title: Breathing adapted radiotherapy: a 4D gating software for lung cancer.
abstract: OBJECTIVE
  Physiological respiratory motion of tumors growing in the lung can be corrected with respiratory gating when treated with radiotherapy (RT). The optimal respiratory phase for beam-on may be assessed with a respiratory phase optimizer (RPO), a 4D image processing software developed with this purpose.
  
  
  METHODS
  Fourteen patients with lung cancer were included in the study. Every patient underwent a 4D-CT providing ten datasets of ten phases of the respiratory cycle (0-100% of the cycle). We defined two morphological parameters for comparison of 4D-CT images in different respiratory phases: tumor-volume to lung-volume ratio and tumor-to-spinal cord distance. The RPO automatized the calculations (200 per patient) of these parameters for each phase of the respiratory cycle allowing to determine the optimal interval for RT.
  
  
  RESULTS
  Lower lobe lung tumors not attached to the diaphragm presented with the largest motion with breathing. Maximum inspiration was considered the optimal phase for treatment in 4 patients (28.6%). In 7 patients (50%), however, the RPO showed a most favorable volumetric and spatial configuration in phases other than maximum inspiration. In 2 cases (14.4%) the RPO showed no benefit from gating. This tool was not conclusive in only one case.
  
  
  CONCLUSIONS
  The RPO software presented in this study can help to determine the optimal respiratory phase for gated RT based on a few simple morphological parameters. Easy to apply in daily routine, it may be a useful tool for selecting patients who might benefit from breathing adapted RT.
authors.affiliation: Department of Radiation Oncology, University Hospital, Geneva, Switzerland. Nicolas.Peguret@hcuge.ch
authors.forename: Nicolas
authors.initials: N
authors.lastname: Peguret
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Vock
authors.forename: Vincent
authors.initials: V
authors.lastname: Vinh-Hung
authors.forename: Pascal
authors.initials: P
authors.lastname: Fenoglietto
authors.forename: David
authors.initials: D
authors.lastname: Azria
authors.forename: Habib
authors.initials: H
authors.lastname: Zaidi
authors.forename: Michael
authors.initials: M
authors.lastname: Wissmeyer
authors.forename: Osman
authors.initials: O
authors.lastname: Ratib
authors.forename: Raymond
authors.initials: R
authors.lastname: Miralbell
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001331:Automation; D005260:Female; D056973:Four-Dimensional Computed Tomography / Q000379:methods; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008175:Lung Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D011878:Radiotherapy / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D012008:Recurrence; D012119:Respiration; D012984:Software