title: Measurement of interfraction variations in position and size of target volumes in stereotactic body radiotherapy for lung cancer.
abstract: OBJECTIVE
  To investigate the interfraction variations in volume, motion range, and position of the gross tumor volume (GTV) in hypofractionated stereotactic body radiotherapy (SBRT) for lung cancer using four-dimensional computed tomography.
  
  
  METHODS
  Four-dimensional computed tomography scans were acquired for 8 patients once at treatment planning and twice during the SBRT period using a stereotactic body frame. The image registration was performed to correct setup errors for clinical four-dimensional computed tomography. The interfraction variations in volume, motion range, and position of GTV were computed at end-inhalation (EI) and end-exhalation (EE).
  
  
  RESULTS
  The random variations in the GTV were 0.59 cm(3) at EI and 0.53 cm(3) at EE, and the systematic variations were 3.04 cm(3) at EI and 3.21 cm(3) at EE. No significant variations in GTV were found during the SBRT sessions (p = .301 at EI and p = .081 at EE). The random variations in GTV motion range for the upper lobe in the craniocaudal direction were within 1.0 mm and for the lower lobe was 3.4 mm. The interfraction variations in the GTV centroid position in the anteroposterior and craniocaudal directions were mostly larger than in the right-left direction; however, no significant displacement was observed among the sessions in any direction.
  
  
  CONCLUSIONS
  For patients undergoing hypofractionated SBRT, interfraction variations in GTV, motion range, and position mainly remained small. An additional approach is needed to assess the margin size.
authors.affiliation: Department of Radiation Oncology and Image-Applied Therapy, Kyoto University Graduate School of Medicine, Kyoto, Japan.
authors.forename: Kiyotomo
authors.initials: K
authors.lastname: Matsugi
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Narita
authors.forename: Akira
authors.initials: A
authors.lastname: Sawada
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Nakamura
authors.forename: Yuki
authors.initials: Y
authors.lastname: Miyabe
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Matsuo
authors.forename: Masaru
authors.initials: M
authors.lastname: Narabayashi
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Norihisa
authors.forename: Takashi
authors.initials: T
authors.lastname: Mizowaki
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hiraoka
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D019583:Dose Fractionation, Radiation; D045853:Exhalation; D005260:Female; D006801:Humans; D001239:Inhalation; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009068:Movement; D019047:Phantoms, Imaging; D016634:Radiosurgery / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods; D047368:Tumor Burden