
authors.lastname: Ma
authors.affiliation: Department of Thoracic Radiation Oncology, Shandong Cancer Hospital, Jinan, China.
authors.forename: Ying-Jie
authors.initials: YJ
authors.lastname: Zhang
authors.affiliation: Department of Thoracic Radiation Oncology, Shandong Cancer Hospital, Jinan, China.
authors.forename: Feng-Xiang
authors.initials: FX
authors.lastname: Li
authors.affiliation: Department of Thoracic Radiation Oncology, Shandong Cancer Hospital, Jinan, China.
authors.forename: Ting-Yong
authors.initials: TY
authors.lastname: Fan
authors.affiliation: Department of Thoracic Radiation Oncology, Shandong Cancer Hospital, Jinan, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Shao
authors.affiliation: Department of Thoracic Radiation Oncology, Shandong Cancer Hospital, Jinan, China.
authors.forename: Min
authors.initials: M
authors.lastname: Xu
mesh_terms: D004938:Esophageal Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D056973:Four-Dimensional Computed Tomography / Q000379:methods; D006801:Humans; D009038:Motion; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D013899:Thoracic Neoplasms / Q000473:pathology* / Q000532:radiotherapy*
keywords: 4D-CT; Image-guided radiotherapy; Interfractional variations; Oesophageal cancer; Target overlap ratio