title: Accuracy of Breath-hold CT in Treatment Planning for Lung Stereotactic Ablative Radiotherapy.
abstract: OBJECTIVE
  The objectives of this study are (1) to measure concordance of tumor position on breath-hold (BH) computed tomography (CT) scans relative to the natural tumor path during free breathing (FB) and (2) to evaluate the benefits of the breathing monitoring device Abches (Apex Medical, Tokyo) for stereotactic ablative radiotherapy (SABR) treatment planning.
  
  
  METHODS
  In 53 lung cancer patients treated with CyberKnife™ robotic radiosurgery system, FB four-dimensional computerized tomography (4DCT) and end-expiration (EE) BH CT images were obtained. Extent of natural tumor motion was assessed with rigid registration derived from end-inspiration (EI) and EE phases of the 4DCT. Tumor displacement in BH scans relative to the natural tumor path was measured relative to the EE 4DCT phase.
  
  
  RESULTS
  Mean tumor motion (+/- 1 SD) during natural FB was 1 ± 1 mm, 2 ± 2 mm, and 6 ± 6 mm in medio-lateral, anterior-posterior, and cranio-caudal directions, respectively. Tumor position on BH CT scan was closer to EE than EI 4DCT phase for 35/53 patients (66%). Difference of BH tumor position vs. EE state was 4 ± 3 mm. Gross tumor displacements perpendicular to natural tumor path were as great as 11 mm (anterior-posterior) and were seen with or without the breathing monitoring device.
  
  
  CONCLUSIONS
  Tumor position during BH CT may not accurately correspond to positions observed on FB 4DCT. Hence, accurate and custom 4D analysis for each individual patient is recommended for treatment planning, especially those involving BH acquisitions.
authors.affiliation: Department of Radiation Oncology, Centre hospitalier de l'université de Montréal (CHUM).
authors.forename: Dominique
authors.initials: D
authors.lastname: Mathieu
authors.affiliation: Department of Radiation Oncology, Centre hospitalier de l'université de Montréal (CHUM).
authors.forename: Charles
authors.initials: C
authors.lastname: Martel
authors.affiliation: Department of Radiation Oncology, Centre hospitalier de l'université de Montréal (CHUM).
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Campeau
authors.affiliation: Department of Radiation Oncology, Centre hospitalier de l'université de Montréal (CHUM).
authors.forename: Édith
authors.initials: É
authors.lastname: Filion
authors.affiliation: Department of Oncology, Division of Radiation Oncology, McGill University Health Center ; Department of Radiology, Radiation Oncology and Nuclear Medicine, University of Montreal ; Department of Radiation Oncology, Centre hospitalier de l'université de Montréal (CHUM) ; Department of Oncology, Division of Radiation Oncology, McGill University Health Center.
authors.forename: David
authors.initials: D
authors.lastname: Roberge
authors.affiliation: Department of Radiation Oncology, Centre hospitalier de l'université de Montréal (CHUM).
authors.forename: Houda
authors.initials: H
authors.lastname: Bahig
authors.affiliation: Department of Radiation Oncology, Centre hospitalier de l'université de Montréal (CHUM).
authors.forename: Toni
authors.initials: T
authors.lastname: Vu
authors.affiliation: Department of Radiation Oncology, Centre hospitalier de l'université de Montréal (CHUM).
authors.forename: Louise
authors.initials: L
authors.lastname: Lambert
authors.affiliation: Department of Radiation Oncology, Centre hospitalier de l'Université de Montréal (CHUM).
authors.forename: Karim
authors.initials: K
authors.lastname: Boudam
authors.affiliation: Department of Radiation Oncology, Centre hospitalier de l'université de Montréal (CHUM).
authors.forename: Jean-Francois
authors.initials: JF
authors.lastname: Carrier
keywords: 4dct; abches; breath-hold; cyberknife™; sabr; treatment planning