title: Geometric uncertainties in voluntary deep inspiration breath hold radiotherapy for locally advanced lung cancer.
abstract: OBJECTIVE
  Deep inspiration breath hold (DIBH) increases lung volume and can potentially reduce treatment-related toxicity in locally advanced lung cancer. We estimated geometric uncertainties in visually guided voluntary DIBH and derived the appropriate treatment margins for different image-guidance strategies.
  
  
  METHODS
  Seventeen patients were included prospectively. An optical marker-based respiratory monitoring with visual guidance enabled comfortable DIBHs, adjusted to each patient's performance. All patients had three consecutive DIBH CTs at each of the treatment fractions 2, 16 and 31. DIBH reproducibility was evaluated as inter- and intra-fractional variations in lung volume, tumour position and differential motion between primary tumour and mediastinal lymph nodes.
  
  
  RESULTS
  Lung volume increased by median 60% in DIBH. Inter- and intra-fractional lung volume variations were median 2.1% and 1.1%, respectively. Inter- and intra-fractional uncertainties in 3D tumour position were 4.8 ± 2.8 mm and 1.7 ± 1.4 mm (mean ± SD). Inter- and intra-fractional differential motion was 4.8 ± 3.3 mm and 0.0 ± 1.1 mm.
  
  
  CONCLUSIONS
  For single targets, visually guided voluntary DIBH radiotherapy is highly reproducible provided an image-guidance strategy with tumour registration is performed. If the primary tumour is separated from the mediastinal lymph nodes, inter-fractional differential motion remains a challenge and margins must be adapted to reflect the image registration strategy.
authors.affiliation: Department of Oncology, Section of Radiotherapy, Rigshospitalet, Copenhagen, Denmark; Niels Bohr Institute, Faculty of Science, University of Copenhagen, Denmark. Electronic address: mirjana.josipovic@regionh.dk.
authors.forename: Mirjana
authors.initials: M
authors.lastname: Josipovic
authors.affiliation: Department of Oncology, Section of Radiotherapy, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Gitte F
authors.initials: GF
authors.lastname: Persson
authors.affiliation: Department of Oncology, Section of Radiotherapy, Rigshospitalet, Copenhagen, Denmark; Niels Bohr Institute, Faculty of Science, University of Copenhagen, Denmark; Paul Scherrer Institute, 5232 Villigen PSI, Switzerland.
authors.forename: Jenny
authors.initials: J
authors.lastname: Dueck
authors.affiliation: Department of Oncology, Section of Radiotherapy, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Jens Peter
authors.initials: JP
authors.lastname: Bangsgaard
authors.affiliation: Department of Oncology, Section of Radiotherapy, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Westman
authors.affiliation: Department of Oncology, Section of Radiotherapy, Rigshospitalet, Copenhagen, Denmark; Faculty of Medical Sciences, University of Copenhagen, Denmark.
authors.forename: Lena
authors.initials: L
authors.lastname: Specht
authors.affiliation: Department of Oncology, Section of Radiotherapy, Rigshospitalet, Copenhagen, Denmark; Niels Bohr Institute, Faculty of Science, University of Copenhagen, Denmark; Faculty of Medical Sciences, University of Copenhagen, Denmark.
authors.forename: Marianne C
authors.initials: MC
authors.lastname: Aznar
mesh_terms: D000368:Aged; D062485:Breath Holding; D005260:Female; D006801:Humans; D006985:Hyperventilation; D008175:Lung Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D008176:Lung Volume Measurements / Q000379:methods; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods; D035501:Uncertainty
keywords: Breath hold; Differential motion; Geometrical uncertainties; Lung cancer; Radiotherapy; Tumour position reproducibility