title: A multi-centre analysis of treatment procedures and error components in dynamic tumour tracking radiotherapy.
abstract: OBJECTIVE
  This study aimed to compare procedures for dynamic tumour tracking (DTT) using a gimbal-mounted linac between centres in Japan (KU-IBRI) and Belgium (UZB), to quantify tracking error (TE), and to estimate tumour-fiducial uncertainties and PTV margins.
  
  
  METHODS
  Twenty-two patients were evaluated. TE was divided into components originating from the patient, fraction, segment, and residuals.
  
  
  RESULTS
  KU-IBRI applied DTT to lung cancer, while UZB treated both the lung and liver. Patients from UZB were younger and had a higher body mass index. DTT procedures differed in the use of body fixation, correction for set-up error, type of fiducial markers, and goodness of fit of correlation model. TE was larger at UZB in the intra-fraction components, whereas the tumour-fiducial uncertainties were estimated to be larger at KU-IBRI. These results ultimately led to similar PTV margins at both centres (2.1, 4.2, and 2.6 mm for KU-IBRI; 2.4, 3.6, and 2.0 mm for UZB in LR, AP, and SI, respectively, for 99% coverage of patients).
  
  
  CONCLUSIONS
  Several differences in procedures and patient characteristics were observed that affected TE and tumour-fiducial uncertainties. This analysis confirmed similar accuracy in DTT delivery and adequate PTV margins in the different centres based on their local specific workflows.
authors.affiliation: Radiotherapy Department, UZ Brussel, Vrije Universiteit Brussel, Belgium; Department of Radiation Oncology and Image-applied Therapy, Kyoto University, Japan. Electronic address: ymatsuo@kuhp.kyoto-u.ac.jp.
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Matsuo
authors.affiliation: Radiotherapy Department, UZ Brussel, Vrije Universiteit Brussel, Belgium.
authors.forename: Dirk
authors.initials: D
authors.lastname: Verellen
authors.affiliation: Radiotherapy Department, UZ Brussel, Vrije Universiteit Brussel, Belgium.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Poels
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Kyoto University, Japan.
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Mukumoto
authors.affiliation: Radiotherapy Department, UZ Brussel, Vrije Universiteit Brussel, Belgium; Department of Radiation Oncology, University Hospitals Leuven, Belgium.
authors.forename: Tom
authors.initials: T
authors.lastname: Depuydt
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Kyoto University, Japan.
authors.forename: Mami
authors.initials: M
authors.lastname: Akimoto
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Kyoto University, Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Nakamura
authors.affiliation: Department of Radiation Oncology and Image-applied Therapy, Kyoto University, Japan.
authors.forename: Nami
authors.initials: N
authors.lastname: Ueki
authors.affiliation: Radiotherapy Department, UZ Brussel, Vrije Universiteit Brussel, Belgium.
authors.forename: Benedikt
authors.initials: B
authors.lastname: Engels
authors.affiliation: Radiotherapy Department, UZ Brussel, Vrije Universiteit Brussel, Belgium.
authors.forename: Christine
authors.initials: C
authors.lastname: Collen
authors.affiliation: Division of Radiation Oncology, Institute of Biomedical Research and Innovation; 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, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hiraoka
authors.affiliation: Radiotherapy Department, UZ Brussel, Vrije Universiteit Brussel, Belgium.
authors.forename: Mark
authors.initials: M
authors.lastname: de Ridder
mesh_terms: D001530:Belgium; D057918:Fiducial Markers; D006801:Humans; D007564:Japan; D009369:Neoplasms / Q000532:radiotherapy*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D035501:Uncertainty
keywords: Dynamic tumour tracking; Error analysis; Multi-centric study