title: Short-term displacement and reproducibility of the breast and nodal targets under active breathing control.
abstract: OBJECTIVE
  The short-term displacement and reproducibility of the breast or chest wall, and the internal mammary (IM), infraclavicular (ICV), and supraclavicular (SCV) nodal regions have been assessed as a function of breath-hold state using an active breathing control (ABC) device for patients receiving loco-regional breast radiation therapy.
  
  
  METHODS
  Ten patients underwent computed tomographic scanning using an ABC device at breath-hold states of end-exhale and 20%, 40%, 60%, and 80% of vital capacity (VC). Patients underwent scanning before treatment and at one third and two thirds of the way through treatment. A regional registration was performed for each target using a rigid-body transformation with mutual information as a metric.
  
  
  RESULTS
  Between exhale and 40% of VC, the mean displacement was 0.27/0.34, 0.24/0.31, 0.22/0.19, and 0.13/0.19 cm anterior/superior for the breast or chest wall, and IM, ICV, and SCV nodes, respectively. At 80% of VC, the mean displacement from exhale was 0.84/.88, 0.76/.79, 0.70/0.79, and 0.54/0.56 cm anterior/superior for the breast or chest wall, and IM, ICV, and SCV nodes, respectively. The short-term reproducibility (standard deviation) was <0.3 and <or=0.4 cm for 40% and 80% of VC, respectively. Displacements up to 1.9 cm were observed for individual patients.
  
  
  CONCLUSIONS
  The short-term reproducibility of target position is <or=0.4 cm using ABC for all structures for all breath-hold states. This information can be used to guide treatment planning optimization studies that consider the effect of motion on target and normal tissue doses with and without active breathing control.
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109-0010, USA. jmmoran@med.umich.edu
authors.forename: Jean M
authors.initials: JM
authors.lastname: Moran
authors.forename: James M
authors.initials: JM
authors.lastname: Balter
authors.forename: Merav A
authors.initials: MA
authors.lastname: Ben-David
authors.forename: Robin B
authors.initials: RB
authors.lastname: Marsh
authors.forename: Marcel
authors.initials: M
authors.lastname: Van Herk
authors.forename: Lori J
authors.initials: LJ
authors.lastname: Pierce
mesh_terms: D001940:Breast; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D005260:Female; D006321:Heart; D006801:Humans; D008198:Lymph Nodes; D009068:Movement; D011859:Radiography; D015203:Reproducibility of Results; D012119:Respiration; D035441:Thoracic Wall