title: Implementation of feedback-guided voluntary breath-hold gating for cone beam CT-based stereotactic body radiotherapy.
abstract: OBJECTIVE
  To analyze tumor position reproducibility of feedback-guided voluntary deep inspiration breath-hold (FGBH) gating for cone beam computed tomography (CBCT)-based stereotactic body radiotherapy (SBRT).
  
  
  METHODS
  Thirteen early-stage lung cancer patients eligible for SBRT with tumor motion of >1cm were evaluated for FGBH-gated treatment. Multiple FGBH CTs were acquired at simulation, and single FGBH CBCTs were also acquired prior to each treatment. Simulation CTs and treatment CBCTs were analyzed to quantify reproducibility of tumor positions during FGBH. Benefits of FGBH gating compared to treatment during free breathing, as well treatment with gating at exhalation, were examined for lung sparing, motion margins, and reproducibility of gross tumor volume (GTV) position relative to nonmoving anatomy.
  
  
  RESULTS
  FGBH increased total lung volumes by 1.5 times compared to free breathing, resulting in a proportional drop in total lung volume receiving 10 Gy or more. Intra- and inter-FGBH reproducibility of GTV centroid positions at simulation were 1.0 ± 0.5 mm, 1.3 ± 1.0 mm, and 0.6 ± 0.4 mm in the anterior-posterior (AP), superior-inferior (SI), and left-right lateral (LR) directions, respectively, compared to more than 1 cm of tumor motion at free breathing. During treatment, inter-FGBH reproducibility of the GTV centroid with respect to bony anatomy was 1.2 ± 0.7 mm, 1.5 ± 0.8 mm, and 1.0 ± 0.4 mm in the AP, SI, and LR directions. In addition, the quality of CBCTs was improved due to elimination of motion artifacts, making this technique attractive for poorly visualized tumors, even with small motion.
  
  
  CONCLUSIONS
  The extent of tumor motion at normal respiration does not influence the reproducibility of the tumor position under breath hold conditions. FGBH-gated SBRT with CBCT can improve the reproducibility of GTV centroids, reduce required margins, and minimize dose to normal tissues in the treatment of mobile tumors.
authors.affiliation: Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
authors.forename: Yong
authors.initials: Y
authors.lastname: Peng
authors.forename: Sastry
authors.initials: S
authors.lastname: Vedam
authors.forename: Joe Y
authors.initials: JY
authors.lastname: Chang
authors.forename: Song
authors.initials: S
authors.lastname: Gao
authors.forename: Ramaswamy
authors.initials: R
authors.lastname: Sadagopan
authors.forename: Martin
authors.initials: M
authors.lastname: Bues
authors.forename: Peter
authors.initials: P
authors.lastname: Balter
mesh_terms: D000465:Algorithms; D016477:Artifacts; D054893:Cone-Beam Computed Tomography / Q000379:methods* / Q000592:standards; D045853:Exhalation; D056228:Feedback, Sensory; D006801:Humans; D007103:Immobilization / Q000379:methods* / Q000502:physiology; D001239:Inhalation; D008168:Lung / Q000000981:diagnostic imaging / Q000528:radiation effects; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D008176:Lung Volume Measurements; D008991:Monitoring, Physiologic / Q000295:instrumentation; D009068:Movement; D056888:Patient Positioning; D016634:Radiosurgery / Q000295:instrumentation / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D015203:Reproducibility of Results; D047368:Tumor Burden