title: The impact of heterogeneity correction on dosimetric parameters that predict for radiation pneumonitis.
abstract: OBJECTIVE
  To determine if heterogeneity correction significantly affects commonly measured dosimetric parameters predicting pulmonary toxicity in patients receiving radiation for lung cancer.
  
  
  METHODS
  Sixty-eight patients treated for lung cancer were evaluated. The conformal treatment technique mostly employed anteroposterior/posterior-anterior fields and off-cord obliques. The percent total lung volume receiving 20 Gy or higher (V20) and mean lung dose (MLD) were correlated with the incidence of radiation pneumonitis. Parameters from both heterogeneity-corrected and heterogeneity-uncorrected plans were used to assess this risk.
  
  
  RESULTS
  Univariate analysis revealed a significant correlation between the development of radiation pneumonitis and both V20 and MLD. A best-fit line to a plot of V20 from the homogeneous plan against the corresponding V20 heterogeneous value produced a slope of 1.00 and zero offset, indicating no difference between the two parameters. For MLD, a similarly significant correlation is seen between the heterogeneous and homogeneous parameters, indicating a 4% difference when correcting for heterogeneity. A significant correlation was also observed between the MLD and V20 parameters (p < 0.0001).
  
  
  CONCLUSIONS
  A high degree of correlation exists between heterogeneity-corrected and heterogeneity-uncorrected dosimetric parameters for lung and the risk of developing pneumonitis. Either V20 or MLD predicts the pneumonitis risk with similar effect.
authors.affiliation: Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, FL 32610-0385, USA.
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Chang
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Olivier
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Morris
authors.forename: Chihray
authors.initials: C
authors.lastname: Liu
authors.forename: James F
authors.initials: JF
authors.lastname: Dempsey
authors.forename: Rashmi K
authors.initials: RK
authors.lastname: Benda
authors.forename: Jatinder R
authors.initials: JR
authors.lastname: Palta
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D008168:Lung / Q000528:radiation effects*; D008175:Lung Neoplasms / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D017564:Radiation Pneumonitis / Q000209:etiology*; D011836:Radiation Tolerance; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal