title: Nonrigid registration method to assess reproducibility of breath-holding with ABC in lung cancer.
abstract: OBJECTIVE
  To study the interfraction reproducibility of breath-holding using active breath control (ABC), and to develop computerized tools to evaluate three-dimensional (3D) intrathoracic motion in each patient.
  
  
  METHODS
  Since June 2002, 11 patients with non-small-cell lung cancer enrolled in a Phase II trial have undergone four CT scans: one during free-breathing (reference) and three using ABC. Patients left the room between breath-hold scans. The patient's breath was held at the same predefined phase of the breathing cycle (about 70% of the vital capacity) using the ABC device, then patients received 3D-conformal radiotherapy. Automated computerized tools for breath-hold CT scans were developed to analyze lung and tumor interfraction residual motions with 3D nonrigid registration.
  
  
  RESULTS
  All patients but one were safely treated with ABC for 7 weeks. For 6 patients, the lung volume differences were <5%. The mean 3D displacement inside the lungs was between 2.3 mm (SD 1.4) and 4 mm (SD 3.3), and the gross tumor volume residual motion was 0.9 mm (SD 0.4) to 5.9 mm (SD 0.7). The residual motion was slightly greater in the inferior part of the lung than the superior. For 2 patients, we detected volume changes >300 cm(3) and displacements >10 mm, probably owing to atelectasia and emphysema. One patient was excluded, and two others had incomplete data sets.
  
  
  CONCLUSIONS
  Breath-holding with ABC was effective in 6 patients, and discrepancies were clinically accountable in 2. The proposed 3D nonrigid registration method allows for personalized evaluation of breath-holding reproducibility with ABC. It will be used to adapt the patient-specific internal margins.
authors.affiliation: Department of Radiotherapy, Centre Léon Bérard, Lyon 69008, France. dsarrut@univ-lyon2.fr
authors.forename: David
authors.initials: D
authors.lastname: Sarrut
authors.forename: Vlad
authors.initials: V
authors.lastname: Boldea
authors.forename: Myriam
authors.initials: M
authors.lastname: Ayadi
authors.forename: Jean-Noël
authors.initials: JN
authors.lastname: Badel
authors.forename: Chantal
authors.initials: C
authors.lastname: Ginestet
authors.forename: Sébastien
authors.initials: S
authors.lastname: Clippe
authors.forename: Christian
authors.initials: C
authors.lastname: Carrie
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D009068:Movement; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal; D015203:Reproducibility of Results; D012119:Respiration; D014057:Tomography, X-Ray Computed / Q000379:methods