title: Variations in CT determination of target volume with active breath co-ordinate in radiotherapy for post-operative gastric cancer.
abstract: OBJECTIVE
  To investigate interobserver and inter-CT variations in using the active breath co-ordinate technique in the determination of clinical tumour volume (CTV) and normal organs in post-operative gastric cancer radiotherapy.
  
  
  METHODS
  Ten gastric cancer patients were enrolled in our study, and four radiation oncologists independently determined the CTVs and organs at risk based on the CT simulation data. To determine interobserver and inter-CT variation, we evaluated the maximum dimensions, derived volume and distance between the centres of mass (CMs) of the CTVs. We assessed the reliability in CTV determination among the observers by conformity index (CI).
  
  
  RESULTS
  The average volumes ± standard deviation (cm(3)) of the CTV, liver, left kidney and right kidney were 674 ± 138 (range, 332-969), 1000 ± 138 (range, 714-1320), 149 ± 13 (range, 104-183) and 141 ± 21 (range, 110-186) cm(3), respectively. The average inter-CT distances between the CMs of the CTV, liver, left kidney and right kidney were 0.40, 0.56, 0.65 and 0.6 cm, respectively; the interobserver values were 0.98, 0.53, 0.16 and 0.15 cm, respectively.
  
  
  CONCLUSIONS
  In the volume size of CTV for post-operative gastric cancer, there were significant variations among multiple observers, whereas there was no variation between different CTs. The slices in which variations more likely occur were the slices of the lower verge of the hilum of the spleen and porta hepatis, then the paraoesophageal lymph nodes region and abdominal aorta, and the inferior vena cava, and the variation in the craniocaudal orientation from the interobserver was more predominant than that from inter-CT.
  
  
  CONCLUSIONS
  First, this is the first study to evaluate the interobserver and inter-CT variations in the determination of the CTV and normal organs in gastric cancer with the use of the active breath co-ordinate technique. Second, we analysed the region where variations most likely occur. Third, we investigated the influence of interobserver variation on the dose distribution.
authors.affiliation: 1 Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China.|2 Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China.
authors.forename: Gui-Chao
authors.initials: GC
authors.lastname: Li
authors.affiliation: 1 Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China.|2 Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: 1 Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China.|2 Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China.
authors.forename: Xue-Jun
authors.initials: XJ
authors.lastname: Ma
authors.affiliation: 1 Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China.|2 Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China.
authors.forename: Xiao-Li
authors.initials: XL
authors.lastname: Yu
authors.affiliation: 1 Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China.|2 Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China.
authors.forename: Wei-Gang
authors.initials: WG
authors.lastname: Hu
authors.affiliation: 1 Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China.|2 Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China.
authors.forename: Jia-Zhou
authors.initials: JZ
authors.lastname: Wang
authors.affiliation: 1 Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China.|2 Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China.
authors.forename: Qi-Wen
authors.initials: QW
authors.lastname: Li
authors.affiliation: 1 Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China.|2 Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China.
authors.forename: Li-Ping
authors.initials: LP
authors.lastname: Liang
authors.affiliation: 1 Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China.|2 Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China.
authors.forename: Li-Jun
authors.initials: LJ
authors.lastname: Shen
authors.affiliation: 1 Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China.|2 Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
authors.affiliation: 1 Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China.|2 Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Fan
mesh_terms: D000328:Adult; D005260:Female; D005743:Gastrectomy; D006801:Humans; D008197:Lymph Node Excision; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D015588:Observer Variation; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D013274:Stomach Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D014057:Tomography, X-Ray Computed / Q000379:methods*; D047368:Tumor Burden