title: Reduction of normal lung irradiation in locally advanced non-small-cell lung cancer patients, using ventilation images for functional avoidance.
abstract: OBJECTIVE
  To investigate the ability of four-dimensional computed tomography (4D-CT)-derived ventilation images to identify regions of highly functional lung for avoidance in intensity-modulated radiotherapy (IMRT) planning in locally advanced non-small-cell lung cancer (NSCLC).
  
  
  METHODS
  The treatment-planning records from 21 patients with Stage III NSCLC were selected. Ventilation images were generated from the 4D-CT sets, and each was imported into the treatment-planning system. Ninetieth percentile functional volumes (PFV90), constituting the 10% of the lung volume where the highest ventilation occurs, were generated. Baseline IMRT plans were generated using the lung volume constraint on V20 (<35%), and two additional plans were generated using constraints on the PFV90 without a volume constraint. Dose-volume and dose-function histograms (DVH, DFH) were generated and used to evaluate the planning target volume coverage, lung volume, and functional parameters for comparison of the plans.
  
  
  RESULTS
  The mean dose to the PFV90 was reduced by 2.9 Gy, and the DFH at 5 Gy (F5) was reduced by 9.6% (SE = 2.03%). The F5, F10, V5, and V10 were all significantly reduced from the baseline values. We identified a favorable subset of patients for whom there was a further significant improvement in the mean lung dose.
  
  
  CONCLUSIONS
  Four-dimensional computed tomography-derived ventilation regions were successfully used as avoidance structures to reduce the DVH and DFH at 5 Gy in all cases. In a subset, there was also a reduction in the F10 and V10 without a change in the V20, suggesting that this technique could be safely used.
authors.affiliation: Division of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Yaremko
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Guerrero
authors.forename: Josue
authors.initials: J
authors.lastname: Noyola-Martinez
authors.forename: Rudy
authors.initials: R
authors.lastname: Guerra
authors.forename: David G
authors.initials: DG
authors.lastname: Lege
authors.forename: Linda T
authors.initials: LT
authors.lastname: Nguyen
authors.forename: Peter A
authors.initials: PA
authors.lastname: Balter
authors.forename: James D
authors.initials: JD
authors.lastname: Cox
authors.forename: Ritsuko
authors.initials: R
authors.lastname: Komaki
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology / Q000532:radiotherapy; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging* / Q000502:physiology; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology / Q000532:radiotherapy; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012119:Respiration; D014057:Tomography, X-Ray Computed / Q000379:methods*