title: Reproducibility of target coverage in stereotactic spot scanning proton lung irradiation under high frequency jet ventilation.
abstract: OBJECTIVE
  To investigate scanned-beam proton dose distribution reproducibility in the lung under high frequency jet ventilation (HFJV).
  
  
  METHODS
  For 11 patients (12 lesions), treated with single-fraction photon stereotactic radiosurgery under HFJV, scanned-beam proton plans were prepared with the TRiP98 treatment planning system using 2, 3-4 and 5-7 beams. The planning objective was to deliver at least 95% of the prescription of 33 Gy (RBE) to 98% of the PTV. Plans were subsequently recomputed on localization CT scans. Additionally, for selected cases, the effects of range uncertainties were investigated.
  
  
  RESULTS
  Median GTV V(98%) was 98.7% in the original 2-field plans and 93.7% in their recomputation (p=0.039). The respective values were 99.0% and 98.0% (p=0.039) for the 3-4-field plans and 100.0% and 99.6% (p=0.125) for the 5-7-field plans. CT calibration uncertainties of ±3.5% led to a GTV V(98%) reduction below 1.5 percentual points in most cases and reaching 3 percentual points for 2-field plans with beam undershoot.
  
  
  CONCLUSIONS
  Through jet ventilation, reproducible tumor fixation for proton radiotherapy of lung lesions is achievable, ensuring excellent target coverage in most cases. In few cases, non-optimal patient setup reproducibility induced density changes across beam entrance channels, leading to dosimetric deterioration between planning and delivery.
authors.affiliation: University of Marburg, Department of Radiotherapy and Radiation Oncology, Germany. Electronic address: santiago@staff.uni-marburg.de.
authors.forename: Alina
authors.initials: A
authors.lastname: Santiago
authors.forename: Urszula
authors.initials: U
authors.lastname: Jelen
authors.forename: Filippo
authors.initials: F
authors.lastname: Ammazzalorso
authors.forename: Rita
authors.initials: R
authors.lastname: Engenhart-Cabillic
authors.forename: Peter
authors.initials: P
authors.lastname: Fritz
authors.forename: Werner
authors.initials: W
authors.lastname: Mühlnickel
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Enghardt
authors.forename: Michael
authors.initials: M
authors.lastname: Baumann
authors.forename: Andrea
authors.initials: A
authors.lastname: Wittig
mesh_terms: D002138:Calibration; D002289:Carcinoma, Non-Small-Cell Lung / Q000532:radiotherapy*; D006611:High-Frequency Jet Ventilation; D006801:Humans; D008175:Lung Neoplasms / Q000532:radiotherapy*; D061766:Proton Therapy / Q000379:methods*; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed
keywords: High frequency jet ventilation; Non small cell lung cancer; Particle therapy; Proton therapy; Reproducibility; SBRT