title: Asymmetric margin setting at the cranial and caudal sides in respiratory gated and non-gated stereotactic body radiotherapy for lung cancer.
abstract: OBJECTIVE
  To evaluate total errors, including setup errors, and tumour motion changes with a electronic portal imaging device (EPID) cine at the cranial and caudal sides in respiratory gated and non-gated radiotherapy.
  
  
  METHODS
  Co-ordinates of the tumour centres (TCs) in the craniocaudal direction were obtained by using four-dimensional CT (4DCT) for each bin and EPID cine frame. During the 100% duty cycle (DC100), 50% duty cycle (DC50) and 30% duty cycle (DC30), both centred on the 50 phase, the co-ordinates of the TCs were compared at the most cranial and caudal positions on both 4DCT and EPID cine.
  
  
  RESULTS
  During DC100, total errors were -0.2 ± 2.1 and 1.1 ± 2.6 mm at the cranial and caudal sides, respectively. During DC50, the corresponding values were -0.2 ± 2.1 and 1.7 ± 3.2 mm, respectively; during DC30, they were -0.1 ± 2.1 and 1.8 ± 2.9 mm, respectively. The tumour motion changes at the caudal side were strongly correlated with tumour motion observed on 4DCT during DC100 (R(2) = 0.59).
  
  
  CONCLUSIONS
  Total errors and tumour motion changes on the caudal side were larger than on the cranial side because of the patients' breathing levels. Owing to variations of the TCs at beam-trigger events, the larger margin was required at the caudal side in gated radiotherapy.
  
  
  CONCLUSIONS
  Variations of the TCs were evaluated at the cranial and caudal sides separately. Providing some margins to compensate for tumour motion changes was a significant requirement at the caudal side in gated and non-gated radiotherapy.
authors.affiliation: 1 Department of Radiation Oncology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan.|2 Department of Radiation Oncology, Graduate School of Medicine, Osaka University, Suita, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Ueda
authors.affiliation: 1 Department of Radiation Oncology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan.|3 Department of Medical Physics and Engineering, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Oohira
authors.affiliation: 1 Department of Radiation Oncology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Isono
authors.affiliation: 1 Department of Radiation Oncology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Miyazaki
authors.affiliation: 1 Department of Radiation Oncology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan.
authors.forename: Teruki
authors.initials: T
authors.lastname: Teshima
mesh_terms: D000368:Aged; D002420:Cauda Equina / Q000000981:diagnostic imaging*; D005260:Female; D056973:Four-Dimensional Computed Tomography; D006801:Humans; D008175:Lung Neoplasms / Q000532:radiotherapy*; D008297:Male; D016634:Radiosurgery; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012119:Respiration; D012886:Skull / Q000000981:diagnostic imaging*