title: Intra- and interfractional variations in geometric arrangement between lung tumours and implanted markers.
abstract: OBJECTIVE
  To quantify the intra- and interfractional variations between lung tumours and implanted markers.
  
  
  METHODS
  Gold markers were implanted transbronchially around a lung tumour in fifteen patients. They underwent four-dimensional computed tomography scans twice, and the centroids of the tumour and markers were determined. Intrafractional variations were defined as the residual tumour motions relative to the markers due to respiration from the end-exhale phase. Interfractional variations were defined as the residual setup errors after correction for the position of the implanted markers in end-exhale phase images.
  
  
  RESULTS
  The intrafractional variations differed between patients. The root mean squares of standard deviations for each phase were 0.6, 0.9, and 1.5mm in the right-left, anterior-posterior, and superior-inferior directions, respectively. The maximum difference in intrafractional variation among 10 phases was correlated with the amplitude of tumour motion in all directions and the tumour-marker distance in the anterior-posterior and superior-inferior directions. The interfractional variations were within 2.5mm.
  
  
  CONCLUSIONS
  The intrafractional variations differed according to the amount of tumour motion and the tumour-marker distance. Additionally, interfractional variations of up to 2.5mm were observed. Thus, a corresponding margin should be considered during implanted marker-based beam delivery to account for these variations.
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Japan.
authors.forename: Nami
authors.initials: N
authors.lastname: Ueki
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Japan. Electronic address: ymatsuo@kuhp.kyoto-u.ac.jp.
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Matsuo
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Nakamura
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Japan.
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Mukumoto
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Iizuka
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Miyabe
authors.affiliation: Faculty of Medical Science, Kyoto College of Medical Science, Nantan, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Sawada
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Mizowaki
authors.affiliation: Department of Radiation Oncology, Kobe City Medical Center General Hospital, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Kokubo
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hiraoka
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D057918:Fiducial Markers; D056973:Four-Dimensional Computed Tomography; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D009068:Movement; D019736:Prostheses and Implants; D012119:Respiration
keywords: 4DCT; Fiducial marker; Lung cancer; Positional variation