title: Dynamic tumor-tracking radiotherapy with real-time monitoring for liver tumors using a gimbal mounted linac.
abstract: OBJECTIVE
  Dynamic tumor-tracking stereotactic body radiotherapy (DTT-SBRT) for liver tumors with real-time monitoring was carried out using a gimbal-mounted linear accelerator and the efficacy of the system was determined. In addition, four-dimensional (4D) dose distribution, tumor-tracking accuracy, and tumor-marker positional variations were evaluated.
  
  
  METHODS
  A fiducial marker was implanted near the tumor prior to treatment planning. The prescription dose at the isocenter was 48-60 Gy, delivered in four or eight fractions. The 4D dose distributions were calculated with a Monte Carlo method and compared to the static SBRT plan. The intrafractional errors between the predicted target positions and the actual target positions were calculated.
  
  
  RESULTS
  Eleven lesions from ten patients were treated successfully. DTT-SBRT allowed an average 16% reduction in the mean liver dose compared to static SBRT, without altering the target dose. The average 95th percentiles of the intrafractional prediction errors were 1.1, 2.3, and 1.7 mm in the left-right, cranio-caudal, and anterior-posterior directions, respectively. After a median follow-up of 11 months, the local control rate was 90%.
  
  
  CONCLUSIONS
  Our early experience demonstrated the dose reductions in normal tissues and high accuracy in tumor tracking, with good local control using DTT-SBRT with real-time monitoring in the treatment of liver tumors.
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Kyoto University Graduate School of Medicine, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Iizuka
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Kyoto University Graduate School of Medicine, 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, Kyoto University Graduate School of Medicine, Japan.
authors.forename: Yoshitomo
authors.initials: Y
authors.lastname: Ishihara
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Kyoto University Graduate School of Medicine, Japan.
authors.forename: Mami
authors.initials: M
authors.lastname: Akimoto
authors.affiliation: Division of Radiation Oncology, Institute of Biomedical Research and Innovation, Kobe, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Tanabe
authors.affiliation: Division of Radiation Oncology, Institute of Biomedical Research and Innovation, Kobe, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Takayama
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Kyoto University Graduate School of Medicine, Japan.
authors.forename: Nami
authors.initials: N
authors.lastname: Ueki
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Kyoto University Graduate School of Medicine, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Yokota
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Kyoto University Graduate School of Medicine, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Mizowaki
authors.affiliation: Division of Radiation Oncology, Institute of Biomedical Research and Innovation, Kobe, Japan; 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, Kyoto University Graduate School of Medicine, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hiraoka
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D008113:Liver Neoplasms / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009010:Monte Carlo Method; D010315:Particle Accelerators; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods
keywords: Dynamic tumor tracking; Liver tumor; Real-time monitoring