title: Speed and amplitude of lung tumor motion precisely detected in four-dimensional setup and in real-time tumor-tracking radiotherapy.
abstract: BACKGROUND
  To reduce the uncertainty of registration for lung tumors, we have developed a four-dimensional (4D) setup system using a real-time tumor-tracking radiotherapy system.
  
  
  METHODS
  During treatment planning and daily setup in the treatment room, the trajectory of the internal fiducial marker was recorded for 1 to 2 min at the rate of 30 times per second by the real-time tumor-tracking radiotherapy system. To maximize gating efficiency, the patient's position on the treatment couch was adjusted using the 4D setup system with fine on-line remote control of the treatment couch.
  
  
  RESULTS
  The trajectory of the marker detected in the 4D setup system was well visualized and used for daily setup. Various degrees of interfractional and intrafractional changes in the absolute amplitude and speed of the internal marker were detected. Readjustments were necessary during each treatment session, prompted by baseline shifting of the tumor position.
  
  
  CONCLUSIONS
  The 4D setup system was shown to be useful for reducing the uncertainty of tumor motion and for increasing the efficiency of gated irradiation. Considering the interfractional and intrafractional changes in speed and amplitude detected in this study, intercepting radiotherapy is the safe and cost-effective method for 4D radiotherapy using real-time tracking technology.
authors.affiliation: Department of Radiology, Hokkaido University School of Medicine, Sapporo, Japan. hshirato@radi.med.hokudai.ac.jp
authors.forename: Hiroki
authors.initials: H
authors.lastname: Shirato
authors.forename: Keishiro
authors.initials: K
authors.lastname: Suzuki
authors.forename: Gregory C
authors.initials: GC
authors.lastname: Sharp
authors.forename: Katsuhisa
authors.initials: K
authors.lastname: Fujita
authors.forename: Rikiya
authors.initials: R
authors.lastname: Onimaru
authors.forename: Masaharu
authors.initials: M
authors.lastname: Fujino
authors.forename: Norio
authors.initials: N
authors.lastname: Kato
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Osaka
authors.forename: Rumiko
authors.initials: R
authors.lastname: Kinoshita
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Taguchi
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Onodera
authors.forename: Kazuo
authors.initials: K
authors.lastname: Miyasaka
mesh_terms: D019583:Dose Fractionation, Radiation; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D009068:Movement; D019736:Prostheses and Implants; D011873:Radiology Information Systems; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*