title: Audio-visual biofeedback for respiratory-gated radiotherapy: impact of audio instruction and audio-visual biofeedback on respiratory-gated radiotherapy.
abstract: OBJECTIVE
  Respiratory gating is a commercially available technology for reducing the deleterious effects of motion during imaging and treatment. The efficacy of gating is dependent on the reproducibility within and between respiratory cycles during imaging and treatment. The aim of this study was to determine whether audio-visual biofeedback can improve respiratory reproducibility by decreasing residual motion and therefore increasing the accuracy of gated radiotherapy.
  
  
  METHODS
  A total of 331 respiratory traces were collected from 24 lung cancer patients. The protocol consisted of five breathing training sessions spaced about a week apart. Within each session the patients initially breathed without any instruction (free breathing), with audio instructions and with audio-visual biofeedback. Residual motion was quantified by the standard deviation of the respiratory signal within the gating window.
  
  
  RESULTS
  Audio-visual biofeedback significantly reduced residual motion compared with free breathing and audio instruction. Displacement-based gating has lower residual motion than phase-based gating. Little reduction in residual motion was found for duty cycles less than 30%; for duty cycles above 50% there was a sharp increase in residual motion.
  
  
  CONCLUSIONS
  The efficiency and reproducibility of gating can be improved by: incorporating audio-visual biofeedback, using a 30-50% duty cycle, gating during exhalation, and using displacement-based gating.
authors.affiliation: Department of Radiation Oncology, Virginia Commonwealth University, Richmond, VA, USA.
authors.forename: Rohini
authors.initials: R
authors.lastname: George
authors.forename: Theodore D
authors.initials: TD
authors.lastname: Chung
authors.forename: Sastry S
authors.initials: SS
authors.lastname: Vedam
authors.forename: Viswanathan
authors.initials: V
authors.lastname: Ramakrishnan
authors.forename: Radhe
authors.initials: R
authors.lastname: Mohan
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Weiss
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Keall
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001296:Audiovisual Aids; D001676:Biofeedback, Psychology / Q000295:instrumentation / Q000379:methods*; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000503:physiopathology / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D009068:Movement; D015203:Reproducibility of Results; D012119:Respiration